Invasive plant species of savanna rangelands: Are they a threat or an opportunity?
By
Gusha Jacob (B.Sc. (Hon) Agriculture, MSc Animal Science UZ)
A thesis submitted in fulfilment of the requirements of the degree of Doctor of
Philosophy in Animal Nutrition
Department of Animal Science
Faculty of Agriculture
University of Zimbabwe
2018
Approved by
Professor P. H. Mugabe Professor M. Masocha Professor T.E. Halimani
...... (Supervisor) (Supervisor) (Supervisor)
Professor N. T. Ngongoni
...... (Associate-supervisor)
Abstract
Invasive and less palatable plant species are prevalent on most rangelands. Finding ways of utilising them should be a research priority. This study evaluated the threats and potential uses of invasive plant species as livestock feed resources. The evaluation was done over four stages. The first stage involved gathering the farmer perceptions in communal farming system, through a pretested semi-structured questionnaires on changes in quality of grazing, carrying capacity and the abundance of invasive plant species. The second stage was done through botanical field measurements and a survey in the three farming systems to confirm the issues raised by farmers in the first study. The collected data were analysed for threats and effects of the perceived changes in the rangelands. Predominant invasive plant species determined in the first and second stage of the study were evaluated for potential uses as animal feeds by determining their nutritive value. The third and fourth stages involved determining the best stage of growth for harvesting and conserving of these forages, analysing the nutrient composition, digestibility and determining how the performance of animals will be affected when fed on the harvested biomass. Data collected and measured were analysed using various procedures of SAS. Farmers reported that they were observing a widespread increase in woody and invasive plant species such as Lantana camara, Helichrysum kraussii, and thickets of Dichrostachys cinerea and Vachellia species. They also revealed that they were noticing the establishment of less palatable grass species such as Hyparrhenia filipendula, Hyperthelia dissoluta, and Sporobolus pyramidalis. Range condition assessment in the three farming systems also showed that communal grazing management was more detrimental to all rangeland parameters measured followed by small-scale commercial system, with commercial grazing management producing desirable results on rangeland productivity. Lantana camara, Hyparrhenia filipendula, and Hyperthelia dissoluta were nutritionally characterised in terms of crude protein (CP), acid detergent fibre (ADF), neutral detergent fibre (NDF) levels and apparent digestibility coefficient and the results showed that they have great potential of being used as animal feeds. L. camara from different locations did not differ significantly at (P> 0.05) in CP but differed in total extractable phenolics, according to site of harvesting. Harvesting H. filipendula and H. dissoluta eight to ten weeks from the onset of the rain season and conserving as silage or hay produced high quality roughage for livestock. In animal feeding trial, animals fed graded levels of L. camara biomass (5%, 10%, 15%, 20%, and 25%) completed the 22 days of feeding trial and without signs of ill health. The rate of microbial nitrogen production and efficiency on microbial nitrogen supply for growth was not significantly different at low rate of inclusion. The result suggested that dried L. camara biomass was safe to use up to 15% inclusion level in diets, beyond which it lowers voluntary feed intake. Increased utilisation of invasive plant species may control their rate of spread in invaded rangelands. Large quantities of L. camara, H. filipendula, and H. dissoluta biomass may be used to bridge the perennial feed deficit in both quality and quantity in tropical and subtropical agro ecosystems during the dry season of the year. Furthermore, harvesting and conserving these species will reduce the risk associated with the occurrence of high intensity wildfire fuelled by the presence of large quantities of biomass from these invasive plant species. These results confirmed that invasive plant species can be used as animal feed and contribute towards sustainable livestock production.
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Dedication
To my sons McJacob, Genius, Brilliant and daughter Mufaro
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Acknowledgements
The dream was to find how best science could solve challenges confronting our communities concerning rangeland degradation and the increase in invasive plant species. To a greater extent, this dream was realised, although the journey had so many rough patches. However, it could not have come to be without these great organisations and people. I wish to express my sincere gratitude to the University of Zimbabwe Research Board and The German Academic
Exchange (DAAD) programme, in-country scholarship for funding this doctoral study. I also thank all those who contributed towards the successful completion of this journey of pursuing a career in rangeland and animal nutrition science.
Let me also acknowledge the contribution made by my supervisors, Professor P. H. Mugabe,
Professor M. Masocha, Professor T. E. Halimani, and Professor N.T. Ngongoni, who helped in shaping my thinking as I tried to understand the threats and opportunities presented by invasive plant species of savanna rangelands. I am also grateful to Makoholi Research Institute and farmers from Zimuto communal farming area, Mushagashe small-scale commercial farming area, and Summerton large-scale commercial farming area who granted access to their farms during fieldwork. I also want to appreciate the efforts of Mr Hove (Livestock Extension
Officer) with Livestock Production Department (LPD) and other LPD officers who helped with fieldwork.
To my parents and friends, especially my father, Michael Jacob Gusha, I thank you for the unwavering support throughout the course of this DPhil study. Fellow staff members in the
Faculty of Veterinary Science and Department of Animal Science, you were more than colleagues; your contributions are highly appreciated.
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Finally, to my wife Pelagia, I acknowledge the hardship you endured during the course of this study. Had it not been your unconditional support, there could be no thesis to talk about. Thank you my darling.
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Table of Contents
Abstract ...... i
Dedication ...... ii
Acknowledgements ...... iii
Table of Contents ...... v
List of Tables ...... xii
List of Figures ...... xiii
List of Publications ...... xv
List of Abbreviations ...... xvi
CHAPTER ONE ...... 1
1 General introduction ...... 1
1.1 Background ...... 1
1.2 Statement of the problem ...... 3
1.3 Justification ...... 4
1.4 Research process ...... 6
1.5 Objectives...... 9
1.6 Hypotheses ...... 9
1.7 Thesis overview and layout...... 10
1.8 References ...... 12
CHAPTER TWO ...... 16
2 Literature review...... 16
2.1 Introduction ...... 16
2.2 Rangeland management in Zimbabwe ...... 16
2.3 Definition of invasive plants ...... 19 v
2.4 Susceptibility of savanna rangelands to degradation ...... 21
2.5 Causes and effects of the invasive plant species in rangelands ...... 22
2.6 Predominant invasive plant species in Zimbabwean rangelands ...... 23
2.6.1 Lantana camara ...... 24
2.6.1.1 Distribution and habitat of Lantana camara ...... 25
2.6.1.2 Toxicity susceptibility in animals ...... 26
2.6.1.3 Toxic principle...... 27
2.6.1.4 Toxicity in animals ...... 29
2.6.1.5 The conundrum with Lantana camara ...... 29
2.6.2 Hyparrhenia filipéndula...... 30
2.6.2.1 Distribution and habitat of Hyparrhenia filipéndula...... 31
2.6.2.2 Potential uses ...... 31
2.6.3 Hyperthelia dissoluta ...... 32
2.6.3.1 Distribution and habitat of H. dissoluta ...... 32
2.6.3.2 Potential uses ...... 33
2.7 Factors affecting the use of these invasive plant species ...... 33
2.7.1 Presence of plant secondary metabolites in forages as feed for livestock ...... 34
2.7.2 Coping strategies used by browsers and herbivores ...... 35
2.7.3 Forage quality in relation plant secondary metabolites ...... 37
2.8 Forage conservation and utilisation ...... 38
2.9 Major drawbacks to be conquered ...... 39
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2.10 Conclusion ...... 40
2.11 References ...... 41
CHAPTER THREE ...... 58
3 Farmers’ perceptions of invasive plant species, rangeland degradation and productivity58
3.1 Abstract ...... 58
3.2 Introduction ...... 59
3.3 Material and method ...... 61
3.3.1 Study sites ...... 61
3.3.2 Data collection ...... 61
3.3.3 Data analysis ...... 62
3.4 Results ...... 62
3.4.1 Perception of farmers on rangeland health status ...... 62
3.4.2 Perception of farmers on major woody species ...... 65
3.4.3 Major floristic changes observed in all the districts ...... 67
3.4.4 Perceived challenges associated with the increase in woody species ...... 69
3.5 Discussion ...... 71
3.6 Conclusion ...... 75
3.7 References ...... 76
CHAPTER FOUR ...... 80
4 Grazing system impacts on rangeland condition and grazing capacity in Zimbabwe...... 80
4.1 Abstract ...... 80
4.2 Introduction ...... 81
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4.3 Materials and methods ...... 82
4.3.1 Study site ...... 82
4.3.2 Sampling protocol ...... 84
4.3.3 Vegetation data collection...... 85
4.3.4 Data analysis ...... 86
4.4 Results ...... 88
4.5 Discussion ...... 97
4.6 Conclusion ...... 100
4.7 References ...... 101
CHAPTER FIVE ...... 105
5 Nutritive value of Lantana camara harvested from different sites in Zimbabwe ...... 105
5.1 Abstract ...... 105
5.2 Introduction ...... 106
5.3 Materials and methods ...... 107
5.3.1 Study site ...... 107
5.3.2 Chemical composition analysis...... 107
5.3.3 Data analysis ...... 108
5.4 Results ...... 108
5.5 Discussion ...... 111
5.6 Conclusion ...... 113
5.7 References ...... 115
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CHAPTER SIX ...... 118
6 Effect of growth stage and method of conservation of Hyparrhenia filipendula and Hyperthelia dissoluta on nutrient composition and digestibility ...... 118
6.1 Abstract ...... 118
6.2 Introduction ...... 119
6.3 Materials and methods ...... 121
6.3.1 Study site ...... 121
6.3.2 Silage and hay preparation ...... 121
6.3.3 Nutrient chemical composition analysis ...... 122
6.3.4 Statistical analysis ...... 122
6.4 Results ...... 123
6.4.1 Quality of silage from the two grass species...... 123
6.4.2 Quality of hay from the two grass species ...... 126
6.4.3 Rate of decline in crude protein and digestibility ...... 126
6.5 Discussion ...... 130
6.6 Conclusion ...... 134
6.7 References ...... 135
CHAPTER SEVEN ...... 139
7 Effects of Lantana camara feed on performance, digestibility, nitrogen balance, microbial protein production and concentration of liver enzymes in Mashona goats...... 139
7.1 Abstract ...... 139
7.2 Introduction ...... 140
7.3 Materials and methods ...... 142 ix
7.3.1 Study site ...... 142
7.3.2 Feed formulation and experimental design ...... 142
7.3.3 Experimental design and animal management...... 145
7.3.4 Nutritional composition analysis ...... 145
7.3.5 Haematology, clinical observation and laboratory assay ...... 146
7.3.6 Physical examination ...... 146
7.3.7 Calculations of feed efficiency parameters ...... 147
7.3.7.1 Nitrogen retention ...... 147
7.3.7.2 Microbial protein yield ...... 147
7.3.8 Statistical analyses ...... 148
7.4 Results ...... 149
7.4.1 Nutritional composition of the treatment diets ...... 149
7.4.2 Dry matter intake and apparent digestibility ...... 151
7.4.3 Nitrogen intake and retention...... 153
7.4.4 Excretion of purine derivatives and microbial protein production ...... 155
7.4.5 Health status of the experimental animals ...... 157
7.5 Discussion ...... 165
7.6 Conclusion ...... 170
7.7 References ...... 171
CHAPTER EIGHT ...... 178
8 General discussion and recommendations...... 178
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8.1 Introduction ...... 178
8.2 Do farming communities observe the decline in quality of grazing and the increase in less palatable plant species? ...... 179
8.3 Is there a link between farming systems and rangeland deterioration? ...... 181
8.4 Which invasive plant species are dominant in Zimbabwean rangelands ...... 182
8.5 Nutritive value of the some invasive plant species ...... 182
8.6 The threats and opportunities of using invasive plant species as animal feeds ...... 184
8.7 Practical relevance of this thesis ...... 185
8.8 General conclusion...... 185
8.9 Suggestions for future research ...... 186
8.10 References ...... 188
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List of Tables
Table 4-1: Proportion of desirable, moderately desirable, and undesirable species and their percentage biomass yield contribution in the three grazing systems ...... 89
Table 4-2: Variation in mean shrub density, grass height, and grazing capacity between different grazing systems of Zimbabwe ...... 92
Table 4-3: Sørensen similarity indices for rangeland management system associated with three different grazing systems...... 96
Table 5-1: Chemical composition (g/kg DM) of Lantana camara leaves harvested from six different sites in Zimbabwe...... 110
Table 6-1: Nutrient composition (% DM) for silages of H. filipendula and H. dissoluta conserved at three different growth stages in summer...... 125
Table 6-2: Nutrient composition (% DM) for hay of H. filipendula and H. dissoluta conserved at three different growth stages in summer...... 127
Table 7-1: Proportion of ingredients in kg used in formulating the treatment diets for the experiment on the effects of feeding Lantana camara on health and goat performance...... 144
Table 7-2: Nutritional composition (% DM) of diets with 5, 10, 15, 20 and 25% Lantana camara inclusion level, commercial goat meal and veld hay...... 150
Table 7-3: Average daily dry matter intake (g d–1) and apparent digestibility in goats given graded levels of Lantana camara, commercial goat meal and veld hay...... 152
Table 7-4: Nitrogen intake and retention (g d-1) in goats given graded levels of Lantana camara hay, commercial goat meal feed and a basal diet of veld hay...... 154
Table 7-5: Excretion of purine derivatives and microbial protein production by goats given graded levels of Lantana camara hay, commercial goat feed and veld hay as a basal diet .. 156
Table 7-6: Measured body temperature, heart rates and respiratory rates of goats fed graded levels of Lantana camara leaf meal...... 164 xii
List of Figures Figure 1-1: Cattle browsing Lantana camara shrub in Mvuma, Midlands Province in
Zimbabwe Photo credit M. Masocha ...... 4
Figure 1-2: A conceptual framework to assess the opportunities and threats presented by the increase of invasive plant species in savanna rangelands...... 8
Figure 2-1: Biochemical structure of the Lantadenes (Sharma et al., 2000) ...... 28
Figure 3-1: Proportion of interviewed farmers who perceived that the above five mentioned challenges were a source of discomfort to communal rangelands users in the six districts of study...... 64
Figure 3-2: Proportion of interviewed farmers who perceived that the above named woody plant species are the dominating species affecting rangelands in six districts of study...... 66
Figure 3-3:Proportion of interviewed farmers who perceived that the above named plant species on the increase and causing decline in rangeland productivity in the six districts of study ...... 68
Figure 3-4: Proportion of interviewed farmers who perceived that the above named major challenges are result of the increase in woody plant species in the six districts of study ...... 70
Figure 4-1: A map showing distribution of sample points (solid circle) among the main grazing systems in the administrative district of Masvingo in Zimbabwe...... 83
Figure 4-2: Average herbaceous biomass yield (± standard error) per hectare recorded in the three major grazing systems of Zimbabwe.CFS is communal farming system, SSC is small- scale commercial farming system, and LSC is large-scale commercial farming system...... 94
Figure 6-1: (A to D) showing rapid decline observed in crude protein content with advancing stage of growth of conserved silage and hay from H. filipendula and H. dissoluta...... 128
Figure 6-2:A to D showing rapid decline observed in digestibility coefficient with advancing stage of growth of conserved silage and hay from H. filipendula and H. dissoluta...... 129
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Figure 7-1: Observed changes in liver enzyme aspartate aminotransferase (AST) concentration in iu/l in goat fed graded levels of Lantana camara leaf meal...... 158
Figure 7-2: Observed changes in liver enzyme alanine aminotransferase (ALT) (iu/L) concentration in blood during the feeding period with graded levels of Lantana camara leaf biomass hay...... 159
Figure 7-3: Observed changes in total protein levels in grams per litre in goats fed with graded levels of Lantana camara leaf biomass hay...... 160
Figure 7-4: Observed changes in urea concentration in mmol/litre of blood in goats fed with graded levels of Lantana camara leaf biomass hay...... 161
Figure 7-5: Observed changes in the level of creatinine in ummol/l in goats fed with graded levels of Lantana camara leaf biomass hay...... 162
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List of Publications 1. Gusha, J., Masocha, M. and Mugabe, P.H., 2017. Impact of grazing system on rangeland condition and grazing capacity in Zimbabwe. The Rangeland Journal, 39(3), 219-225.
2. Gusha, J., Chambwe, T., Mugabe, P.H., Halimani, T., Katsande, S. and Masocha, M., 2016. Neglected grass species of Southern Africa: Nutritive value of conserved Hyperthelia dissoluta harvested at different growth stages. Tropical Grasslands- Forrajes Tropicales, 4(3), 179-184. 3. Gusha, J., Masocha, M, Muchaya, K., and Ncube, S. 2016. Chemical analysis of the potential contribution of Lantana camara to the nutrition of browsing livestock Tropical and Subtropical Agroecosystems, 19: 337–42. 4. Gusha, J., Mugabe P.H., Masocha, M. and Halimani T.E. 2016. Invasive species impacts and management in communal rangelands in Zimbabwe Grassroots, 16 (4): 45–49. 5. Gusha, J. and Mugabe, P.H. 2013. Unpalatable and wiry grasses are the dominant grass species in semi-arid communal rangelands in Zimbabwe International Journal of Development and Sustainability (2): 1075–83.
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List of Abbreviations
ADF Acid Detergent Fibre
ADIN Acid detergent Insoluble Nitrogen ALT Alanine Aminotransferase AST Aspartate Aminotransferase
CFS Communal Farming Area CP Crude Protein DLS District Livestock Specialist
DM Dry Matter, DMTP Digestible Microbial True Protein DOM Degradable Organic Matter
FTRL Fast Track Land Redistribution GPS Global Positioning System
Hb Haemoglobin
LEW Livestock Extension Worker LPD Livestock Production Department LSC Large-Scale Commercial Farming Area
N Nitrogen NDF Neutral Detergent Fibre
PSM Plant Secondary Metabolite RBC Red Blood Cell RDP Rumen Degradable Protein
RUDP Rumen Undegradable Digestible Protein SSC Small-Scale Commercial Farming Area TDN Total Digestible Nutrient
TEPH Total Extractable Phenolics TTL Tribal Trust lands
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CHAPTER ONE
1 General introduction
1.1 Background
Bush encroachment and rangeland invasion by less palatable herbaceous plant species is a global problem and the trend is expected to continue (Ward, 2005; Wiegand et al., 2006;
Masocha, 2010). This increase poses a threat to ecosystem functioning and native plant species biodiversity. Herbivory and fire are key disturbance factors driving rangeland dynamics in savanna systems (Trollope et al., 1998; Kauffman et al., 1994; Van Langevelde et al., 2003).
For example on African rangelands, frequent human-lit fires and overstocking with domestic herbivores such as cattle, coupled with climate change, trigger an increase in woody vegetation and accelerate rate of rangeland invasions by invasive alien and native plant species (Wiegand et al., 2005; Tefera et al., 2008; Masocha and Skidmore, 2011). These processes in turn change the floristic composition of savanna rangelands thus potentially undermining their ability to provide forage for livestock production. This rangeland deterioration and degradation threatens livestock production and human livelihoods (Landsberg and Crowley, 2004; Wiegand et al.,
2006), especially in developing countries where livestock farming contributes to gross domestic product and drive national economies (Hall, 2011). The change in the vegetation type and species is associated with both the threats and opportunities to livestock production
(Pucheta et al., 1998; Glendinning, 2002; Tefera et al., 2008). To provide a sustainable control strategy, the usefulness of these invasive plant species as energy and proteins sources to animals needs to be evaluated.
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Invasive plant species such as Lantana camara, Hyparrhenia filipendula, and Hyperthelia dissoluta are outcompeting desirable shrub and grass species in most rangelands in Zimbabwe, yet they are still not seriously considered as strategic livestock feed resources. There are some inevitable changes in floristic composition on savanna rangeland because of complex factors.
Invasive plant species may be the dominant plant species in future rangelands. Therefore, research should find ways of incorporating these species as livestock feed resources if livestock production is to be sustained. Invasive plant species are primary producers by virtue of having chlorophyll hence; they trap sunlight energy from the sun and convert it into simple sugars and polysaccharides. All plants with the capacity to fix carbon into organic molecules are widely accepted as sources of energy (Kimball and Provenza, 2003; Glendinning, 2002; Estell, 2010), and should be incorporated into livestock feeding programmes. Grazing and browsing livestock have been observed consuming these plant species during periods of feed shortages (Osuga et al., 2006; Mtui et al., 2008; Gusha et al., 2016). However, the nutritional contribution of these plant species to grazing animals is not clear. If the effect of stage of growth at harvesting, conservation method, and feeding methods is determined, opportunities presented by these plant species may be clearly understood. This may lead to establishment of appropriate harvesting time, conservation method and feeding strategy and in turn, a strategy of controlling their spreading in savanna rangelands may be developed.
On the other hand L. camara is considered toxic to livestock (Glisalberti, 2000; Day et al.,
2003; Cooper, 2007; Day and Zalucki, 2009), but, livestock especially goats and cattle (Fig
1.1) are often seen browsing on L. camara leaves. Reports from Kenya (Osuga, 2006),
Tanzania (Mtui et al., 2008), South Africa (Ide and Tutt 1998; Botha and Penrith 2008; Basha et al., 2012) and Zimbabwe (Gusha et al., 2016) have shown that native animals may consume
L. camara leaves with no negative effects, with a few naive animals sometimes succumbing to 2
L. camara poisoning. Animals respond differently after consuming L. camara with some animals showing no negative effects while others suffer from L. camara poisoning. It is this paradox that needs an explanation.
1.2 Statement of the problem
There is widespread invasion of savanna rangelands by invasive plant species (Chatanga, 2007;
Masocha, 2010) thereby reducing grazing capacity and threatening sustainable livestock production programmes (Gusha et al., 2017). Control of these species using biological methods, chemical and mechanical methods have not yielded favourable results (DiTomasso,
2000; Mooney, 2005; Tessema, 2012).Controlling the spread of the invasive plant species through utilization as animal feed resources is limited because of inadequate information on feeding potential of invasive plant species (Villalba et al., 2014). Invasive plant species are known to be chemically defended and not much is known about level of tolerance of browsing animals to the chemicals. Ruminants are exposed to thousands of chemicals in infinite combinations and concentrations that are constantly changing both temporally and spatially
(Lauchbaugh et al., 2001; Glendinning, 2002; Estell, 2010). The concentrations of these chemicals vary with the stage of growth and season of the year. There is dearth of information to guide farmers on the specific season and growth stage when to harvest a more palatable and nutritious invasive plant species biomass. Knowledge about the best harvesting period and best method of conservation is limited, yet it is critical in developing strategies for incorporating these undesirable species in mainstream livestock forage production. Identifying the growth stage when invasive plant species have the highest nutrient composition is useful to guide when to harvest and conserve for later use during critical periods of feed deficit should be considered.
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Figure 1-1: Cattle browsing Lantana camara shrub in Mvuma, Midlands Province in
Zimbabwe Photo credit M. Masocha
1.3 Justification
Invasive plant species such as L. camara, H. dissoluta, and H. filipendula produce high biomass that farmers and researchers neglect as potential animal feed resources. The large quantities of leaf biomass produced create numerous opportunities for bridging the perennial feed deficit gap experienced during the dry season. In tropical and subtropical regions, feed deficit gap during the dry season is a major constraint to cattle production. The fact that the invasive species are thriving in degraded rangelands creates numerous opportunities for utilising the high biomass they produce to meet the nutritional needs of livestock. The stage of growth, method of conservation and inclusion levels in animal diet affect the quality of forage from 4 these invasive plant species. It is essential to determine the scientific basis and empirical evidence for harvesting, conservation, and threshold inclusion levels that benefits the animals feeding on the resources.
The stages of growth, season of harvest as well as environmental factors influence the level concentration of secondary metabolites and other anti-nutritional factors. Therefore, understanding the variation in plant secondary metabolites and nutrient composition of invasive plants leaves as they mature and from different locations will help in selecting appropriate stage of growth with minimum levels of Plant Secondary Metabolite (PSM).
According to Estell (2010), all plants are heavily defended with chemicals, and herbivores must either contend with these PSM or avoid a significant component of the available forage. The success with which herbivores navigate this complex environment is in part attributed to their ability to cope with PSM. Therefore, despite the presence of chemicals in infinite combinations and concentrations, they can provide the nutrients required in animal production in the form of simple sugars, minerals, vitamins, and amino acids (Glendinning, 2002).
Invasive plant species produce large quantities of biomass during the rainy season. Harvesting of invasive plant species through ensiling or drying them before deterrents such as lignin and secondary metabolites reach critical thresholds that inhibit digestion and render them useless for livestock production may increase animal performance. Understanding the nutrient quality variations with different conservation methods at different growth stages is important.
Therefore, investigating the nutritive value, palatability, and digestibility of invasive plant leaves may form the scientific basis for conservation and utilization of these plant species in livestock production.
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Despite having cases in some areas, where animals consume L. camara herbage (Roothaert and
Franzel, 2001: Gusha et al., 2016) not much is known about the species contribution to protein nutrition and effects on health status of the animals. Because of interbreeding and hybridization, concentration of extractable total phenolic compounds including toxic lantadene
A and lantadene B should vary significantly between generations (Ghisalberti, 2000; Sharma et al., 2007). Hence, current lantana plants may be significantly different from those that were known to be poisonous to livestock. Based on these received reports, it is clear that toxicity of
L. camara has many questions than answers. Identifying regional differences in concentration of extractable phenolic compounds and animal responses to graded inclusion levels of lantana leaf meal in animal rations could provide the baseline knowledge for regulated feeding and lantana utilization. This in turn will improve livestock performance hence increase availability of animal products such as milk, meat, and draught power. The increase in milk and meat yield may contribute towards reducing malnutrition in human beings and at the same time generate income for farmers. The knowledge generated here may go a long way in addressing global challenges of invasive species and may help to formulate strategies for managing degraded rangelands thus contributing to the board knowledge on rangeland science. Thus, the use of these plants in animal nutrition research can be an effective way to manage invasive plant species. As far as the toxicity is concerned, it can be prevented by the using restrictive feeding strategy in which animals are fed quantities below the threshold levels that are not detrimental to the animal health, yet meeting the protein nutrition requirement of the animal.
1.4 Research process
Figure 1-2 below is conceptual framework for the research process. The first stage involves the farmers and stakeholders perception collected through a semi-structured questionnaire and the verification of findings by way of vegetation characterization on selected communal, small-
6 scale, and commercial farming rangelands. The first stage process gave the first set of potential opportunities and threats. Desk studies on effects of invasive plant species were also done and the effects were added to the list. The second stage tested potential interventions with the aim of determining the potential uses for invasive plant species in feeding ruminant animals.
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Figure 1-2: A conceptual framework to assess the opportunities and threats presented by the increase of invasive plant species in savanna rangelands.
Designed by the author. The amber colour represents the potentil threats, green for the opportunities and the blue represents the investigation routes
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1.5 Objectives
The general objective of this study was to assess the potential uses of invasive plant species in livestock production systems through evaluating their threats and opportunities if used as livestock feed. The specific objectives were to:
i. Assess farmer perception about invasive plant species and rangelands degradation;
ii. Evaluate the botanical composition and productivity of invaded rangelands in relation
to different farming systems and land management system; iii. Evaluate the chemical composition of L. camara leaves as potential protein
supplements for ruminants; iv. Investigate the effects of stage of growth and method of conservation of H. filipendula
and H. dissoluta on nutritional composition and digestibility coefficient; and
v. Test the nutritional contribution of L. camara leaf meal to animal health and
performance in goats.
1.6 Hypotheses
The following null hypotheses were tested:
i. The farmers are not able to identify invasive plant species and have no knowledge on
rangelands degradation; ii. Botanical composition and productivity of invaded rangelands in relation to different
farming systems and land management system are the same; iii. Lantana camara leaves does not have the potential to be used as protein supplements
for ruminants; iv. Stage of growth and method of conservation of H. filipendula and H. dissoluta does not
have effect on nutritional composition and digestibility coefficient; 9 v. Lantana camara leaf meal does not have effect on goat health and performance.
1.7 Thesis overview and layout
The overall objective of this study was to investigate the threats and opportunities presented by invasive plant species (L. camara, H. dissoluta and H. filipendula) when incorporated into livestock feeding systems as feeds. Through administering a pretested questionnaire, botanical survey on rangelands in three different farming systems, harvesting and conservation of invasive plant species at different growth stages, performing in vitro digestibility studies and finally conducting an animal performance feeding trial, the objective of the study was achieved.
In total, this thesis has eight chapters. Chapters 3-7 are structured as manuscripts for publication, complete with abstract and list of references.
Chapter 1 is the general introduction, problem statement, justification, conceptual framework, and objectives of the study chapter.
Chapter 2 is a literature review and discusses the challenges associated with the increase of invasive plant species and influence of rangeland management systems to the increase in invasive plant species. The chapter also looked at how these species could add value to livestock production systems.
Chapter 3 is a survey done using a pre-tested questionnaire. Part of the chapter was published in International Journal of Development and Sustainability while the other article was published as a feature article in the Grassroot, Newsletter of the Grassland society of Southern
Africa.
Chapter 4 is a research paper on the effects different farming systems on floristic composition and rangeland productivity. The research was reviewed and published in The Rangeland
Journal.
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Chapter 5 is a research paper on the effect of site of harvest on chemical composition of dried
L. camara leaf meal and the potential as a protein supplement. The manuscript was published in Tropical and Subtropical Agro ecosystems.
Chapter 6 is a research paper on the effects of stage of growth and method of conservation of
H. filipendula and H. dissoluta on nutritional composition and digestibility coefficient. Part of this work was published in Tropical Grasslands as a short note.
Chapter 7 is a research paper on the feeding value of dried L. camara leaf meal in goats. At the time of publishing this thesis, the manuscript was under review in the Small Ruminants
Research.
Chapter 8 synthesises the key findings of this work. The main results are discussed in the context of implications for animal nutrition and rangeland management.
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1.8 References
Basha, N.A.D., Scogings, P.F., Dziba, L.E., Nsahlai, I.V. 2012. Diet selection of Nguni goats
in relation to season, chemistry and physical properties of browse in sub-humid
subtropical savanna. Small Ruminant Research, 102(2): 163-171.
Botha, C.J. Penrith, M.L., 2008. Poisonous plants of veterinary and human importance in
southern Africa. Journal of Ethnopharmacology, 119(3): 549-558.
Chatanga, P. 2007. Impact of the invasive alien species, Lantana camara (L) on native
vegetation in Northern Gonarezhou National Park, Zimbabwe. MSc Thesis, University
of Zimbabwe.
Cooper, R.G. 2007. Accidental poisoning from Lantana camara (cherry pie) hay fed to
ostriches (Struthio camelus). Turkish Journal of Veterinary and Animal Sciences, 31(3):
213-214.
Day, M.D., Zalucki, M.P. 2009. Lantana camara Linn. (Verbenaceae).Biological control of
tropical weeds using arthropods. Cambridge University Press, Cambridge, UK, pp.211-
246.
Day, M.D., Wiley, C.J., Playford, J., Zalucki, M.P. 2003. Lantana: current management status
and future prospects. ACIAR, Canberra.
DiTomasso, J.M. 2000. Invasive weeds in rangelands: species, impacts, and management.
Weed science, 48(2): 255-265.
Ghisalberti, E.L. 2000. Lantana camara L. (Verbenaceae). Fitoterapia, 71(5): 467-86
Glendinning, J.I. 2002. How do herbivorous insects cope with noxious secondary plant
compounds in their diet? In Proceedings of the 11th International Symposium on Insect-
Plant Relationship (15-25). Springer, Dordrecht.
12
Gusha, J., Masocha, M., Mugabe, P.H. 2017. Impact of grazing system on rangeland condition
and grazing capacity in Zimbabwe. The Rangeland Journal, 39(3): 219-225.
Gusha, J., Masocha, M., Muchaya, K., Ncube, S. (2016). Chemical analysis of the potential
contribution of Lantana camara to the nutrition of browsing livestock. Tropical and
Subtropical Agroecosystems, 19: 337-342.
Hall, R. 2011. Land grabbing in southern Africa: the many faces of the investor rush. Review
of African Political Economy, 38(128): 193-214.
Ide A., Tutt, C.L.C. 1998. Acute Lantana camara poisoning in a Boer goat kid: Case report.
Journal of the South African Veterinary Association, 69(1): 30-32.
Kaufmann, J.B., Cummings, D.L., Ward, D.E. 1994. Relationships of fire, biomass, and
nutrient dynamics along a vegetation gradient in the Brazilian cerrado. Journal of
Ecology, 82: 519–531
Kimball, B.A., Provenza, F.D. 2003. Chemical defense and mammalian herbivores. USDA
National Wildlife Research Center - Staff Publications. 236.
http://digitalcommons.unl.edu/icwdm_usdanwrc/236
Landsberg, J., Crowley, G. 2004. Monitoring rangeland biodiversity: plants as indicators.
Australian Journal of Ecology, 29(1): 59-77.
Launchbaugh, K.L., Provenza, F.D. Pfister, J.A. 2001. Herbivore response to anti-quality
factors in forages. Journal of Range Management, 431-440.
Masocha, M. 2010. Savanna aliens, Ph.D thesis, Wageningen University, The Netherlands
Masocha, M., Skidmore, A.K. 2011. Integrating conventional classifiers with a GIS expert
system to increase the accuracy of invasive species mapping. International Journal of
Applied Earth Observation and Geoinformation, 13: 487-494.
13
Mooney, H.A. 2005. Invasive alien species: the nature of the problem. Scope-scientific
committee on problems of the Environment International Council of Scientific Unions,
63: pp.1.
Mtui, D.J., Shem, M.N., Lekule, F.P., Ichinohe, T., Fujihara, T. 2008. Evaluation of chemical
composition and in vitro gas production of browses collected from Tanzania. Journal of
Food, Agriculture, and Environment, 6(3&4): 191–195.
Osuga, I.M. 2006. Rumen degradation and in vitro gas production parameters in some browse
forages, grasses and maize stover from Kenya.Journal of Food, Agriculture and
Environment, 4(2): 60–64.
Pucheta, E., Cabido, M., Díaz, S., Funes, G. 1998. Floristic composition, biomass, and
aboveground net plant production in grazed and protected sites in mountain grassland of
central Argentina. Acta Oecologica 19(2): 97-105
Roothaert, R.L., Franzel, S. 2001. Farmers' preferences and use of local fodder trees and shrubs
in Kenya. Agroforestry Systems, 52(3): 239-252.
Sharma, O.P., Sharma, S., Pattabhi, V., Mahato, S.B., Sharma, P.D. 2007. A review of the
hepatotoxic plant Lantana camara. Critical Reviews in Toxicology, 37(4): 313-352.
Tefera, S., Dlamini, B.J., Dlamini, A.M., Mlambo, V. 2008. Current range condition in relation
to land management systems in semi‐arid savannas of Swaziland. African Journal of
Ecology, 46(2): 158-167.
Tessema, Y.A. 2012. Ecological and economic dimensions of the paradoxical invasive species-
Prosopis juliflora and policy challenges in Ethiopia. Journal of Economics and
Sustainable Development (www. iiste. org), 3(8).
14
Trollope, W.S.W. 1998. Effects and use of fire in the savanna areas of Southern Africa,
Department of Livestock and Pasture Science, Faculty of Agriculture, University of Fort
Harare, Alice, South Africa.
Van Langevelde, F., Van De Vijver, C.A., Kumar, L., Van De Koppel, J., De Ridder, N., Van
Andel, J., Skidmore, A.K., Hearne, J.W., Stroosnijder, L., Bond, W.J., Prins, H.H.T.,
Rietkerk, M. 2003. Effects of fire and herbivory on the stability of savanna ecosystems.
Ecology, 84(2): 337-350.
Villalba, J.J., Miller, J., Ungar, E.D., Landau, S.Y., Glendinning, J. 2014. Ruminant self-
medication against gastrointestinal nematodes: evidence, mechanism, and origins.
Parasite, 21(31): 1-8.
Ward, D. 2005. Do we understand the causes of bush encroachment in African savannas?
African Journal of Range and Forage Science, 22(2): 101-105.
Wiegand, K., Saltz, D. and Ward, D. 2006. A patch-dynamics approach to savanna dynamics
and woody plant encroachment–insights from an arid savanna. Perspectives in Plant
Ecology, Evolution and Systematics, 7(4): 229-242.
Wiegand, K., Ward, D., Saltz, D. 2005. Multi-scale patterns and bush encroachment in an arid
savanna with a shallow soil layer. Journal of Vegetation Science, 16(3): 311-320.
15
CHAPTER TWO
2 Literature review
2.1 Introduction
This literature review discusses problems associated with the increase of invasive plant species in savanna rangelands. Firstly, the broader definition of invasive plant species is given in the context of this thesis. Secondly, the management of rangelands in Zimbabwe is reviewed with the aim to identify the potential cause of rangeland degradation and invasion by less palatable invasive alien and native plant species. The strength and weaknesses of rangeland management systems are reviewed for the benefit of decision makers in livestock system. This review will also give an appraisal on rangeland management problems and identify areas of interventions to mitigate the effects and impacts of invasive plant species. This review is limited to three species, which were found to be abundant in most rangelands of Masvingo, Midlands,
Mashonaland West, Mashonaland East, and Mashonaland Central Provinces of Zimbabwe.
2.2 Rangeland management in Zimbabwe
Rangeland management in Zimbabwe is linked to land tenure systems. The Land
Apportionment Act of 1930 set aside 51% of the land to white settlers and prohibited native blacks from owning land in white commercial areas
(https://www.hrw.org/reports/2002/Zimbabwe/ZimLand0302-02.htm). The government of that day further created African Purchase area between indigenous reserves and the commercial white settlers, which was used as buffer area. The indigenous reserves became the Tribal Trust lands (TTL) through a gazetted Act in 1965 (Rukuni, 2006). These TTL were later changed to communal areas through the communal lands act of 1981 while the African Purchase area became the small-scale commercial farming areas. By 1981 three main land classifications
16 existed namely communal farming area (CFS), small-scale commercial farming area (SSC) and large-scale commercial farming area (LSC). Resettlement areas were created in 1982 to reduce overcrowding in communal areas and people were settled on farms purchased from white commercial farmers. Land redistribution continued until the recent Fast track land redistribution (FTRL) of 2000 where many commercial farms were acquired for rural distribution. The FTRL of the 2000 further created more land ownership methods. There were two models for resettlement in FTLR: model A1, "the decongestion model for landless people with a villagized and a self-contained variant," and model A2, aimed at creating small- to medium-scale black indigenous commercial farmers (Rukuni, 2006). In this study, rangeland management systems were defined according the tenure systems or land ownership.
Key distinctions between the three systems are associated with rights to arable land and grazing land, which characterise the land tenure system. Land in the CFS belongs to the State and the
State claims the rights to allocate land but the State powers are contested by traditional authorities, local notables, and lineage elders. On the other hand, the LSC has some property rights supported by legal documents such as title deeds conferring right of use. The land tenure system, which is used to categorise grazing systems, applies to other African countries such as
South Africa (Vetter, 2013). In communal ownership, land is held under traditional or communal tenure that confers individual rights to plots for houses, gardens, and arable fields, with shared access to grazing land (Muir-Leresche, 2006). Rangelands are communally managed in communal farming area, resettlement area and the FTLR model A1. In this review, all areas that practice communal grazing are referred to as a CFS. The grazing areas are shared and used by all farmers in a community, with no deliberate rangeland management interventions. Since livestock plays an integral role, peasant farmers in CFS are reluctant to sell their cattle and look instead to grow their herd size. Stocking rates are not regulated and 17 where there is arable land shortages, people tend to encroach onto grazing areas. In addition,
CFS rangelands are continuously grazed with no planned rest periods except in the dry season, when grazing animals use both crop residues in arable lands and forage in rangelands. CFS rangelands are also characterised by the absence of deliberate efforts to improve the rangeland through introduction of more productive pasture species and rotational grazing, since there are usually no fenced paddocks to control animal movement.
On the other hand, farmers in the African purchase area and FTLR Model A2 area occupy what is known as the small-scale commercial farming areas (SSC). Rangeland management systems in the SSC and LSC rangelands differ from those in the CFS. Small-scale commercial farming system is characterised by small, individually-owned farms usually operated as family trusts
(Muir-Leresche, 2006).The title deeds may be in the name of the elder member of the family, but decisions on how the farm is used are shaped by the knowledge family members possess.
For instance, if family members are not aware of the basic principles of rangeland management then range improvement may not be implemented. Most SSC farms have a perimeter fence with no internal demarcations to allow rotational grazing. Small-scale commercial farms range in size from 40 to 100 ha (Rukuni, 1994). SSC rangelands are generally classified as stocked below optimum. Previous research indicates that in agro-ecological zone IV, SSC rangelands are stocked at approximately 0.4 times the recommended stocking rate for this zone (Muir-
Leresche, 2006). Rangelands in the SSC are continuously grazed and there are no planned rangeland improvements and resting periods. Thus, the rangeland management system of these
SSC farms is similar to CFS, with both characterised by continuous grazing.
In contrast to CFS and SSC farms, LSC farms are privately owned properties in excess of 200 ha. They are usually managed by owners or ranch managers with technical knowledge and access to financial resources (Rukuni, 1994; Gambiza et al., 2000). The principles of range 18 management are typically followed. For example, LSC farms usually have a well-developed paddock system, through which animals are rotationally, grazed using such systems as the one- herd to four-paddock system or the high-intensity short duration grazing system (Sibanda and
Khombe, 2006). In most cases, the LSC rangelands are protected from fire by firebreaks. Fire is only used to control woody encroachment or ticks, or to promote grass regrowth. The veld is occasionally improved with forage legumes such as fine-stem stylo (Stylosanthes guianensis), silver leaf Desmodium (Desmodium uncinatum), and siratro (Macroptilium atropurpureum) (Phelan et al., 2014; Gambiza et al., 2000; Sibanda and Khombe, 2006).
Owing to differences in the grazing management systems, cattle performance, that of cattle, in the CFS has been reported to be lower than that of a LSC grazing systems (Mavedzenge et al.,
2005). In addition, rangelands in a CFS are reported to be overgrazed and at high risk of woody species encroachment, as well as invasion by unpalatable species (Vetter, 2003; Ward, 2005;
Masocha et al., 2011; Gusha et al., 2017). However, rather than speculate about the relationship between grazing systems and rangeland condition, empirical data are required to test whether there is a link between rangeland condition and the grazing systems described above for informed rangeland management. Information on the links between land tenure, existing range management system and the current health status of rangelands is vital considering the close relationship between animal health, animal performance and livelihoods in Zimbabwe (Swiswa et al., 2016; Gusha et al., 2017).
2.3 Definition of invasive plants
This study adopted the definition by MacIsaac and Colautti (2004) and Jeschke et al. (2014) which includes both indigenous or native and non-native plant species, which colonise or
19 invade economically, environmentally, or ecologically and disrupt by dominating a region.
However, Vila and Weiner (2004) defined invasive plant species as plants, which are not native and have a tendency to spread to a degree of causing environmental, human economy and health challenges. Lantana camara is rated 10th in the world list of most dangerous invasive plant species (Achhireddy and Singh, 1984; Johnson and Jensen, 1998; Ghisalberti, 2000; Saraf et al., 2011; Taylor and Kumar, 2013). Currently, L. camara, H. filipendula, and H. dissoluta are found in most parts of Zimbabwe and dominate most rangelands (Masocha, 2010; Gusha et al., 2017). These species have shown properties of invasive plant species such as altering the environment affecting the behaviour of herbivores and creating a negative impact on other species. Hyparrhenia filipendula and H. dissoluta are C4 African grass species which, were introduced in American pastures, ostensibly to enhance livestock production but instead these grass species have invaded savanna and forest edges throughout the neotropics (D’Antonio and
Vitousek, 1992; Angassa and Baars, 2000).
The African invaders grasses have the potential to affect ecosystem function by: a). Altering productivity/tropic structure, b). Altering microclimate and shifting the rate of consumption and supply of light, water and mineral nutrients, c). Increasing the frequency and intensity of fire, d). Altering competitive interaction and e). Compromising ecosystem stability.
Hyparrhenia filipendula and H. dissoluta have altered most landscapes and ecosystem functioning thereby further affecting the abundance of other plant species and native biodiversity. In Zimbabwe, it is estimated that over thirty percent of rangelands are invaded with L. camara (Chatanga, 2007; Gusha et al., 2016a). In the USA and South Africa for instance, the economic losses due to invasive plant species runs into billions of United State dollars (Pimentel et al., 2005; Huxman et al., 2014; Dickie et al., 2014). These three species are the primary focus of this study because of the observed dominance in most rangelands 20
(Masocha 2010) and invasive properties of changing the landscape ecological functions and undermining their potential or ability to sustain livelihoods in various communities in
Zimbabwe.
2.4 Susceptibility of savanna rangelands to degradation
The largest diversity of mammal herbivores on the planet and half the total human population in Africa is supported by the savanna biome (Scholes and Archer, 1997). Savanna biome occupies approximately 12% of the world land area and is characterised by the coexistence of trees and grasses (van Jaarsveld et al., 2005; Blaum et al., 2007; Masocha, 2010).
Anthropogenic factors and climatic factors promote invasion of the savanna biome by invasive plant species which have negative effects on ecological diversity functioning (Houlahan and
Findlay, 2004; Hellmann et al., 2008; Pimentel et al., 2005; Torchin and Mitcheil, 2014), and economic losses through loss of productive land thus affecting profitable ranching (Kandeh,
2002). Indeed, these ecological changes, which brought about numerous plant species with less economic value and at the same time forcing valuable plant species into extinction, in turn affect the functioning of savanna rangelands. Biodiversity, economic and rangeland structural functioning loss due to the increase in invasive plant species are key environmental problems confronting the rangeland managers and ecologist worldwide (Pyke et al., 2002; Henderson,
2007; Powel et al., 2011; Carter et al., 2014).
Considering that the increase in invasive species spread has been documented in rangelands worldwide (Grime, 2001; MacDougall and Turkington, 2005), rangeland management protocols should be appropriate and suitable for each agro-pastoral system and not be blanket.
Grazing management practices characterised by overgrazing and over-exploitation of rangelands resources may drive invasion of rangelands by less palatable and toxic plants as
21 well as increase rates of soil erosion and land degradation (Vetter, 2003; Ward, 2005). Bush encroachment and palatable plant species loss resulting in decline in rangeland productivity have been reported in grazing systems that experience overgrazing and unsustainable use of rangelands (Beeskov et al., 1995; Neely and Butterfield, 2004; Ward, 2005; Vetter, 2012). This implies there may be a link between vulnerability to invasion by invasive species, rangeland degradation, land tenure, and grazing systems.
2.5 Causes and effects of the invasive plant species in rangelands
Rangeland degradation due to high stocking rate coupled with poor grazing practice leads to grass species compositional changes with the highly palatable species disappearing, leaving toxic and non-palatable species as dominant species (Smit et al., 1999; Mavedzenge et al.,
2005). The combination of heavy grazing and highly variable climate has contributed to extensive environmental problems throughout Southern Africa (Darkoh, 2009: Dreber et al.,
2011) and an increase in these invasive species. Sustained high grazing intensity in rangelands leads to loss of palatable species such as Themeda triandra and their replacements by grazing tolerant, unpalatable species such as Eragrostis curvula, E. plana, and Sporobolus pyramidalis
(Gusha and Mugabe, 2013). Species richness of highly palatable species decline, further opening spaces for more invasive species thus affecting output from the rangelands. Invasive plants cause a significant challenge to biodiversity in savanna rangelands.
Invasive plant species are a threat to viable livestock production in all farming systems under savanna rangelands. In Zimbabwe’s Masvingo province the presence of Helichrysum kraussii is a key rangeland problem (Gusha and Mugabe, 2013; Gusha, et al., 2016b). On the other hand, Lantana camara is taking over rangelands since its introduction in Zimbabwe as an
22 ornamental plant in the mid 1900 by the colonial settlers. It has since spread to rural areas with a potential to take over all natural pasture if the invasion continues unchecked. Native grasses such Hyperthelia dissoluta and H. filipendula with low nutritive value have dominated the rangelands (Moyo et al., 2010; Masocha et al., 2011), causing floristic compositional changes which are affecting livestock production. Nutritious grass species have been replaced with less palatable species thus in turn reducing the nutrient harvested of the grazing animals. The scenario has lowered output from communal and smallholder livestock farming areas since these farmers have limited capacity to supplement their animals with better quality feeds. In order to appreciate the changes taking place in the rangelands, the relationship between rangeland management and the spread of invasive plant species should be understood.
It is believed that some exude biochemicals that are highly allelopathic thus suppressing growth of native species and microbes in invaded communities (Gentle and Duggin, 1997). Since farming systems vary in the way the rangeland resources are exploited and managed, it is important to establish if they is an association between farming system and the spread of invasive plant species. The changes in floristic composition should also be checked to ascertain if they are rangeland management system specific as that will help in making future decisions on rangeland management.
2.6 Predominant invasive plant species in Zimbabwean rangelands
There are a number of invasive plants in savanna rangelands of Zimbabwe but for the purpose of this study, three key species found to be dominant in most rangelands are reviewed namely
L. camara, H. dissoluta and H. filipendula. In the preliminary work to this study by Masocha
(2010) and Gusha and Mugabe (2013), these species were observed to be widespread on rangelands. These plant species are either monopolisers or donors of a limiting resource and
23 can affect indirectly other plant species and the ecosystem by changing soil properties, promoting erosion, and fire. These invasive plant species are thriving well in rangelands and they seem to be the present and the future important plant species of most savanna rangelands.
If their abundance is to go by, then present and future research must find a way to incorporate them in livestock feeding systems so as to unlock their potential feeding value. If research finds a way of using these species, their abundance will be monitored and may have a positive contribution to livestock production. Therefore, this review aims to find possibilities of using them as animal feeds and at the same time monitor their spread on rangelands.
2.6.1 Lantana camara
Lantana camara is a shrub that belongs to the Verbenacea family (Reddy, 2013). The genus is difficult to classify taxonomically because species are not stable due to widespread hybridisation, shape of inflorescence changes with age, and flower colours varation with age and maturity (Ghisalberti, 2000). Lantana camara is a perennial noxious weed of native forests, grasslands and pastures affecting over 60 countries worldwide (Parimoo and Sharma, 2014).
Lantana camara was introduced in Zimbabwe in the early 1900 as an ornamental plant, and more often used as hedge around urban houses as well as rural homesteads (Maroyi, 2012).
The plant is a heavily branched thicket-forming shrub with square-shaped stems, short curved, hooked prickles, and grows to a height of about 2-4 metres. The leaves are bright green and rough on their upper surface whereas the under surface is pale and hairy. Depending on type, maturity and location, L. camara plant has flowers which form in dense clusters, with varying in colour from red to yellow, orange to pink, and white (Ghisalberti, 2000; Day et al., 2003).
Where there is adequate soil moisture, high humidity, and temperature, the plant flowers and reproduces all year round. Lantana fruits are green when unripe and turn to a shiny dark purple- black when ripe and occur in clusters.
24
Lantana camara is a complex polyploid of interbreeding taxa with other complex species like
Lantana urticifolia (Urban et al., 2011). Because of hybridization, the world now has various separate species, forms, cultivars, biotypes as well as subspecies or varieties of L. camara
(Kumar et al., 2016). As a result of hybridization and variability, variations occur in terms of concentration of toxins, shape of leaves, flower colours and susceptibility to herbivore attack
(Day et al., 2003). Based on flower colours there are five main varieties that were identified namely pink, pink-edged, red, orange, and white plants (Day et al., 2003). Out of these five, the red Lantana type is the most toxic (Day et al., 2009; Sharma et al., 2007).
2.6.1.1 Distribution and habitat of Lantana camara
Lantana is found in many African countries and is a natural weed in approximately 60 countries between 35°N and 35°S (Sharma et al., 2007). According to Nang’alelwa (2010), the plant grows well near wetlands and low-lying areas. The plant is a weed of economic importance, which grows along riverbanks, fence-lines, roadsides, forestry, pastures, and rangelands.
Lantana invasibility increases with high rainfall (Masocha, 2010). In Zimbabwe, L. camara is widely distributed in all agro ecological regions, especially in the high rainfall areas such as the Eastern Highlands (Chatanga, 2007; Maroyi, 2012; Zende, 2016; Gusha et al., 2016a).
Lantana camara invasion in savanna rangelands was reported to have a mean annual rate of spread of at least twice that of native encroachers during year of above average rainfall
(Masocha, 2010).Whilst Lantana prefers growing in moist soils, the plant can survive prolonged dry spells. Lantana does not grow in areas with temperatures below 5°C and is very sensitive to frost. Lantana camara is encroaching cultivated lands at a fast alarming rate
(Henderson, 2007; Sharma et al., 2005) and is considered noxious in the Noxious Weeds Act of Zimbabwe (chapter 19:07). Because of its broad distribution, invasive aptitude in both
25 agricultural and natural ecosystems, L. camara plant is considered one of the worst invasive shrubs in tropical savanna rangelands (Chatanga, 2007: Masocha et al., 2011).
Lantana camara is known to be allelopathic (Sharma et al., 2005) and seed dispersal by birds and small ruminants such as goats increase the rate of invasion in most rangelands. The plant is known to suppress the regeneration of neighbouring plants in the rangeland through its allelopathic effects (Achhireddy and Singh, 1984; Gentle and Duggin, 1997; Kong et al., 2006;
Hussain et al., 2011). According to Kohli et al. (2006), caffeic acid, p-OH-benzonate, p- coumaric acid, vallic acid, syringic acid, and gentistic acid are known allelochemicals produced by Lantana. The latter causes the plant to outcompete other plants thus dominating and transforming the landscape (Sharma et al., 2006). The red flower variety (L. camara var aculeate) was found to be prevalent in tropical and subtropical countries.
2.6.1.2 Toxicity susceptibility in animals
Both ruminant and non-ruminant animals were found to be susceptible to Lantana poisoning according to Day and Zalucki (2009). Toxicity is very common in newly introduced stock to areas where toxic forms of Lantana are already growing. Ide and Tutt (1998) reported acute
Lantana poisoning in Boer goat kid that died when introduced to a new place infested with
Lantana while other goats in this flock consumed the plant but appeared healthy with no toxicity signs (Ide and Tutt, 1998; Cooper, 2007). Older cattle that are accustomed to grazing
Lantana infested areas are not as susceptible as their young counterparts are. This could be because the animals have developed a way of mixing the forage or regulate their intake in order to reduce detrimental effects. Livestock are more likely to graze the plant during periods of
26 green fodder scarcity. Therefore, the presence of the shrub offers an opportunity for restrictive feeding where animals are given an amount that will have beneficial effects.
2.6.1.3 Toxic principle
Lantadenes are the pentacyclic triterpenoids from the lantana plant. They have many biological functions. Triterpene derivative lantadene A (LA) is the main toxic principle (Pattnaik and
Pattnaik, 2010). Some authors state that Lantadene B, lantadene C (LC), lantadene D (LD) and icterogenic acid also have a profound effect on lantana toxicity (Kong et al., 2006; Parimoo et al., 2015). According to Sharma et al. (2000), a concentration of 491.5 ± 6.3 and 805.9 ±
52.8mg per 100 grams of dry weight in young and mature leaves of L. camara respectively was observed. The lantadenes are found mainly in leaves of L. camara (Sharma et al., 2007), with their varying toxic effects among different species and strains of livestock. There are over 155 species of L. camara plant in the tropical and subtropical regions (Pattnaik and Pattnaik, 2010).
Since Lantana varieties are well known to hybridize freely (Gujral and Vasudevan, 1983;
Levin, 2002), not all varieties contain the hepatotoxins found within the L. camara complex
(Ghisalberti, 2000). The current Lantana camara is a result of hybridisation between several Lantana species resulting in Lantana plants that maybe morphologically similar but with visible differences in flower colours, spininess of the stems and hairiness of the leaves
(Baars and Neser, 1999: Williams and Madire, 2008). This therefore, explains why some varieties are more toxic to cattle than others as well as why the non-toxic taxa either do not contain LA or LB or at the very least, would contain very small amounts of toxins (Sharma et al., 2007).
27
Figure 2-1: Biochemical structure of the Lantadenes (Sharma et al., 2000)
28
2.6.1.4 Toxicity in animals
Acute and chronic clinical manifestations of intoxication with Lantana occur in both ruminants and non-ruminants. Acute clinical signs usually occur within 24 hours of plant, ingestion whilst with sub-acute clinical signs occur with pronounced mortality (Parimoo et al., 2015). Sharma et al. (2007) reported that the clinical signs follow a pattern, which begins with the loss of appetite and decrease in ruminal motility within 24 hours. This is followed by photosensitization in un-pigmented areas, which leads to necrosis within 24-48 hours and then icterus within 48-72 hours. In more severe cases, death may occur within 2 to 4 days whilst in less severe cases death may occur within 1-3 weeks. Other clinical signs to be noticed in
Lantana toxicity are weight loss, anorexia, frequent urination, followed by constipation and dehydration, ruminal stasis, melena, cracks and fissures on muzzle, conjunctivitis, ulceration of the tip and under surface of the tongue (if un-pigmented), photophobia, as well as active seeking of shade (Ghisalberti, 2000; Sharma et al., 2007; Day and Zalucki, 2009). It was ascertained that, the median lethal dose (LD50) value of the lantadene toxicity in sheep was 1-
3 mg/kg body weight and 60 mg/kg body weight when given by intravenous and oral routes respectively (Kumar et al., 2016). In laboratory guinea pigs, the oral dosage rate of 25 mg/kg body weight only produced hepatotoxic and nephrotoxic effects, which were observable on histopathology as well as biochemical evaluation. The latter results were suggestive of sub- acute Lantana toxicity (Parimoo et al., 2015).
2.6.1.5 The conundrum with Lantana camara
On the contrary, L. camara is not as toxic to livestock as what is known and reported
(Ghisalberti, 2000; Day et al., 2003; Cooper, 2007; Day and Zalucki, 2009).Farmers in
Zimbabwe (Chatanga, 2007; Gusha, et al., 2016a), Kenya (Osuga et al., 2006; Ouédraogo-koné
2008; Osuga and Abdulrazak 2005), Tanzania (Obiri, 2011; Mtui et al., 2008), and South
29
African (Ide and Tutt, 1998; Henderson, 2007; Basha et al., 2012; Plessis et al., 2004) have reported seeing animals such as goats and cattle foraging on L. camara. Some have reported that L. camara is one of the preferred browse forage shrub by goats. Hence, it is important to assess whether browsing animals obtain nutritional value from the invasive shrub. If this is the case, it may warrant a shift from eradicating this invasive species to utilisation. L. camara survival in grazing areas could be an indication of a supportive agronomic environment for this species. In some areas in Zimbabwe, farmers feed their animals with L. camara during periods of feed deficit by simply cutting branches of Lantana camara and placing them in pens for goats to feed on the leaves (Gusha et al., 2016a).It is however, not clear as to why animals that are feeding on L. camara do not die from poisoning. Pfister (1999) reported that L. camara toxins are not cumulative and toxicity is dose dependent, however, if any animal consumes more than 1% of its body weight lantana poisoning may occur.
To date, previous research has concentrated on the toxicity of L. camara to livestock (Ide and
Tutt, 1998), hence not much is known about the potential nutritional contribution of the species to livestock. To fill this knowledge void, it is important to assess the nutritional composition of L. camara. Considering that Osuga et al., (2008) reported that L. camara is high in crude protein (22% CP), its use as a protein supplement should be assessed. If L. camara can be used as an alternative protein supplement, animal productivity might be improved in a sustainable way since the shrub is drought tolerant and invasive.
2.6.2 Hyparrhenia filipéndula
Hyparrhenia filipendula is a grass of Andropogoneae genus, which is native to semi-arid Africa and an important component of acacia savanna (Skerman and Riveros, 1990). Hyparrhenia filipendula is also known as fine thatching grass, which is mostly found in bushveld regions as
30 well as in open grasslands. H. filipendula is relatively densely tufted perennial grass that flowers from November to April. There are two varieties of H. filipendula: var. filipendula and var. pilosa (Oudstshoorn, 2002). This species is closely related to H. anamesa and H. hirta
(Oudstshoorn, 2002).It grows up 1.5 metres high under favourable conditions.
2.6.2.1 Distribution and habitat of Hyparrhenia filipéndula
Hyparrhenia filipendula is found throughout tropical Africa, Madagascar, Sri Lanka, Burma, and Australia. In Zimbabwe, it is common in the low to and high veld areas along highways, roads sides, old fields, and contour ridges in arable lands. According to Oudstshoorn (2002), this species is found in all types of soil, but is more often found in gravelly soils. In areas of low rainfall, it commonly found in damp places. Hyparrhenia filipendula is well adapted to heavy grazing and burning, leading to its increase in abundance in rangelands (Mufandaedza,
1976a). Smith (1962) reported that tannins and oils in this Andropogoneae family of grasses act as a repellent for herbivory. Hyparrhenia filipendula is highly lignified especially once it reaches flowering stage of growth. This results in reduced use by herbivores and its accumulation into fuel for intense veld fires.
2.6.2.2 Potential uses
Hyparrhenia filipendula offers palatable grazing early in the rainy season; however, its palatability decreases with maturity. In a field study in Zimbabwe H. filipendula was cut at a height of 4 or 12 cm every 2-16 weeks (Mufandaedza, 1976a) and higher yields were obtained with increasing cutting intervals and greater cutting height. In potted trials, plants cut at 4 or
10 cm every 2-8 weeks, had similar leaf yields for all treatments but stem yields increased with cutting interval (Mufandaedza, 1976b). It was also observed that root, stubble, and total non- structural carbohydrates had higher yields in less frequent and less severe cutting treatments.
However, in Ugandan grasslands, twice as much harvest was obtained in the 5 cm treatment
31 when cutting monthly at a height of 5 and 20 cm (Strugnell and Pigott, 1978). This species can produce up 13 to 25 tonnes of herbage per hectare in one season (Strugnell and Pigott, 1978).
Hyparrhenia filipendula tolerated herbivory by increased photosynthetic rate (Wallace et al.,
1984), through continued production of young tissues.
2.6.3 Hyperthelia dissoluta
Hyperthelia dissoluta is a grass under the genus Andropogoneae. It is a robust, perennial tufted grass, which usually flowers from December to June. The entire plant is predominantly yellow and green. It is the only Hyperthelia species found in the in southern Africa and is often confused with the Hyparrhenia species. It grows to above 3 metres (Burkill, 1985).
2.6.3.1 Distribution and habitat of H. dissoluta
Hyperthelia dissoluta is known as yellow thatching grass and is widely dispersed throughout tropical Africa and according to Williams and Baruch (2000); it was introduced in tropical
America as a pasture grass. This species is a dominant perennial grass wherever it is. In
Zimbabwe, it is widely distributed and is found in most areas. It was observed in roadsides along highways and in open grass lands (Tavirimirwa et al., 2012: Gusha et al., 2016b).It is also known to do very well in disturbed soils, damp areas and abandoned field even with very low soil nutrients, though it prefers to grow in sandy soils. H. dissoluta can grow in most areas from low-lying area up to over 3000 masl (Wild, 1972; Heuzé et al., 2012). This type of grass is very difficult to eradicate. In trials conducted in Zambia over three years, it demonstrated that it is tolerant to annual burning and out competed other grass species creating a one species rangeland (Heuzé et al., 2012). The tolerance to annual burning could be the reasons for its dominance in most rangelands where, veld fires occur annually.
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2.6.3.2 Potential uses
H. dissoluta is grazed early in the rainy season before it becomes too tough for grazing with maturity. According to Skerman and Riveros, (1990), Kativu, 92011) and Heuze et al., (2012),
H. dissoluta is highly productive with an average yield of above 26 tonnes of dry matter biomass per hectare. It is known also for its rapid growth habit, which gives it an advantage over other species. This grass quickly becomes hard and lignified thus limiting its utilisation to a few days after the onset rains. During maturation, the fiber level increase resulting in increase in lignification, decline in protein content and non-structural carbohydrates (Ball et al., 2001;
Smith, 2002; Sokolović et al., 2011; Teague et al., 2013). Once this process of maturation is completed, the biomass from this species becomes unpalatable and animals cannot consume it except during severe feed shortages (Mapiye et al., 2006). Even though, animals may be forced to consume it under feed shortages research has reported that animals suffer negative N balance unless when protein supplements are offered to boost microbial activities in the rumen (Mapiye et al., 2010; Katsande et al., 2016). Some beneficial uses include thatching, basket making and nest for indigenous chicken. This species is considered an invasive plant species in this study because it has dominated rangelands and completely changed the rangelands functions and ecosystem. It has also changed fire regimes and intensity, with increased prevalence of uncontrollable fires occurring annually in areas dominated by this species.
2.7 Factors affecting the use of these invasive plant species
Utilization of invasive plant species is limited by the presence of anti-nutritional factors. Some plants have plant secondary metabolites while others have physical structures that deter animals from browsing them. The following factors are discussed as possible challenges that lower the nutritive value of some of the species in animal feeding programmes.
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2.7.1 Presence of plant secondary metabolites in forages as feed for livestock
All plants produce a diversity of plant secondary metabolites (PSM) (Mazid et al., 2011). This is specifically to cope with various kinds of biotic and abiotic stress factors. Plant secondary metabolites cause variation in nutritive value and utilization of plant diets as fodder. Salem et al. (2006) observed that the presence and concentration of PSM in plants is the key in determining the amount taken in by sheep and goats. There are three chemically distinct groups of PSM namely terpenes, phenolic, nitrogen and sulphur containing compounds. Plant secondary metabolites cause a diversity of effects when consumed by herbivores. Terpenes and phenolic compounds are known to affect dry matter, protein, carbohydrate digestibility and nitrogen retention (Mapiye et al., 2010; Jayanegara et al., 2011; Nasri et al., 2011). These compounds also cause a shift in the sites of protein digestion and nitrogen excretion from the rumen to post ruminal sites and from urinary nitrogen to faecal nitrogen losses respectively.
Plant secondary metabolites also lower the nitrogen availability and fermentation pattern in the rumen hence lowering the nutritional value of some plant diets.
Terpenes were observed to have negative effects on in vitro digestibility due to negative effects on ruminal fermentation (Ormeño et al., 2008). Some PSM, such as phenolic compounds are toxic to the rumen microbes, they poison cellulolytic bacteria and negatively affect degradation of fibre in the rumen. On the contrary, some PSM such as saponins are known to increase bacterial protein flow to post ruminal sites and reduce methane production (Rogosic et al.,
2008). This therefore means that plants higher in saponins can be used to promote microbial protein production resulting in high volumes of microbial protein reaching the post ruminal sites for digestion and utilization by herbivores (Sirohi et al., 2012; Inamdar et al., 2015).
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The concentration of PSM varies within and between plant species. They range from harmless to lethal depending on how acutely toxic a compound is and whether the amount consumed is above critical threshold to overwhelm the detoxification system (Mazid et al., 2011). There is variation in nutritive value, mechanical and chemical defense according to stage of growth and plant species. Plant secondary metabolites are a necessary evil in that their production involves a cost to the plant yet they protect the plant from herbivores and pathogens (Pfister et al., 2010;
Mazid et al., 2011). The concentration and degree of toxicity of PSM depends on location, climate factors including microclimate, growing season, type of soil, fertilization, plant variety and age (Chandra et al., 2012) Pre-treatment of poisonous plants also affects the degree of toxicity. Processes such as drying, chewing, cooking (Chandra et al., 2012), and ensiling
(Moore et al., 1991) reduce the concentration and degree of toxicity. Toxicity is also dose dependent and consumption of levels lower than the threshold for toxicity will not affect the animal (Glendinning, 2002; Estel, 2010).
2.7.2 Coping strategies used by browsers and herbivores
Due to the abundance of chemical defended plants, herbivores are forced to choose between two equally challenging options of starving or consuming a potentially toxic plant. Glendinning
(2007) reported that many herbivores have mixed success in overcoming these defenses.
Therefore, during browsing or grazing there are chances that an herbivore may end up taking a plant species that affects its health condition. Herbivores must cope or face starvation and there is no easy solution to this challenge. This explains why animals are seen consuming some species that are known to be toxic. Their survival depends on the concentration of the PSM consumed at once and the level of adaptability of the animal to the substance. Bryant et al.
(1991) reported that mammals have evolved anatomical, physiological, and behavioural
35 counters to plants defences. It is believed that ruminants have increased tolerance to PSM due to the metabolic processes that are carried by the microbes in the rumen (Glendenning, 2007).
In the 1970s, Leucaena leucocephala was not promoted as a protein supplement because of mimosine toxicity. However, Synergistes jonessii a rumen bacterium was discovered (Palmer et al., 2010) in sheep, which were feeding on L. leucocephala in Hawaii. This bacterium metabolises mimosine in L. leucocephala. Mimosine is a toxic goitrogen (Jones and Megarrity,
1981), and is metabolized by S. jonessii which enables ruminants with this bacterium to use L. leucocephala without problems. Fermentation of PSM such as oxalic acid by Oxalobacter formigenes is another metabolic process performed by ruminal microbes to render it harmless to ruminants (Kimball and Provenza, 2003; Glendinning, 2007; Ormeño et al., 2008). Some of the phenolic are used by the animal for self-medication purpose against gastrointestinal nematodes (Villalba et al., 2002, 2014), hence these compounds have a beneficial role to herbivores.
Animals use different strategies to render plant toxins harmless. In some cases animals produces saliva, which cause plant toxins to form complexes with salivary protein as a way of inactivating them. The proline-rich protein in saliva has a high affinity for tannins thereby forming a complex with tannins and increase palatability of plants with tannins (Glendinning,
2007) and reduces toxicity (Shimada, 2006). Processing the plant diet is another way of reducing the concentration of toxics. Roy and Bergeron (1990a) reported that Meadow voles cut and abandon branches of toxic plant for several days and then return latter to consume them.
This is believed to allow some toxins such as phenolic and tannins to decay and become harmless before they consume them. Therefore, conservation of forages high in phenolic and tannins should render them less toxic (Roy and Bergeron, 1990b). Dearing (1997) observed 36 similar behaviour in pikas where they sting a chemical defended plant and delay eating until the concentration of toxin has diminished to below a critical level to cause toxicity. Another method of coping with chemically defended plants is explained by the toxin dilution hypothesis. The hypothesis states that animals regulate intake of toxic plants so that the concentration of consumed toxins never exceed the threshold for toxicity (Swihart et al., 2009).
Animals also rely on biotransformation enzymes systems to detoxify plants toxins when consumed (Ghisalberti, 2000; Dearing et al., 2005; McLean and Duncan, 2006). The results of this biotransformation are varied and dose dependent (Estell, 2010). Some may cause a decrease in pH where other may shut the cellular metabolic functions (Shimada, 2006).
2.7.3 Forage quality in relation plant secondary metabolites
The most important asset in any livestock production operation is the forage, as it forms the foundation of all forage-based diets (Sokolović et al., 2011; Walter et al., 2012). Animal performance is a function of the forage availability and the nutrient composition in the forage.
However, these forages contain different chemical constituents that determine the palatability and accessibility of nutrients by the herbivores. Forage can have chemical, physical, and structural traits that affect its quality. Therefore, forage quality could be defined in various ways depending on the main property being looked for. The most important properties of quality are associated with nutrients content, energy, protein, digestibility, fibre level, mineral, vitamins, and ultimately the expected performance of the target animal (Halmemies-Beauchet-
Filleau et al., 2013). The ultimate quality test will be the performance of the animal being fed on the forage. Forage quality should encompass both the nutritive value thus the total digestible nutrient (TDN) and the palatability measured as voluntary feed intake (Schnaider et al., 2014).
37
The quality of the forage is determined by the number of factors and not every plant will have the same nutritive value even if they come from the same species. The edaphic factors have a great influence on the quality of the forage (Teague et al., 2013).The level of nitrogen fertilizer application influences the level of crude protein in the forage plant. Soils that are highly fertile produce better quality forage plants. Forage quality is negatively correlated with maturity. Rotz and Muck (1994) reported that during the first 2-3 weeks after growth initiation digestibility
1 will be above 80% and from there digestibility declines by /3 to ½% units per day until it reaches levels below 50%. Maturity also influence forage consumption by animals. As the forage matures, it becomes fibrous and intake declines. The ratio of non-fibre constituents of forage decline with age so as the intake potential. Therefore, invasive plant species cannot be neglected based on the current thinking that they have high levels of PSM or are highly fibrous.
There is need to scientifically evaluate nutritive value and see how their quality is compromised by the presences of plant secondary metabolites.
2.8 Forage conservation and utilisation
Sustaining livestock in subtropical savanna with challenging dry season environment is the chief constraint to livestock production in Africa. In Zimbabwe, animals perform well during the rainy season from November to end of March and in most case suffer from nutritional deficiencies during the dry period resulting in sub-optimal reproduction performance (Scoones,
1995; Gusha et al., 2014). There is high mortality in both calves and lactating cows because of dry season malnutrition resulting in low livestock productivity index (Bellido, 1981; Gunter et al., 2003; Mokantla et al., 2004). Therefore, it becomes imperative that for successful livestock production, forage conservation methods should be embraced and any potential forage available should be conserved in order to bridge the perennial feed deficit gap experienced in the dry season.
38
Forage conservation is the process of keeping or storing animal feed material during periods of excess for later use in the dry season when there is a deficit. Forage can be conserved as hay or silage and be fed to animal during the dry season. Conserved forage, if harvested and properly conversed will have higher nutrient composition than crop residue or standing crop harvested after senescence (Lauchbaugh, et al., 2001; Ward, 2011). Therefore, harvesting forage at the right time before accumulation of anti-nutritional factors is vital. The forage plant has to be harvested at a growth stage when usable nutrients are at their highest quantities and at the same time digestibility is optimum (Halmemies-Beauchet-Filleau et al., 2013). Neutral detergent fibre content increases as the plant age hence timing to harvest before the concentration of NDF starts to affect the potential intake is important. The increase in stem to leaf ratio is a major cause of the decline in forage quality with maturity. Hence, when conserving forage timing of the optimum period of harvesting is most important. Hay and silage are the main form of conserved forage for later use.
2.9 Major drawbacks to be conquered
The major obstacles that hinder the control and management of these invasive plant species are multifaceted. Firstly, there is an overemphasis on the negative attributes of these invasive plant species resulting in very little being done to identify the best methods of incorporating them in mainstream livestock production systems. Secondly, researchers have not embraced the inevitable changes in floristic composition due to complex factors such as changes in grazing intensity, stocking rates, rainfall distribution and amounts. Most researchers focused on eradication of invasive plant species and the introduction of exotic grasses species, which seem to be productive in other environments but not productive under local environment. However, herbivores have lead the way, evolving and eating species previously known to be toxic. The
39 effects of such foraging behaviour need interrogation in order to be clear and know the contribution of invasive plants to the nutrients requirement of animals. Because these invasive species outcompete desirable native species and often reduces livestock output from invaded rangelands embracing them and identifying appropriate harvesting, conservation and utilisation strategies that make them useful in livestock production is crucial for sustainable development and utilisation of our rangeland resources. Furthermore, utilisation through harvesting as animal feed is likely to control and monitor the invasibility of invasive plant species in rangelands.
2.10 Conclusion
In conclusion, Lantana camara, H. filipendula, and H. dissoluta like all other plants have anti- nutritional factors and are chemically defended. The concentration of anti-nutritional factors and PSM should vary with location, stage of growth, and stress factors. At the same time, these anti-nutritional factors and PSM poses both adverse and beneficial effects. Their inclusion in animal feeds should increase herbage available for animal production. By determining the best harvesting growth stage of H. filipendula and H. dissoluta and conserving the biomass as hay or silage of high nutrient density should benefit animal production. This study seeks to obtain concentration of PSM at different growth stages and identify the nutritive value of these species. Once, these species become available as animal feeds, their use should reduce their impacts on rangelands and animal production. The presence of high total extractable phenolics in L. camara and the high lignin in late harvested H. filipendula and H. dissoluta limit the utilization of these feed materials.
40
2.11 References
Achhireddy, N.R., Singh, M. 1984. Allelopathic Effects of Lantana (Lantana camara) on Milk
weed vine (Morrenia Odorata). Weed Science 32 (6). Weed Science Society of America
and Allen Press: 757– 761.
Baars, J.R., Neser, S. 1999. Past and present initiatives on the biological control of Lantana
camara (Verbenaceae) in South Africa. African Entomology Memoir, (1): 21-33.
Ball, D.M., Collins, M., Lacefield, G.D., Martin, N.P., Mertens, D.A., Olson, K.E., Putnam,
D.H., Undersander, D.J., Wolf M.W. 2001. Understanding forage quality. American
Farm Bureau Federation Publication, 1(01).
Basha, N.A.D., Scogings, P.F., Dziba, L.E. Nsahlai, I.V. 2012. Diet selection of Nguni goats
in relation to season, chemistry and physical properties of browse in sub-humid
subtropical savanna. Small Ruminant Research, 102(2–3): 163–71.
Beeskow, A.M., Elissalde, N.O., Rostagno, C.M. 1995. Ecosystem changes associated with
grazing intensity on the punta ninfas rangelands of Patagonia, Argentina. Journal of
Range Management, http://www.jstor.org/stable/4003063.
Bellido, M.M. 1981. Influence of breed, calving season, supplementation and year on
productivity of range cows. Journal of Animal Science, 455–62.
http://www.journalofanimalscience.org/content/52/3/455.short.
Blaum, N., Rossmanith, E., Schwager, M. Jeltsch, F. 2007. Responses of mammalian
carnivores to land use in arid savanna rangelands. Basic and Applied Ecology, 8(6):
552–64.
Bryant, J.P., Provenza, F.D., Pastor, J. 1991. Interactions between woody plants and browsing
mammals mediated by secondary metabolites Annual Review, 22(1): 431–46.
http://arjournals.annualreviews.org/doi/abs/10.1146/annurev.es.22.110191.002243.
41
Burkill, H.M. 1985. Entry for Hyperthelia dissoluta (Nees) WD Clayton [family POACEAE].
In: The useful plants of West Tropical Africa. 2nd Edn. Royal Botanic Gardens, Kew,
UK.
Carter, J., Jones, A., O’Brien, M., Ratner, J., Wuerthner, G. 2014. Holistic Management:
Misinformation on the science of grazed ecosystems. International Journal of
Biodiversity, 1–10. https://doi.org/10.1155/2014/163431.
Chandra, S.J., Sandhya, S., Vinod, K.R., Banji, D., Sudhakar K., Chaitanya, R. 2012. Plant
Toxins-Useful and harmful effects. Journal for Drugs and Medicines, 4: 79–90.
Chatanga, P. 2007. Impact of the invasive alien species, Lantana camara (L) on native
vegetation in Northen Gonarezhou National Park, Zimbabwe. University of Zimbabwe.
Cooper, R.G. 2007. Accidental poisoning from Lantana camara (Cherry Pie) hay fed to
ostriches (Struthio Camelus). Turkish Journal of Veterinary and Animal Sciences,
31(3): 213–14.
D’Antonio, C.M., Vitousek, P.M. 1992. Biological invasions by exotic grasses, The Grass/Fire
Cycle, and Global Change. Annual Review of Ecology and Systematics, 23 (1): 63–87.
https://doi.org/10.1146/annurev.es.23.110192.000431.
Darkoh, M.B.K., 2009. An overview of environmental issues in Southern Africa. African
Journal of Ecology, 47: 93-98.
Day, M,D., Zalucki, M.P., 2009. Lantana camara Linn. (Verbenaceae). Biological control of
tropical weeds using Arthropods. Cambridge University Press, Cambridge, UK,
pp.211-246.
Day, M.D., Wiley, C.J. Playford, J., Zalucki, M.P. 2003. Lantana: Current management status
and future prospects. Canberra. ACIAR Monograph 102. Vol. ACIAR Mono.
42
Dearing, M.D. 1997. The manipulation of plant toxins by a food hoarding herbivore,
Ochontona princeps Ecology, 78: 774-781.
Dearing, M.D., Foley, W.J., McLean, S. 2005. The influence of plant secondary metabolites
on the nutritional ecology of herbivorous terrestrial vertebrates. Annual Reviews of
Ecology Evolution System, 36: 169-189
Dickie, I.A., Bennett, B.M., Burrows, L.E., Duane, A., Peltzer, A.P., Richardson, D.M.,
Rejmnek, M., Rundel, P.W., van Wilgen, B.W. 2014. Conflicting values: ecosystem
services and invasive tree management. Biological Invasions, 16(3): 705–19.
https://doi.org/10.1007/s10530-013-0609-6.
Dreber, N. Esler, K.J., 2011. Spatio-temporal variation in soil seed banks under contrasting
grazing regimes following low and high seasonal rainfall in arid Namibia. Journal of
Arid Environments, 75(2): 174-184.
Estell, R.E. 2010. Coping with shrub secondary metabolites by ruminants. Small Ruminant
Research, 94 (1–3). https://doi.org/10.1016/j.smallrumres.2010.09.012.
FTLR. 2002. https://www.hrw.org/reports/2002/Zimbabwe/ZimLand0302-02.htm accessed on
17 February 2017
Gambiza J., Frost B.W., Higgins, S. 2000. Land use options in dry tropical woodland
ecosystems in Zimbabwe. Ecological Economics, 33: 353–368.
Gentle, C.B., Duggin, J.A. 1997. Allelopathy as a competitive strategy in persistent thickets of
Lantana camara L. in three Australian forest communities. Plant Ecology, 132(1): 85–
95. https://doi.org/10.1023/A:1009707404802.
Ghisalberti, E.L. 2000. Lantana camara L. (Verbenaceae). Fitoterapia, 4(40): 1–10.
http://www.sciencedirect.com/science/article/pii/S0367326X00002021.
Glendinning, J.I. 2007. How do predators cope with chemically defended foods? In Biological
Bulletin, 213: 252–66 https://doi.org/213/3/252 [pii]. 43
Glendinning, J.I., 2002. How do herbivorous insects cope with noxious secondary plant
compounds in their diet? In Proceedings of the 11th International Symposium on Insect-
Plant Relationships (pp. 15-25). Springer, Dordrecht.
Grime, J.P. 2001. Plant strategies, vegetation processes, and ecosystem properties. John Wiley
and Sons, Chichester, UK.
Gujral, S.S., Vasudevan, P. 1983. Lantana camara L. a problem weed Journal of Scientific and
Industrial Research, 42(5): 281-286.
Gunter, S.A., Beck, P.A., Phillips, J.M. 2003. Effects of supplementary selenium source on the
performance and blood measurements in beef cows and their calves. Journal of Animal
Science, 81(4): 856–64.
Gusha, J, Masocha, M., Mugabe, P.H. 2017. Impact of grazing system on rangeland condition
and grazing capacity in Zimbabwe. Rangeland Journal 39(3): 219–25.
https://doi.org/10.1071/RJ15130.
Gusha, J., Mugabe, P.H. 2013. Unpalatable and wiry grasses are the dominant grass species in
semi-arid communal rangelands in Zimbabwe. International Journal of Development
and Sustainability, 2(2): 1075–83.
Gusha, J., Halimani, T.E., Katsande, S., Zvinorova, P.I. 2014. Performance of goats fed on low
quality veld hay supplemented with fresh spiny cactus (Opuntia Megacantha) mixed
with browse legumes hay in Zimbabwe. Tropical Animal Health and Production, 46(7):
1257–63. https://doi.org/10.1007/s11250-014-0636-z.
Gusha, J., Masocha, M, Muchaya, K., Ncube, S. 2016a. Chemical analysis of the potential
contribution of Lantana camara to the nutrition of browsing livestock. Tropical and
Subtropical Agro ecosystems, 19: 337–42.
44
Gusha, J., Mugabe, P.H., Masocha, M., Halimani, T.E. 2016b. Invasive species impacts and
management in communal rangelands in Zimbabwe, Grassroots, 16 (4): 45–49.
Halmemies-Beauchet-Filleau, A., Kairenius, P., Ahvenjarvi, S, Crosley, L.K., Muetzel, S., P
Huhtanen, A. Vanhatalo, V. Toivonen, R.J Wallace, Shingfield, K.J. 2013. Effect of
forage conservation method on ruminal lipid metabolism and microbial ecology in
lactating cows fed diets containing a 60:40 forage-to-concentrate ratio. Journal of Dairy
Science, 96 (4) https://doi.org/10.3168/jds.2012-6043.
Hellmann, J.J., Byers, J.E. Bierwagen, B.G, Dukes, J.S. 2008. Five potential consequences of
climate change for invasive species. Conservation Biology, 22 (3): 534–43.
https://doi.org/10.1111/j.1523-1739.2008.00951.x.
Henderson, L. 2007. Invasive, naturalized and casual alien plants in southern Africa : A
Summary Based on the Southern African Plant Invaders Atlas (SAPIA). Bothalia, 37
(2): 215–48.
Heuzé, V., Tran, G., Hassoun, P. 2012. Yellow thatching grass (Hyperthelia dissoluta).
Feedipedia.org. A programme by INRA, CIRAD, AFZ and FAO. p. 2–3. Available at:
http://www.feedipedia.org/node/429.
Huxman, T.E., Bradford, P.W, Breshears, D.D., Scott, R.L., Snyder, A., Small, E.E., Kevin, H.
K. 2014. Ecohydrological implications of woody plant encroachment. Ecology, 86 (2):
308–19.
Ide, A., Tutt, C.L. 1998. Acute Lantana camara poisoning in a Boer goat kid. Journal of the
South African Veterinary Association, 69(1): 30–32.
https://doi.org/10.4102/jsava.v69i1.807.
Inamdar, A.I., Chaudhary, L.C., Agarwal. N., Kamra, D.N. 2015. Effect of Madhuca longifolia
and Terminalia chebula on methane production and nutrient utilization in buffaloes.
45
Animal Feed Science and Technology, 201: 38–45.
https://doi.org/10.1016/j.anifeedsci.2014.12.016.
Jayanegara, A., Togtokhbayar, N., Makkar, H.P. Becker, K., 2009. Tannins determined by
various methods as predictors of methane production reduction potential of plants by
an in vitro rumen fermentation system. Animal Feed Science and Technology, 150(3):
230-237.
Jeschke, J.M., Bacher, S., Blackburn, T.M., Dick, J.T., Essl, F., Evans, T., Gaertner, M.,
Hulme, P.E., Kühn, I., Mrugała, A., Pergl, J., 2014. Defining the impact of non‐native
species. Conservation Biology, 28(5): 1188-1194.
Jones, R.J., Megarrity, R.G., 1986. Successful transfer of DHP‐degrading bacteria from
Hawaiian goats to Australian ruminants to overcome the toxicity of
Leucaena. Australian Veterinary Journal, 63(8): 259-262.
Kandeh, J.M.K. 2002. Geographic information system on invasive alien plant species. MSc
Thesis, ITC, http://www.itc.nl/library/Papers/msc_2002/nrm/korsu_kandeh.pdf.
Kativu, S. 2011. Hyperthelia dissoluta (Nees ex Steud.) Clayton. [Internet] Record from
PROTA4U. Brink M; Achigan-Dako EG, eds. PROTA (Plant Resources of Tropical
Africa / Ressources végétales de l’Afrique tropicale), Wageningen, Netherlands.
Available at: http://www.prota4u.org/search.asp.
Katsande, S., Baloyi, J.J., Nherera-Chokuda, F.V., Ngongoni, N.T., Matope, G., Zvinorova,
P.I. Gusha, J., 2016. Apparent digestibility and microbial protein yield of Desmodium
uncinatum, Mucuna pruriens and Vigna unguiculata forage legumes in goats. African
Journal of Range and Forage Science, 33(1): 53-58.
46
Kimball, B.A., Provenza, F.D. 2003. Chemical defense and mammalian herbivores. USDA
National Wildlife Research Center - Staff Publications, 236.
http://digitalcommons.unl.edu/icwdm_usdanwrc/236
Kohli, R.K., Batish, D.R., Singh, P.H., Dogra, D.S. 2006. Status, invasiveness and
environmental threats of three tropical American invasive weeds (Parthenium
Hysterophorus L., Ageratum Conyzoides L., Lantana camara L.) in India. Biological
Invasions, 8(7): 1501–10. https://doi.org/10.1007/s10530-005-5842-1.
Kong, C.H., Wang, P, Zhang C.X., Zhang, M.X, Hu, F. 2006. Herbicidal potential of
allelochemicals from Lantana camara against Eichhornia Crassipes and the Alga
(Microcystis Aeruginosa).Weed Research, 46(4): 290–95.
https://doi.org/10.1111/j.1365-3180.2006.00509.x.
Kumar, R, Katiyar, R., Kumar, S., Kumar, K., Singh, V. 2016. Lantana camara: An alien weed,
its impact on animal health and strategies to control. Journal of Experimental Biology
and Agricultural Sciences, 4(3S): 321-337. https://doi.org/10.18006/2016.
Lauchbaugh, K.L., Provenza F.D., Pfister J. 2001. Herbivore response to anti-quality factors
in forages. Journal of Range Management, 54(4): 431–40.
http://www.jstor.org/stable/4003114.
Levin, D.A. 2002. Hybridization and extinction: in protecting rare species, conservationists
should consider the dangers of interbreeding, which compound the more well-known
threats to wildlife. American Scientist, 90(3): 254-261.
MacDougall, A.S., Turkington, R. 2005. Are invasive species the drivers or passengers of
change in degraded ecosystems? Ecology, 86(1): 42-55. https://doi.org/10.1890/04-
0669.
47
MacIsaac, H.J., Colautti, R.I. 2004. A neutral terminology to define invasive species. Diversity
and Distributions, 10(2): 135–41.
Mapiye, C., Chimonyo, M., Dzama, K. Marufu, M.C. 2010. Protein status of indigenous nguni
and crossbred cattle in the semi-arid communal rangelands in South Africa. Asian-
Australasian Journal of Animal Sciences, 23(2): 213-17.
Maroyi, A. 2012. Garden Plants in Zimbabwe: Their ethnomedicinal uses and reported toxicity.
Ethnobotany Research and Applications, 10: 45-57.
Masocha, M., Skidmore, A.K., Poshiwa, X., Prins, H.H.T. 2011. Frequent burning promotes
invasions of alien plants into a Mesic African Savanna. Biological Invasions, 13(7):
1641-48. http://link.springer.com/article/10.1007/s10530-010-9921-6.
Masocha, M. 2010. Savanna Aliens. Ph.D thesis, Wageningen University, The Netherlands.
Mavedzenge, B.Z., Mahenehene, J., Murimbarimba, F., Scoones, I., Wolmer, W. 2005.
Changes in the livestock sector in Zimbabwe following land reform: The Case of
Masvingo Province. A Report of a Discussion Workshop, IDS, Brighton.
Mazid, M., Khan, T.A., Mohammad, F. 2011. Role of secondary metabolites in defense
mechanisms of plants. Review Literature and Arts of the Americas, 3(2): 232–49.
http://www.biolmedonline.com/Articles/MAASCON-1/Vol3_2_232-249.pdf.
McLean, S., Duncan, A.J. 2006. Pharmacological perspectives on the detoxification of plant
secondary metabolites: Implications for Ingestive behavior of herbivores. Journal of
Chemical Ecology, 32(6): 213–28. https://doi.org/10.1007/s10886-006-9081-4.
Mokantla, E., McCrindle, C.M.E, Sebei, J.P., Owen, R. 2004. An investigation into the causes
of low calving percentage in communally grazed cattle in Jericho, North West Province.
Journal of the South African Veterinary Association, 75(1): 30–36.
48
http://www.cabdirect.org/abstracts/20043094663.html%5Cnhttp://www.ncbi.nlm.nih.
gov/pubmed/15214692.
Moyo, B., Dube S., Lesoli, M., Masika, P.J. 2010. Herbaceous biomass, species composition
and soil properties of key grazing patches in coastal forest thorn veld and two grassland
types of the Eastern Cape Province, South Africa. African Journal of Range and Forage
Science, 27(3): 151–62. https://doi.org/10.2989/10220119.2010.520677.
Mtui, D.J., Martin, N.S., Lekule, F.P, Ichinohe, T., Fujihara, T. 2008. Evaluation of chemical
composition and in vitro gas production of browses collected from Tanzania. Journal
of Food Agriculture and Environment 6(3–4): 191–95.
Mufandaedza, J.T. 1976a. Effects of frequency and height of cutting on the yield, composition,
and quality of grass only and grass legume mixtures. Rhodesia Division of Livestock
and Pastures Annual Report. Salisbury. (Herbage Abstracts 48 [1978])
Mufandaeza, J.T. 1976b. Effects of frequency and height of cutting on some tropical grasses
and legumes. Hypharrenia filipendula and Heteropogon contortus. Rhodesian Journal
of Agricultural Research, 14:21-38
Muir-Leresche, K. 2006. Agriculture in Zimbabwe. Zimbabwe’s Agricultural Revolution
Revisited’ (Eds M. Rukuni, P. Tawonezvi, CK Eicher, M. Munyuki-Hungwe and P.
Matondi.), pp.99-116.
Nang'alelwa, M.M. 2010. Effects of treatment on Lantana camara (L.) and the restoration
potential of riparian seed banks in cleared areas of the Victoria Falls World Heritage
Site, Livingstone, Zambia (Doctoral dissertation, Rhodes University).
Nasri, S, Salem H.B., Vasta V., Abidi, S, Makkar H.P.S, Priolo A. 2011. Effect of increasing
levels of quillaja saponaria on digestion, growth and meat quality of barbarine lamb.
Animal Feed Science and Technology, 164(1–2): 71–78.
https://doi.org/10.1016/j.anifeedsci.2010.12.005. 49
Neely, C.L, Butterfield, J. 2004. Holistic Management of African Rangelands. Magazine on
Low External Input.
http://libarynth.f0.am/_media/permaculture_case_study_zimbabwe.pdf.
Obiri, J.F. 2011. Invasive plant species and their disaster-effects in dry tropical forests and
rangelands of Kenya and Tanzania. Journal of Disaster Risk Studies, 3(2): 417–28.
https://doi.org/10.4102/jamba.v3i2.39.
Ormeño, E, Baldy V., Ballini C., Fernandez, C. 2008. Production and diversity of volatile
terpenes from plants on calcareous and siliceous soils: Effect of soil nutrients. Journal
of Chemical Ecology, 34(9): 1219–29. https://doi.org/10.1007/s10886-008-9515-2.
Osuga, I.M., Abdulrazak S.A. 2005. Chemical composition, degradation characteristics and
effect of tannin on digestibility of some browse species from Kenya harvested during
the wet season. Asian-Australian. Journal of Animal Science, 18(1): 54–60.
http://www.ajas.info/upload/pdf/18_11.pdf.
Osuga, I.M., Abdulrazak S.A., Ichinohe, T. Fujihara, T. 2006. Rumen degradation and in vitro
gas production parameters in some browse forages, grasses and maize stover from
Kenya. Journal of Food, Agriculture and Environment 4(2): 60–64.
Oudtshoorn, F.V. 2002. Guide to grasses of Southern Africa. Briza Publications, Pretoria,
South Africa.
Ouédraogo-koné, S. 2008. The potential of some sub-humid zone browse species as feed for
ruminants. Doctoral Thesis, Swedish University of Agricultural Science, Uppsala,
Sweden.
Palmer, B., Jones, R.J., Poathong, S., Chobtang, J. 2010. Within-country variation in the ability
of ruminants to degrade DHP following the ingestion of Leucaena leucocephala-a
Thailand experience. Tropical Animal Health and Production, 42(2): 161–64.
https://doi.org/10.1007/s11250-009-9398-4. 50
Parimoo, H.A., Sharma, R., Patil, R.D. Patial, V. 2015. Sub-acute toxicity of lantadenes
isolated from Lantana camara leaves in guinea pig animal model. Comparative
Clinical Pathology, 24(6): 1541-1552.
Pattnaik, S. Pattnaik, B. 2010. A study of Lantana camara linn aromatic oil as an antibacterial
agent. International Journal of Pharmaceutical Science, 1: 32.
Pfister, J. 1999. Behavioral strategies for coping with poisonous plants. in grazing behaviour
of livestock and wildlife, edited by Launchbaugh KL, Sanders KD, and Mosley JC.
Pfister, J.A., Gardner, D.R., Cheney, C.C., Panter, K.E. Hall, J.O., 2010. The capability of
several toxic plants to condition taste aversions in sheep. Small Ruminant
Research, 90(1): 114-119.
Phelan, P, Moloney, PA., McGeough EJ., Humphreys, J. Bertilsson, J., O’Riordan, E.G.,
O’Kiely P. 2014. Forage legumes for grazing and conserving in ruminant production
systems. Critical Reviews in Plant Sciences, 34: 37–41.
https://doi.org/10.1080/07352689.2014.898455.
Pimentel, D., Zuniga R., Morrison D. 2005. Update on the environmental and economic costs
associated with alien-invasive species in the United States. Ecological Economics, 52
(3): 273–88. https://doi.org/10.1016/j.ecolecon.2004.10.002.
Plessis, I,C Van Der Waal, Webb E.C. 2004. A comparison of plant form and browsing height
selection of four small stock breeds – Preliminary Results. South African Journal of
Animal Science, 34 (1): 31–34.
Powell, KI, Chase J.M., Knight T.M. 2011. A synthesis of plant invasion effects on biodiversity
across spatial scales. American Journal of Botany, 98(3): 539–48.
https://doi.org/10.3732/ajb.1000402.
Provenza, F.D., Villalba, J.J., Dziba, L.E., Atwood, S.B. Banner, R.E. 2003. Linking herbivore
51
experience, varied diets, and plant biochemical diversity. Small Ruminant
Research, 49(3): 257-274.
Pucheta E., Cabido M., Díaz, S, Funes G. 1998. Floristic composition, biomass, and
aboveground net plant production in grazed and protected sites in mountain grassland
of central Argentina. Acta Oecologica, 19(2): 97-105
Pyke, D.A., Herrick J., Shaver P., Pellant, M. 2002. Rangeland health attributes and indicators
for qualitative assessment. Journal of Range Management, 55(6): 584–97.
https://doi.org/10.2307/4004002.
Rajendiran, K., Yogeswari, D., Arulmozhi, D. 2014. Allelopathic and cytotoxic effects of
aqueous extracts of Lantana camara l. On Vigna mungo l. var. Vamban-16.
International Journal of Food, Agriculture and Veterinary Science, 4(1):179–185.
Ramaswami, G., Sukumar, R., 2014. Lantana camara L . ( Verbenaceae ) invasion along
streams in a heterogeneous landscape. Journal of Biosciences, 39(4):717–726.
Reddy, N.M. 2013. Review Article Lantana camara Linn . Chemical Constituents and
Medicinal Properties : A Review 2 (6): 445–48.
Rogosic, J., Estell, R.E, Ivankovic, S., Kezic J., Razov J. 2008. Potential mechanisms to
increase shrub intake and performance of small ruminants in Mediterranean shrubby
ecosystems. Small Ruminant Research, 74(1–3): 1–15.
https://doi.org/10.1016/j.smallrumres.2007.07.006.
Rotz, C.A, Muck, R.E. 1994. Changes in forage quality during harvest and storage. Forage
Quality, Evaluation, and Utilization, 1: 828-868.
https://doi.org/10.2134/1994.foragequality.c20.
Roy, J. Bergeron, J.M. 1990a. Branch-cutting behavior by the vole (Microtus
pennsylvanicus). Journal of Chemical Ecology, 16(3): 735-741. 52
Roy, J.Bergeron, J.M. 1990b. Role of phenolics of coniferous trees as deterrents against
debarking behavior of meadow voles (Microtus pennsylvanicus). Journal of Chemical
Ecology, 16(3): 801-808.
Rukuni, M. 1994. Report of the commission of inquiry into appropriate agricultural land tenure
systems Volume II: Technical Reports. Harare: Government Printers.
Rukuni, M., Tawonezvi, P., Eicher, C. with Munyuki-Hungwe, M. and Matondi, P. (Eds)
(2006) Zimbabwe’s Agricultural Revolution Revisited, University of Zimbabwe
Publications, Harare.
Salem, A.Z.M., Salem, M.Z.M., El-Adawy, M.M. Robinson, P.H. 2006. Nutritive evaluations
of some browse tree foliages during the dry season: secondary compounds, feed intake
and in vivo digestibility in sheep and goats. Animal Feed Science and
Technology, 127(3): 251-267.
Saraf, A, Quereshi S, Sharma K., Khan, N.A. 2011. Antimicrobial Activity of Lantana camara
L. Journal of Experimental Sciences, 2(10): 50–54.
Schnaider, M.A., Ribeiro-Filho, H.M.N, Kozloski, G.V., Reiter, T, Orsoletta, A.C.D.,
Dallabrida, D.L. 2014. Intake and digestion of wethers fed with dwarf elephant grass
hay with or without the inclusion of peanut hay. Tropical Animal Health and
Production, 46(6): 975–80. https://doi.org/10.1007/s11250-014-0594-5.
Scholes, R.J., Archer, S.R. 1997. Tree-grass interactions in savannas. Review of Ecology and
Systematics, 28(1): 517-544.
Scoones, I. 1995. Exploiting heterogeneity: habitat use by cattle in Dryland Zimbabwe. Journal
of Arid Environments, 29(2): 221–37. https://doi.org/10.1016/S0140-1963 (05)80092-
8.
53
Sharma, G.P., Singh, J.S., Raghubanshi, A.S. 2005. Plant invasions: emerging trends and future
implications. Current Science, 88(5): 726-734.
Sharma, O.P, Singh, A, Sharma, S. 2000. Levels of lantadenes, bioactive pentacyclic
triterpenoids, in young and mature leaves of Lantana camara Var. Aculeata.
Fitoterapia, 71(5): 487–91. https://doi.org/10.1016/S0367-326X (00)00156-8.
Sharma, O.P., Sharma, S., Pattabhi, V., Mahato, S.B., Sharma, P.D. 2007. A review of the
hepatotoxic plant Lantana camara. Critical Reviews in Toxicology, 37(4): 313-352.
Shimada, T. 2006. Salivary proteins as a defense against dietary tannins. Journal of Chemical
Ecology, 32(6): 1149-1163.
Sibanda, S., Khombe, C.T. (2006) Livestock Research and Development; In Rukuni, M.,
Tawonezvi, P., Eicher, C.K., Munyuki-Hungwe, M. and Matondi, P. (Eds) Zimbabwe’s
agricultural revolution revisited, University of Zimbabwe Publications, Harare: 442-
449.
Sirohi, S.K., Goel, N., Pandey, P. 2012. Efficacy of different methanolic plant extracts on anti-
methanogenesis, rumen fermentation and gas production kinetics in vitro. Open
Veterinary Journal, 2(1): 72–77.
Skerman, PJ; Riveros, F. 1990. Tropical grasses. FAO Plant Production and Protection Series
No (23). FAO, Rome.
Smit, G.N., Richter, C.G.F., Aucamp, A.J. 1999. Bush encroachment: an approach to
understanding and managing the problem. Veld management in South Africa.
University of Natal Press, Scottsville, 246-260.
Smith, T. 2002. Some tools to combat dry season nutritional stress in ruminants under African
conditions.
54
http://www.iaea.org/inis/collection/NCLCollectionStore/_Public/33/032/33032982.pd
f accessed on 28 October 2017.
Smith, C.A. 1962. The utilization of Hyparrhenia veld for the nutrition of cattle in the dry
season III. Studies on the digestibility of the produce of mature veld and veld hay, and
the effect of feeding supplementary protein and urea. The Journal of Agricultural
Science, 58(2): 173-178.
Sokolović, D., Radović, J. Tomić, Z. 2011. Perennial Forage Grasses, from Breeding to healthy
ruminant feed. Biotechnology in Animal Husbandry, 27(3): 599–614.
Strugnell, R.G., Pigott, C.D. 1978. Biomass, shoot production, and grazing of two grasslands
in the Rwenzori National Park, Uganda. Journal of Ecology, 66: 73-96.
Swihart, R.K., DeAngelis, D.L., Feng, Z. Bryant, J.P. 2009. Troublesome toxins: time to re-
think plant-herbivore interactions in vertebrate ecology. BMC Ecology, 9(1): 5-13.
Tavirimirwa, B., Manzungu, E. Ncube, S. 2012. The evaluation of dry season nutritive value
of dominant and improved grasses in fallows in Chivi district, Zimbabwe. Online
Journal of Animal Feed Research, 2(6): 470-474.
Taylor, S, Kumar, L. 2013. Potential distribution of an invasive species under climate change
scenarios using climex and soil drainage: A Case Study of Lantana camara L. in
Queensland, Australia. Journal of Environmental Management, 114: 414-422.
Teague, R., Provenza, F., Kreuter, U., Steffens, T., Barnes, M. 2013. Multi-paddock grazing
on rangelands: Why the perceptual dichotomy between research results and rancher
experience? Journal of Environmental Management, 128: 699–717.
Torchin, M.E., Mitcheil, E. 2014. Parasites, pathogens, and invasions by plants and animals
Frontiers in Ecology and Environment, 2(4): 183–90.
55
Urban, A.J., Simelane, D.O., Retief, E, Heystek, F., Williams, H.E., Madire, G.L. 2011. The
invasive ‘Lantana camara L.’ hybrid complex (Verbenaceae): a review of research into
its identity and biological control in South Africa. African Entomology, 19(2): 315–48.
https://doi.org/10.4001/003.019.0225.
Van Jaarsveld, A.S., Biggs, R., Scholes, R.J., Bohensky, E., Reyers, B., Lynam, T., Musvoto,
C. Fabricius, C. 2005. Measuring conditions and trends in ecosystem services at
multiple scales: the Southern African Millennium Ecosystem Assessment (SAfMA)
experience. Philosophical Transactions of the Royal Society of London B: Biological
Sciences, 360(1454): 425-441.
Vetter S. 2013. Development and sustainable management of rangeland commons – aligning
policy with the realities of South Africa's rural landscape. African Journal of Range
and Forage Science 30(1&2): 1-9.
Vetter, S. 2003. What are the costs of land degradation to communal livestock farmers in South
Africa ? The Case of the Herschel District, Eastern Cape. Doctoral dissertation,
University of Cape Town, South Africa.
Vila, M. Weiner, J. 2004. Are invasive plant species better competitors than native plant
species?–evidence from pair‐wise experiments. Oikos, 105(2): 229-238.
Villalba, J.J., Miller, J., Ungar, E.D., Landau, S.Y., Glendinning, J. 2014. Ruminant self-
medication against gastrointestinal nematodes: evidence, mechanism, and
origins. Parasite, 21(31): 1-8
Villalba, J.J., Provenza, F.D. Bryant, J.P. 2002. Consequences of the interaction between
nutrients and plant secondary metabolites on herbivore selectivity: benefits or
detriments for plants? Oikos, 97(2): 282-292.
56
Wallace, L.L., McNaughton, S.J., Coughenour, M.B. 1984 Compensatory photosynthetic
responses of three African graminoids to different fertilization, watering, and clipping
regimes. Botanical Gazette, 145: 151-156.
Walter, J., Kerstin, G., Carl, B., Jürgen, K., Michael, W., Anke, J. 2012. Increased rainfall
variability reduces biomass and forage quality of temperate grassland largely
independent of mowing frequency. Agriculture, Ecosystems and Environment, 148: 1–
10. https://doi.org/10.1016/j.agee.2011.11.015.
Ward D. 2005. Do we understand the causes of bush encroachment in African savannas?
African Journal of Range and Forage Science, 22(2): 101-105.
Ward, R. 2011. Analyzing silage crops for quality: What is most important? Western Alfalfa
and Forage, 11–13.
Wild H. 1972. A Rhodesian botanical dictionary of African and English plant names,
Government Printer, Salisbury Rhodesia.
Williams, D.G., Zdravko, B. 2000. African grass invasion in the Americas: Ecosystem
consequences and the role of ecophysiology. In Biological Invasions.
https://doi.org/10.1023/A:1010040524588.
Williams, H.E. Madire, L.G., 2008. Biology, host range and varietal preference of the leaf-
feeding geometrid, Leptostales ignifera, a potential biocontrol agent for Lantana
camara in South Africa, under laboratory conditions. Biological Control, 53(6): 957-
969.
Zende, M., 2016. Impact of Lantana camara invasion on a cattle/wildlife ranch: A case of
Imire Ranch, Wedza District, Zimbabwe, Doctoral dissertation, University of
Zimbabwe, Zimbabwe.
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CHAPTER THREE
3 Farmers’ perceptions of invasive plant species, rangeland degradation and
productivity
3.1 Abstract
Bush encroachment and rangeland invasion by unpalatable plant species is a global problem.
A pre-tested questionnaire was administered to understand the perception of communal livestock production farmers with regards to invasive plant species, and rangeland degradation so as to obtain baseline information on the problems and suggest future studies on the best sustainable interventions and rangeland management practices. A total of 210 farmers from communal farming areas were interviewed in six administrative districts of Zimbabwe.
Descriptive statistic methods of SAS, (2010) were used in the analysis of data. Farmers revealed that alien invasive Lantana camara and other native species such as Helichrysum kraussii, Vachellia species and Dichrostachys cinerea species were increasing in abundance.
Grass species changes were also reported, with wiry and unpalatable species replacing the palatable species. Aristida species, Hyparrhenia species, and Sporobolus species were reported as the current dominant species. The respondents agreed that there is a reduction in grazing lands, an increase in bush encroachment and invasive plant species. Farmers also revealed that the increase in woody species and the changes in the grass species were threatening livestock production as well as hindering poverty alleviation programmes. Therefore, appropriate strategies should be implemented immediately to rescue communal livestock production and improve their livelihoods.
Key words: impenetrable thickets; unpalatable species; vegetation changes; wiry grass
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3.2 Introduction
Major negative changes in floristic composition (Kaufman et al., 1994; Milton and Dean, 1995;
Pucheta et al, 1998; Ward, 2005; Kraaij and Ward, 2006), increase in woody and invasive plant species, associated increase in rangeland degradation (Gambiza et al., 2000; Vetter, 2013) have been observed in communal rangelands in southern Africa. The changes have negative effects on grazing animals and rural people who depend on rangeland resources for survival. It is widely accepted that cattle productivity is positively correlated to rangeland healthy status
(Tainton, 1999). Rangelands in good health provide adequate quality forage for herbivores to grow and multiply regularly (Raghu et al., 2006; Pyke et al., 2010). In Africa, livestock especially beef cattle in communal farming systems have low productivity (Hangman and
Prasad, 1995; Ouédraogo-koné, 2008; Gusha and Mugabe, 2013). Some of the contributing factors to the low cattle productivity include poor grazing in both quality and quantity and the absence of correct animal husbandry skills in communal farmers.
Communal areas are rural areas where land is owned on a usufruct basis. Most of Zimbabwe’s communal areas lie mainly in ecological zones characterized by low erratic rainfall and low fertile soils (Rukuni et al., 2006). Seventy percent of Zimbabwe’s population is located in communal areas. The land is held under traditional or communal tenure, where the farmers have distinctive rights to arable land and a residential plot. Under communal ownership, members of the community have shared access to grazing land (Scoones, 1992). This creates problems in the management of communal rangelands. There are no deliberate interventions for rangeland improvement. Conventional grazing rotation is not practiced but there may be a temporal pattern of use of key resources such as riverine areas, vleis and top lands (Scoones,
1992).
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Since livestock plays an integral role in the survival of communities, cattle owners are reluctant to sell but look at increasing their herd size. To the wealthier farmers livestock are a source of power, patronage, and accumulation while the poor farmers look at cattle as security against dependence on wealthier and against drought (Cousins, 1992). In general, stocking rates are said to be two and half times more than the conventionally recommended stocking rate
(Scoones, 1992; Mavedzenge et al., 2005).
The consequences of communal farming systems needs proper understanding through monitoring of the changes that are taking place in rangelands. Farmers may have a better explanation of the factors that affect their well-being and their livestock. The farmer’s understanding of the problem can be used to generate proper interventions, which the farmers will be willing to adopt and implement. Interventions coming from outside are received with scepticism, as farmers are reluctant to adopt practices they are not familiar with. Issues of invasive plant species, bush encroachment, and rangeland degradation from the farmers’ perception need attention. The farmers should be in the forefront when dealing with issues that affect them. The objective of this study was to gather the views of the farming community with regards to invasive plant species, bush encroachment, and rangeland degradation. This information, which was gathered, will enable interrogating the possibility of a bottom up approach in seeking solutions to challenges the farmers are facing. Furthermore, the information gathered may help the rangelands specialists to interrogate different way of managing the problems and improve the livelihoods of the communal communities.
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3.3 Material and method
3.3.1 Study sites
The study was conducted out in six districts of Zimbabwe namely; Shurugwi District (19o45’
S ; 30o10’ E)in Midlands Province, Masvingo(20o30’ S ; 31o05’ E) in Masvingo province,
Chegutu(21o45’ S ; 31o15’ E) and Magunje(21o45’ S ; 31o15’ E) in Mashonaland West province, Masembura(18o75’ S ; 29o10’ E) in Mashonaland Central province, and
Goromonzi(18o55’ S ; 31o40’ E) in Mashonaland East province. Zimbabwe is divided into agro ecological regions I-V according to Vincent and Thomas (1960). Under the classification,
Goromonzi, Masembura and Chegutu are under agro ecological region II, Shurugwi and
Majunge are under the region III whilst Masvingo is under region IV and V according to
Vincent and Thomas (1960). The study sites have sour to mixed veld according to the classification of Zimbabwe rangelands by Rattray (1957). In all the studied sites, mixed farming activities are practised though in agro ecological zone III to V crop farming activities are considered risky because of highly variable rainfall within and between seasons (Vincent and Thomas, 1960). Three farming models in Zimbabwe A1, old resettelement and communal areas were included in the study. This was because in all these land tenure systems, communal grazing is practiced.
3.3.2 Data collection
In each district, a list of villages was obtained from the District Livestock Specialist (DLS).
From the list, seven villages were randomly selected in a district. Lists of household in each village were obtained from the area’s Livestock Extension Worker (LEW). Names of key informants and study five participants were also randomly selected from the provided list in each village. A total of 35 elderly farmers per district with adequate knowledge about the area were interviewed. Village heads, ward councilors and Livestock Extension Workers in each
61 district were key informant using an interview guide. A structured questionnaire was used to interview participants on rangeland health variables, dominant invasive plant species, bush encroachment, observable species change, water availability, and their effects to grazing capacity as well as animal health and condition. The questionnaire was pretested for accuracy and clarity in Domboshava area with a sample of ten randomly selected farmers and corrections were made before the district interviews were conducted. The interviews were conducted using the local languages and translated by the author and botanical names were obtained from guide book by Oudtshoorn (2002).
3.3.3 Data analysis
Data collected from the study were analysed using Statistical Analysis System (SAS, 2010), using the SURVEY MEANS and SURVEYFREQ to obtain frequencies and means for the qualitative data. Descriptive statistics were computed to investigate the relationship between district and rangeland health status, and dominant invasive plant species, and major challenges associated with the widespread increase in woody plant species.
3.4 Results
3.4.1 Perception of farmers on rangeland health status
All the respondents in the study reported that they have observed some decline in the rangeland condition and productivity as shown in Figure 3-1. More than 50% of respondents in Masvingo,
Shurugwi, and Majunge reported that the rangeland condition was poor whereas in Masembura,
Goromonzi, and Chegutu, less than 40% of the respondents indicated that rangeland condition was moderate. Shortage of grazing forage in both quality and quantity was a common problem in all the six districts, with respondents revealing that forage shortage was due to high livestock numbers as well as the increase in unpalatable grass. Most of the participants were of the opinion that, the deterioration of rangeland health was a result of over exploitation of the 62 rangeland resources. All farmers in the six districts revealed that, grazing area was no longer sufficient due to increase in household numbers. It was further revealed that new farmers were being settled in areas initially designated for livestock grazing. The respondents also indicated that, vegetation cover, soil erosion, water availability and the general condition and size of animals have all declined.
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100
90
80
70
60
50
40 % of% respondents 30
20
10
0 Shurugwi Masvingo Chegutu Masembura Goromonzi Magunje District
Range condition Pasture Shortage Vegetation cover Soil Erosion Water Shortage
Figure 3-1: Proportion of interviewed farmers who perceived that the above five mentioned challenges were a source of discomfort to communal rangelands users in the six districts of study.
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3.4.2 Perception of farmers on major woody species
The plant species that were perceived to be on the increase in the rangelands are shown in
Figure 3-2. Lantana camara, Vachellia species, and Dichrostachys cinerea were reported in all the six districts whereas Helichrysum kraussii was predominant in Masvingo, Shurugwi, and Goromonzi. Terminalia sericea was also reported as problematic species in five districts except Chegutu area where L. camara was the major problem. In the study, all thorny woody species were recorded as Vachellia or D. cinerea and were the most common woody shrubs in
Shurugwi, Masvingo and some villages in Masembura in Mashonaland Central.
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60
50
40
30 % of respndents %of 20
10
0 Shurugwi Masvingo Chegutu Masembura Goromonzi Magunje District
L. camara H. kraussii Terminalia spp Vachellia spp
Figure 3-2: Proportion of interviewed farmers who perceived that the above named woody plant species are the dominating species affecting rangelands in six districts of study
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3.4.3 Major floristic changes observed in all the districts
Almost all the farmers in all the six districts revealed that they were observing an increase in the L. camara, H. kraussii, Vachellia species, Dichrostachys cinerea, and Terminalia sericea shrubs as shown in Figure 3-3. Participants in Shurugwi reported that when they were settled in 1981 L. camara and most Vachellia species were not present. They reported that the scenario has since changed with L. camara shrub now seen everywhere including homesteads and grazing areas. Farmers from higher rainfall areas such as Goromonzi, Magunje, and
Masembura had more Sporobolus species and Hyparrhenia than Helichrysum kraussii. In all districts farmers indicated that grass species have changed with an increase of species such as
Hyparrhenia filipendula, Sporobolus species Aristida barbicollis, and Aristida junciformis that farmers believed were not good for grazing animals. Most respondents were of the opinion that when they occupied those areas in 1980 soon after independence of Zimbabwe, the most available grass species during the time were more palatable than the current available species.
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100
90
80
70
60
50
40 % of% respondents
30
20
10
0 Shurugwi Masvingo Chegutu Masembura Goromonzi Magunje District
L. camara H. kraussii Hyparrhenia spp Vachellia spp Terminalia spp D. cinerae S. pyramidalis
Figure 3-3:Proportion of interviewed farmers who perceived that the above named plant species on the increase and causing decline in rangeland productivity in the six districts of study
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3.4.4 Perceived challenges associated with the increase in woody species
Most farmers with rangelands dominated by L. camara revealed that the bushes were harbouring wild pigs that were destroying their crops. They also revealed that wild pigs were difficult to control as they quickly hide in Lantana bushes surrounding their fields. Thickets of both L. camara and Vachellia species were also reported to have created impenetrable bushes thus reducing land available for grazing as well as affecting animal movement and control.
Figure 3-4 shows some of the perceived challenges caused by the spread of woody species.
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100
90
80
70
60
50 % of% respondents 40
30
20
10
0 Harbour Impenetrable Reduce grazing Grass species Low grazing preditors thickets change capacity Major challenges
Figure 3-4: Proportion of interviewed farmers who perceived that the above named major challenges are result of the increase in woody plant species in the six districts of study
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3.5 Discussion
The changes observed by farmers on vegetation cover, formation of gullies, decline in water resources and diminishing of grazing capacity is consistent with changes in communally managed rangelands in South Africa and Botswana (Tainton, 1999; Vetter, 2003). Sheuyange et al. (2004) observed similar results in Namibia when different farming systems were assessed.
When the farmers started farming in these areas at independence 1980 or resettled in in 1982 from other overcrowded communal areas in Shurugwi, Goromonzi and Magunje, fences for paddocks were provided for grazing schemes by government and non-governmental donors with the aim to promote rotational grazing. The fences were either stolen or vandalised thus affecting the implementation of the rotational grazing method. The farmers resorted to communal grazing methods that normally have many negative impacts on rangeland ecosystems.
The perceived increase in unpalatable grasses and shrubs in the rangelands is a common observation reported in Masvingo (Gusha et al., 2017). The increase in undesirable less palatable species in these communally grazed rangelands is consistent with communal grazing method as reported by Vetter (2003). Uncontrolled utilisation of a grazing land, with fewer than recommended number of livestock, promotes selective grazing thus promoting the development of rangelands with undesirable grass (Beeskov et al., 1995). It was reported by
Neely and Butterfly (2004) that continuous grazing of a particular desirable grass species can completely destroy the species reserves thus lead to extinction and creation of bare spaces in the rangelands. The creation of bare spaces promote soil erosion and soil compaction leading to less infiltration and percolation capacity thus depleting underground water reserves and further damage to the rangeland ecosystem and floristic composition.
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Farmers rated their rangelands as poor and inadequate. This rating is consistent with low production rates reported in communally managed rangelands (Mavedzenge et al., 2005).
Work done in Masvingo province by Mavedzenge et al. (2005) reported that communal rangelands are inadequate, causing low calving rate which was reported to be below 45 percent in communal farming systems. High calf mortality (Mavedzenge et al., 2005), high livestock mortality (Ngongoni et al., 2006), long calving intervals and stunted growth in young animals
(Zvinorova et al., 2013) are all a function of the rangeland health status and are reported be a results of inadequate and poor quality of grazing in communal rangelands. Similar perceptions were recorded in a study conducted by Zvinorova et al. (2013) with smallholder dairy farmers in Zimbabwe. The way the rangelands are grazed determines their state of health. Grass species with high tolerance to heavy grazing survive whilst those desirable species, which are not tolerant to heavy grazing, are either completely uprooted or left with very low plant vigour
(Todd and Hoffman, 1999). Apart from the effects of grazing method on rangeland health status, livestock stocking density also can cause extinction of some species and change of the floristic composition of rangelands (Smit et al., 1999; Tainton, 1999; Vetter, 2003).
In the A1 and resettled area in Shurugwi and Masvingo, farmers revealed that they were allocated grazing land sufficient for 8 – 12 livestock units per household. However, that livestock restriction law was not enforced hence more than recommended livestock units were kept per household. Cousins (1992) reported that commercialization of draft power have become a lucrative source of income for farmers thus causing farmers to be reluctant to reduce the number oxen. This has negative effects on the rangelands thus causing deterioration of the rangelands. The livestock in the area consume more than the rangelands can provide, leading to deterioration of the healthy status of the rangelands.
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It was also reported that male children who get married are allocated land in the grazing area thus expanding arable land at the expense of grazing area. Furthermore, new outside people are brought in and allocated land by the village head thus, reducing the land available for animal grazing. More pressure is exerted on the already under performing rangelands leading to more soil erosion and further deterioration. Uncontrolled burning of rangelands and over exploitation of resources in rangelands was also very common. These factors are all possible causes for the perceived changes reported by farmers in this study. Each new farmer owns livestock and thus increasing livestock density per unit area. On the contrary, the grazing lands are getting smaller and smaller since new occupants are clearing lands for homesteads and arable land in the designated grazing sites. The higher the animal density in the area the more severe the impacts to species diversity change. When the palatable species are destroyed, new species or wiry grass species with low nutritional quality become dominant like the Sporobolus species,
Aristida species, and Hyparrhenia species, which do not support livestock production. These changes were similar in pattern to changes observed in overgrazed rangelands by Jeffries and
Klopatek (1987) on the vegetation of the Blackbrush and Al-Rowaily (2003) on rangelands in
Saudi Arabia.
The respondents also revealed that there was an increase in woody plant species in the grazing lands. This observation was consistent with area where improper grazing management strategies are implemented. Similar results were reported by Burrows et al., 1990 and Ward,
2005. The spread of Lantana camara (MacDougall and Turkington, 2005; MacDougall, 2014) and Helichrysum kraussii (Wild, 1972) are signs of disturbed rangelands because these species invade poorly managed rangelands (Prins and Rietkerk, 2003). Such observations should be a cause for concern as Burrows et al. (1990) reported the spread of woody species threatens productivity in commercial ranching. Teague and Smit (1992); Richter et al. (2001); Ward,
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(2005); Vetter, (2009) reported that the increase of woody species lead to a reduction in grazing capacity. Grazing capacity loss of between 58 – 331 % was observed when tree equivalent density increase from 400 to 2500 per hectare in semi-arid savanna in South Africa (Richter et al., 2001). Negative relationships between woody species and biomass production were also reported by Sheuyange et al. (2004) in Namibia. The increase in woody plant species should prompt policy makers to promote a change on the schemes arrangement and grazing methods in resettlement areas and all communal areas. This therefore means the number of hectares assigned per livestock unit in the inception of the resettlement scheme and the recent A1 farming areas have changed because of the influx of new occupants in the areas. There should be a related change in animal numbers in order to optimise animal performance. Communal livestock production may become unviable and expensive if the issue related to bush encroachment and grazing capacity are not addressed. Livestock production options should also be changed to cater for the loss in biomass production as a result of the spread in this unpalatable species in communal rangelands.
Apart from the effects of woody species on grazing capacity and animal performance, farmers revealed the spread of L. camara is harbouring wild pigs that destroy their maize crops in summer. Thickets of Acacia and Lantana restrict animal movement and access to some area thus reducing land available for rangeland purpose. Farmers did not complain about L. camara toxins, which are known to poison animals in some areas (Day et al., 2003). Day et al. (2003) reported Lantana foliage is poisonous to livestock especially goats, sheep and cattle. To the contrary, animals in the studied area are report to rely on L. camara leaves during the dry season.
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3.6 Conclusion
This study confirmed the increase in wood plant species, increase in less palatable plants such as H. filipendula, S. pyramidalis and other wiry grasses with little biomass yield. The study further shows that H. kraussii and L. camara are major invasive plants species in most regions in Zimbabwe. The presence of these species presents threats to grazing livestock and may in turn cause a decline in cattle productivity in the communal resettlement in Zimbabwe. The increase in woody plant species, invasive plant species, bush encroachment, and rampant rangeland degradation reported in this study is a clear testimony to the fact that communal grazing is detrimental and is linked to rangeland invasion. The results obtained hereby- reaffirmed earlier assertions by Cousins (1992) that diagnosed the communal tenure system as inherently problematic and in need of reforms. These changes in floristic composition are likely to affect national herd rebuilding exercise as well as the viability of the current livestock production systems. Bush clearing techniques should be taught to farmers in order to control the invasion of rangelands by unpalatable woody species. New livestock production options should be promoted such as goat production in areas with a lot of acacia browse and farmers should now increase the use of crop residue in order to boost productivity. Finding possible way of using these species currently in the rangeland could unlock opportunities of monitoring and checking spread of these species.
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3.7 References
Al-Rowaily, S.L. 2003. Present condition of rangelands of Saudi Arabia: Degradation steps
and management options (Arabic). Arab Gulf Journal of Scientific Research, 21: 188-
196.
Beeskov, A., Elissalde, N.O., Rostagno, C.M. 1995. Ecosystem changes associated with
grazing intensity on the Punta Ninfas rangelands of Patagonia, Argentina. Journal of
Range Management, 48: 517-522.
Burrows, W.H., Carter, J.O., Scanlan, J.C., Anderson, E.R. 1990. Management of savannas for
livestock production in north-east Australia: contrasts across the tree-grass continuum.
Journal of Biogeography, 17: 503 - 512.
Cousins, B. 1992. Managing communal rangeland in Zimbabwe: Experiences and lessons.
London: Food Production and Rural Development Division, Commonwealth Secretariat.
Day, M.D., Wiley C.J., Playford, J., Zalucki M.P. 2003. Lantana camara: Current management
status and future prospects. Canberra. ACIAR Monograph, 102.” Vol. ACIAR Mono.
Gambiza, J., Bond, W., Frost, P.G.H, Higgins, S. 2000. Land use options in dry tropical
woodland ecosystems in Zimbabwe. Ecological Economics, 33: 353-368.
Gusha, J., Masocha, M., Mugabe, P. H. 2017. Impact of grazing system on rangeland condition
and grazing capacity in Zimbabwe. Rangeland Journal, 39(3): 219–25.
https://doi.org/10.1071/RJ15130.
Jeffries, D.L, Klopatek, J.M. 1987. Effects of grazing on the vegetation of the blackbrush.
Journal of Range Management, 40: 390-392.
76
Kaufmann, J.B, Cummings, D.L, Ward, D. 1994. Relationships of fire, biomass and nutrient
dynamics along a vegetation gradient in the Brazilian cerrado. Journal of Ecology, 82:
519-531.
Kraaij, T, Ward, D. 2006. Effects of rain, nitrogen, fire and grazing on tree recruitment and
early survival in bush-encroached savanna, South Africa. Plant Ecology, 186(2): 235-
246.
MacDougall, A.S, Turkington, R. 2005. Are invasive species the drivers or passengers of
change in degraded ecosystem? Ecology, 86(1): 45-55.
Mavedzenge, B.Z, Mahenehene, J., Murimbarimba, F., Scoones, I., Wolmer, W. 2005.
Changes in the livestock sector in Zimbabwe following land reform: The Case of
Masvingo Province. A Report of a Discussion Workshop, IDS, Brighton.
Milton, S.J., Dean, W.R.J. 1995. South Africa’s arid and semiarid rangelands: why are they
changing and can they be restored? In Desertification in Developed Countries: 245-
264, Springer Netherlands.
Neely, C.L., Butterfield, J. 2004. Holistic management of African rangelands. Leisa Magazine,
December 2004.
Ngongoni, N.T., Mapiye, C., Mwale, M., Mupeta, B. 2006. Factors affecting milk production
in the smallholder dairy sector of Zimbabwe. Livestock Research for Rural
Development, 18(05): 1‒21. Available at:
http://www.lrrd.org/lrrd18/5/ngon18072.htm.
Ouédraogo-koné, S. 2008. The potential of some sub-humid zone browse species as feed for
ruminants. Doctoral Thesis, Swedish University of Agricultural Science, Uppsala,
Sweden.
Prins, H.H.T., Rietkerk, M. 2003. Effects of fire and herbivory on stability of savanna
ecosystems. Ecology, 84(2): 337-350. 77
Pucheta, E., Cabido, M., Díaz, S., Funes, G. 1998. Floristic composition, biomass, and
aboveground net plant production in grazed and protected sites in mountain grassland
of central Argentina. Acta Oecologica, 19(2): 97-105.
Pyke, D.A., Brooks, M.L., D'Antonio, C. 2010. Fire as a restoration tool: a decision framework
for predicting the control or enhancement of plants using fire. Restoration
Ecology, 18(3):274-284.
Raghu, S., Anderson, R.C., Daehler, C.C., Davis, A.S., Wiedenmann, R.N., Simberloff, D.,
Mack, R.N. 2006. Adding biofuels to the invasive species fire? Science-New York Then
Washington, 313(5794):1742.
Rattray, J.M. 1957. The grasses and grass associations of Southern Rhodesia. Government
Printer, South Africa.
Richter, C.G.F., Snyman, H.A., Smit, G.N. 2001 The influence of tree density on the grass
layer of three semi-arid savanna types of southern Africa, African Journal of Range and
Forage Science, 18(2&3):103-109, DOI:10.2989/10220110109485762
Rukuni, M., Tawonezvi, P. Eicher, C. with Munyuki-Hungwe, M., Matondi, P. (Eds) (2006)
Zimbabwe’s Agricultural Revolution Revisited, University of Zimbabwe Publications,
Harare.
SAS Institute. 2010. SAS/STAT user's guide. 9 ed. (SAS Institute, Cary).
Scoones, I. 1992. Land degradation and livestock production in Zimbabwe's communal areas,
Land Degradation and Rehabilitation 3: 99-113.
Sheuyange, A., Oba, G., Weladji, R.B. 2005. Effects of anthropogenic fire history on savanna
vegetation in north eastern Namibia. Journal of Environmental management, 75(3):
189-198.
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Smit, G.N., Richter, C.G.F, Aucamp, A.J. 1999. Bush encroachment: an approach to
understanding and managing the problem. Veld management in South Africa.
University of Natal Press, Scottsville, 246-260.
Tainton, N. 1999. Veld management in South Africa. University of Natal Press, South Africa
Teague, W.R., Smit, G.N. 1992. Relations between woody and herbaceous components and
the effects of bush‐clearing in southern African savannas. Journal of the Grassland
Society of Southern Africa 9(2): 60-71.
Todd, S.W., Hoffman, M.T. 1999. A fence-line contrast reveals effects of heavy grazing on
plant diversity and community composition in Namaqualand, South Africa, Plant
Ecology, 142:169-178.
Vetter, S. 2003. What are the costs of land degradation to communal livestock farmers in South
Africa? The case of the Herschel District, Eastern Cape. PhD thesis, University of Cape
Town, South Africa.
Vetter, S. 2009. Drought, change, and resilience in South Africa’s arid and semi-arid
rangelands. South African Journal of Science 105: 29-33
Vetter, S. 2013. Development and sustainable management of rangeland commons – aligning
policy with the realities of South Africa's rural landscape. African Journal of Range
and Forage Science 30(1&2): 1-9.
Vincent, V, Thomas, R.G. 1960. An Agricultural Survey of Southern Rhodesia: Part 1 Agro-
ecological Survey, Project No. 698 0491- 5615903. Harare.
Ward, D. 2005. Do we understand the causes of bush encroachment in African savannas?
African Journal of Range and Forage Science 22(2): 101-105.
Wild, H. 1972. A Rhodesian botanical dictionary of African and English plant names,
Government Printer, Salisbury, Rhodesia.
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CHAPTER FOUR
4 Grazing system impacts on rangeland condition and grazing capacity in Zimbabwe
4.1 Abstract
The influence of different land tenure and rangeland management systems on rangeland condition and livestock grazing capacity in African rangelands is not well documented. A rangeland condition assessment was carried out at 15 sites located in the communal grazing system, small-scale commercial grazing system and the large-scale commercial grazing system in Masvingo. Rangeland indicators assessed were floristic composition, herbaceous biomass yield, shrub stem density, and grazing capacity. Grass species composition and forage value were analysed using PROC FREQ procedure of SAS 9.3. Fisher’s exact test was performed to test for independence of the grass variables between grazing systems. Multivariate analysis of variance was carried out using the PROC MIXED procedure of SAS 9.3 (SAS Institute, 2010).
Duncan’s multiple range test was used to test for significant differences (P < 0.05) in floristic composition, shrub stem density, herbaceous biomass yield, and grazing capacity among the three grazing systems. It was observed that communal rangelands had significantly higher levels of woody species, unpalatable wiry grass species, low biomass yield and were dominated by the invading shrub Helichrysum kraussii compared to the other rangeland management systems. These results suggest that if control measures are not put in place, ruminant animal production may not be feasible in communal rangelands in the near future because of high levels of rangeland deterioration when compared to the commercially managed rangelands.
Furthermore, the observed high stem density of unpalatable woody species and the low grazing capacity of communal rangelands affect livestock production, a primary source of livelihood.
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This warrants a change in rangeland management system in favour of the rest-rotation grazing system, which is beneficial to both livestock and the range.
Key words: bush encroachment; grazing capacity; Helichrysum kraussii; livestock unit per hectare,
4.2 Introduction
Savanna rangelands respond differently to various levels of anthropogenic disturbance exerted on them (Scoones 1992; Scholes and Archer 1997). Herbivory and fire, which are to a large extent controlled by human beings, are considered key disturbance factors driving rangeland dynamics in savanna systems (Kaufmann et al., 1994; Trollope 1998; van Langevelde et al.,
2003). For example, previous studies in African savannas have documented that heavy continuous grazing by introduced domestic herbivores such as cattle and frequent human-lit fires trigger an increase in woody vegetation and accelerate rate of rangeland invasions by invasive plant species (Tefera et al., 2008; Masocha et al., 2011). These processes in turn change the floristic composition of rangelands, thus potentially undermining their ability to provide forage and support animal production. If other factors such as rainfall hold constant, the rate at which species composition and primary production in African savanna rangelands change in response to disturbances is shaped by the rangeland management system in place
(Ward, 2005). For instance, if the basic principles of range management such as giving the range enough rest after grazing to maintain plant vigour and grazing to the right use level are not practised, the rangeland would be less resilient to the impact of stress such as frequent human disturbance (Tefera et al., 2008; Teague et al., 2013).
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The aim of this study was to determine 1) whether and to what extent rangeland vegetation characteristics such as floristic composition change with grazing and land tenure system. 2) To determine the impact of different rangeland management systems on biomass yield and grazing capacity. If these relationships are found to be significant, that can form the basis for planning an alternate grazing system for these diverse grazing systems. Knowing the correct and current status of rangelands in different grazing systems may also help in developing sustainable rangeland management protocols.
4.3 Materials and methods
4.3.1 Study site
The study was carried out in the three different production systems, Communal Farming
System (CFS), Small scale commercial (SSC), and large scale commercial (LSC) grazing systems in the administrative district of Masvingo. The study site is located at latitude 19º 23' south and longitude 30º 75' east (Fig 4-1). The three grazing systems are contiguously located, with the SSC system in the middle. The study site falls within agro-ecological zone IV of the
Zimbabwean classification system (Vincent and Thomas, 1960). Zone IV is suitable for extensive grazing and receives total annual (summer) rainfall ranging from 350 mm to 500 mm. Mean maximum temperature during summer is 280C. The minimum temperature during winter is 60C. The soils are sandy with low organic matter and low fertility (Nyamapfene,
1991). Rainfall is erratic and variable from year to year; hence, crop failures are common. Due to the high risk of crop failure, livestock grazing is an important economic activity in the selected grazing systems (Vincent and Thomas, 1960).
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Figure 4-1: A map showing distribution of sample points (solid circle) among the main grazing systems in the administrative district of Masvingo in Zimbabwe.
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4.3.2 Sampling protocol
Five sites were randomly selected for each grazing system studied for rangeland health condition assessment. First, a list of CFS villages, SCC farms, and LSC farms located in the same agro-ecological zone was obtained from the Ministry of Agriculture, Mechanisation, and
Irrigation Development at the Masvingo District offices. Then, from a list of 13 CFS villages, five were randomly selected. Five farms were also selected at random from 16 SSC farms identified. Likewise, five rangeland areas were randomly selected from nine LSC farms identified.
Selected villages and farms were mapped by navigating the perimeter using a handheld Global
Positioning System (GPS) receiver. The polygon maps were converted from shape files to keyhole markup language (kml) format using Geographic Information System software to facilitate visualisation in Google Earth. To minimise the confounding effect of variation related to topography and soil moisture content, low-lying areas and wetlands were digitised in Google
Earth and excluded from the sampling protocol. For each grazing system, ten sampling points were generated at random using the Integrated Land and Water Information System (ILWIS-
GIS) Software (version 3.3). Figure 4-1 illustrates the distribution of these 30 sample points in the three grazing systems considered. The coordinates of the selected sampling points were uploaded into a handheld GPS receiver for ground navigation.
On the ground, a plot measuring 20-m by 20-m was laid with a GPS identified point as the centre point. A 1-m by 1-m subplot was placed with its centre coinciding with the plot centre.
Within the larger 400-m2 plot, four other 1-m2 subplots were placed 10 m away from the centre point at 900, 1800, 2700, and 3600. The larger plot was used for collecting tree and shrub
84 abundance data, while the five smaller subplots provided the frame for collecting species composition and abundance data on herbaceous vegetation.
4.3.3 Vegetation data collection
In each 1-m2 sample plot, grass species were recorded and their height measured. Where species identification was problematic, plant samples were preserved in a plant press and taken to the National Herbarium and Botanic Garden in Harare for identification. Each identified grass species was classified as desirable, moderately desirable, and undesirable in terms of forage value as described by Oudtshoorn (2002). To mimic grazing stubble height, fresh grass biomass was clipped at 5 cm above the ground at species level. Clipped fresh biomass was weighed in the field using a digital scale. Each harvested species was stored in khaki pockets and later transported to Makoholi Research Institute laboratory near Masvingo for dry matter measurements. Dry matter weights were obtained by weighing replicate samples of 100 g and drying them in the oven at 600C for 48 hours (AOAC, 2000). For each grazing system, the dry weight of all the clipped and recorded species was summed to obtain the total herbaceous standing dry matter biomass yield ha-1. The standing herbaceous biomass yield was used to calculate carrying capacity in each grazing system following Minson and McDonald (1987) as:
(1)
Where:
y = grazing capacity measured as ha per livestock unit (LU)
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d = number of days in a year
DM = total herbaceous standing dry matter yield measured in kg ha-1
F = utilization factor taken as 0.4
r = daily grass DM required per LU (15 kgLU-1).
For the purpose of this study, browse forage was not included in the calculation of grazing capacity, as it accounts for less than 5% of daily consumption in beef production (Tainton
1999). However, individual stems of the dominant native shrub Curry bush (Helichrysum kraussii) as well as other woody species rooted in each 400m2 plot were counted and recorded.
Then, a similarity index between different grazing systems was calculated based on the
Sørensen (1948) index as follows:
(2)
Where:
QS = Sørensen similarity index between two grazing systems
a = number of species in sample A
b = number of species in sample B
c = number of species common between samples A and B. Note, A and B represent any
two grazing systems whose species composition is being compared.
4.3.4 Data analysis
Multivariate analysis of variance was used to test whether the number of grass species classified as desirable, moderately desirable and undesirable significantly differed across the three grazing systems. Analysis of variance was also used to test whether mean shrub stem density ha-1, mean stem density of H. kraussii ha-1, mean grass height, mean herbaceous
86 biomass yield and the mean calculated grazing capacity significantly differed across the three grazing systems. The PROC MIXED procedure of SAS 9.3 (SAS Institute, 2010) was used to test for these differences. The mixed model takes the following form:
Yijk = μ + I (i) +F (j) + (IF) (ij) + έijk (3)
Where:
Yijk is response variable (that is, shrub stem density, H. kraussii stem density, grass
height, herbaceous biomass yield and grazing capacity);
μ is overall mean common to all observations;
th I (i) is effect of the i farm in each grazing system;
th F (j) is effect of the j grazing system;
(IF) (ij) is interaction effects of individual farm and the grazing systems; and
έijk are the random residuals distributed as N ̴ (0; σ=1)
All the data were tested for normality using the Shapiro Wilk’s test and log-transformed where necessary to achieve normality prior to performing the MANOVA. Parameters were tested at
5% level of significance.
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4.4 Results
A total of 32 grass species were identified in the three grazing systems. Twenty-two grass species were found in the SSC grazing system, whereas both the LSC and CFS grazing systems each had 21 grass species. Plant species contributing approximately 90% of herbaceous biomass yield are shown in Table 4-1. Heteropogon contortus, considered a species of high forage value (Oudtshoorn, 2002), was the dominant grass species in the LSC grazing system.
By contrast Digitaria pentzii, a wiry grass of poor forage value (Oudtshoorn, 2002), was the dominant grass species in both the CFS and SSC grazing systems. Other grass species found in these latter two grazing systems were also predominantly wiry, with low leaf production and poor forage quality.
Differences were recorded in the percentage of grass species classified in the literature as desirable, moderately desirable, and undesirable in terms of their contribution to livestock production in the three grazing systems (Table 4-1). The LSC had twice as many desirable grass species as the CFS and SSC, and the CFS and SSC had a significantly higher percentage of undesirable grass species compared to the LSC (Table 4-1). Specifically, two thirds of grass species found in the CFS and SSC grazing systems were of poor forage value, yet only half of grass species found in LSC were poor forage species.
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Table 4-1: Proportion of desirable, moderately desirable, and undesirable species and their percentage biomass yield contribution in the three grazing systems
Grass species CFS SSC LSC
Desirable grass species
Schizachyrium jeffreysii 7 5 7
Urochloa mosambicensis - 2 8
Panicum maximum - - 4
Panicum dregeanum - - 3
% Proportion of desirable species 6.3a 7a 14b
Moderately desirable grass species
Heteropogon contortus 3 4 17
Digitaria pentzii 14 12 10 Cynodon dactylon 7 - 2
Brachiaria brizantha - - 3
Eragrostis rigidior 11 8 -
Setaria pallide-fusca - - 10
% Proportion of Moderately desirable species 31.7a 30a 39b Undesirable grass species
Aristida barbicollis 8 4 8
Pogonarthria squarrosa 9 6 7
Eragrostis superb - - 6 Eragrostis trichophora 2 7 5
Hyparrhenia filipéndula 1 9 4
Melinis repens 5 5 4
Trichoneura grandiglumis - - 3
Eragrostis gummiflua - 5 -
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Microchloa kunthii 3 5 -
Perotis patens 4 4 -
Aristida congesta - 2 - Eragrostis inamoena 6 - -
Sporobolus pyramidalis 2 - -
% Proportion of undesirable grass species 63a 63a 47b
CFS is communal farming system, SSC is small-scale commercial farming system, and LSC is large-scale commercial farming system. Mean percentage values for desirable, moderately desirable, and undesirable grass species with different letters of the alphabet in the same row differ significantly (P< 0.05).
90
Variation was recorded between the three grazing systems in mean shrub stem density ha-1, mean grass height, and mean grazing capacity (Table 4-2). Mean shrub stem density was highest in the CFS followed by the SSC system, which had two times more shrub stem density than the LSC system. A similar pattern was observed for H. kraussii - a dominant unpalatable native encroaching shrub. The calculated grazing capacity was 10 and 15 times lower in CFS compared to the SSC and LSC, respectively.
91
Table 4-2: Variation in mean shrub density, grass height, and grazing capacity between different grazing systems of Zimbabwe
Rangeland condition indicator Farming system CFS SSC LSC LSD Shrubs density (stems ha-1) 249a 61b 36c 141.04 Helichrysum kraussii density (stems ha-1) 2621a 1619b 13c 98.59 Grass height (cm) 15a 52b 46b 12.21 Grazing capacity (ha LU-1) 65.3a 6.2b 4.3b 13.71 CFS is communal farming system, SSC is small-scale commercial farming system, and LSC is large-scale commercial farming system. Means with different superscripts in the same row differ at α = 0.05 level of significance. Note, one livestock unit (LU) is equivalent to a 500 kg animal. LSD indicates least significant difference.
92
Significant differences in mean herbaceous biomass yield were observed between the three grazing systems during the study period (Figure 4-2). The lowest yield (less than 300 kg ha-1) was recorded in the CFS while the highest yield (above 3,000 kg ha-1) was found in the LSC system.
93
3500
) 1
- 3000
2500
2000
1500
1000
Herbaceous biomass (kgbiomass yield ha Herbaceous 500
0 CFS SSC LSC Farming system
Figure 4-2: Average herbaceous biomass yield (± standard error) per hectare recorded in the three major grazing systems of Zimbabwe.CFS is communal farming system, SSC is small- scale commercial farming system, and LSC is large-scale commercial farming system.
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The species composition in the SSC and CFS was similar and characterised by a high Sørensen similarity index (68%). The results show that LSC has a Sørensen similarity index with SSC of 30%, and a relatively low similarity index of 37% with CFS (Table 4-3).
95
Table 4-3: Sørensen similarity indices for rangeland management system associated with three different grazing systems.
Farming system LSC CFS SSC
LSC - 0.37 0.30
CFS 0.37 - 0.68
SSC 0.30 0.68 -
CFS is communal farming system, SSC is small-scale commercial farming system, and LSC is large-scale commercial farming system.
96
4.5 Discussion
The results indicate that both the CFS and SSC had a significantly higher proportion of undesirable wiry grass species compared to the LSC system, which had the highest proportion of desirable grass species. This result is consistent with the expected rangeland condition in
LSC systems, where rangeland management principles anchored on allowing a period of rest, a regulated period of utilisation, and controlled stocking rate are applied (Tainton, 1999; Smit et al., 1999). The low proportion of desirable species in the SSC was an unexpected result, but one which corroborates previous findings by Todd and Hoffman (1999). These authors proposed preferential grazing as a potential mechanism leading to mass mortality and the local extinction of desirable forage species such as Panicum maximum.
The differences in the proportion of desirable and undesirable grass species point towards a link between grazing system and rangeland condition. In the CFS system, repeated defoliation of the same palatable grass plants under continuous grazing potentially leads to a loss of desirable species (Beeskow et al., 1995). While over-stocking possibly explains the low proportion of desirable grass species observed in the CFS, the fact that the SSC with a relatively low stocking rate also had a significantly lower proportion of desirable species supports the deduction that stocking below optimum can also create similar changes in floristic composition to those observed in overstocked rangelands. In grazing systems with below optimum stocking rates, a greater degree of preferential grazing is possible as inter-animal competition is lower
(Todd and Hoffmann, 1999; Vetter and Bond, 2012).
Another important aspect of the results is that grass stubble height in the CFS was shorter than that of the LSC. This could be related to continuous heavy grazing. In a previous study, the
97 observed higher stocking rates in a CFS were reported to be 2.5 greater than the recommended stocking rate (Mavedzenge et al., 2005). Overstocking exacerbates repeated defoliation of the same desirable species, shortening sward height. Eventually, desirable species may be uprooted or die due to nutrient reserve depletion. This results in a lower proportion of high forage quality grass species in CFS rangelands as observed elsewhere in Zimbabwe (Neely and Butterfield,
2004), in overgrazed South African rangelands (Vetter, 2003) and in Saudi Arabian rangelands
(Al-Rowaily, 2003), among others.
The grazing capacity was observed to be lowest in the CFS and highest in the LSC. The responsible ecological mechanism to explain low grazing capacity in the CFS was not explored in this study, but low grazing capacity was found to be inversely related to high shrub stem density, dominated by the unpalatable H. kraussii. If the influence of grazing system on woody encroachment is confirmed by subsequent studies, especially those based on field experiments, it could substantiate earlier claims that heavy grazing followed by the loss of desirable species has negative effects on livestock performance and biodiversity (Burrows et al., 1990; Prins and
Rietkerk, 2003; Ward, 2005; Masocha, 2010). Further studies on the effect of the invader H. kraussii on rangeland productivity are warranted to identify appropriate control and management options.
Grass biomass yield in CFS rangelands was estimated at less than one third of a tonne ha-1, a figure in agreement with previous work (Richter et al., 2001). At the same time, shrub density exceeded 2,000 stems ha-1 in the assessed CFS rangelands, a result consistent with observations made in South African savanna rangelands (Teague and Smit, 1992). The combined effect of a low proportion of desirable species, high abundance of shrubs, (which are involved in competitive interactions with grasses (Pucheta et al., 1998; Prins and Rietkert, 2003)), and 98 shorter grass stubble is that the grazing capacity in CFS rangelands is now approximately 65 ha LU-1, a result also consistent with previous studies (Teague and Smit, 1992; Richter et al.,
2001; Sheuyange et al., 2005; Vetter, 2009). Prins and Rietkert (2003) reported that high tree/shrub density modifies light availability, as well as the water and nutrient environment of grasses, and this has a negative influence on biomass production in South African rangelands
(Milton and Dean, 1995).
The Sørensen similarity index suggests that the CFS and SSC systems have a similar grass species composition, despite the latter being overstocked while the other is stocked below optimum (Sorensen, 1948). If this similarity is observed in other rangelands with similar management systems, this pattern implies stocking below optimum reduces inter-animal competition thereby causing depletion of desirable species and promoting the dominance of wiry grasses such as Sporobolus pyramidalis. The relatively low similarity index of the CFS when compared to the SSC to LSC separately, which was found to be below 40%, may support the inference that rangeland management system influences herbaceous species composition in southern African rangelands.
Overall, the results of this study imply that the CFS and SSC rangeland management systems promote woody species dominance, and reduce forage biomass yield, which, act together to cause rangeland deterioration. The implication is that a major revision in rangeland management and livestock production practices in CFS and SSC rangelands of Zimbabwe is now warranted to guarantee rangeland health and increased animal performance.
99
4.6 Conclusion
This study tested whether there is a link between rangeland health status and the grazing systems in relation to land tenure in Zimbabwe. The study has shown clear differences in the grazing capacity, grass stubble height, and the proportion of desirable species between rangelands in communal, small-scale and large-scale commercial farming systems in south- central Zimbabwe. The overall conclusion is that the management of communal rangeland is the most deleterious management system in Zimbabwe. By far the most significant factor accounting for the rangeland deterioration in the CFS is the absence of enough rest, which would allow forage plants to recover from defoliation and build new metabolic reserves.
Considering the similarity between the CFS in Zimbabwe and that practised in communal rangelands in other subtropical countries such as Botswana and South Africa, it is recommended that rest and rotational grazing systems be installed to allow plant recovery and seed set. In a communal setup in which there are no paddock fences and grazing is shared, resting some areas could be achieved through a coordinated grazing system in which livestock are communally herded in designated areas and moved to new areas once the stubble height is below a set threshold. This requires the cooperation of beneficiary farmers. However, future research should explore viable strategies for implementing a rest-rotation grazing system in communal rangelands since the current CFS grazing system fails the test of sustainable rangeland utilisation.
100
4.7 References
AOAC (Association of Agricultural Chemists). 2000. AOAC official methods of analysis. 17th
Edn. AOAC, Gaithersburg, MD, USA.
Al-Rowaily, S.L. 2003. Present condition of rangelands of Saudi Arabia: Degradation steps
and management options (Arabic). Arab Gulf Journal of Scientific Research,21:188-
196.
Beeskow, A., Elissalde, N.O., Rostagno, C.M. 1995. Ecosystem changes associated with
grazing intensity on the Punta Ninfas rangelands of Patagonia, Argentina. Journal of
Range Management,48:517-522.
Burrows, W.H., Carter, J.O., Scanlan, J.C. Anderson, E.R. 1990. Management of savannas for
livestock production in north-east Australia: contrasts across the tree-grass continuum.
Journal of Biogeography,17:503-512.
Kaufmann, J.B., Cummings, D.L., Ward, D.E. 1994. Relationships of fire, biomass and nutrient
dynamics along a vegetation gradient in the Brazilian cerrado. Journal of
Ecology,82:519-531.
Masocha, M, Skidmore AK, Poshiwa X, Prins H.H.T. 2011. Frequent burning promotes
invasions of alien plants into a Mesic African Savanna. Biological
Invasions,13(7):1641-48. http://link.springer.com/article/10.1007/s10530-010-9921-6.
Masocha, M. 2010. Savanna aliens. PhD thesis, Wageningen University, Wageningen.
Mavedzenge, B. Z., Mahenehene, J., Murimbarimba, F., Scoones, I. Wolmer, W. 2005.
Changes in the Livestock Sector in Zimbabwe Following Land Reform: The Case of
Masvingo Province. A Report of a Discussion Workshop, IDS, Brighton.
Milton, S.J., Dean, W.R.J. 1995. South Africa’s arid and semiarid rangelands: why are they
changing and can they be restored? In Desertification in Developed Countries, 245-
264, Springer Netherlands. 101
Minson, D.J., McDonald, C.K. 1987. Estimating forage intake from the growth of beef cattle.
Tropical Grasslands, 21:116-122.
Neely, C.L., and Butterfield, J. (2004). Holistic management of African rangelands. Leisa
Magazine, December 2004.
Nyamapfene, K. 1991. Soils of Zimbabwe. Nehanda Publishers (Pvt) Ltd, Harare.
Oudtshoorn, F.V. 2002. Guide to grasses of Southern Africa. Briza Publications, Pretoria,
South Africa.
Prins, H.H.T., Rietkerk. M. 2003. Effects of fire and herbivory on stability of savanna
ecosystems. Ecology, 84:337-350.
Richter, C.G.F., Snyman, H.A., Smit, G.N. 2001. The influence of tree density on the grass
layer of three semi-arid savanna types of southern Africa, African Journal of Range and
Forage Science,18:103-109.
SAS Institute, 2010. SAS/STAT user's guide. 9.3 ed. (SAS Institute, Cary).
Scholes, R.J., Archer, S.R. 1997. Tree-grass interactions in savannas. Annual review of Ecology
and Systematics, 28:517-544.
Scoones, I. 1992. Land degradation and livestock production in Zimbabwe's communal areas,
Land Degradation and Rehabilitation, 3:99-113.
Sheuyange, A., Oba, G., Weladji, R.B. 2005. Effects of anthropogenic fire history on savanna
vegetation in north eastern Namibia. Journal of Environmental Management, 75:189-
198.
Smit, G.N., Richter, C.G.F., Aucamp, A.J. 1999. Bush encroachment: an approach to
understanding and managing the problem. Veld Management in South Africa.
University of Natal Press, Scottsville, 246-260.
102
Sørensen, T.A. 1948. A method of establishing groups of equal amplitude in plant sociology
based on similarity of species content and its application to analyses of the vegetation
of Danish commons. K dan Vidensk Selsk Biol Skr, 5:1-34.
Tainton, N. 1999. Veld management in South Africa. University of Natal Press, Scottsville.
Teague, R., Provenza, F., .Kreuter, U., Steffens, T., Barnes, M. 2013. Multi-paddock grazing
on rangelands: Why the perceptual dichotomy between research results and rancher
experience? Journal of Environmental Management, 128:699-717.
Teague, W.R., Smit, G.N., 1992. Relations between woody and herbaceous components and
the effects of bush‐clearing in southern African savannas. Journal of the Grassland
Society of Southern Africa, 9:60-71.
Tefera, S., Dlamini, B.J., Dlamini, A.M., and Mlambo, V. 2008. Current range condition in
relation to land management systems in semi‐arid savannas of Swaziland. African
Journal of Ecology, 46:158-167.
Todd, S.W., Hoffman, M.T. 1999. A fence-line contrast reveals effects of heavy grazing on
plant diversity and community composition in Namaqualand, South Africa. Plant
Ecology 142: 169-178.
Trollope, W.S.W. 1998. Effects and use of fire in the savanna areas of Southern Africa,
Department of Livestock and Pasture Science, Faculty of Agriculture, University of
Fort Harare, Alice, South Africa.
Van Langevelde, F., Van De Vijver, C.A., Kumar, L., Van De Koppel, J., De Ridder, N., Van
Andel, J., Skidmore, ASK., Hearne, JAW., Stroosnijder, L., Bond, W.J., Prins, H.H.T.,
Rietkerk, M. 2003. Effects of fire and herbivory on the stability of savanna ecosystems.
Ecology, 84:337-350.
Vetter, S. 2009. Drought, change and resilience in South Africa’s arid and semi-arid
rangelands. South African Journal of Science, 105:29-33 103
Vetter, S. Bond, W.J. 2012. Changing predictors of spatial and temporal variability in stocking
rates in a severely degraded communal rangeland. Land Degradation and Development,
23:190–199.
Vincent, V. Thomas, R.G. 1960. An Agricultural Survey of Southern Rhodesia: Part 1 Agro-
ecological Survey, Project No. 698 0491- 5615903. Harare
Ward, D. 2005. Do we understand the causes of bush encroachment in African savannas?
African Journal of Range and Forage Science, 22:101-105.
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CHAPTER FIVE
5 Nutritive value of Lantana camara harvested from different sites in Zimbabwe
5.1 Abstract
Contrary to what is known and reported that Lantana camara is poisonous to livestock, animals have been seen consuming it with no cases of poisoning reported in most communal areas in
Zimbabwe. A study was conducted to determine the total phenolic compounds and nutrient composition of L. camara leaves in six different sites in Zimbabwe. L. camara leaves harvested from the University of Zimbabwe farm, Goromonzi area, Masvingo, Shurugwi, Chegutu, and
Magunje were air-dried and ground to facilitate chemical analysis of their crude protein (CP), dry matter (DM), neutral detergent fibre (NDF), acid detergent fibre (ADF), and total extractable phenolics. The DM, CP, ADF, and NDF content of L. camara from the six sites did not differ significantly (P > 0.05). The mean total phenolic compounds of the University of
Zimbabwe farm(6.8 ± 1.2%); was almost twice as high as that from Goromonzi (3.7 ± 1.2%); and was significant different (P < 0.05) from the leaves from all the other sites. The CP content ranged from 218 to 240 g/kg of among the L. camara leaves from different sites, with the highest protein content in leaves harvested from Chegutu. The results from this study demonstrate L. camara leaves from the six sites exceeded the minimal levels of CP required to sustain animal production and qualify to be used as a protein supplement. Also the level of total extractable phenolics (TEPH) was lower than the concentration found in some of the well promoted browse legumes hence it could be a good source of protein supplement. However, more research should be done to determine feeding levels, which are not detrimental to animal health.
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Key words: browse forage; browsing livestock; nutrient composition; total phenolic compounds,
5.2 Introduction
Feed shortage, in both quantity and quality, is the principal constraint to livestock production in subtropical Africa (Smith, 2002; Gusha et al., 2014). During periods of feed shortage, animals are sustained with native rangeland grasses and crop residues, which are too often deficient of essential nutrients (Ngongoni et al., 2006; Mapiye et al., 2006; Gusha et al., 2015).
However, during the same dry periods of feed shortages, weedy shrubs such as L. camara continue to flourish (Mtui, 2008). Cattle, sheep, and goats have been observed feeding on L. camara (Osuga, 2006; Gusha et al., 2016).
Lantana camara has also been noted to maintain relatively high levels of crude protein content
(Mtui, 2008) throughout its growing season. It therefore not surprising that in heavily grazed communal land of Zimbabwe such as Murehwa, Magunje, Shurugwi, Mhondoro and Masvingo area, L. camara is browsed by animals (Gusha et al., 2016). Such foraging behaviour, which goes against conventional understanding that L. camara is toxic to livestock (Day et al., 2003, warrants further research to establish whether the species could be exploited as a feed resource to offset forage scarcity in degraded rangelands under threat from climate change. Given the recurrent droughts affecting tropical rangelands and field observations indicating voluntary utilisation of L. camara by ruminant livestock such as cattle, studies that examine its nutritional composition are needed to inform the species’ management and boost livestock production.
However, since previous work classify L. camara as toxic to livestock (Day et al., 2003), research has tended to shun away from determining its nutritional contribution to livestock.
106
The study evaluated the nutrient composition of L. camara, which is readily available in most provinces of Zimbabwe. Lantana camara leaf biomass was harvested during the dry season in six different locations in Zimbabwe.
5.3 Materials and methods
5.3.1 Study site
L. camara leaves were collected from six sites; the University of Zimbabwe farm, Goromonzi area, Masvingo, Shurugwi, Chegutu, and Magunje. The leaves were harvested during dry season between August and early September 2016. The fresh leaves were packed in khaki sachets and transported to the Department of Veterinary Science at the University of
Zimbabwe. The leaves were dried under shade before processing.
5.3.2 Chemical composition analysis
Dry matter content was determined by oven drying at 60ºC over 48 hours followed by weighing.
The samples were then ground through a 1 mm sieve and analysed for nitrogen (N), acid detergent insoluble nitrogen (ADIN), and ash according to AOAC (2000). Acid detergent fibre
(ADF) and neutral detergent fibre (NDF) were determined using the method of Goering and
Van Soest (1970). The extraction of the phenolic compounds was done by using 70% aqueous acetone solution. Total extractable phenolics (TEPH) were determined using the Folin
Ciocalteu method as described by Makkar (2003). The concentrations of the total phenols were calculated using the regression equation of the tannic acid standard (Makkar, 2003).
107
5.3.3 Data analysis
Data analysis was carried out using the General Linear Model (GML) procedure of SAS version 9.3 (SAS, 2010). Significance between the means was tested using the least significant difference (LSD). The General Linear Model used was:
Yij = µ + Ti + Ɛij
Where:
Yij = is response variable (i.e., DM, CP, DM, NDF, ADF, and TEPH);
µ = overall mean;
Ti = is the location effect with six levels (i.e., UZ farm, Goromonzi, Masvingo,
Shurugwi, Chegutu, and Magunje); and
Ɛij = is the random residual error.
5.4 Results
The CP, ADF, ADIN NDF, and ash content of L. camara from the six sites did not significantly differ (P< 0.05; Table 5.1). The mean DM and total extractable phenolic of were significantly different (P< 0.05). The highest TEPH were observed in leaves harvest in UZ farm (68g/kg of
DM) whereas the lowest were in leaves harvested from Chegutu. Data presented in Table 5.1 also show that the CP content ranged from 218 to 240 g/kg of DM. The means for ADF was less than 35% for all the sites. The level of ash content was comparable to what is found in
Acacia angustissima leaves (Mtui, 2008; Gusha et al., 2015). The values ranged between 82 to
102 g/kg DM, these figures are comparable to figures reported by Osuga et al. (2006). Acid detergent insoluble nitrogen was very low and similar to what is found in most browse legumes
108 as reported by Gusha et al. (2015) and Osuga et al. (2006). This is a positive attribute of this
Lantana camara as this indicates that its leaves could be easily digested.
109
Table 5-1: Chemical composition (g/kg DM) of Lantana camara leaves harvested from six
different sites in Zimbabwe
Site of Nutritional composition harvesting DM CP NDF ADF ADIN ASH TEPH
g/kg ------g/kg of DM------
Goromonzi 924a 223a 422 a 311 a 118 a 101 a 37 b
Masvingo 916ab 233 a 428 a 301 a 91 a 90 a 41b
Shurugwi 907b 224 a 418 a 317 a 78 a 102 a 46b
UZ farm 910b 218 a 432 a 309 a 69 a 112 a 68 a
Chegutu 899c 240 a 424 a 308 a 23 a 110 a 38 b
Magunje 919ab 218 a 426 a 320 a 102 a 108 a 40 b
SEM 31.8 85.5 17.3 16.8 7.6 3.5 4.8
LSD(p < 0.05) 13.3 35.6 29.4 24 56.8 31.2 12.2 DM= dry matter, CP= crude protein, ADIN = Acid detergent Insoluble Nitrogen, ADF = Acid
detergent fibre, NDF = Neutral detergent fibre, Ash. TEPH = total extractable phenolics; SEM:
Standard errors of means. LSD: least significant difference. Least squares means with different
superscript abc in the same row denote significantly different at (P < 0.05). UZ = University of
Zimbabwe
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5.5 Discussion
The CP content in the current study, which was above 20%, is comparable to the CP of widely used browse species such as Gliricidia sepium (26.5%), Leucaena leucocephala (28.2%) and
Acacia angustissima (28%) reported previously (Osuga, 2006; Aregheore et al., 2006; Basha et al., 2012; Gusha et al., 2015). This result suggests that the CP levels of different L. camara varieties, which are abundant in invaded rangelands, could form a potential feed resource. The
L. camara biomass could be used chiefly as protein supplements to ruminants, addressing the deficiencies in nitrogen common in most basal roughages during the dry seasons. Basal roughages have CP values ranging between 30-70 g/ kg DM during the dry season (Mtui,
2008). Crude protein lower than 70g/kg is not enough for maintenance and growth for most ruminant livestock such as cattle and goats since it reduces voluntary feed intake, the rate of fermentation in the rumen and microbial protein production causing a decline in animal productivity (Aregheore et al., 2006).
Previous research has demonstrated that animal feeds with less than 6% crude protein content are unlikely to provide the minimum ammonia levels required for maximum microbial growth in the rumen (Mokoboki et al., 2005). Hence, the high CP content of raw L. camara leaves obtained in this study, which was nearly four times higher than the minimum 6% CP level, indicates that L. camara biomass may be considered to support minimum ruminant production and may potentially be used as protein supplement. Considering that maximum microbial production could supply 95% of the maintenance protein requirement under low levels of production (Wickersham et al., 2008), the CP levels of L. camara plant obtained in this study are well above the acceptable range of 78 – 110 g/kg dry matter recommended to meet lactation requirements in goats (Mokoboki et al., 2005).
111
However, optimal use of L. camara as a crude protein supplement requires careful consideration of the levels of soluble phenolic compounds hence feeding L. camara biomass, to ruminants ad lib may not be the best option (Mangan, 1988). According to Estell (2010), preference/ intake of browse were affected by concentration of phenolic compounds and or tannins. Although the TEPH levels in L. camara biomass was lower than the values reported for C. calothyrsus and Acacia angustissima, restrictive feeding is ideal and to this end, further experimental research is warranted to establish threshold feeding levels beyond which L. camara poisoning may occur.
Another interesting aspect of results of the nutritive composition of L. camara biomass is that the measured NDF content was low to moderate, ranging from 422 to 432g/kg DM. Such low
NDF values indicate that the shrub had high cell contents, which correlates positively with high digestibility (Mangan, 1988) given that ADF, which contains lignin and cellulose constituted a small fraction (<35%) of DM. Thus, the digestibility of the fibre may not be a problem for ruminant livestock. It is also important to note that the results of cell wall examination presented as ADF and NDF in this study, were both relatively low and thus provide empirical evidence to support the idea that the fibre content of L. camara shrub are not a deterrent in the utilisation of the species as a feed for ruminants that are capable of tolerating higher levels of
< 36% NDF and, 22% ADF.
The results of this study demonstrate that L. camara variety had lower quantities of the total phenolic compounds compared to the other recommended browse legumes such as A. angustissima (106 g/kg of DM) and C. calothyrsus (223 g/kg of DM) (Osuga et al., 2005). The value obtained on L. camara agrees with the previous studies, which were carried out at the
University of Queensland in Australia (Mangan, 1988) and those done in Kenya and Nigeria 112
(Mtui, 2008). The levels of TEPH observed in this study were not high enough to potentially affect the production of ruminants. This finding corroborates the work of Goel and Makkar
(2012) as well as Waghorn (2008) which documented a number of benefits associated with feeding livestock forages with phenolic compounds. For instance, phenolic compounds lower methane production thus reducing global warming. Tannins reduce rumen protein degradation thus increase post ruminal digestion of protein (Jayanegara et al., 2009). Key phenolic compounds in the diet such as tannin and saponins have also been shown to play an important role in control of internal parasites (Goel and Makkar, 2012) hence the levels of less than 6% total phenolics measured in six site where L. camara biomass was harvested could be beneficial rather than detrimental to ruminants.
What makes this study different is in characterising the nutritional composition of L. camara as a potential protein supplement and this is in contrast to most previous studies considering that L. camara is regarded as a poisonous invasive species not to be fed or consumed by livestock. Ironically, this conventional wisdom is inconsistent with field observations indicating that livestock in particular goats and cattle consume L. camara in Zimbabwean rangelands.
5.6 Conclusion
Overall, the results of this study demonstrate that the nutritional composition of Lantana camara from different locations are a potential source of feed for ruminant livestock with the biomass harvested from all sites in Zimbabwe being the most suitable source due to its low total phenolic compounds and high CP. Although this study showed that Lantana camara has high crude protein content it is recommended that further field studies should be done to
113 determine the soil factors on concentration of TEPH compounds and influence on animal feeding if allowed to voluntarily feed. Together with the current information, such studies could help in deciding whether or not L. camara could be used exploited to mitigate food shortages for livestock in invaded rangelands with reduced resilience to climate change.
114
5.7 References
AOAC (Association of Agricultural Chemists). 2000. AOAC official methods of analysis. 17th
Edn. AOAC, Gaithersburg, MD, USA.
Aregheore, E.M., Ali, I., Ofori, K., Tiria, R. 2006. Studies on Grazing Behavior of Goats in the
Cook Islands: The Animal-Plant Complex in Forage Preference/Palatability
Phenomena. International Journal of Agriculture Biology, 8:147–152.
Basha, N.A.D., Scogings, P.F., Dziba, L.E., Nsahlai, I.V. 2012. Diet selection of Nguni goats
in relation to season, chemistry and physical properties of browse in sub-humid
subtropical savanna.Small Ruminant Research, 102(2):163-171.
Day, M.D., Wiley, C.J., Playford, J., Zalucki, M.P. 2003. Lantana: current management status
and future prospects. ACIAR, Canberra.
Goel, G., Makkar, H.P., 2012. Methane mitigation from ruminants using tannins and
saponins.Tropical Animal Health and Production, 44(4):729-739.
Goering, H.K., Van, Soest, P.J. 1970. Forage fiber analyses (apparatus, reagents, procedures,
and some applications). USDA Agricultural Handbook No 379, Agricultural Research
services, Washington D.C, USA.
Gusha, J., Katsande, S., Zvinorova, P.I., Halimani, T.E., Chiuta, T. 2015. Performance of
growing cattle on poor‐quality rangelands supplemented with farm‐formulated protein
supplements in Zimbabwe. Journal of Animal Physiology and Animal Nutrition,
99(5):905-912.
Gusha, J., Halimani, T.E., Katsande, S., Zvinorova, P.I. 2014. Performance of goats fed on low
quality veld hay supplemented with fresh spiny cactus (Opuntia Megacantha) mixed
115
with browse legumes hay in Zimbabwe Tropical Animal Health and Production, 46
(7): 1257–63. https://doi.org/10.1007/s11250-014-0636-z.
Gusha, J., Masocha, M, Muchaya, K., Ncube, S. 2016. Chemical analysis of the potential
contribution of l. camara to the nutrition of browsing livestock Tropical and Subtropical
Agro ecosystems, 19: 337–42.
Jayanegara, A., Togtokhbayar, N., Makkar, H.P., Becker, K. 2009. Tannins determined by
various methods as predictors of methane production reduction potential of plants by
an in vitro rumen fermentation system. Animal Feed Science and Technology,
150(3):230-237.
Kaur, D. 2007. Development of a cheap and rapid method to determine calcium in milk fraction
in an industrial environment, Master of Applied Science Thesis, Auckland University of
Technology, Auckland, New Zealand.
Mangan, J.L. 1988. Nutritional effects of tannins in animal feeds. Nutrition Research Reviews,
1(01):209-231.
Mapiye, C., Mwale, M., Mupangwa, J.F., Poshiwa, X., Mugabe, P.H., Chikumba, N. 2006. A
review of improved forage grasses in Zimbabwe. Tropical and Subtropical
Agroecosystems, 6:125‒131. http://www.redalyc.org/pdf/939/93960301.pdf
Mokoboki, H.K., Ndlovu, L.R., Ng'ambi, J.W., Malatje, M.M., Nikolova, R.V. 2005. Nutritive
value of Acacia tree foliages growing in the Limpopo Province of South Africa. South
African Journal of Animal Science, 35(4):221-228.
Mtui, D.J., Shem, M.N., Lekule, F.P., Ichinohe, T., Fujihara, T. 2008. Evaluation of chemical
composition and in vitro gas production of browses collected from Tanzania. Journal
of Food, Agriculture and Environment, 6(3&4): 191–195.
116
Ngongoni, N.T., Mapiye, C., Mwale, M., Mupeta, B. 2006. Factors affecting milk production
in the smallholder dairy sector of Zimbabwe. Livestock Research for Rural
Development, 18(5):1‒21. Available at: http://www.lrrd.org/lrrd18/5/ngon18072.htm.
Osuga, I.M. 2006. Rumen degradation and in vitro gas production parameters in some browse
forages, grasses and maize stover from Kenya, Journal of Food Agriculture and
Environment, 4(2):60–64.
SAS Institute, (2010). SAS/STAT user's guide. 9th Edn. (SAS Institute, Cary).
Smith, T. 2002. Some tools to combat dry season nutritional stress in ruminants under African
conditions. http://www.iaea.org/inis/collection/NCLCollectionStore/_Public/33/032/33032982.pdf
accessed on 28 October 2017.
Waghorn, G. 2008. Beneficial and detrimental effects of dietary condensed tannins for
sustainable sheep and goat production—Progress and challenges. Animal Feed Science
and Technology, 147(1):116-139.
Wickersham, T.A., Titgemeyer, E.C., Cochran, R.C., Wickersham, E.E., Moore, E.S. 2008.
Effect of frequency and amount of rumen-degradable intake protein supplementation
on urea kinetics and microbial use of recycled urea in steers consuming low-quality
forage. Journal of Animal Science, 86(11):3089-3099.
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CHAPTER SIX
6 Effect of growth stage and method of conservation of Hyparrhenia filipendula and
Hyperthelia dissoluta on nutrient composition and digestibility
6.1 Abstract
Native species such Hyparrhenia filipendula and Hyperthelia dissoluta have great potential in livestock production but not much has been done to improve their contribution to animal nutrition. This factorial study examined 2 grass species (H. filipendula and H. dissoluta) x 2 conservation methods (drying and ensiling) x 3 different growth stages: elongation stage
(January), early flowering (February) and late flowering stage (March)in terms of nutritional composition and digestibility. Silage and hay samples were air dried and ground to facilitate chemical composition analysis of their crude protein (CP), dry matter (DM), neutral detergent fibre (NDF), acid detergent fibre (ADF), phosphorus (P) and calcium (Ca) using the standard methods. Digestibility was measured using the two stage method by Tilley and Terry. There was no significant different (P>0.05) in nutritional composition between the two grass species.
The method of conservation had an effect (P<0.05) on nutritive value, with silage having greater P, NDF and CP levels than hay. Stage of growth had an effect (P<0.05) on all nutritional properties of both hay and silage. Phosphorus, Ca, NDF and CP concentrations and digestibility of hay and silage decreased with maturity, while ADF concentration increased.
Silage pH value was significantly higher at elongation (5.1) and (4.9) for H. filipendula and
H. dissoluta, respectively. Silage pH for early flowering stage was within the recommended ranges from 4.1 to 4.4 on the pH scale, with higher than the recommended range for the late flowering growth stages (4.8 and 4.5) for H. filipendula and H. dissoluta, respectively. Dry
118 matter digestibility of the conserved material reached levels as high as 80% for silage made at the elongation stage with all having a minimum value of 60%. The study results revealed that
H. filipendula and H. dissoluta can be conserved as both silage and hay to produce a good quality feed. Harvesting at the early flowering stage provides a good compromise between quantity and quality of harvested forage. Further studies are necessary to assess the acceptability of the forage by livestock as well as to determine dry matter yields in different areas and a range of seasonal conditions.
Keywords: air-drying; hay; neglected perennial native grass species; plastic bag silo; quality; silage.
6.2 Introduction
In tropical and subtropical regions, almost every smallholder farmer faces feed shortage in both quality and quantity during the annual dry period of 7‒9 months (Mapiye et al., 2006;
Ngongoni et al., 2006). The quality of forage generally declines as plants mature and become more fibrous and crude protein levels fall to as low as 2% DM (Smith, 2002), resulting in accumulation of poor quality biomass, which is lowly digestible and low in nutrients(Ball et al., 2001). The biomass is either consumed by veld fire during the dry season or breaks down during the following rainy season. This results in low productivity, long calving intervals, and high livestock mortality (Lukuyu et al., 2011).Zimbabwe has abundant native, well-adapted grass resources of tropical C4 grass species such as H. filipendula and H. dissoluta, which have been neglected as animal feeding resources. Very little attempts were made to find ways of utilizing these grass species except few studies that were done by Mufandaedza in 1976
(Mufandaedza, 1976a ; 1976b). Thereafter, these species were not considered as options for improving livestock production.
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Earlier studies by Smith (1962), reported the nutritive value of the mature Hyparrhenia grasslands which include (H. filipendula and H. dissoluta) as ‘standing hay’ progressively dropped to 38% digestible organic matter and negative crude protein (CP) digestibility by mid-dry-season in July and are grossly deficient in both energy and protein.
These results were not encouraging to pastures and rangelands researchers. Researchers then shifted their attention to exotic species with better nutritive value such as Cynodon nlemfuensis.
Most exotic forage species require fertilisers for them to grow well and most communal farmers and many smallholder farmers may not be able to afford the growth requirements to produce a good yield. Traditionally, exotic fodder species and cereals have been planted to produce hay and silage; but the rate of success under dry land farming is low and some are in direct competition with for land with those crops used to produce foodstuffs for human consumption
(Gusha et al., 2014). H. filipendula and H. dissoluta grass species do not require land preparation, irrigation, weeding, and fertiliser application but to identify the optimum time to harvest from the rangelands and conserve only.
Because of the increase in abundance of H. filipendula and H. dissoluta, a rethink with regards to research and utilization of these species is imperative. These species are well adapted to local climatic conditions and the most dominant grass species in most communal rangelands (Gusha et al., 2017). H. filipendula and H. dissolute may have the potential to reduce the perennial feed deficit problems if appropriate techniques are applied during harvesting and conservation.
In order to improve livestock productivity, the use of native high-producing veld grasses is important. A good quality feed from forages can only be produced if harvesting is done when pastures are at a vegetative stage and still nutritious (Ball et al., 2001) and then conserved as hay or silage for later use during times of deficit.
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In order to bridge the perennial feed deficit and to reduce occurrence of high intensity veld fires fuelled by these grass species which are neglected in the rangelands, utilisation of this species in vital. The study was aimed to evaluate the potential of adapted native grass species, with Hyperthelia dissoluta and Hyparrhenia filipendula as example, to produce conserved forages for dry season feeding. The study also identified the most suitable harvesting and conservation strategies to produce high quality herbage for livestock feeding. The study further evaluated the effects of stage of growth and conservation method of H. filipendula and H. dissoluta on nutrient composition and digestibility.
6.3 Materials and methods
6.3.1 Study site
The study was conducted at Henderson Research Institute, 30 km north of Harare (17°35’ S,
30°58’ E; 1,300 masl). Henderson Research Institute is a livestock research centre with the mandate to conduct research on animal nutrition and production. The area receives an average rainfall of 870 mm annually (www.drss.com), which falls mainly between December and late
March. The vegetation consists mainly of tree savanna or bush clump savanna with tall perennial grasses such as Hyperthelia dissoluta and Hyparrhenia filipendula on red clay soils.
6.3.2 Silage and hay preparation
The experimental design was a 2*2*3 factorial treatment. There were two grass species (H. filipendula and H. dissoluta) and two methods of conservation of the grass (either ensiled or dried as hay) and three growth stages [elongation stage in January (early growth stage), early flowering stage in February (middle growth stage), and late reproductive stage in March (late growth stage)]. At each stage of harvest, 60 kg per site of H. filipendula and 60 kg per site of
H. dissoluta were harvested by cutting with a sickle at 5 cm above the ground from three different sites within the farm. The harvested H. filipendula and H. dissoluta forage was 121 transported to the Pasture section at Henderson research institute and chopped into approximately 3 cm pieces manually using machetes. Ten-kilogram samples of the chopped herbage were thoroughly mixed with 500 grams molasses to improve fermentation before packing in polythene bags with a thickness of 150 microns. The contents of the bags were compacted and the bags compressed to remove air, tied to prevent the entry of air and inserted into another polythene bag. Three samples were prepared at each site and each stage of growth.
The bags were left to ferment for seven weeks at room temperature of about 25 ºC. The other
30 kg herbage at each site was divided into three 10 kg heaps, which were spread and dried under shade for 7 days, and the dried material was stored in hessian bags at room temperature.
Nine bags of silage and nine heaps of hay were made at each harvesting stage for each grass species and were used as replicates in the study.
6.3.3 Nutrient chemical composition analysis
Representative samples were collected from each treatment bag at day 35 post ensiling and were oven-dried for 48 h at 60 ºC. The samples were then ground through a 1 mm sieve and analysed for nitrogen (N), dry matter (DM), acid detergent insoluble nitrogen (ADIN), and ash according to AOAC (2000). Acid detergent fiber (ADF) and neutral detergent fiber (NDF) were determined using the method of Goering and Van Soest (1970). Phosphorus and calcium concentrations were determined by the spectrophotometric method (Danovaro, 2009) and the
EDTA method (Kaur, 2007), respectively. Digestibility was determined according to Tilley and Terry (1963) and pH using a digital pH meter.
6.3.4 Statistical analysis
The experiment was carried out in factorial design of three harvesting periods x 2 conservation methods x 2 grass species. The model for data analysis included the main factors of harvesting time, conservation method, the grass species, and their interaction. Analysis of variance was
122 carried out using the general linear model procedure (SAS, 2010). Significant differences of means were tested using the least significant difference (LSD) method. Only the main effects are reported and discussed in this experiment because there were no interactions of these main factors at (P> 0.05). The following model was fitted:
푌푖푗푘푙 = 휇 + 훼푖 + 훽푗 + 퐶푘 + (훼 ∗ 훽 ∗ 퐶) + 휀푖푗푘푙
Where:
Yijk= the response variable (digestibility and nutritive content);
µ = the overall mean common to all observations;
th αj= effect of i grass species (H. filipendula and H. dissoluta);
th βj = effect of j conservation method (Silage and hay);
th Ck = effect of the k harvesting time (elongation stage, early flowering stage,
late reproductive stage);
(훼 ∗ 훽 ∗ 퐶)= interaction between the three factors and
εijkl = the residual error.
6.4 Results
6.4.1 Quality of silage from the two grass species
H. dissoluta and H. filipendula silage made during the elongation stage of growth had the highest CP concentrations of 11.2 and 12.1% (DM basis), respectively (Table 6-1). Crude
123 protein concentrations declined progressively with later harvesting to 4.5% for both H. dissoluta and H. filipendula grass species at late reproductive stage. Silage pH values were 4.9 and 5.2 at the elongation stage, 4.3, and 4.4 at the early reproductive stage and 4.7 and 4.5 at the late reproductive stage for H. dissoluta and H. filipendula respectively. Corresponding DM concentrations of the silages were H. dissoluta (26.3, 31.7, and 38.3%) and H. filipendula (25.9,
33.7, and 38.0%) for elongation stage, early reproductive and late reproductive stage respectively. Phosphorus and calcium concentration in conserved forage declined significantly with age and at all stages but not different between these species. Apparent digestibility of dry matter declined significantly as harvesting stage was delayed for both grass species and was generally higher for H. dissoluta than for H. filipendula for all the stages.
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Table 6-1: Nutrient composition (% DM) for silages of H. filipendula and H. dissoluta conserved at three different growth stages in summer.
H. dissoluta H. filipendula
Stage of harvest: Early Middle Late Early Middle Late LSD
DM 26.3d 31.7c 38.3a 25.9d 33.7b 38.0a 1.26 Ash 8.3a 7.5b 6.1c 6.0c 5.4e 5.7d 0.35 P 1.66c 1.19d 2.16b 2.5a 2.63a 1.64c 0.31 Ca 0.03a 0.01a 0.21a 0.03a 0.03a 0.03a 0.06 NDF 77.9a 72.5b 64.9c 64.9c 66.5c 57.7d 1.83 ADF 42.2dc 47.5ab 49.0a 44.6c 45.8c 47.0b 1.89 ADIN 0.2a 0.3a 0.3a 0.2a 0.2a 0.3a 0.04 CP 11.2a 9.3b 4.5d 12.1a 7.6c 4.5d 0.62 Dig 80.0a 74.3b 64.4d 69.4c 62.7d 60.0de 2.80 pH 4.9b 4.3d 4.8b 5.1a 4.4cd 4.5c 0.12 Early = elongation stage; middle = early reproductive stage; late = late reproductive stage; DM
= dry matter; Phosphorus; Ca = calcium; NDF = neutral detergent fiber; ADF = acid detergent fiber; ADIN = acid detergent insoluble nitrogen; CP = crude protein; and Dig = DM digestibility coefficient. Means within rows followed by different superscript letters differ
(P<0.05). LSD = Least significant difference.
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6.4.2 Quality of hay from the two grass species
H. dissoluta and H. filipendula hay which was made during the elongation stage of growth had
the highest CP concentrations of 9.5 and 8.2% (DM basis), respectively (Table 6.2). Crude
protein concentrations declined progressively with later harvesting to 3.2% and 3.5 for H.
dissoluta and H. filipendula grass species, respectively. Dry matter concentrations of the hay
were H. dissoluta (90.1, 90.2, and 91.4%) and H. filipendula (89.6, 89.7, and 90.7%) for
elongation stage, early reproductive and late reproductive stage respectively. Apparent
digestibility coefficient of dry matter declined significantly with maturity for both grass species
and was generally higher for H. dissoluta than for H. filipendula for all the stages. Apparent
digestibility coefficient was ranging between 72.1 to 63.1% for H. dissolute and between 68.1
to 56.6% for H. filipendula.
6.4.3 Rate of decline in crude protein and digestibility
The decline in crude protein was show a liner trend from as high as 10 – 12 % at elongation
stage to as low as 3% in April. Likewise, there was a similar trend in digestibility as shown in
Figures 6-1 and 6-2. There is rapid accumulation of structural carbohydrates when a plant
reaches flowering stage. This was shown by the decline in those two parameters mentioned
above.
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Table 6-2: Nutrient composition (% DM) for hay of H. filipendula and H. dissoluta conserved at three different growth stages in summer.
Hyperthelia dissoluta Hyparrhenia filipendula
Stage of harvest: Early Middle Late Early Middle Late LSD
DM 90.1ab 90.2a 91.4a 89.6b 89.7b 90.7a 1.26 Ash 9.3a 6.4b 6.0c 6.4b 6.6b 3.5d 0.35 P 2.66a 1.93b 1.56c 2.04b 1.67b 1.76b 0.31 Ca 0.21b 0.19c 0.16c 1.69a 0.63b 0.64b 0.06 NDF 65.9a 63.5b 54.3d 67.6a 62.4b 56.8c 1.83 ADF 41.7d 49.5c 54.6a 44.4d 50.1bc 51.8b 1.89 ADIN 0.26b 0.26b 0.31a 0.24b 0.23b 0.26b 0.04 CP 9.5a 5.1c 3.2d 8.2b 5.6c 3.5d 0.62 Dig 72.1a 71.0ab 63.1c 68.1b 58.6d 56.6d 2.80 Early = elongation stage; middle = early reproductive stage; late = late reproductive stage; DM
= dry matter; P = phosphorus; Ca = calcium; NDF = neutral detergent fiber; ADF = acid detergent fiber; ADIN = acid detergent insoluble nitrogen; CP = crude protein; and Dig = DM digestibility coefficient. Means within rows followed by different letters differ (P<0.05). LSD
= Least significant difference.
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A B
D C
Figure 6-1: (A to D) showing rapid decline observed in crude protein content with advancing stage of growth of conserved silage and hay from H. filipendula and H. dissoluta.
1 = elongation stage; 2 = early reproductive stage; 3 = late reproductive stage;
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A B
D C
Figure 6-2:A to D showing rapid decline observed in digestibility coefficient with advancing stage of growth of conserved silage and hay from H. filipendula and H. dissoluta.
Early = elongation stage; middle = early reproductive stage; late = late reproductive stage;
129
6.5 Discussion
The most striking finding was the high apparent in vitro DM digestibility of the conserved material. The highest digestibility coefficient obtained was 80% for silage made at the elongation stage of growth, while the lowest was 56.6% for hay made at late flowering. These values were higher than the values of 54.5% reported by Heuzé et al., (2012) and below 50% as reported by Smith (1962). They are outstanding for a tropical grass and strongly suggest that these species warrant further study as a potential source of forage for livestock. According to
Ball et al. (2001), immature leaf plant tissues may be 80 to 90% digested, while less than 50% of mature stemmy material is digested. The outstanding results for digestibility coefficient could be related to harvesting time before the physical incrustation of plant fibres by lignin rendering them inaccessible to enzymes that would normally digest them (Mertens, 2009;
McDonald et al., 2011). Smith (1962) reported that the seasonal drop in digestibility values is accentuated by the drop in dry-matter intake so that a diet of mature veld herbage in mid dry season is grossly deficient in both energy and protein.
The degree of lignification and formation of strong chemical bonds, which exist between lignin and many plant polysaccharides and cell wall proteins, that renders the compounds unavailable during degradation increase with maturity of the plant (McDonald et al., 2011; Dilley et al.,
2013). It is widely accepted that tropical grasses have lower digestibility coefficient than temperate grass species but more should be done with regards to these tropical native species, which do not require a lot of fertiliser input to produce large quantities of biomass. Cell wall digestibility also depends on the structure of the plant tissues hence it should make sense to harvest the biomass before the physical incrustation with lignin thus changing the structure of the plant tissues rendering them indigestible. Harvesting H. filipendula and H. dissoluta during the dry season for hay produce poor quality hay with more stems to leaf ratio. Leaf materials
130 are lost due to shattering thus affecting the digestibility coefficient. According to Smith (1962)
Ball et al. (2001) and Scarbrough et al. (2005), mature veld grasses harvested at the late reproductive growth stages as veld hay or green forage, contain below 50% digestible organic matter and further delays in harvesting is accompanied by a progressive decline to 38% digestible organic matter by mid-dry-season in July. Even at late reproductive stage of growth, the material will be still moist enough to be highly digestible. Unfortunately, very little studies were conducted at those growth stages with this particular species hence from this work it is strongly recommended to do more and exploit the potential shown using in vivo studies.
As would be expected, quality, in terms of CP and fiber concentrations and DM digestibility coefficient of the conserved material, declined as harvesting was delayed from the elongation stage to the late flowering stage. This is consistent with the findings reported by Rotz and Muck
(1994), Ball et al. (2001) and Scarbrough et al. (2005). They reported that with prolonged delay in harvesting CP digestibility decline to below 0.6%. Very low levels of crude protein of approximately 3% found in veld grass harvested at the end of rain season resulted in a low apparent CP digestibility. Forage quality decline with advancing maturity and this is related to increase in structural carbohydrates at the expense of cell components. Moore et al. (1991) reported that at late maturity forages become lignified with reduced digestibility. It was also reported by Scarbrough et al. (2005) that during the first 3 weeks after growth initiation at the onset of the rain season, digestibility will be greater than 80% and will progressively decline by 1/3% to ½% units per day until it reaches a level below 50%. This assertion agrees with this study results on digestibility and CP levels as they progressively decrease from as high as 80% and 12.1% to as low as 56.6 and 3.2 percent respectively. Animals sustained on such forage conserved late at the end of rain season consequently suffer from protein deficiency. Smith
131
(1962) reported that animals feeding standing hay by mid-dry-season in July might have negative crude protein digestibility and suffer from protein and energy imbalance.
Neutral detergent fiber (NDF) represents the cell wall portion of a feed, comprising ADF and hemicellulose and affects feed intake, with intake declining as NDF concentration in feed increases (Bosworth and Hudson, 2005). The desirable level of NDF in feedstuffs is <55%
(Mertens, 2009). In this study, the values of NDF obtained were higher than the desirable levels. Despite the higher levels of NDF than the recommended desirable levels, harvesting the grasses at elongation and early flowering growth stage produces better quality feed with high digestibility coefficient. This could be due to less degree of lignification at those growth stages especially at elongation and early reproductive growth stage (Moores et al., 1991; Ball et al.,
2001). According to Mertens (2009), the amount of lignin varies with maturity and the strong chemical bonds between lignin and other compounds increases with maturity. In our study, all treatments had values above this, which should depress intake. It would be expected that intake of forage with DM digestibility in the range 60‒82% would be quite acceptable, suggesting that feeding studies with animals to test acceptability of the material, possible intake levels and in vivo digestibility are needed.
Silage is preserved by lowering the pH through lactic acid formation. For grass silages the recommended pH for a well-preserved silage is between 4.2 and 4.7 (Pyatt and Berger, 2000;
Bosworth, 2005). The pH values for elongation growth stages for the two grasses were above these recommended levels for grass silage. This could be related to low soluble sugars during the elongation stage of growth (Bosworth, 2005) combined with high moisture levels in the fast-growing crop. The silage quality at late flowering stages was within the range but on the higher side and could be a result of the low moisture levels at late flowering that prevented
132 adequate compaction to remove air effectively (Ball et al., 2001). Pyatt and Berger (2000) reported that forages with a DM above 35% at ensiling, as the material ensiled at late flowering, have less efficient fermentation because they are difficult to compact.
While the decline in CP and P concentrations in conserved material with delay in harvesting time were to be expected, the consistently higher CP and P concentrations in silage compared with hay were surprising. MacDonald and Clark (1987) reported results from eight separate studies, showing there is an average of 34% CP loss during the drying process. Thus in our study the lower CP levels in hay could be associated with leaf loss and weathering damage during drying. These results reaffirms what was reported by Scarbrough et al. (2005) that leafy shattering, respiration and leaching during field drying of hay can cause a significant reduction in forge quality. Method of conservation had no significant effect on the Ca levels but stage of ensiling had a significant effect in silage with a trend of increasing Ca concentration with maturity (Morales et al., 2011). The Ca concentration in both hay and silage was below the minimum requirement for all classes of livestock (Fox et al., 1988) and if hay made from H. dissoluta is to be fed as a complete ration, a Ca supplement like limestone flour should be fed
(Fox et al., 1988). Silage contained adequate levels of P for livestock feeding but hay made at early or late flowering had insufficient levels of P for livestock, especially lactating females
(Coates and Ternouth, 1992) and supplements may be necessary if this material constitutes a major part of the diet.
The CP concentrations in hay were generally lower than the levels found in previous studies of
6.4% in late summer (Heuzé et al., 2012). If these conserved fodders were to be fed as a major part of the ration for livestock, especially lactating females, a protein supplement would need to be added to the ration. Acid detergent insoluble nitrogen (ADIN) is an indicator of the quantity of N that is indigestible in the rumen and intestines, and reflects the quantity of heat-
133 damaged silage or hay (Dilley et al., 2013). In this study ADIN concentration was similar for both methods of conservation and stages of harvest and the quantity of ADIN was less than
12% of the total N in the forages, indicating that little heat damage took place during drying and ensiling (Seglar, 2003).
6.6 Conclusion
It can be concluded that H. filipendula and H. dissoluta can produce good quality forage, which could be conserved as silage or hay for dry season feeding of livestock. Timing of harvest would depend on whether quantity or quality of conserved material was more important.
Whether hay or silage is made would depend to some extent on weather conditions during the optimal time of harvesting and the ability to reliably dry hay. More research is needed to determine the fermentation patterns of the silages. Further studies seem warranted to confirm that the high in vitro digestibility levels recorded in this study can be repeated with animals and to determine acceptability and intake with and without N and P supplements. Dry matter yields of this forage during a range of seasons and on a range of soil, types would provide evidence whether satisfactory DM yields can be obtained in a range of situations.
134
6.7 References
AOAC (Association of Agricultural Chemists). 2000. AOAC official methods of analysis. 17th
Edn. AOAC, Gaithersburg, MD, USA.
Ball, D.M., Collins, M., Lacefield, G.D., Martin, N.P., Mertens, D.A., Olson, K.E., Putnam,
D.H., Undersander, D.J., Wolf, M.W. 2001. Understanding forage quality. American
Farm Bureau Federation Publication, 1(01).
Bosworth, S. 2005. Corn silage forage quality in Vermont for 2005. In: The Vermont Crops
and Soils Home Page, Plant and Soil Science Department, University of Vermont,
Burlington, VT, USA.
http://pss.uvm.edu/vtcrops/articles/ForTestLab/CornSilageQuality05.pdf
Bosworth, S., Hudson, D. 2005. Sensory evaluation of hay for quality. Plant and Soil Science
Department, University of Vermont, Burlington, VT 05405.
Coates, D.B., Ternouth, J.H. 1992. Phosphorus kinetics of cattle grazing tropical pastures and
implications for the estimation of their phosphorus requirements. The Journal of
Agricultural Science, 119(3):401-409.
Danovaro, R. 2009. Total organic carbon, total nitrogen and organic phosphorus in marine
sediments. In ‘Methods for the study of deep-sea sediments, their functioning and
biodiversity’. In Danovaro R Ed (2009) Methods for the study of deep-sea sediments
for functioning and biodiversity CRC Press, NW, USA
Dilley, A., Bell, M.A., Coite, E., Honeycutt, E. 2013. Hay making.
https://onslow.ces.ncsu.edu/wp- content/uploads/2013/07/FenceJuly-
Sept13.pdf?fwd=no accessed on 10 July 2015
Fox, D.G., Sniffen, C.J., O'Connor, J.D. 1988. Adjusting nutrient requirements of beef cattle
for animal and environmental variations. Journal of Animal Science, 66(6):1475-
1495. 135
Goering, H.K., Van Soest, P.J. 1970. Forage fiber analyses (apparatus, reagents, procedures,
and some applications). USDA Agricultural Handbook No 379, Agricultural Research
services, Washington D.C, USA.
Gusha, J., Halimani, T.E., Katsande, S., Zvinorova, P.I. 2014. “Performance of goats fed on
low quality veld hay supplemented with fresh spiny cactus (Opuntia Megacantha)
mixed with browse legumes hay in Zimbabwe” Tropical Animal Health and
Production, 46(7):1257–63. https://doi.org/10.1007/s11250-014-0636-z.
Gusha, J., Masocha, M., Mugabe, P.H. 2017. Impact of grazing system on rangeland condition
and grazing capacity in Zimbabwe. The Rangeland Journal, 39(3): 219-225.
Heuzé, V., Tran, G., Hassoun, P. 2012. Yellow thatching grass (Hyperthelia dissoluta).
Feedipedia.org. A programme by INRA, CIRAD, AFZ and FAO: 2–3. Available at:
http://www.feedipedia.org/node/429.
Kaur, D. 2007. Development of a cheap and rapid method to determine calcium in milk fraction
in an industrial environment, Master of Applied Science Thesis, Auckland University
of Technology, Auckland, New Zealand.
Lukuyu, B., Franzel, S., Ongadi, P.M., Duncan, A.J. 2011. Livestock feed resources: Current
production and management practices in central and northern Rift Valley provinces of
Kenya. Livestock Research for Rural Development, Volume 23, article #112.
Retrieved October 28 2017, from http://www.lrrd.org/lrrd23/5/luku23112.htm
MacDonald, A.D., Clark, E.A. 1987. Water and quality loss during field drying of hay.
Advances in Agronomy, 41:407-437.
Mapiye, C., Mwale, M., Mupangwa, J.F., Poshiwa, X., Mugabe, P.H., Chikumba, N. 2006. A
review of improved forage grasses in Zimbabwe. Tropical and Subtropical
Agroecosystems, 6:125‒131. http://www.redalyc.org/pdf/939/93960301.pdf
136
McDonald, P., Edwards, R.A., Greenhalgh, J.F.D., Morgan, C.A., Sinclair, L.A., Wilkinson,
R.G. 2011. Animal nutrition. 7th edition Saffron house, 6-10 Kirby street London UK.
Mertens, D.R. 2009. Impact of NDF content and digestibility on dairy cow performance.
Western Canadian Dairy Seminar Advances in Dairy Technology, 21: 191-201.
Moore, K.J., Moser, L.E., Vogel, K.P., Waller, S.S., Johnson, B.E., Pedersen, J.F. 1991.
Describing and Quantifying Growth Stages of Perennial Forage Grasses. Agronomy
and Horticulture, Faculty Publications, Paper
507.http://digitalcommons.unl.edu/agronomyfacpub/507
Morales, J.U., Alatorre, J.A.H., Escalante, A.A., Lopez, S.B., Vazquez, H.G., Gomez, M.O.D.
2011. Nutritional characteristics of silage and hay of pearl millet at four phenological
stages. Journal of Animal and Veterinary Advances, 10(11):1378-1382.
Mufandaedza, J.T. 1976a. Effects of frequency and height of cutting on the yield, composition,
and quality of grass only and grass legume mixtures. Rhodesia Division of Livestock
and Pastures Annual Report. Salisbury. (Herbage Abstracts 48 [1978])
Mufandaeza, J.T. 1976b. Effects of frequency and height of cutting on some tropical grasses
and legumes. Hypharrenia filipendula and Heteropogon contortus. Rhodesian Journal
of Agricultural Research, 14:21-38
Ngongoni, N.T., Mapiye, C., Mwale, M., Mupeta, B. 2006. Factors affecting milk production
in the smallholder dairy sector of Zimbabwe. Livestock Research for Rural
Development, 18(05):1‒21. Available at:
http://www.lrrd.org/lrrd18/5/ngon18072.htm.
Pyatt, N.A., Berger, L.L. 2000. Management and storage alternatives for corn silage.
http://livestocktrail.illinois.edu/dairynet/paperDisplay.cfm?ContentID=440 accessed
28 October 2017.
137
Rotz, C.A., Muck, R.E. 1994. Changes in forage quality during harvest and storage. Forage
Quality, Evaluation, and Utilization, 1:828-868.
https://doi.org/10.2134/1994.foragequality.c20.
SAS Institute, 2010. SAS/STAT user's guide. 9th Edn. (SAS Institute, Cary).
Scarbrough, D.A., Coblentz, W.K., Humphry, J.B., Coffey, K.P., Daniel, T.C., Sauer, T.J.,
Jennings, J.A., Turner, J.E., Kellogg, D.W. 2005. Evaluation of dry matter loss, nutritive
value, and in situ dry matter disappearance for wilting orchardgrass and bermudagrass
forages damaged by simulated rainfall. Agronomy Journal, 97(2):604-614.
Seglar, B. 2003. Fermentation analysis and silage quality testing.
http://conservancy.umn.edu/bitstream/handle/11299/108997/1/Seglar.pdf, accessed
on 28 October 2015.
Skerman, P.J., Riveros, F. 1990. Tropical grasses. FAO Plant Production and Protection Series
No (23). FAO, Rome.
Smith, T. 2002. Some tools to combat dry season nutritional stress in ruminants under African
conditions.
http://www.iaea.org/inis/collection/NCLCollectionStore/_Public/33/032/33032982.p
df accessed on 28 October 2017.
Smith, C.A. 1962. The utilization of Hyparrhenia veld for the nutrition of cattle in the dry
season III. Studies on the digestibility of the produce of mature veld and veld hay, and
the effect of feeding supplementary protein and urea. The Journal of Agricultural
Science, 58(2):173-178.
Tilley, J.M.A., Terry, R.A. 1963. A two-stage technique for the in vitro digestion of forage
crops. Journal of the British Grassland Society, 18:104-111.
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CHAPTER SEVEN
7 Effects of Lantana camara feed on performance, digestibility, nitrogen balance,
microbial protein production and concentration of liver enzymes in Mashona goats
7.1 Abstract
Lantana camara is listed as one of the worst invasive species worldwide considered poisonous to livestock. However, in invaded Zimbabwean rangelands, voluntary intake by domestic livestock especially goats of this shrub is common, yet, little is understood about the effect of this browse on animal performance. A feeding trial was therefore conducted to assess the effects of L. camara browse on the performance, digestibility, nitrogen balance, microbial protein synthesis, and concentration of liver enzymes in Mashona goats of Zimbabwe. Dried leaf biomass of L. camara harvested in winter was incorporated in goat feed as a protein source at 5%, 10%, 15%, 20%, and 25% inclusion levels of a formulated supplementary feed for 21 days. Veld hay and water were offered ad-libitum. A total of eighteen castrated goats aged six to ten months were randomly assigned to treatments in a completely randomised design. In all the treatments, the average daily dry matter intake was above the minimum recommended of
3% of the animal’s metabolic body weight. Higher nitrogen intakes were observed with diets that were highly palatable such as commercial diet and 5% L. camara. Higher microbial protein supply was observed in groups fed diets with high levels of L. camara. Likewise, the levels of liver enzymes did not differ in all the treatments and no signs of ill-health were observed on the goats in the study. Twenty-five percent L. camara leafy biomass inclusions were safe though, to balance for voluntary feed intake of 15% and below would be the best inclusion levels. However, more research is needed to determine the long-term performance of the animals.
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Key words: digestibility; Lantana camara leaf meal; protein supplement; purine derivatives
7.2 Introduction
Ruminants, mainly goats and cattle, have been observed consuming L. camara ad-libitum in
Zimbabwean rangelands (Gusha, et al., 2016). Yet, this invasive shrub native to the Americas has been reported to be poisonous to livestock due to the secondary metabolites such as
Lantadene A and B (Ghisalberti, 2000; Day et al., 2003). For example, toxicity leading to death in Boar goat kid was reported in South Africa by Ide and Tutt (1998). Lantana camara is among the world’s most invasive plant species (Sharma et al., 2005; Day et al., 2003), and is widespread and abundant in Zimbabwe (Chatanga, 2007, Masocha et al., 2017).While some studies reported that L. camara is toxic to livestock, others have reported that the species has high crude protein (>22% CP) and (>67%) digestibility (Osuga et al., 2005). Therefore, exploring the potential uses of L. camara, as a protein supplement to ruminants grazed in invaded tropical and subtropical rangelands with poor quality native grass biomass is necessary.
Ruminants are an ideal group for such a study because of they have evolved to subside on poor quality roughages provided the microbes in the rumen obtain adequate sources of nitrogen (N) and energy for microbial protein production. Several microbes such as Ruminococcus flavefacians, Ruminococcus albus, Bacteriodes succinogenes, and Butyrivibrio fibrisolvens are resident in the rumen (De Ondarza, 2008; De Ondarza and Engstrom, 2009). These microbes perform dual important roles in the degradation of fibrous feeds and provision amino acids for the host animal. In fact, previous work has estimated that 50% of amino acids absorbed from the small intestines are of rumen microbial protein origin (Dewhurst et al., 2000). However, little is known about nutritive value, microbial protein production, and efficiency of utilisation
140 of L. camara biomass nitrogen in ruminants that feed on this invasive shrub or given the biomass as a protein supplement.
It is estimated that 30% of Zimbabwean rangelands have been degraded through the increase of L. camara and other less palatable plant species (Gusha et al., 2017). Communal cattle and goats have been observed consuming the shrub with no adverse effects. However, it is not yet clear whether rumen microbes are able to detoxify the toxins in L. camara or adapt to it.
Literature has also claimed that consuming L. camara leafy biomass can only become detrimental when an animal consumes more than 1% of its metabolic body weight (Ghisalberti,
2000). A widely established technique to assess whether eating forage such as L. camara is detrimental to animal health and likely to cause mortality is to measure the levels of blood parameters such as liver enzymes such aspartate aminotransferase (AST) and alanine aminotransferase (ALT) (Kida et al., 2007). Moreover, blood profiling is capable of detecting subclinical metabolic disorders (Gwaze et al., 2012) and hence, reflects the actual status of the animal (Caldeira et al., 2007).
Lantana camara is high in crude protein ranging from 220 to 267 grams per kilogram of dry matter (Gusha et al., 2016) and above 0.67 digestibility coefficient (Osuga et al.,
2005).Therefore, it is a potential protein supplement to poor quality native grass biomass in the tropical environments where quality fodder for ruminants is scarce. While consumption of L. camara has been confirmed, it is not clear whether animal performance is enhanced or compromised. Considering these conflicting results from researchers, some pointing out that
L. camara is poisonous, and others regarding it as a potential protein supplement, it is
141 imperative to assess the effect of feeding it to ruminants. To settle these conflicting results and questions, a feeding trial was conducted to assess whether L. camara cause variation in animal performance when fed at different inclusions of leaf biomass to the animals. Therefore, the study hypothesised that different L. camara dried leafy biomass inclusion levels in goats’ diets may cause variations in rumen microbial protein production, apparent digestibility, liver enzymes production, and the overall health status of the animal. The study determined microbial nitrogen (N) production using the urinary purine derivative excretion technique while apparent digestibility and efficiency of utilisation of these formulated diets in microbial nitrogen supply were determined using a nitrogen balance trial.
7.3 Materials and methods
7.3.1 Study site
Red L. camara variety leaves were harvested from the University of Zimbabwe, Faculty of
Veterinary Science animal paddocks in Harare in June 2016. The harvest was done in Harare because the Harare L. camara leaves materials had the highest concentrations of extractable total phenolics (see Chapter 5 Table 5-1). The University of Zimbabwe lies 17o49’ S and
31o03’E at altitude of between 1200 to 1550 m. The maximum monthly mean temperature during wet season is around 28oC while dry season temperatures fall to below 7oC in June. The feeding trial was carried out at the Bioassay laboratory in the Department of Animal Science at the University of Zimbabwe.
7.3.2 Feed formulation and experimental design
The leaves were shade dried for ten days until a constant dry matter was obtained. Two hundred grams of dried leaf biomass of L. camara was ground before a proximate analysis was done.
142
Results of the proximate analysis were used during formulation of diets. Lantana camara leaf biomass hay and soya bean meal were used as protein ingredients, with L. camara replacing soya bean at 5%, 10%, 15%, 20%, and 25% of formulated supplementary feed (Table 7.1). The formulated diets were iso-nitrogenous and iso-energetic. Veld hay and water were offered ad- libitum.
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Table 7-1: Proportion of ingredients in kg used in formulating the treatment diets for the experiment on the effects of feeding Lantana camara on health and goat performance
Treatment diets (LC inclusion levels) Ingredient 5%LC 10%LC 15%LC 20%LC 25%LC
Maize 27.2 28.0 25.4 25.4 23.2
Soya cake 4.8 4.0 3.4 2.6 2.0
L. camara leaves 2.0 4.0 6.0 8.0 10.0
molasses 4.0 2.0 3.2 2.0 2.8
mineral premix 1.2 1.2 1.2 1.2 1.2
salt 0.8 0.8 0.8 0.8 0.8
Note LC represents Lantana camara
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7.3.3 Experimental design and animal management
A total of eighteen, six to ten months old castrated goats with a mean± (SD) weight of 13.6±4.9 kg were randomly assigned to the six treatment diets in a completely randomised design. The goats were housed individually in metabolism cages to allow for individual feeding and collection of urine and faeces. Each goat was given the treatment diet at 9 am in the morning for 21 days. The first 11 days were used as adaptation period where there was no data collection. During the ten days of data collection, total faeces, urine and refusal samples were collected and weighed. Ten percent faecal samples were taken and stored in a cold room at 4oC before being analysed for dry matter, organic matter, and nitrogen. Urine was collected in buckets containing 100 ml of 1% sulphuric acid v/v to keep the pH below 3 for purine derivatives preservation and to minimise loss of nitrogen. Ten percent of the collected urine was frozen pending analysis for allantoin and N. The urine samples were filtered through surgical gauze and stored at −20oC. The urine was diluted with 8 litres of distilled water to reduce the concentration of purine derivatives. Urine samples were analysed for allantoin using the spectrophotometric method outlined in the IAEA technical document (IAEA, 1997).
Digestible organic matter fermented in the rumen (DOMR) was assumed to be digestible organic matter multiplied by 0.65 (Masama et al., 1997), while microbial protein yield was calculated as 32 g N/kg DOMR. Average daily feed intake was calculated and each goat was weighed at the start and at the end.
7.3.4 Nutritional composition analysis
Dry matter content was determined by oven drying at 60oC over 48 hours followed by weighing. The samples were then ground through a 1 mm sieve and analysed for nitrogen (N), acid detergent insoluble nitrogen (ADIN), and ash according to AOAC (2000). Acid detergent fibre (ADF) and neutral detergent fibre (NDF) were determined using the method of Goering
145 and Van Soest (1970). The extraction of the phenolic compounds was done by using 70% aqueous acetone solution. Total extractable phenolics (TEPH) were determined using the procedures of Folin Ciocalteu method as described by Makkar (2000). The concentrations of the total phenols were calculated using the regression equation of the tannic acid standard
(Makkar, 2000).
7.3.5 Haematology, clinical observation and laboratory assay
All experimental animals were handled by a qualified person, without infringement of animal rights issues. Prior approval for use of these animals was obtained from the Faculty of
Veterinary Science Experimental Research Ethics Committee. Blood samples were collected into 7 ml ethylenediamine tetra-acetic acid (EDTA) - coated vacutainer tubes at 0900 hours at the beginning of the experiment. From day 12 to day 14, blood samples were collected before feeding and 6 hours after feeding from the jugular vein. Blood samples were examined for full blood counts which included haemoglobin concentration (Hb), red blood cell (RBC) and white blood cells counts, packed cell volume (PCV), mean corpuscular volume (MCV) and mean corpuscular haemoglobin concentration (MCHC) by standard method (Schalm et al., 1975).
Disease progression was monitored using biochemical profiles of hepatorenal function and haematology. Sera was analysed for activities of aspartate aminotransferase (AST) and alanine aminotransferase (ALT) according to the method of Reitman and Frankel (1957).
7.3.6 Physical examination
On the commencement and at the end of the experiment all the animals were physically examined for health condition by a qualified and practising veterinarian. The parameters
146 evaluated were body temperature, heart rate, respiratory rate, presence of nasal and ocular discharges and capillary refill time.
7.3.7 Calculations of feed efficiency parameters
7.3.7.1 Nitrogen retention
Nitrogen retention was computed by subtracting total nitrogen output (faecal N [FN] and urinary N [UN] losses) from dietary N intake (NI).
Nitrogen retention (g d-1) = NI − (FN + UN)…...... (1)
Apparent Nitrogen digestibility (g d-1) = NI − (FN + UN)/NI × 100...... (2)
Digestible organic matter intake (DOMI) was computed by subtractingfaecal organic matter from the organic matter (OM) intake.
DOMI (g d-1) = OM intake – faecal OM…...... (3)
Metabolisable energy (ME) intake and DOMR were calculated from the DOMI content according to AFRC (1993):
ME intake (MJ d-1) = 0.0157 × DOMI…...... (4)
DOMR (g d-1) = 0.65 × DOMI…...... (5)
7.3.7.2 Microbial protein yield
Daily urinary purine derivatives and allantoin excretion were used to calculate the microbial protein yield using the equations of Chen and Gomes (1992) and IAEA, (1997):
Y = 0.84X + (0.15W0.75e−0.25X)...... (6)
Where;
Y = purine derivative excretion in urine (mmol d−1) and;
147
X = concentration of microbial purines absorbed after duodenal and intestinal digestion
(mmol d−1).
Newton–Raphson iterative process was performed in calculating of X until it approaches a constant value (Chen and Gomes, 1992). W0.75 represents the metabolic body weight (kg) of the animal.
Microbial nitrogen yield (MNY) (g d−1) = X*70/ (0.83*0.116*1 000) = 0.727X... (7)
Where;
70 is a constant for the nitrogen content of purines (mg N mmol−1),
0.83 is the average digestibility of mixed microbial purines based on observations
reported in the literature (Chen and Gomes, 1992),
0.116 is the proportion of purine nitrogen in the total microbial nitrogen of mixed
rumen microbes, and
1/1 000 is to convert the estimate from milligrams to grams per day.
Digestible microbial true protein (DMTP), Microbial true protein (MTP) and efficiency of microbial nitrogen supply (Emns) were computed in accordance with AFRC (1993).
MTP (g d−1) = 0.80 × MNY × 6.25...... (8)
Digestible microbial true protein (g d−1) = 0.85 × MTP...... (9)
Emns (g kg−1DOMR) = MNY/DOMR...... (10)
7.3.8 Statistical analyses
All the data on daily feed intake were tested for normality using the Shapiro-wilk’s test and transformed where necessary prior to being analysed using the model procedure for repeated measures (SAS, 2010). The general linear model procedure was used to determine the effect of diet on growth parameters and slaughter weight, digestibility, nitrogen retention, microbial
148 protein production, and haematology parameters. Data on liver enzymes were analysed following a response surface quadratic equation, which gives the best fit, to the model of dose related responses to the different inclusion levels of L. camara. Data collected by the veterinarian during physical examination were analysed using qualitative and quantitative methods. All quantitative response variables were tested for normality using the shapiro-wilk’s test and log10 transformed where necessary prior to statistical analyses using SAS proc mixed procedure while qualitative data were analysed using SAS proc freq procedure.
7.4 Results
7.4.1 Nutritional composition of the treatment diets
The diets were iso-nitrogenous and iso-energetic. The crude protein CP level was 15±1% of
DM/kg while the gross energy (GE) was 14±13 of Mj/kg of DM. The diets differed significantly on DM and the total extractable phenolics (TEPH) with 20%LC having higher phenolic compounds than 25%LC. Dry matter and TEPH were significantly higher in 15%LC than 10%LC. Total extractable phenolics were significantly lower in 5%LC diet than the control diet of commercial goat meal as shown in Table 7-2.
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Table 7-2: Nutritional composition (% DM) of diets with 5, 10, 15, 20 and 25% Lantana camara inclusion level, commercial goat meal and veld hay.
Feed DM ASH N GE NDF ADF TEP
Veld hay 90.43 7.05 0.65 15.93 40.78 36.17 0.52
5% LC 81.40 4.60 2.56 13.34 11.97 4.88 0.24
10% LC 83.78 4.99 2.50 12.81 19.73 6.28 0.46
15% LC 83.67 4.99 2.51 13.71 20.04 8.79 0.56
20% LC 86.42 6.30 2.52 14.81 17.46 9.94 0.80
25% LC 85.00 8.19 2.54 14.42 16.49 8.93 0.57
GF (Control Diet) 89.07 6.49 2.49 14.57 24.23 8.46 0.38
DM= dry matter, CP = crude protein, GE = gross energy, NDF = neutral detergent fibre, ADF
= acid detergent fibre, TEP= Total extractable phenolics, LC represents Lantana camara, GF
= Goat feed
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7.4.2 Dry matter intake and apparent digestibility
Goats fed on 10%LC consumed significantly lower quantities of hay than 5%LC, but were not significantly different from goat feed (GF), 15%LC, 20%LC and 20%LC (Table 7-3). The amount of GF and 5%LC diets consumed were not significantly different. 5%LC and GF intake were higher and significantly different from 10% LC. Goats on 10%LC consumed significantly higher quantities than those on treatments 15%LC, 20%LC and 25%LC. Significantly more dry matter faecal excretion (g/day) was observed on goats supplemented with GF than the other five treatment diets. Total faecal output on 5%LC and 10%LC treatments were significantly different from 15%LC, 20%LC, and 25%LC. Significantly higher digestible organic matter intake (DOMI) was observed on 5%LC, followed by GF and 10%LC. Very low DOMI was observed on goats given 25%LC that was only 187.8 grams per day. There was significantly higher metabolisable energy intake by goats at 5%LC than those in the other treatments. No significant difference in ME intake were observed in goats given GF, 10%LC, 15%LC and
20%LC which significantly consumed higher ME than goats in 25%LC treatment. Apparent digestibility coefficient values were significantly different with goats given 5%LC having higher value but not significantly different from 10%LC, 15%LC, 20%LC. The lowest value was observed in the group fed 25%LC and GF that were significantly lower than the other four treatments (Table 7-3).
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Table 7-3: Average daily dry matter intake (g d–1) and apparent digestibility in goats given graded levels of Lantana camara, commercial goat meal and veld hay
Parameter Treatment
GF 5%LC 10%LC 15%LC 20%LC 25%LC LSD
Basal diet (Veld hay intake) (g d−1) 236.8ab 266.5a 220.8b 232.8ab 254.0ab 230.9ab 43.41
Supplement ration intake (g d−1) 368.8a 350.5a 283.7b 151.5c 151.5c 124.9c 29.96
Total Dry matter intake (g d−1) 605.6a 617.0a 516.5b 405.6c 382.5cd 344.8d 55.86
Dry matter faecal elimination (g d−1) 228.2a 180.2b 165.4b 135.8c 133.2c 126.9c 25.21
Organic matter faecal elimination 213.2a 168.3b 154.5b 126.8c 124.4c 118.5c 23.55
Organic matter intake (g d−1) 540.5a 554.5a 464.9b 360.2c 340.6cd 306.3d 49.13
Digestible organic matter intake (g d−1) 212.0b 386.2a 309.5b 233.4c 216.2cd 187.8d 41.24
Metabolisable energy intake (MJ d−1) 5.14b 6.06a 4.85b 3.66c 3.40cd 2.95d 0.56
Apparent digestibility coefficient:
Dry matter digestibility 0.62c 0.71a 0.68ab 0.66ab 0.65ab 0.63bc 0.06
Organic matter digestibility 0.61c 0.70a 0.67ab 0.65abc 0.63bc 0.61bc 0.06
Means in the same row followed by different superscript letters are significantly different (P < 0.05), LC mean Lantana camara. 152
7.4.3 Nitrogen intake and retention
Goats given GF and 5%LC consumed significantly higher N in feed than the other goats on other treatments. 10%LC had significantly higher N intake value than 15%LC, 20%LC and
25%LC (Table 7-4), whereas 25%LC had significantly the lowest. The highest total N loss was observed in the group of goats given 10%LC, but the value was not significantly different from the groups given GF and 5%LC. Feed levels 10% -25% LC had the least N loss. Significantly higher N retention values were observed in groups fed on 5%LC and GF compared to the other groups (Table 7-4).
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Table 7-4: Nitrogen intake and retention (g d-1) in goats given graded levels of Lantana camara hay, commercial goat meal feed and a basal diet of veld hay
Parameter Treatment diet GF 5%LC 10%LC 15%LC 20%LC 25%LC LSD Nitrogen intake 12.00a 11.79a 9.78b 6.76c 6.40c 5.52d 0.91 Nitrogen in faeces 3.25 a 2.61ab 2.44ab 1.97b 1.81b 1.73b 0.85 Nitrogen in urine 2.31b 2.46b 3.64a 1.33c 1.34c 0.99c 0.63 Total nitrogen in faeces and urine 5.56 a 5.07a 6.08a 3.30b 3.15b 2.72b 1.32 Nitrogen retention 6.43 a 6.62a 3.60b 3.36b 3.25b 2.70b 1.63 Means in the same row followed by different superscript letters are significantly different (P < 0.05), LC = Lantana camara and GF = commercial goat feed.
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7.4.4 Excretion of purine derivatives and microbial protein production
The highest volume of purine derivatives were recorded in the group fed on 5%LC (Table 7-
5). Significantly high microbial protein supply was observed in groups fed 5% and 10% inclusion levels of L. camara than what was recorded with GF. The value was significantly different from the other treatments, followed by GF and the least was from the group fed
25%LC. Microbial protein production followed the same trend. Significantly high digestible microbial true protein (DMTP) value was recorded in 5%LC followed by GF and 10%LC and the lowest was on 25%LC. Significantly higher efficiency in microbial nitrogen supply per
DOMR was observed with 25%LC and the least in GF (Table 7-5).
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Table 7-5: Excretion of purine derivatives and microbial protein production by goats given graded levels of Lantana camara hay, commercial goat feed and veld hay as a basal diet
Parameter Treatment diets GF 5% LC 10% LC 15%LC 20%LC 25%LC LSD Allantoin (mmol d−1) 9.34b 11.95a 9.60b 7.59c 7.07c 6.26c 1.97 Microbial nitrogen yield (MNY) (g d−1) 6.79b 8.69a 7.01b 5.52c 5.14c 4.53c 1.69 Microbial true protein (MTP) (g d−1) 34.0b 43.5a 35.04b 27.6c 25.7c 22.7c 9.14 Digestible Microbial true protein (g d−1) 28.9b 36.9a 29.8b 23.4c 21.9c 19.3c 8.21 Fermentable organic matter in the rumen (g d-1) 212.0b 251.0a 201.0b 152.0c 141.0cd 122.0d 25.10
−1 c b b a a c Emns(g kg DOMR) 31.9 34.7 34.8 36.4 36.6 37.9 8.25 Means in the same row followed by different superscript letters are significantly different (P < 0.05), LC = Lantana camara and GF = commercial goat feed. Emns= efficiency of microbial nitrogen synthesis (AFRC 1993) DOMR = Digestible organic matter in the rumen.
156
7.4.5 Health status of the experimental animals
The period of study was not sufficient to measure growth, weight gain and overall production parameters, however a veterinarian satisfied the goats clinically health before the end of the study after 21 days. There was no significant difference on liver enzymes AST and ALT while the same was observed on urea, creatinine, and total protein. The values of all these haematological and haematochemical parameters recorded were within the normal range for goats. The results are graphical presented from in Figure 7-1 to Figure 7-5.
157
230
210
190 /litre
iu 170
150
130 Level of AST in AST in Levelof 110
90
70 1 2 3 4 Sampling periods
Control 5% L. camara 10% L. camara 15% L. camara 20% L. camara 25% L. camara normal level
Figure 7-1: Observed changes in liver enzyme aspartate aminotransferase (AST) concentration in iu/l in goat fed graded levels of Lantana camara leaf meal.
1= day 0 animals coming from the farm; 2= day 14 after adaptation period; 3 = day 15 and 4 = day 16, Control refers to goat feed
158
40
35
30
25
/litre iu
20
15 Level of ALT in in ALT Levelof
10
5
0 1 2 3 4 Sampling times
Control 5% L. camara 10% L. camara 15% L. camara 20% L. camara 25% L. camara normal level
Figure 7-2: Observed changes in liver enzyme alanine aminotransferase (ALT) (iu/L) concentration in blood during the feeding period with graded levels of Lantana camara leaf biomass hay.
1= day 0 animals coming from the farm; 2= day 14 after adaptation period; 3 = day 15 and 4 = day 16; Control refers to goat feed
159
80
75
70
65
60
Total protein g/lprotein Total 55
50
45
40 1 2 3 4 Sampling periods
Control 5% L. camara 10% L. camara 15% L. camara 20% L. camara 25% L. camara Normal level
Figure 7-3: Observed changes in total protein levels in grams per litre in goats fed with graded levels of Lantana camara leaf biomass hay
1= day 0 animals coming from the farm; 2= day 14 after adaptation period; 3 = day 15 and 4 = day 16; Control refers to goat feed
160
10
9
8
7
6
5
Urea in in Urea mmol/l 4
3
2
1
0 1 2 3 4 Sampling periods
Control 5% L. camara 10% L. camara 15% L. camara 20% L. camara 25% L. camara normal level
Figure 7-4: Observed changes in urea concentration in mmol/litre of blood in goats fed with graded levels of Lantana camara leaf biomass hay
1= day 0 animals coming from the farm; 2= day 14 after adaptation period; 3 = day 15 and 4 = day 16; Control refers to goat feed
161
170
150
130
110 ummol/l
90 Creatinine Creatinine 70
50
30 1 2 3 4 Sampling periods
Control 5% L. camara 10% L. camara 15% L. camara 20% L. camara 25% L. camara normal level
Figure 7-5: Observed changes in the level of creatinine in ummol/l in goats fed with graded levels of Lantana camara leaf biomass hay
1= day 0 animals coming from the farm; 2= day 14 after adaptation period; 3 = day 15 and 4 = day 16; Control refers to goat feed
162
All the experimental animals were examined and certified health by the veterinarian. There were no significant differences observed on heart rate, respiratory rate, and capillary refill time and temperature measurements (Table 7-6).
163
Table 7-6: Measured body temperature, heart rates and respiratory rates of goats fed graded levels of Lantana camara leaf meal.
Treatment Diet Body Temperature (T0C) Heart rate Respiratory rate 5% L. camara 39.5a 101a 31a 10% L. camara 39.9a 108a 21a 15% L. camara 38.7a 117a 28a 20% L. camara 38.7a 98a 24a 25% L. camara 38.4a 105a 27a Goat meal (Control Diet) 39.0a 88a 27a LSD 1.93 56.1 11.27 Means in the same column followed by different superscript letters are significantly different (P < 0.05),
164
7.5 Discussion
All the diets used in the study met the maintenance and fattening requirements for goats, whichis recommended to be above 80g CP per kg DM (AFRC, 1993; Mokoboki et al., 2005;
Mapiye et al., 2010). The level of CP was 150g /kg of DM, which was also above the recommended level hence it was supposed to be adequate to support the normal growth and production levels such as growth and fattening. In ruminants, feeds with lower crude protein
(CP) than 70 g/kg DM are known to reduce voluntary feed intake resulting in stunted growth and sub-optimal reproduction performance (Matizha et al., 1997; Ngongoni et al., 2007; Gusha et al., 2014).
The levels of total extractable phenolics (TEPH) were lower than those found in Acacia angustissima (8.1%) (Ncube et al., 2017), Calliandra calothyrsus(10.8%) andLeucaena leucocephala(7.6%)(Gusha et al., 2013) which are browse legume trees that have successfully been incorporated into livestock feeding systems as protein supplementary feed for poor roughage diets in communal areas and small-scale livestock production systems (Katsande et al., 2016, Ncube et al., 2017). The aforementioned have however, improved performance of goats and cattle when given as supplements to animals feeding on poor roughage grass straws in Zaka and at Makoholi Research Institute in Zimbabwe (Gusha et al., 2015, 2016). Based on the level of TEPH obtained in these formulated diets, using these diets to feed animals should not be detrimental to the animals’ health. The concentration of TEPH per unit DM was also lower than the values measured in L. camara leaves harvested in Harare (6.8 % of dry matter results shown in Chapter 5), these results show the importance of mixing it with other feed ingredients before feeding as it dilutes the concentration of anti-nutritional factors and other secondary metabolites. The concentrations become lower than the threshold of toxicity but producing a diet sufficient to meet the nutritional needs of the animal. 165
The average daily dry matter intake was above the minimum recommended of three percentage of the animal’s metabolic body weight (Mokoboki et al., 2005; Salem et al., 2007; Nasri et al.,
2011). However, animals fed on commercial formulated diets and those that were given diets with ≤10% L. camara biomass consumed more than what the goats in treatment with more than
10% L. camara inclusion rate consumed. The low intake observed with the increase in L. camara inclusion could be due to acceptability of the diets. The more the L. camara biomass included in the diet the stronger the smell in the diet. Plants have variable nature of secondary chemistry, which forms the basis for differential use within and among plant species (Shimada,
2006; Rogosic et al., 2008; Estell, 2010). There is varying preference for L. camara accessions by animals hence differential consumption pattern of the plant in different locations in
Zimbabwe as reported by farmers and observed by Gusha et al. (2016). Preference of browse intake is negatively affected by a wide array of secondary metabolites presented in the plants
(Salem et al., 2006). In particular, intake is affected by the concentration of phenolic compounds and tannins (Estell, 2010). Villalba et al. (2002); Provenza et al. (2003); Swihart et al. (2009); Feng et al. (2009) and Kambashi et al. (2014) reported that the concentration of condensed tannins, total phenolic, saponins and essential oils in a forage are good indicators of intake patterns in sheep and goats. The more the concentration of these anti-nutritional compound in a diet the less it is consumed. L. camara has some of the above-mentioned compounds hence the increase in inclusion level resulted in reduced intake in goats in this study.
The apparent organic matter digestibility coefficient was above 60% of kg dry matter. The observed high apparent organic matter digestibility coefficients give the impression that these diets were good enough for ruminants. The results are consistent with the results reported by
Osuga et al. (2008) that L. camara is high digestible. It is high in non-structural carbohydrates
166 and low in ADF (less than 31% of dry matter) as reported in chapter 5. Highly fermentable carbohydrates in a diet are good for microbial growth and production. If the highly fermentable metabolisable carbohydrates are coupled with highly digestible nitrogen also found in these diets, more efficiency in microbial protein production is expected. Therefore, animals under such feeding regimes and on these types of diets are expected to perform, thus improving growth and animal productivity.
In addition, a very high apparent N digestibility coefficient was obtained. However, it should be noted that this measurement is sometimes not a very useful parameter of measuring protein digestibility especially in ruminants. It does not reflect the true undigested dietary nitrogen since some of the nitrogen is undigested microbial protein, sloughed off cells of the gut lining and enzymes secreted into digestive tract (Kida et al., 2009; Kozloski et al., 2014). Gusha et al. (2015) reported that animals given poor quality grass straws incur a negative nitrogen retention due abrasion of epithelial wall. They may be an increase in metabolic faecal nitrogen from enzymes, sloughed off cells from digestive tract and microbial residues hence relying on these measurement especially apparent digestibility coefficient, may give a false indicator of what the animals may be getting (Kozloski et al., 2014). It is believed that grazing animals use conventional wisdom when eating highly fibrous diets and in most case may not eat these standing hays straws of poor quality in order not to incur a negative energy and nitrogen balance. In order to supply the rumen microbes with ammonia, the animals may have to increase breakdown its own muscle or turnover of body protein and this is an unnecessary cost incurred by animals grazing or feeding on straws and poor quality fibrous diets.
Higher N intakes were observed with diets that were highly palatable such as commercial diet and five percent L. camara. However, the opposite was observed with regards to N retention 167 with diets with more 15% of L. camara inclusion levels producing higher N retention values.
This could be because that the lower the DM intake or rumen-fill, the longer the rumen residence time for the feed to be degraded by microbes (Ngongoni et al., 2007) and the higher the digestibility coefficient. In addition, animals feeding on forages with plant secondary metabolites evolve a variety of intertwined mechanisms to cope with consumption of these compounds. Some of the coping strategies range from physiological to behavioural mechanisms which include regulation of intake below critical threshold, cautious sampling, altering size and pattern of feeding bout, diet switching, consuming diverse and complementary diets (Estell, 2010). The results show that the animals regulated their daily dry mater and N intake probably to reduce the concentration of unwanted substances entering the rumen as low intake levels were recorded on diets with higher levels of L. camara. The regulation of intake in turn causes a shift in sites of digestion hence higher apparent digestibility coefficient and N retention values were observed on diets with lower intake and higher L. camara level.
Allantoin values ranging between 6.25 and 11.95 mmol per day in 25% and 5% L. camara inclusion rate respectively, were observed which were higher than value reported by Katsande et al., 2015). In sub primate mammals, purine metabolism produces uric acid, which is oxidised to allantoin before being excreted in urine (Chen and Gomes, 1992). Therefore, the level of allantoin or total urinary purine derivatives (TUPD) namely allantoin, uric acid, xanthine, hypoxanthine and hypuric acid are used to estimate microbial protein production. Allantoin has been used more often to estimate microbial protein production (MPP) as it constitute 85% of the total urinary purine derivatives and there was no significant difference in MPP estimates when allantoin and TPD were used to estimate total microbial protein production. Diets with
L. camara recorded high levels of MPP and the process of defaunation could not be ruled out
168 as a possible reason why there were significantly higher MPP and efficiency of microbial nitrogen supply in groups of animals fed on diets with higher levels of L. camara. In animal feeding studies, where animals are fed with forages high in PSM, it have been reported that compounds such as phenolic compounds could be toxic to rumen cellulolytic bacteria (Pfister,
1999; Lauchbaugh et al., 2001). Poisoning of rumen cellulolytic bacteria resulted in lowering fibre degradation in the rumen (Swihart et al., 2009).However, the presence of saponins may cause defaunation of ruminal protozoa thus promoting an increase in microbial nitrogen flow from rumen as well as a decrease in methane gas production (Rogosic et al., 2008; Estell, 2010;
Pfister et al., 2010). However, in this study, there is no evidence of reduced degradation and hence toxicity to rumen cellullytic bacteria could be ruled out because of the very high apparent digestibility recorded.
There was absence of ill health in all the goats in the study. The levels of liver enzymes, which are supposed to increase with increase in stress and toxin levels, did not differ as well. Leakage enzymes are an indicator of liver integrity or injuries or death of liver cells (Teoh, 2011). The increase of AST and ALT in the blood indicates the damages done to the liver cell (Gwaze et al., 2012) hence from the evidence from this study, no damages were observed based on the values obtained. The twenty five percent L. camara inclusion level was safe to this class of ruminant because no signs of ill health were observed by the veterinarian hence the diets were not poisonous. The results also could be interpreted as showing that the animals were consuming diets, which had lower level of toxins to induce toxicity. Goats fed on diet with high level of L. camara biomass consumed lower quantities as compared to goat given low L. camara inclusion rate and probably that was a coping strategy.
169
Creatine is a by-product of muscle breakdown, which is oxidised to creatinine and then excreted in urine (Guan et al., 2013). It is expected that an animal subsiding on a diet that is deficient in nutrients, higher levels of creatinine than normal are recorded. The animal will be breaking down its own muscle to supply nutrients for vital processes of the body to continue functioning. In this study, the values recorded were lower than the normal range in all treatment diets. Therefore, we can safely say the diets were good enough to meet the nutrient demands of the goats. There was no average weight gain or loss over the period hence we could not deduce the influences of these diets on growth and overall performance of the animals.
7.6 Conclusion
We conclude that L. camara can produce good quality forage, which can be conserved as hay for dry season supplementary feeding. Twenty-five percent L. camara leafy biomass inclusion level was safe but affected voluntary feed intake. Therefore, this study recommend a maximum of 15% and below which produced better dry matter intake and performances that were comparable to the conventional supplementary feed. More research is needed to determine the long-term performance of the animals. In all the treatments, the average daily dry matter intake was above the minimum recommended of 3% of the animal’s metabolic body weight. Higher nitrogen intakes were observed with diets that were highly palatable such as commercial diet and 5% L. camara. Higher microbial protein supply was observed in groups fed diets with high levels of L. camara. Further studies are required to confirm that the high microbial protein production levels recorded in this study can be repeated with other ruminant species and to determine acceptability and intake levels.
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7.7 References
AOAC. 2000. Official methods of analysis (16th ed., Vol. I) Association of Official Analytical
Chemists. Washington, DC.
Caldeira, R.M., Belo, A.T., Santos, C.C., Vazques, M.I., Portugal, A.V. 2007. The effect of
long-term feed re-striction and over-nutrition on body condition score, blood metabolites
and hormonal profiles in ewes. Small Ruminant Research, 68: 242‒255.
Chatanga, P. 2007. Impact of the invasive alien species, Lantana camara (L). on native
vegetation in northen Gonarezhou National Park, Zimbabwe. University of Zimbabwe.
Chen, X.B., Gomes, M.J. 1992. Estimation of microbial protein supply to sheep and cattle
based on urinary excretion of purine derivatives- An overview of the technical details.
Rowett Research Institute. University of Aberdeen, UK.
Day, M.D., Playford, W.J., Zalucki, M.P. 2003. Lantana: current management status and
future prospects. Canberra: ACIAR.
De Ondarza, M.B., Engstrom, M. 2009. Production and Reproduction Responses of Dairy
Cows to Supplemental Beta-carotene. In Penn State Dairy Cattle Nutrition Workshop. de Ondarza, M.B. 2008, March. Bacterial direct-fed microbials for dairy cows: Theory and
practice. In conference sponsors: 50.
Dewhurst, R.J., Davies, D.R., Merry, R.J., 2000. Microbial protein supply from the
rumen. Animal Feed Science and Technology, 85(1&2):1-21.
Estell, R.E. 2010. Coping with shrub secondary metabolites by ruminants. Small Ruminant
Research, 94(1):1-9.
171
Feng, Z., Liu, R., DeAngelis, D.L., Bryant, J.P., Kielland, K., Chapin, F.S., Swihart, R.K. 2009.
Plant toxicity, adaptive herbivory, and plant community
dynamics. Ecosystems, 12(4):534-547.
Ghisalberti, E.L. 2000. Review: Lantana camara. Fitoterapia, 71: 467-486.
Goering, H.K., Van Soest, P.J. 1970. Forage fiber analyses (apparatus, reagents, procedures,
and some applications). USDA Agricultural Handbook No 379, Agricultural Research
services, Washington D.C, USA.
Guan, M., Xie, L., Diao, C., Wang, N., Hu, W., Zheng, Y., Jin, L., Yan, Z., Gao, H. 2013.
Systemic perturbations of key metabolites in diabetic rats during the evolution of diabetes
studied by urine metabolomics. PloS one, 8(4):604-09
Gusha, J., Halimani, T.E., Katsande, S., Zvinorova, P.I. 2014. Performance of goats fed on low
quality veld hay supplemented with fresh spiny cactus (Opuntia megacantha) mixed with
browse legumes hay in Zimbabwe. Tropical Animal Health and Production, 46(7):1257-
1263.
Gusha, J., Halimani, T.E., Ngongoni, N.T., Ncube, S. 2015. Effect of feeding cactus-legume
silages on nitrogen retention, digestibility, and microbial protein synthesis in
goats. Animal Feed Science and Technology, 206:1-7.
Gusha, J., Masocha, M., Mugabe, P.H. 2017. Impact of grazing system on rangeland condition
and grazing capacity in Zimbabwe. The Rangeland Journal, 39(3): 219-225.
Gusha, J., Masocha, M., Muchaya, K., Ncube, S. 2016. Chemical analysis of the potential
contribution of Lantana camara to the nutrition of browsing livestock. Tropical and
Subtropical Agroecosystems, 19(3):29-36.
172
Gusha, J., Ngongoni, N.T., Halimani, T.E. 2013. Nutritional composition and effective
degradability of four forage trees grown for protein supplementation. Online Journal of
Animal Feed Research, 3(4):170-175.
Gwaze, F.R., Chimonyo, M., Dzama, K., 2012. Effect of season and age on blood minerals,
liver enzyme levels, and faecal egg counts in Nguni goats of South Africa. Czech Journal
Animal Science, 57(10):443-453.
International Atomic Energy Agency (IAEA). 1997. Estimation of rumen microbial protein
production from purine derivatives in urine. A laboratory manual for FAO/IAEA Co-
ordinated Research Programme. IAEA-TECDOC-945, IAEA, Vienna
Kambashi, B., Picron, P., Boudry, C., Thewis, A., Kiatoko, H., Bindelle, J. 2014. Nutritive
value of tropical forage plants fed to pigs in the Western provinces of the Democratic
Republic of the Congo. Animal Feed Science and Technology, 191:47-56.
Katsande, S., Baloyi, J.J., Nherera-Chokuda, F.V., Ngongoni, N.T., Matope, G., Zvinorova,
P.I., Gusha, J. 2016. Apparent digestibility and microbial protein yield of Desmodium
uncinatum, Mucuna pruriens and Vigna unguiculata forage legumes in goats. African
Journal of Range and Forage Science, 33(1):53-58.
Kida, Y. 2009. Estimation of protein intake using urinary urea nitrogen in patients with liver
cirrhosis. Scandinavian Journal of Gastroenterology, 44(5):615-618.
Kozloski, G.V., Oliveira, L., Poli, C.H.E.C., Azevedo, E.B., David, D.B., Ribeiro Filho,
H.M.N., Collet, S.G. 2014. Faecal nitrogen excretion as an approach to estimate forage
intake of wethers. Journal of Animal Physiology and Animal Nutrition, 98(4):659-666.
Launchbaugh, K.L., Provenza, F.D., Pfister, J.A. 2001. Herbivore response to anti-quality
173
factors in forages. Journal of Range Management, 54:431-440.
Mapiye, C., Chimonyo, M., Dzama, K., Marufu, M.C. 2010. 29 Protein Status of Indigenous
Nguni and Crossbred Cattle in the Semi-arid Communal Rangelands in South
Africa. Asian-Australasian Journal of Animal Sciences, 23(2):213-17.
Masama, E., Topps, J.H., Ngongoni, N.T., Maasdorp, B.V. 1997. Effects of supplementation
with foliage from the tree legumes Acacia angustissima, Cajanus cajan, Calliandra
calothyrsus and Leucaena leucocephala on feed intake, digestibility and nitrogen
metabolism of sheep given maize stover ad libitum. Animal Feed Science and
Technology, 69(1&3):233-240.
Masocha M, Dube, T., Skidmore, A., Holmgren, M., Prins H. 2017. Assessing effect of rainfall
on rate of alien shrub expansion in a southern African savanna. African Journal of Range
and Forage Science, 34 (1):39-44.
Matizha, W., Ngongoni, N.T., Topps, J.H. 1997. Effect of supplementing veld hay with tropical
legumes Desmodium uncinatum, Stylosanthes guianensis and Macroptilium
atropurpureum on intake, digestibility, outflow rates, nitrogen retention, and live weight
gain in lambs. Animal Feed Science and Technology, 69(1):187-193.
Mokoboki, H.K., Ndlovu, L.R., Ng'ambi, J.W., Malatje, M.M. Nikolova, R.V. 2005. Nutritive
value of Acacia tree foliages growing in the Limpopo Province of South Africa. South
African Journal of Animal Science, 35(4):221-228.
Nasri, S., Salem, H.B., Vasta, V., Abidi, S., Makkar, H.P.S., Priolo, A. 2011. Effect of
increasing levels of Quillaja saponaria on digestion, growth, and meat quality of Barbarine
lamb. Animal Feed Science and Technology, 164(1):71-78.
174
Ncube, S., Halimani, T.E., Tivapasi, M.T., Dhliwayo, S., Chikosi, E.V.I., Saidi, P.T. 2017.
Stomach adaptations of broilers fed Acacia angustissima leaf meal based diets. Online
Journal Animal Feed Research, 7(3):27-43.
Ngongoni, N.T., Mapiye, C., Mwale, M., Mupeta, B. 2007. Effect of supplementing a high-
protein ram press sunflower cake concentrate on smallholder milk production in
Zimbabwe. Tropical Animal Health and Production, 39(4):297-306.
Osuga, I.M., Abdulrazak, S.A., Ichinohe, T., Fujihara, T. 2005. Chemical composition,
degradation characteristics and effect of tannin on digestibility of some browse species
from Kenya harvested during the wet season. Asian-Australian Journal of Animal
Science, 18(18):54-60.
Osuga, I.M., Wambui, C.C., Abdulrazak, S.A., Ichinohe, T., Fujihara, T. 2008. Evaluation of
nutritive value and palatability by goats and sheep of selected browse foliages from
semiarid area of Kenya. Animal Science Journal, 79(5):582-589.
Pfister, J.A. 1999. Behavioral strategies for coping with poisonous plants. K. Launchbaugh,
KL, KD Sanders, and JC Mosley [EDS.]. Grazing behavior of livestock and wildlife.
Moscow, ID: Idaho Forest, Wildlife, and Range Experimental Station Bulletin, 70: 45-59.
Pfister, J.A., Gardner, D.R., Cheney, C.C., Panter, K.E., Hall, J.O. 2010. The capability of
several toxic plants to condition taste aversions in sheep. Small Ruminant
Research, 90(1):114-119.
Provenza, F.D., Villalba, J.J., Dziba, L.E., Atwood, S.B., Banner, R.E. 2003. Linking herbivore
experience, varied diets, and plant biochemical diversity. Small Ruminant
Research, 49(3):257-274.
175
Reitman, S., Frankel, S. 1957. A colorimetric method for the determination of serum glutamic
oxalacetic and glutamic pyruvic transaminases. American Journal of Clinical
Pathology, 28(1):56-63.
Rogosic, J., Estell, R.E., Ivankovic, S., Kezic, J., Razov, J. 2008. Potential mechanisms to
increase shrub intake and performance of small ruminants in Mediterranean shrubby
ecosystems. Small Ruminant Research, 74(1):1-15.
Salem, A.Z.M., Robinson, P.H., El-Adawy, M.M., Hassan, A.A. 2007. In vitro fermentation
and microbial protein synthesis of some browse tree leaves with or without addition of
polyethylene glycol. Animal Feed Science and Technology, 138(3):318-330.
SAS Institute (2010). SAS/STAT user's guide. 9th Edn. (SAS Institute, Cary).
Schalm, O.W., Jain, N.C., Carroll, E.J. 1975. Veterinary Haematology (No. 3rd edition). Lea
and Febiger, USA.
Sharma, G.P., Raghubanshi, A.S., Singh, J.S. 2005. Lantana invasion: an overview. Weed
Biology and Management, 5(4), pp. 157-165.
Shimada, T. 2006. Salivary proteins as a defense against dietary tannins. Journal of Chemical
Ecology, 32(6), pp. 1149-1163.
Swihart, R.K., DeAngelis, D.L., Feng, Z., Bryant, J.P. 2009. Troublesome toxins: time to re-
think plant-herbivore interactions in vertebrate ecology. BMC ecology, 9(1), p.5.
Teoh, N.C. 2011. Hepatic ischemia reperfusion injury: contemporary perspectives on
pathogenic mechanisms and basis for hepatoprotection—the good, bad and
deadly. Journal of Gastroenterology and Hepatology, 26, pp.180-187
Villalba, J.J., Provenza, F.D., Bryant, J.P. 2002. Consequences of the interaction between 176 nutrients and plant secondary metabolites on herbivore selectivity: benefits or detriments for plants? Oikos, 97(2): 282-292.
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CHAPTER EIGHT
8 General discussion and recommendations
8.1 Introduction
The chief objective of this thesis was to investigate and gain an understanding of the threats and opportunities presented by invasive plant species of savanna rangelands in Zimbabwe.
Three major plants, two grass species and one alien invasive plant were used as key model invasive plants to determine their threats and opportunities. Widespread rangeland invasion have been reported worldwide and research has mostly focused on their negative attributes and the methods of eradicating these species. Chemicals, biological control, and mechanical methods have been implemented in pursuit of control of L. camara invasion but very little success has been recorded. On the other hand, grasses with low forage quality are not grazed under extensive grazing where selective grazing is high, resulting in high volumes of biomass.
The biomass is burnt during the dry season destroying the environment, life, and property and according to Herald issue of 03/10/2017; it is reported that over the years, an average of one million hectares are destroyed annually. Because, research has focused on control through eradication or introducing better pastures, little has been done to identify opportunities of incorporating these biomass in livestock feed and improve feed availability and animal production.
This thesis has several chapters aimed at answering the research question of whether invasive plant species are a threat or an opportunity for future livestock farmers. The thesis looked at community perceptions about their rangelands, the link between farming systems and the widespread of invasive plant species, different methods of conservation, periods of harvesting
178 and nutritive values, and the response of animals feeding L. camara at graded levels of inclusion in their diets.
In this final chapter, the main results from the previous chapters are brought together. This was done to understand clearly the main threats or opportunities presented by these invasive plant species. The opportunities presented by these species are highlighted and applicability of our results to other problematic species in other locations is discussed. Finally, we highlighted the practical relevance of the thesis in managing and utilisation of invasive plant species. Three suggestions for future research are made in order to continuous interrogate challenges associated with the increase in invasive plant species in rangelands.
8.2 Do farming communities observe the decline in quality of grazing and the increase in less palatable plant species?
Floristic composition changes were observed by the farming communities. These changes together with rangeland degradation and shortage of forage for livestock production have been pointed out as causes for the failures of poverty alleviation programmes in rural communities
(Pejchar and Mooney, 2009). The changes in floristic composition is consistent with the finding observed in Namibia (Sheuyange et al., 2005; Stafford et al., 2016), in South Africa (Vetter,
2003; Ward, 2005) and Saudi Arabia (Al-Rowaily, 2003). More shrubs such as Helichrysum kraussii, L. camara, Dodonaea viscosa, Dichrostachys cinerea, Acacia species, and stretches of Terminalia sericea were reported to be the main shrubs in different provinces of Zimbabwe.
The increase in these species increase the competition for soil moisture and nutrients hence there is low yield of desirable grass biomass for livestock production (Scholes and Archer,
1997; Kraaij and Ward, 2006; Setterfield et al., 2014). Reports of reduced grazing capacity with increase in shrub were documented by (Sheuyange et al., 2005; Vetter, 2005; 2013, Gusha et al., 2017) and in this thesis the decrease in grazing capacity was observed in all the study
179 sites. A botanical survey conducted in Masvingo revealed that in most areas of Zimuto communal area and Gutu, more grazing land is now required to sustain one livestock unit (>65 ha/LU) (Gusha et al., 2017). This implies that for profitable livestock production more outsourced feeds should be made available. Outsourcing feeds will not be a sustainable option because most communal and small-scale commercial farmers are financially crippled.
Livestock production especially cattle production will become an expensive enterprise to venture on in all our communities if this decline grazing capacity due to increase invasive species continues unchecked. Grass species changes were also reported with less palatable and wiry grasses becoming the dominant and key forage resources available for grazing (Gusha and Mugabe, 2013; Gusha et al., 2016a; 2017). Stretches of H. filipendula and H. dissoluta were observed and were not readily grazed by livestock. This has caused a decrease in animal performance as reported by Mavedzenge et al., (2006). Furthermore, the reduction in reproductive performance reported by other scholars such as Ngongoni et al., (2007) and
Tavirimirwa et al., (2012) could be attributed to these changes. The low quality forage available may fail to meet the nutrient demand for grazing livestock leading to stunted growth, sub- optimal reproduction performance, and high mortality. Impenetrable thickets of thorny shrubs also reduce available land for productive purposes. On the other hand, shrub thickets that harbour wild pigs and other predators were detrimental to community livelihoods. These results are in agreement with results and problems associated with savanna rangelands in most communal farming system in South Africa and Botswana as reported by Vetter (2003; 2013) and Ward 2005 hence the need to find lasting solutions. Rangelands that are continuously grazed are the worst affected among the studied sites, therefore there is a need to shift from the traditional common property grazing system to a self-contained type of grazing where farmers put enough commercial value to their rangelands.
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8.3 Is there a link between farming systems and rangeland deterioration?
Results obtained in this thesis reflected that there is a strong link between farming system and the decline in grazing quality as well as the rate of rangeland invasions. Shrubs and invasive plant species such Helichrysum kraussii, L. camara, Dodonaea viscosa, Dichrostachys cinerea, Vachellia species and stretches of Terminalia sericea were observed in most communal farming systems and where non-existent in commercial farming systems. This consistent with previous results reported by Masocha (2010) in Zimbabwe, Vetter (2009) and
(2013) in communal farming area in South Africa and by Gusha et al,(2017)where communal rangelands collapsed due to high stocking number and continuous grazing. Communal grazing is the most deleterious grazing system promoting the increase in less palatable grasses and shrub invasion. The carrying capacity has declined severely in Gutu, Shurugwi and Masvingo districts of Zimbabwe. There is need to stimulate community ownership of these rangelands so that all stakeholders participate in rangeland management and control grazing animal movements. Creating paddocks could help but previous expensive has shown that as long as not all community members are in the schemes, it is likely to fail. There were reports of high vandalisation of fences installed by the government and development partners in most resettlement areas in Zimbabwe. Community participation in rangeland resources management, where village heads could be assigned the tasks of controlling animal movements to avoid over exploitation of natural resources. This study also reaffirmed the findings by
Cousins (1992) that diagnosed communal grazing and land ownership as the most detrimental tenure systems hence the need to shift from this type of tenure to a more secure land ownership forms.
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8.4 Which invasive plant species are dominant in Zimbabwean rangelands
The dominant plant species found in this study vary greatly according to region, soil type and rainfall amount received in the region. Helichrysum kraussii was dominant in sandy soils, especially in Masvingo and Midlands provinces. In H. kraussii invaded rangelands in Zimuto and Serima communal area in Zimbabwe grazing capacity of the rangelands were reduced from an average of 5-10 to more than 65 hectares livestock unit (Gusha et al., 2017). On the other hand, L. camara was observed in all provinces of Zimbabwe including urban centre (Gusha et al., 2016b) with largest quantities found in low-lying areas or water chains. Thorny shrubs such as Vachellia species and Dichrostachys cinerea were observed in Shurugwi, Masvingo, and
Magunje in Zimbabwe. Thickets of these thorn shrubs have made animal movements difficulty during grazing and some areas are no longer usable especially in Masvingo and Shurugwi.
Large quantities of H. filipendula and H. dissoluta were observed throughout the country along highway roads and in abandoned arable lands. The observation offers opportunity for utilisation of these resources, as they are abundant in most areas especially the L. camara, H. filipendula, and H. dissoluta.
8.5 Nutritive value of the some invasive plant species
Harvesting H. filipendula, and H. dissoluta at eight –ten weeks from the onset of the rainy season has yielded the best forage quality. At early reproductive/flowering stage both H. filipendula, and H. dissoluta produced good quality silage with above 80 per kilogram crude protein density. Both conservation methods (silage and hay making) can be used depending on the availability of proper storage facilities. For smallholder dairy and beef farmers, silage could be made using polythene bags with little addition of molasses as demonstrated in this study.
Drying chopped H. filipendula, and H. dissoluta herbaceous biomass harvested at eight –ten
182 weeks from the onset of the rainy season could be done on small-scale at farm level. At that growth stage both hay and silage were high nutrition with high apparent digestibility coefficient. This implies that harvesting and conserving as hay or silage could increase biomass available for livestock feed and at the same time bridging the perennial feed deficit gap that exists during the dry season in Zimbabwe and most tropical African countries.
The quality of conserved feed was above the minimum requirements for maintenance for ruminant animals hence utilization of the study invasive plant species is a feasible opportunity to increase livestock production despite the decline in grazing area and capacity. Using the forage could in turn reduce accumulation of biomass, which fuel high intensity veld fire, and put both the lives of human and animals at risk. This therefore, implies that this thesis presents possible solutions to threats presented by invasive grasses species since identified harvesting and conservation methods could help as follows:(1) Bridging the perennial quality and quantity feed deficit gap, which occur, annually from April to November throughout the country and beyond our borders. (2) Reducing the accumulation of biomass which fuel high intensity fire resulting in destruction of properties, human and animal life and ecosystem functioning. High intensity wild fires are a perennial problem in Zimbabwe and it is estimated that over one million hectares of grazing land are destroyed every season, thus producing large quantities of carbon and increasing global warming.
On the other hand, L. camara harvested from different location had high CP value more 220 grams per kilogram dry matter, which is comparable or better than the values, reported in many studied forage legumes such as Vachellia species and L. leucocephala, which are often used as protein supplements. The levels of total extractable phenolics varied with location but were lower than the concentrations in Calliandra calothyrsus and Acacia angustissima. The animals fed on this biomass did not show any detrimental effects. This therefore implies that L. camara
183 has plant secondary metabolites levels, which could be regulated by grazing animal provided there is adequate grass biomass to complement Lantana camara intake.
8.6 The threats and opportunities of using invasive plant species as animal feeds
The major threat observed in this thesis are to do with decline in grazing capacity, increase in wild fire intensity and occurrence and the creation of impenetrable thickets with the increase in invasive plant species both grass and shrub species. Less palatable grasses do not contribute much to the grazing livestock and at the same time, they outcompete palatable grass species in terms of growth and productivity. With some having been reported to have allelopathic properties, these invasive plant species can destroy palatable forage grass with good forage value (Gusha et al., 2017) resulting in rangelands with wiry grasses and shrubs that do not support livestock production. Shrubs were seen to have formed impenetrable thickets that affect animal movement, lower the value of agricultural land, and harbour predators, which destroy livestock and crops. Furthermore accumulation of their leaf biomass fuel high intensity veld fire which destroy the ecosystem life and properties. High intensity fire could also possibly contribute to carbon dioxide in the atmosphere thus contributing to global warming. These species also affects poverty alleviation production and other livelihood projects.
The opportunities for use as silage and hay for livestock seems to be the main control strategy available with regards to these species. High quality silage was made and good quality hay was made from both grasses and lantana leaf biomass. This study also highlighted the need to understand that all plants have secondary metabolites and animals have to cope with these anti- nutritional factors. The consequences range from harmless to lethal depending on factors such as dose, animal species, plane of nutrition and the physiological status of the animal (Provenza et al., 2003; Rogosic et al., 2006; Estell, 2010). 184
8.7 Practical relevance of this thesis
This work is the first of its own kind, changing the focus from eradicating invasive plant species or neglecting native grass to finding the potential feeding values of these invasive plant species of savanna rangelands. The belief that anything exotic is good should be removed and native grasses that are very much adaptable and thriving in savanna rangelands should be harnessed for the beneficiation of humankind. Anyone with animals can make feeds using these species and obtain higher returns from animal production. The feeding levels described in the previous
Chapters could be implemented at farm level. The other invasive plant species could be used in this manner.
8.8 General conclusion
The major aim of this thesis was to assess the potential uses of invasive plant species in livestock production system through evaluating their threats and opportunities if used as livestock feed resources. The general conclusion of this work is that there is a decline in rangeland condition and grazing capacity with the increase in woody plant species. Secondly, this thesis demonstrated that there is a link between grazing system and the widespread of woody shrubs such as H. kraussii and L. camara, as well the increase in less palatable grass species such as H. filipendula, S. pyramidalis, and H. dissoluta. Thirdly, it clearly showed that grass species such as H. filipendula and H. dissoluta, if harvested and conserved as hay or silage at early flowering stage or ten weeks from the onset of rains have high nutrient composition and digestibility coefficient. On the other hand, L. camara dried hay has high nutrient composition especially the crude protein content that was found to be above 220g/kg
DM. The high nutrient composition indicate that these plant species which are the current predominant plant species in communal rangelands have high potential of supporting
185 maintenance and fattening requirement of grazing animals such as goats and cattle. However, restrictive feeding method may be used until further studies are carried on effects on long-term performance of animal feeding on L. camara biomass.
Therefore, invasive plant species studied in this thesis can contribute to livestock production when appropriate harvesting stage and conservation techniques are applied while at the same time minimising the risks associated with their increase in savanna rangelands. The conserved feed material could be used during periods of feed scarcity and curb the decline in animal body condition as well as the increase animal mortality during the same periods. A planned use of these plant species could in turn help in controlling their invisibility. Given that these species will be selectively harvested and conserved, the other rangelands desirable species may also benefit because of the reduced competition from these species for soil nutrients and may gain ground to replenish and grow.
8.9 Suggestions for future research
Three suggestions were made for future research out of this thesis. Firstly, the impact of H. kraussii observed in most rangelands on production capacity of those areas should be considered. This investigation would inform rangeland scientist on how best to improve the condition of rangeland as well as provide solutions to improve livestock production under those conditions.
Secondly, long-term animal performance research should be carried out to investigate the performance of animals feed on hay and silage made from H. filipendula and H. dissoluta. The results on economic performance will go a long way on convincing farmers to use these grass species. The response of animals will remove any doubts among scientists resulting in adoption and utilisation of invasive plant species.
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Thirdly, the long-term ramifications of feeding L. camara on fertility, longevity and the whole production cycle need great attention. Furthermore, changes that take place in the rumen microflora after feeding needs thorough investigation to ensure that detrimental effects on digestion are controlled. Also understanding the mechanism of adaptation to toxins in these plants should also be investigated. Insights from these suggested future researches may contribute towards how best these invasive plant species could be utilised.
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8.10 References
Al-Rowaily, S.L. 2003. Present condition of rangelands of Saudi Arabia: Degradation steps
and management options. Arab Gulf Journal of Scientific Research, 21(3):188-196.
Cousins, B. 1992. Managing communal rangeland in Zimbabwe: Experiences and lessons,
London: Food Production and Rural Development Division, Commonwealth Secretariat.
Estell, R.E. 2010. Coping with shrub secondary metabolites by ruminants. Small Ruminant
Research, 94(1): 1-9.
Gusha, J., Mugabe, P.H. 2013. Unpalatable and wiry grasses are the dominant grass species in
semi-arid communal rangelands in Zimbabwe International Journal of Development
and Sustainability, 2 (2): 1075–83.
Gusha, J., Masocha, M., Muchaya, K., Ncube, S. 2016a. Chemical analysis of the potential
contribution of l. camara to the nutrition of browsing livestock. Tropical and
Subtropical Agro ecosystems, 19: 337–42.
Gusha, J., Masocha, M., Mugabe, P.H. 2017. Impact of grazing system on rangeland condition
and grazing capacity in Zimbabwe. The Rangeland Journal, 39(3): 219-225.
Gusha, J., Mugabe P.H., Masocha, M., Halimani T.E. 2016b. Invasive species impacts and
management in communal rangelands in Zimbabwe Grassroots, 16 (4): 45–49.
Kraaij, T., Ward, D. 2006. Effects of rain, nitrogen, fire and grazing on tree recruitment and
early survival in bush-encroached savanna, South Africa. Plant Ecology, 186(2): 235-
246.
Masocha, M. 2010. Savanna aliens. Ph.D thesis, Wagengin University, The Netherlands
Mavedzenge, B.Z., Mahenehene, J., Murimbarimba, F., Scoones, I., Wolmer, W. 2006.
Changes in the livestock sector in Zimbabwe following land reform: the case of Masvingo 188
province. Institute for Development Studies, Brighton, available from: http://www. Ids.
ac. uk/index. cfm.
Ngongoni, N.T., Mapiye, C., Mwale, M., Mupeta, B. 2007. Effect of supplementing a high-
protein ram press sunflower cake concentrate on smallholder milk production in
Zimbabwe. Tropical animal health and production, 39(4):297.
Pejchar, L., Mooney, H.A. 2009. Invasive species, ecosystem services and human well-being.
Trends in ecology and evolution, 24(9): 497-504.
Provenza, F.D., Villalba, J.J., Dziba, L.E., Atwood, S.B., Banner, R.E. 2003. Linking herbivore
experience, varied diets, and plant biochemical diversity. Small ruminant research, 49(3):
257-274.
Rogosic, J., Estell, R.E., Ivankovic, S., Kezic, J., Razov, J. 2008. Potential mechanisms to
increase shrub intake and performance of small ruminants in Mediterranean shrubby
ecosystems.Small Ruminant Research, 74(1): 1-15.
Scholes, R.J. and Archer, S.R., 1997. Tree-grass interactions in savannas. Annual review of
Ecology and Systematics, 28(1): 517-544.
Setterfield, S.A., Rossiter-Rachor, N.A., Douglas, M.M., McMaster, D., Adams, V.M.,
Ferdinands, K. 2014. The impacts of Andropogon gayanus (gamba grass) invasion on the
fire danger index and fire management at a landscape scale. In 19th Australasian Weeds
Conference, Hobart, Tasmania. (Ed. M. Baker.) : 125-128).
Sheuyange, A., Oba, G., Weladji, R.B. 2005. Effects of anthropogenic fire history on savanna
vegetation in northeastern Namibia. Journal of Environmental management, 75(3): 189-
198.
189
Stafford, W., Birch, C., Etter, H., Blanchard, R., Mudavanhu, S., Angelstam, P., Blignaut, J.,
Ferreira, L., Marais, C. 2017. The economics of landscape restoration: benefits of
controlling bush encroachment and invasive plant species in South Africa and Namibia.
Ecosystem Services, 27: 193-202.
Tavirimirwa, B., Manzungu, E., Ncube, S. 2012. The evaluation of dry season nutritive value
of dominant and improved grasses in fallows in Chivi district, Zimbabwe. Online Journal
of Animal Feed Research, 2(6): 470-474.
Vetter, S. 2003. What are the costs of land degradation to communal livestock farmers in South
Africa?: the case of the Herschel District, Eastern Cape (Doctoral dissertation, University
of Cape Town)
Vetter, S. 2005. Rangelands at equilibrium and non-equilibrium: recent developments in the
debate. Journal of Arid Environments, 62(2): 321-341.
Vetter, S. 2009. Drought, change, and resilience in South Africa's arid and semi-arid
rangelands. South African Journal of Science, 105(1-2): 29-33.
Vetter, S. 2013. Development and sustainable management of rangeland commons–aligning
policy with the realities of South Africa's rural landscape African journal of range and
forage science, 30(1-2): 1-9.
Ward, D. 2005. Do we understand the causes of bush encroachment in African savannas?
African Journal of Range and Forage Science, 22(2): 101-105.
190