The estimation of protein degradability in the rumen from incubation measurements weighted according to rate of passage

Journal of Agricultural Science - Tập 92 Số 2 - Trang 499-503 - 1979
E. R. Ørskov1, I. McDonald1
1The Rowett Research Institute, Bucksburn, Aberdeen AB2 9SB

Tóm tắt

SummaryA method is proposed for estimating the percentage of dietary protein that is degraded by microbial action in the rumen when protein supplement is added to a specified ration. The potential degradability, p, is measured by incubating the supplement in artificial-fibre bags in the rumen and is related to incubation time, t, by the equation p = a+b(1 – e-ct). The rate constant k, measuring the passage of the supplement from the rumen to the abomasum, is obtained in a separate experiment in which the supplement is combined with a chromium marker which renders it completely indigestible. The effective percentage degradation, p, of the supplement, allowing for rate of passage, is shown to be p = a+[bc/(c+k)] (1-e-(e+k)t) by time, t, after feeding. As t increases, this tends to the asymptotic value a+bc/(c+k), which therefore provides an estimate of the degradability of the protein supplement under the specified feeding conditions.The method is illustrated by results obtained with soya-bean meal fed as a supplement to a dried-grass diet for sheep. The incubation measurements showed that 89% of the soya-bean protein disappeared within 24 h and indicated that it was all ultimately degradable with this diet.When the dried grass was given at a restricted level of feeding the allowance for time of retention in the rumen reduced the estimate of final degradability to 71% (69% within 24 h). With ad libitum feeding there was a faster rate of passage and the final degradability was estimated to be 66% (65% within 24 h).

Từ khóa


Tài liệu tham khảo

Ørskov, 1977, Estimation of extent of protein degradation from basal feeds in the rumen of sheep, Proceedings of the Nutrition Society, 36, 78A

Ganev G. , Ørskov E. R. & Smart R. (1979). Effect of type of substrate and retention time on rate and extent of degradation of protein supplements in the rumen. (Submitted.)

Burroughs, 1974, A system of protein evaluation for cattle and sheep involving metabolizable protein (amino acids) and urea fermentation potential of feedstuffs, Veterinary Medicine. Small Animal Clinician, 69, 713

10.1079/BJN19560015

Uden, 1978, Investigation of chromium, cerium and cobalt as markers in digesta rate of passage studies, Journal of the Science of Food and Agriculture

Mekrez, 1978, Protein degradation and optimum urea concentration in cerealbased diets for sheep, British Journal of Nutrition, 40, 337, 10.1079/BJN19780130

Roy, 1977, Protein Metabolism and Nutrition, 126

Ørskov, 1974, Protein Metabolism and Nutrition, 457

10.1017/S0021859600037321

10.1079/PNS19730019

Ørskov, 1970, Proceedings of the Fourth Nutrition Conference, 20

Ørskov, 1977, Protein Metabolism and Nutrition, 110

Thông tin
Thông tin xuất bản

Journal of Agricultural Science

Tập 92 Số 2

499-503

Thông tin tác giả