J. Anim Sci.
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J. Anim Sci. 1976. 43:828-834.
© 1976 American Society of Animal Science
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Degradation of Amino Acids by the Mixed Rumen Microbial Population

William Chalupa1 ,2,

SmithKline Corporation, West Chester, Pennsylvania 19380

Abstract

Degradation of physiological quantities of amino acids by rumen microbes was determined under both in vitro and in vivo conditions. In vitro rate constants for EAA indicated that Arg and Thr were rapidly degraded (.5 to .9 mM/hr); Lys, Phe, Leu and Ile formed an intermediate group (.2 to .3 mM/hr); and Val and Met were least rapidly degraded (.1 to .14 mM/hr). In vivo EAA degradation rates were about 1.5x greater than estimates derived from in vitro rate constants, but a significant (P<.05) linear relationship between in vitro and in vivo rates suggested that similar degradative pathways predominated in both systems. Incubating Thr, Arg, Lys, Phe, Leu and Ile alone or in combination with a mixture of EAA yielded similar amounts of degradation for these EAA. Met and Val degradation was approximately twice as great (P<.05) when fermented alone vs in conjunction with other EAA. Combining a mixture of NEAA (Asp, Ser, Glu, Ala, Tyr, Orn) with the EAA mixture did not influence EAA degradation. Tyr and Orn were the only NEAA degraded to lesser (P<.05) extents (30%) when the fermentation system contained both NEAA and EAA mixtures. Data presented demonstrated that specific amino acids are degraded at different rates and that there are interactions between certain amino acids. With the possible exception of Met, supplements of free amino acids cannot survive ruminal degradation.

Footnotes

1 Applebrook Research Center, Smith Kline Animal Health Products Division, 1600 Paoli Pike, West Chester, PA 19380.

2 Present address: Department of Dairy Science, University of Maryland, College Park 20740.






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Copyright © 1976 by the American Society of Animal Science.