QUICK SEARCH:   [advanced] Author: Keyword(s): Year:  Vol:  Page:

This Article Full Text (PDF) Purchase Article View Shopping Cart Alert me when this article is cited Alert me if a correction is posted Services Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via Google Scholar Google Scholar Articles by Polan, C. E. Search for Related Content PubMed PubMed Citation Articles by Polan, C. E.

Update: Dietary Protein and Microbial Protein Contribution¹

Department of Dairy Science, College of Agriculture and Life Sciences, Virginia Agricultural Experiment Station, Virginia Polytechnic Institute and State University, Blacksburg, VA 24061-6999

Factors influencing microbial protein synthesis in the rumen have been reviewed several times in recent years. Original publications in the past 3 yr have reported microbial and feed protein nitrogen contribution postruminally when feeding a variety of dietary proteins. Ammonia is a satisfactory source of nitrogen for growth of the majority of rumen species, but substitution of intact protein for urea (source of ammonia) usually stimulates microbial protein production. Protein sources such as soybean meal appear to possess properties (perhaps rate of degradability) that optimize microbial growth in vivo. Protein sources more undegradable than soybean meal, when fed as the major nitrogen source, sometimes reduce microbial growth. However, nondegradable proteins may compensate for less microbial protein by supplying intact dietary protein postruminally, so the amino acids potentially available may be equal to or greater than those available when readily degradable protein is fed. Soybean meal may reduce microbial growth in diets containing grass silage at protein exceeding 16.8%. Various measurements of microbial and intact dietary protein postruminally show that the contribution of each can be manipulated. Accuracy of quantitative predictions of postruminal contribution depends on several factors that require more research.

KEY WORDS: • ruminal microbial protein • protein synthesis • degradable protein

¹ Presented as part of the 28th Annual Ruminant Conference: Potential for Altered Productivity of the Rumen Ecosystem, given at the 71st Annual Meeting of the Federation of American Societies for Experimental Biology, Washington, DC, March 29, 1987, and supported by grants from American Cyanamid Company, Cargill Nutrena Feed Division, Eastman Kodak Company Chemical Division, Eli Lilly and Company, Merck & Co., Inc. and SmithKline Beckman Corporation.

Manuscript received 15 May 1987. Revision accepted 22 July 1987.