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Journal of Dairy Science Vol. 54 No. 8 1150-1161
© 1971 by American Dairy Science Association ®
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In Vitro 15Nitrogen-tracer Technique for Some Kinetic Measures of Ruminal Ammonia1

M. F. Al-Rabbat2, R. L. Baldwin and W. C. Weir

Department of Animal Science, University of California, Davis 95616

ABSTRACT

To quantitate the several nitrogen fluxes which participate in the synthesis of ruminal microbes, an in vitro technique utilizing l5N ammonia was developed. The technique involves incubation of 15NH4-labelled rumen contents and analysis for 15N-ammonia and total ammonia N at specific time intervals during the incubation period. for a cow fed twice daily and a sheep fed at 2-hourly intervals, respectively, the technique yielded estimates of mean fractional turnover rates (Kam) of.226 and .314 per hour, and mean rates of ammonia nitrogen incorporation into cell materials (am) of 2.68 and 2.89 mg per hour per 50 of whole rumen digesta. The effect of rumen content donor on Kam was highly significant (P < 0.01); but the effect of am was not significant. For sheep fed alfalfa pellets continuously, about 9.2 g of ruminal cells per 100 g digestible synthesized via ammonia nitrogen and about 61% of microbial nitrogen is derived from ammonia N. Presumably, 39% is derived from other nitrogen sources such as amino acid and peptide nitrogen.

FOOTNOTES

1 This paper is part of a dissertation submitted by M. F. Al-Rabbat to, the Graduate Division, University of California, Davis, in partial fulfillment of Requirements for the Ph.D. degree.

2 Present address: College of Agriculture, Department of Animal Production, University of Damascus, Damascus, Syria.






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Copyright © 1971 by the American Dairy Science Association ®.