Chemical Composition, Nutritive Value and Voluntary Intake of Tropical Tree Foliage and Cocoyam in Pigs
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Journal of the Science of Food and Agriculture J Sci Food Agric 85:1725–1732 (2005) DOI: 10.1002/jsfa.2177 Chemical composition, nutritive value and voluntary intake of tropical tree foliage and cocoyam in pigs† Pascal Leterme,1∗ Angela M Londono,˜ 1 Fernando Estrada,1 Wolfgang B Souffrant2 and Andre´ Buldgen3 1Universidad Nacional de Colombia, sede Palmira, Carrera 32, Palmira (Valle), Colombia 2Research Institute for the Biology of Farm Animals (FBN), Department of Nutritional Physiology ‘O. Kellner’, D-18196 Dummerstorf, Germany 3Faculte´ universitaire des Sciences agronomiques, B-5030 Gembloux, Belgium Abstract: The composition of the leaves of cocoyam (Xanthosoma sagittifolium) and of two trees (Trichanthera gigantea and mulberry, Morus alba), their nutritive value in pigs and voluntary intake by pigs were determined. The average protein content ranged from 170 to 240 g kg−1 dry matter (DM) and that of neutral detergent fibres from 218 to 398 g kg−1 DM. The leaves are interesting sources of calcium (up to 69 g kg−1 DM), potassium, iron and manganese. The proteins are well balanced in essential amino acids, with lysine ranging from 43 to 57 g kg−1 proteins. The apparent faecal digestibility was determined by difference in 35 kg pigs fed a diet containing 35% leaf meal. The digestibility coefficients of DM, N and energy were, respectively, 47–57, 33–36 and 51–53%. The digestible energy value ranged from 1.674 to 2.037 kcal kg−1 DM. The voluntary intake of Trichanthera and Xanthosoma was measured in sows weighing 100 kg on average. The intake reached 3.4 kg fresh leaves day−1 (0.51 kg DM) and 1.0–1.1 kg dry leaf meal/day. It is concluded that low energy density is the main limiting factor of tree foliage for pig nutrition but that they are good sources of minerals and well-balanced proteins. 2005 Society of Chemical Industry Keywords: tree foliage; pig; digestibility; intake; Xanthosoma; Morus; Trichanthera INTRODUCTION A better knowledge of the nutritive potential of these Pig production can improve the welfare of small forages and of the voluntary intake by pigs would help farmers in developing countries, in terms of income to improve sustainable pig production systems. and food quality. Pigs are prolific, omnivorous, The present work aimed at determining the chemical have a low feed conversion ratio and small space composition, nutritive value in pigs and voluntary requirements. Numerous tropical crops and by- intake by pigs of the foliage of three species widely products not consumed by humans could be used used in the tropics to feed these animals: nacedero to feed these animals. However, most of them are [Trichanthera gigantea (H & B) Nees], mulberry poor in proteins. (Morus alba L) and cocoyam (Xanthosoma sagittifolium On the sloping land of the foothills of the Colombian Schott), also called giant taro, malanga, yautia or Andes as well as in many other parts of the world, elephant ear. the small farmers use browse trees as protein sources to feed their pigs. The trees protect against erosion and their leaves contain from 14 to 28% proteins,1 MATERIAL AND METHODS sometimes with good essential amino acid content.2,3 Chemical composition Tree leaves can be used in pig nutrition as long Samples of the three species were collected in as they are poor in antinutritional factors, are well three villages, located either in the Cauca river digested, have good palatability and good amino acid valley of Colombia (Jamundi and Palmira, with profile. However, other criteria should be considered, different rainfalls—1.800 and 1.000 mm water year−1, such as fibre degradability or bulking properties.4,5 respectively) or on the foothills bordering the valley Unfortunately, information on the nutritive value of (El Dovio, at 1.800 m above sea level vs. 1.000 m for these forages in pigs is scarce and generally limited.1–3 the two others). At El Dovio, the trees were fertilized ∗ Correspondence to: Pascal Leterme, ENVL-Zootechnie, 1 avenue Bourgelat, F-69280 Marcy l’Etoile, France E-mail: [email protected] †Part of these results were presented at the 9th International Symposium on Digestive Physiology in Pigs, Banff, Canada, May 14–17, 2003 (Received 12 May 2004; revised version received 6 September 2004; accepted 20 December 2004) Published online 31 March 2005 2005 Society of Chemical Industry. J Sci Food Agric 0022–5142/2005/$30.00 1725 P Leterme et al Cambridge, UK). Methionine and cysteine were determined by the same method after oxidation with performic acid before hydrolysis. Tryptophan was also analysed but after alkaline hydrolysis using 4 M Ba(OH)2. Crude energy was determined using a Parr 1341 calorimeter (Parr Instruments, Moline, MA, USA). The water-holding capacity of the leaf meals was determined after soaking of the meals in water (20 g l−1 water) for 6 h and centrifugation for 5 min at 5 × g. The supernate was suctioned off with a vacuum pump. Nutritive value Animals Twelve male, castrated pigs (commercial breed × Pietrain),weighingfrom29to38kg(34± 3kg, on average), were placed in metabolic cages and adapted to their respective diet for 10 days. Diets The tree leaves were hand-collected, immediately sun- dried and ground through a 3 mm mesh screen by means of a hammer-mill. The leaves of cocoyam did not include the stems (Fig 1). Four diets were prepared (Table 1), a basal one and three diets composed of 650 g of the basal diet kg−1 dry matter (DM) and 350 g of forage. During a previous experiment Figure 1. Whole plant of cocoyam (Xanthosoma sagittifolium). (not reported), we established that this amount corresponds to the maximal intake capacity of the with pig manure. In each farm, seven samples of young pigs of this weight. The intake level ranged from 80 to −1 0.75 −1 and mature leaves were collected. The young leaves 90 g DM kg weight (W) day depending on the had a maximum one month of age (after the previous pig’s appetite. harvest) and the mature ones 3–4 months. The leaves are generally harvested at 3–4 months of age. Since Methodology cocoyam is not really a tree but a plant composed of The experimental design was a completely randomized giant leaves (80 cm long), long stems and a starchy scheme: the 12 pigs were randomly allocated to one corm (Fig 1), and since the whole plant is used to feed of the four diets (three per diet). They were fed three the pigs, the chemical composition of the three parts was determined. The samples were kept in cool boxes Table 1. Composition of the experimental diets of the digestibility − and immediately brought to the laboratory, where they experiment (g kg 1 DM) were frozen, freeze-dried and ground through a 1 mm Diets based on mesh screen. The flour was analysed for its content in ash (furnace Basal Trichan- Xantho- at 550 ◦C for 8 h), nitrogen (Kjeldahl method) and oil diet thera Morus soma (ether extract by the Soxhlet system) as described 6 Ingredients by the AOAC. The neutral and acid detergent Maize 620 400 400 400 fibres (NDF and ADF) and acid detergent lignin Soyabean meal 160 100 100 100 were determined by means of an ANKOM fibre Ground rice hulls 60 40 40 40 analyser (Ankom Technology, Madecon, NY, USA) Sucrose 100 70 70 70 using nylon bags. The minerals were determined by Premix 60 40 40 40 atomic absorption spectroscopy after mineralization Trichanthera — 350 — — in a furnace and recovery in a HNO3 –HClO4 (2:1) Morus — — 350 — solution, by means of a Perkin Elmer Zeeman AAS Xanthosoma — — — 350 800 spectrophotometer (Wellesley, MA, USA), with Composition the exception of chlorine and phosphorus, which were Ash 73 95 105 129 determined by titrimetry and colorimetry, respectively. Crude protein 167 166 160 170 The total and reducing sugars were analysed by NDF 234 274 259 286 colorimetry after extraction with ethanol7 and the ADF 94 148 129 158 Crude energy 4105 3883 3940 4025 amino acids by ion exchange chromatography, using − (kcal kg 1 DM) a Biochrome 20 analyser (Pharmacia Biotech Ltd, 1726 J Sci Food Agric 85:1725–1732 (2005) Tropical tree foliage and cocoyam as feed for pigs times per day (7:00, 12:00 and 17:00) in order to with an equal amount of water. The animals received increase DM intake. The diets were mixed with an initially 50 g DM kg−1 W0.75 day−1 of the basal diet and equal amount of fresh water and the pigs had constant 30 g DM kg−1 W0.75 day−1 of forage. The amount of access to fresh water. The temperature varied from forage distributed was adjusted every day according to 18 ◦C during the night to a maximum of 32 ◦Cin the animal’s appetite, in order to reduce the refusals. the afternoon and was quite constant during the After an 8 day adaptation period, the total intake was experiment. After an adaptation period of 10 days, the measured for 5 days. The refusals were taken after each faeces were totally collected for 10 days. The refusals meal and their DM content immediately measured were taken after each meal, weighed and immediately usinganovenat60◦C. After the first period, the diets dried at 60 ◦C in order to determine their DM content. were permuted and the experiment repeated during The faeces were collected individually once a day, three other consecutive periods. Each diet was tested weighed and an aliquot was formed with 5% of the on the eight sows. total excreted.