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Journal of Dairy Science Vol. 46 No. 12 1431-1433
© 1963 by American Dairy Science Association ®
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Nitrogen Source Availability and Activity of Rumen Microorganisms1

William Chalupa3, J. L. Evans and M. C. Stillions4

Department of Animal Sciences, Rutgers—The State University, New Brunswick, New Jersey

ABSTRACT

Protein solubility has been reported to be a major factor affecting the degree of proteolysis by rumen microorganisms (2, 6, 11, 12). Burroughs et al. (7) and Belasco (5) indicated that rumen microorganisms exhibited a requirement for nitrogen that could be adequately supplied by NH3-N. Drori (10) reported that sheep fed urea diets had greater microbial numbers as indicated by turbidity measurements. Since net utilization of dietary nitrogen sources is influenced by rumen microbial activity, it appeared desirable to investigate further the availability of some dietary nitrogen sources.

EXPERIMENTAL PROCEDURE

In the present study microbial activity was measured by the disappearance of cellulose, a known substrate for rumen microorganisms. Since the nitrogen requirements of rumen microorganisms can be supplied by NH3-N (5, 7), it is reasonable to assume that this measure of microbial activity provides an indication of protein hydrolysis and nitrogen availability.

A 0.5-g sample of crystalline cellulose (Avicel2) was fermented at 39 ± 0.5 C in a 100-ml lipless beaker equipped with a Bunsen-type valve and containing 20 ml of filtered rumen fluid and 30 ml of a phosphate buffer (3).

FOOTNOTES

1 Paper of the Journal Series, New Jersey Agricultural Experiment Station, Rutgers—The State University, New Brunswick. Data presented are from a thesis submitted by the senior author in partial fulfillment of the requirements for the Ph.D. degree.

3 Present address: Department of Dairy Science, Clemson College, Clemson, South Carolina.

4 Present address: Morris Research Laboratories, Topeka, Kansas.






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