Studies on the degradability of proteins and protected proteins in the rumen of cattle
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Date
1985
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Department of Animal Nutrition, College of Veterinary and Animal Sciences, Mannuthy
Abstract
An investigation was carried out to determine the ruminal protein degradability of groundnut cake, gingelly cake, rubber seed cake, coconut
cake yellow maize, wheat bran and guinea grass and to determine the correlation between their degradability in rumen and solubility in mineral solvents and autoclaved rumen fluid. The effect of heat treatment and the formaldehyde treatment on the protein degradability of groundnut cake, gingelly cake and rubber seed cake was also studied. The effect of different levels of degradable proteins in the ration on the rumen fermentation pattern in cows and on growth rate and digestibility of nutrients in calves were also studied. The degradability of proteins of the feed stuffs in the rumen were estimated employing the nylon bag technique using five fistulated cows. The effective protein degradability was determined using the formula P = a + bc where k is the c+k fractional outflow rate from the rumen and a, b and c are the constants of the exponential equation p = a + b (1 – e–ct). The effective protein degradability values of groundnut cake, gingelly cake, rubber seed cake, coconut cake, yellow maize, wheat bran and guinea grass at a rumen outflow rate of 0.05/h were 66.76, 85.12, 68.12, 68.61, 19.09, 22.83, 77.02 and 41.50 per cent respectively. Among the oil cakes coconut cake was least degradable in the rumen and was found to be a good source of bypass protein for ruminants. Heat treatment (1500C for 2 hours) reduced the protein degradability of groundnut cake, gingelly cake and rubber seed cake by 83.18, 76.80 and 70.10 per cent respectively at an outflow rate of 0.05/h and the formaldehyde
treatment (1 g/100g CP) reduced the protein degradability of these cakes by 55.98, 45.45 and 44.33 per cent respectively at the same outflow rate. Significant correlations were observed between protein degradability of feed stuffs in the rumen and their solubility in 0.15 M sodium chloride (r = 0.79), McDoughal’s artificial saliva (r = 0.74) and autoclaved rumen fluid (r = 0.81). No correlation could be observed between the protein degradability in the rumen and the solubility in Burroughs mineral solution. A significantly high correlation (r = 0.91) was also observed between protein degradability in the rumen and the percentage of protein loss from control bags due to washing. Rumen pH and ammonia nitrogen concentration were significantly higher in the animals receiving rations with higher levels (76.90%) of degradable proteins. The total volatile fatty acid concentration was significantly high in the animals receiving rations with lower levels (45.30%) of degradable protein.
The effect of three levels (44.50, 60.50 and 71.30 per cent) of degradable proteins in the ration on growth and digestibility of nutrients was studied using 18 growing calves divided into three groups. The final body weight and the daily weight gain of the calves receiving the lower levels (44.50%) of degradable protein in the ration were significantly high as compared with those obtained in the case of calves receiving higher levels (60.50 and 71.30%) of degradable protein. The drymatter intake and the digestibility of nutrients of the rations were not influenced by the level of degradable proteins in the ration. The optimum level of degradable protein sufficient to support growth was found to be 45 per cent.
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