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Adaptation of Rumen Microorganisms to Biuret as an NPN Supplement to Low Quality Roughage Rations for Cattle and Sheep^1,2,3,

Department of Animal Sciences and Industry, Oklahoma State University, Stillwater, Oklahoma 74074

Two trials with sheep and one with cattle were conducted to study the influence of the length of time of biuret supplementation of a poor quality roughage on the development of the ability of the rumen microorganisms to utilize biuret. Rumen NH₂ did not increase after biuret feeding on day 4 of adaptation to biuret but on day 84 a marked release of NH₃ from biuret was obvious. When the ability of rumen contents to hydrolyze biuret in vitro was measured, slight activity was observed on days 14 and 21 with marked activity by day 42. Ammonia appearance during the biuretolytic tests was apparent on days 42 and 66 and marked on day 84. In experiment 2, biuret adaptation was apparent but not as great in magnitude as in experiment 1. In experiment 3, biuretolytic activity in steer rumen contents was fully developed after 30 days of biuret feeding but disappeared within 4 days after removing biuret from the ration. Biuretolytic activity in the rumen contents was removed by slow speed centrifugation.

KEY WORDS: • biuret • rumen • NPN • microbial adaptation

¹ Journal Article J-2530 of the Agricultural Experiment Station, Oklahoma State University, Stillwater.

² Supported in part by the Lone Star Gas Company, Dallas.

³ A preliminary report of portions of this research was presented at the Annual meeting of the American Society of Animal Science, August, 1971, at Davis, California. Johnson, R. R., Biuretolytic activity in lambs adapted to pure biuret, J. Anim. Sci. 33: 288 (1971), abstr.

Manuscript received 14 July 1972.