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

Published online by Cambridge University Press:  27 March 2009

E. R. Ørskov  and
I. McDonald
E. R. Ørskov
Affiliation:
The Rowett Research Institute, Bucksburn, Aberdeen AB2 9SB
I. McDonald
Affiliation:
The Rowett Research Institute, Bucksburn, Aberdeen AB2 9SB
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A 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).

Type
Research Article
Information
The Journal of Agricultural Science , Volume 92 , Issue 2 , April 1979 , pp. 499 - 503
Copyright
Copyright © Cambridge University Press 1979

References

Blaxter, K. L., Graham, N. McC. & Wainman, P. W. (1966). Some observations on the digestibility of food by sheep and on related problems. British Journal of Nutrition 10, 69–91.CrossRefGoogle Scholar
Burroughs, W., Trenkle, A. & Vetter, R. L. (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, 713–722.Google ScholarPubMed
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.)Google Scholar
Mehrez, A. Z. & Ørskov, E. R. (1977). A study of the artificial fibre bag technique for determining the digestibility of feeds in the rumen. Journal of Agricultural Science, Cambridge 88, 645–650.CrossRefGoogle Scholar
Mekrez, A. Z. & Ørskov, E. R. (1978). Protein degradation and optimum urea concentration in cerealbased diets for sheep. British Journal of Nutrition 40, 337–345.Google Scholar
Miller, E. L. (1973). Evaluation of foods as sources of nitrogen and amino acids. Proceedings of the Nutrition Society 32, 79–84.CrossRefGoogle ScholarPubMed
Ørskov, E. R. (1970). Nitrogen utilization by the young ruminants. Proceedings of the Fourth Nutrition Conference, Nottingham, pp. 20–35.Google Scholar
Ørskov, E. R. (1974). Factors influencing protein and non-protein nitrogen utilization in young ruminants. In Protein Metabolism and Nutrition (ed. Taminga, S.), pp. 457–476. Wageningen, The Netherlands: Centre for Agricultural Publishing.Google Scholar
Ørskov, E. R. (1977). Dietary protein:energy relationships for growth in young ruminants. In Protein Metabolism and Nutrition (ed. Taminga, S., pp. 110–114. Wageningen, The Netherlands: Centre for Agricultural Publishing.Google Scholar
Ørskov, E. R. & Mehrez, A. Z. (1977). Estimation of extent of protein degradation from basal feeds in the rumen of sheep. Proceedings of the Nutrition Society 36, 78A.Google ScholarPubMed
Roy, J. H. B., Balch, C. C., Miller, E. L., Ørskov, E. R. & Smith, R. H. (1977). Calculation of the N-requirements for ruminants from nitrogen metabolism studies. In Protein Metabolism and Nutrition (ed. Taminga, S., pp. 126–129. Wageningen, The Netherlands: Centre for Agricultural Publishing.Google Scholar
Uden, P., Colucci, P. E. & Van Soest, P. J. (1978). Investigation of chromium, cerium and cobalt as markers in digesta rate of passage studies. Journal of the Science of Food and Agriculture. (In the Press.)Google Scholar