Original Paper Czech J. Anim. Sci., 49, 2004 (4): 144–150 Czech J. Anim. Sci., 49, 2004 (4): 144–150 Original Paper Nutritive value of broad-leaved dock (Rumex obtusifolius L.) and its effect on the quality of grass silages S. H�����1, P. D������2 1Department of Forage Crops and Grassland Management, 2Department of Animal Nutrition, Faculty of Agronomy, Mendel University of Agriculture and Forestry, Brno, Czech Republic ABSTRACT: The effect of broad-leaved dock (Rumex obtusifolius L.) on the impaired nutritive value of grassland herbages was studied together with the effect of dock and addition of microbial inoculant on the fermentation process in grass silages. The herbage of broad-leaved dock exhibits low DM content, CP and fibre contents com- parable with red clover, yet its NEL concentration is low. Quality of silages made of dock at DM content over 300 g/kg is good but the silages show significantly lower contents of lactic acid (35.9%), acetic acid (70.0%) and higher pH values (4.69 vs. 4.35) as compared with the grass silage. Silages made of dock do not contain butyric acid and exhibit lower rates of proteolysis. The presence of broad-leaved dock in herbage poses a danger of slow wilting and low production of fermentation acids. The addition of lactic acid bacteria (LAB) showed in the studied set of silages and in dock silages by an increased content of lactic acid (+18.9% and +27.0%, resp.) and by a significant reduction of pH value (–0.17 and –0.14, resp.). Keywords: broad-leaved dock; nutritive value of herbage; ensiling; fermentation Broad-leaved dock is together with creeping lower doses of applied fertilisers, increased defo- thistle (Cirsium arvense (L.) Scop.) and dandelion liation and trampling. High doses of N-fertilisers (Taraxacum officinale Wigg.) one of the most fre- were put into connection with higher occurrence quently occurring grassland weeds in the Czech of Rumex obtusifolius. Novák (1994) described as- Republic (Martinková and Honěk, 2001). Broad- sociations with dominating broad-leaved dock at leaved dock belongs to the group of plants with grazing sites overfertilized with animal excrements, the highest requirement for nitrogen and other which can be long without any change in the spe- nutrients. Its ecological requirements and herbage cies composition and which are avoided by graz- quality differ only li�le from those of curled dock ing animals. In the system of organic agriculture (Rumex crispus L.) and the two species can therefore the broad-leaved dock is a very serious problem be assessed together (Weissbach, 1998). According as it cannot be controlled by herbicides and docks to Klimeš (1993), there are also unfertile hybrids of markedly reduce the sward nutritive value (Pötsch, the two species occurring in grass stands, referred to 2000). as R. ×pratensis. These species represent aggressive With respect to the fact that sward herbages are plants which force cultural grasses and legumes fed on most farms in the form of grass silages, it out from their surroundings and cause problems at is vitally important to know individual factors af- herbage conservation due to their low DM contents. fecting their nutritive value and also the quality of Humpreys et al. (1999) demonstrated that grazed fermentation process during their production. It swards in Britain were related to a higher mortality was shown (Harrison and Johnson, 2001; Sommer of docks as compared with mown swards due to and Petrikovič, 2003) that the quality of preserved The results were obtained and processed under the financial support of the Ministry of Education, Youth and sports of the Czech Republic (Project No. 432100001). 144 145 Original Paper Czech J. Anim. Sci., 49, 2004 (4): 144–150 Czech J. Anim. Sci., 49, 2004 (4): 144–150 Original Paper fodders is decisive not only for total DM intake of storage in order to measure standard qualitative and productivity of animals but also for the health fermentation characteristics and basic parameters of condition of dairy cows. The main technological nutritive value. The total number of experimental reason for the worse quality of fermentation is usu- silages analysed and evaluated a�er the fermenta- ally inadequate DM content, long wilting period tion was 6 variants at six replications. Oxalic acid and unsuitable ensiling additive (Kalač and Míka, was determined by the method of extraction in 1977). HCl, precipitation with Ca(COO)2 and titration The goal of this paper was to assess the influence with KMnO4 according to Davídek et al. (1977). The of the proportion of broad-leaved dock in herbage analyses were made in the laboratories of S.O.S. and the effect of the application of microbial in- Skalice nad Svitavou. The NEL value of silages and oculant with strains of lactic fermentation homo- herbage was predicted by the in sacco method. The fermentative bacteria (Lactobacillus rhamnosus and results were statistically evaluated by the analysis Enterococcus faecium) as active substances on the of variance and processed by Tukey’s test using the process of fermentation and on the nutritive value of Statgraphics 7.0 statistic programme. silage from wilted sward with a proportion of dock In order to compare the nutritive value of broad- and silage made of dock herbage itself. Another goal leaved dock, a sample of herbage was taken at the was to evaluate the effect of dock on the reduction locality Jindřichov u Hranic, collected 6 weeks of sward herbage nutritive value. a�er the 1st cut from a permanent sward together with the herbage of red clover. The two samples were measured for the content of basic nutrients, MATERIAL AND METHODS the analyses serving to add data on the quality of broad-leaved dock herbage. A model experiment was established with wilted sward herbage to determine preservation effects of ensiling additive and broad-leaved dock on RESULTS AND DISCUSSION the process of fermentation. The ensilaged herb- age originated from the 2nd cut of permanent Herbage quality sward harvested on 24 July 2001. The herbage was supplied from the Research Station of Grassland DM content of broad-leaved dock is gener- Management and Forage Crops in Vatín. Grasses ally known to be very low. With respect to former dominating in the silage were meadow fescue experience, the dock herbage wilting was made (Festuca pratensis Huds.), red fescue (Festuca rubra artificially in a drier. The grass herbage reached a L.), cock’s foot (Dactylis glomerata L.), from legumes desired DM content in the open within 24 hours. A only white clover (Trifolium repens L.) was present, very low DM content in dock forage was also found other forb species such as ribwort (Plantago lanceola- by Derrick et al. (1993) – 114 g/kg, and by Bockholt ta L.) and common yarrow (Achileum millefolium L.). and Kannewurf (2001) – from 130 g/kg (whole The wilted herbage was cut on a stationary chopper month of May) to 270 g/kg at the end of July. The into pieces of theoretical length from 40–60 mm. DM content of harvested dock herbage is markedly Prior to being placed into the silo, the experimental affected by the level of fertilization. Hatcher et al. variant was treated with an inoculant composed (1997) detected 185 g DM in unfertilized plants, and of homofermentative strains of lactic fermentation DM content in fresh herbage below 100 g/kg at a bacteria Lactobacillus rhamnosus and Enterococcus higher level of fertilization with NH4 ions. faecium (hereina�er LAB) at 1 g of dry prepara- It follows from the results presented in Table 1 tion (1.1011 CFU) per 1 000 kg herbage in the form that broad-leaved dock fresh herbage contains of aqueous solution. The silages were placed into somewhat more fibre, ash and rumen-degradable experimental containers of 50 litres in volume. The proteins but markedly lower concentrations of net fermentation process occurred in laboratory condi- energy for lactation (NEL), WSC and Ca. The dock tions at temperatures ranging from 20–25°C. A�er green forage exhibited a much higher concentration a thorough ramming of their contents the contain- of potassium (by 46.8%) than the clover forage. The ers were air-sealed with a lid and their brims were tetanic ratio of K/Ca + Mg (calculated as milligram covered up with the aqueous solution of molasses. equivalents) reaches the value by 58.8% higher The silages were opened and analysed a�er 70 days in dock herbage than in clover forage, being still 144 145 Original Paper Czech J. Anim. Sci., 49, 2004 (4): 144–150 Czech J. Anim. Sci., 49, 2004 (4): 144–150 Original Paper Table 1. Nutritive value and substance contents in the dry ma�er of Taraxacum officinale and Rumex obtusifolius har- vested at a stage of leaf rose�e (Bohner, 2001) and Trifolium pratense as compared with Rumex obtusifolius herbage, 2nd cut, 6 weeks a�er 1st cut, permanent grassland, Jindřichov u Hranic (Hejduk, unpublished) According to Bohner (2001) Hejduk (unpublished) Parameter dandelion leaves dock leaves red clover dock Crude protein g/kg 210.0 294.0 191.0 193.7 RDP (N degr) – – 140.1 152.6 Crude fibre g/kg 121.0 107.0 238.2 261.5 Ash g/kg 94.0 101.0 88.9 105.0 NEL MJ/kg – – 5.76 4.82 WSC g/kg 74.0 30.0 48.3 20.8 Ca g/kg 9.30 5.40 10.98 7.66 P g/kg 3.60 4.80 2.83 4.31 Na g/kg 0.47 0.22 0.12 0.22 K g/kg 25.30 37.40 28.76 42.23 Mg g/kg 4.80 4.90 2.96 4.49 K/Ca + Mg 0.75 1.42 0.93 1.44 Oxalat g/kg 1.30 6.80 0 9.3 RDP = rumen degradability of proteins, WSC = water soluble carbohydrates, NEL = net energy for lactation below the critical value of 2.2 (Pavlů, 1994).