School of Agriculture, Food and Ecosystem Sciences - Theses
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ItemThe nutritive value of white clover pasture for cows in mid-lactation when supplemented with maize silage( 1992)In a completely randomised grazing trial, 8 cows in mid-lactation were offered white clover pasture (35kg DM/cow/day) with 4 of the cows given a supplement of maize silage (8 kg DM/cow/day). Factors evaluated over a 28 day period were total DMI, pasture DM/maize silage DM substitution rate, herbage selection in the pasture, milk yield, fat and protein concentration. Supplementing cows with maize silage increased total DMI by 22% and lowered pasture herbage DMI by 21%; equivalent to a substitution rate of 0.5 kg pasture DM /kg of maize silage DM. Selection of herbage in the pasture was not affected by supplementation, but cows on both treatments selectively grazed the white clover. Supplementing cows with maize silage increased milk yield by 34%, fat yield by 35% and protein yield by 35% (P<0.05), but did not affect milk fat and protein concentration. In a metabolism trial, 6 rumen fistulated cows in mid-lactation were fed similar diets in a crossover experiment but with white clover fed ad libitum. Digestibility, nitrogen balance, milk yield, fat and protein concentration were evaluated over a 7 day period. Maize silage DM and white clover DM digestion in the rumen were evaluated by DM disappearance rates from nylon bags over a 96 hr period. Measurments of rumen fluid volume, fluid mean retention time, fluid outflow, pH, ammonia and VFA concentration and the acetate/propionate ratio were estimated over a 24 hr period. Supplementing cows with maize silage increased total DMI by 34%, without affecting DM digestibility (DMD). However, OMD was reduced by 5% and fibre digestion by 18% (P<0.05). Supplementing cows with maize silage did not affect the rate of digestion of maize silage DM or white clover DM in nylon bags, but white clover was digested at a faster rate than maize silage (P<0.05). The increased DOMI by cows supplemented with maize silage was highly correlated with a 24% increase in milk yield (P<0.05; iI=61 ) but had no effect on milk fat and protein concentration. At similar nitrogen intakes cows supplemented with maize silage produced 2.3 kg more milk (P<0.050='66) but there was no effect on milk fat and protein concentration. Rumen fluid volume, mean retention time and fluid outflow rate were not significantly altered by the maize silage supplement, although rumen pH and ammonia concentration were significantly lower (P<0.05). Total VFA concentration was not significantly different between the two diets, but acetate concentration was significantly lower (P<0.05), while propionate concentration was significantly higher (P<0.05) in supplemented cows. The reduction in acetate and the corresponding increase in propionate, lowered the acetate/propionate ratio. Butyrate concentration was not affected. It was concluded that for cows in mid-lactation fed on good quality white clover dominant pasture, maize silage supplementation can increase milk yield, without affecting milk fat and protein concentration. The increase in milk yield was attributed to increased apparent energy intake as nitrogen intake did not change markedly. However further work is required to quantify whether increased nitrogen utilization occurred and whether the lower ammonia concentration in maize silage supplemented cows were due to improved rumen microbial synthesis. The possibility also exists that improved milk yields were due to by-pass rumen starch, thereby providing glucose to the animal, after enzymatic digestion in the small intestine.
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ItemAnti-nutritional factors in legume seeds( 1990)The aim of this study was to assess the presence of lectins and trypsin inhibitors in the seeds of selected species of legume namely: lab lab purpureus L. (lablab) Vigna unguiculata [L.] Walp. (cowpea) and Phaseolus vulgaris (navybean) and to examine the degradation of these anti-nutritional factors in the rumen of sheep. This study also attempted to investigate whether laboratory measures of haemagglutinating activity or trypsin inhibitor activity of the legume seeds could be related to in vivo measurements i.e. animal growth and d-xylose absorption. Seeds of the selected legume species were tested with erythrocytes from three animal species (sheep, goat and cattle) to determine their haemagglutinating activity . Enterocytes were also used in the in vitro measurements of lectin content of the legume seeds. The results indicated that the legume seeds contain various levels of haemagglutinating activity and trypsin inhibitor activity, with navybean exhibiting the highest amount, followed by Lablab batch A, Lablab batch B, cowpea and lupin, the lowest. No significant difference was observed in the haemagglutination reactions when red blood cells from three animal species (sheep, goat and cattle) were used in the test. There was a high correlation (r=0.994) obtained between the haemagglutination activity of erythrocytes and enterocytes. A feeding trial was conducted over a 4-week experimental period . Twenty-five Merino wethers were housed indoors in metabolism crates and were divided into five treatment groups. All sheep were offered daily a mixture of equal parts of oaten chaff and barley straw ad libitum and of the five supplements at 1% of LW. The supplements were lupins, lablab batch A, lablab batch B, cowpea and navybean. The amounts of legume seed supplements given were on an air dry basis. (The five diets offered were; T1= 1% LW Lupin + roughage ; T2= 1% LW Lablab batch A + roughage ; T3= 1% LW Lablab t batch B + roughage ; T4= 1% LW cowpea + roughage ; and T5= 1% LW navybean + roughage. The roughage, which consisted of a mixture of equal parts of oaten chaff and barley straw, was offered ad libitum. The amounts of legume seed supplements given were on an air dry basis.) Samples of legume seeds placed in nylon bags were incubated in the rumen of the sheep at different periods (3, 6, 12, 24 ,48 hour) and examined for haemagglutination and trypsin inhibitor activity. A diminishing trend in activity was observed for all the legume seeds as the incubation time progressed. Minimal activity was still detected at 12 hour post incubation and virtually no activity was measured at 24 and 48 hour periods. The reduction in activity could probably be due to washing of the seeds in the rumen, hence, no apparent symptoms of toxicity were demonstrated by the sheep in contrast to a previously reported study of Ismartoyo (1989) Results of d-xylose test , feed intake and growth of sheep showed no significant difference among the treatment diets including other related experiments which involved supplementation of similar legume seeds. There was no clear relationship observed between the in vitro and in vivo measurements obtained in this experiment. Therefore, the anti-nutritional role of legume seeds on the sheep appeared to be of lesser significance compared to the monogastrics. This has been substantiated by the diminishing levels of toxic activity as determined in this experiment and absence of toxic symptoms in the sheep fed with legume of seeds at 1% of LW.