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Performance, Ruminal Measurements and Blood Plasma Amino Acids of Steers Fed Ronnel

U.S. Department of Agriculture, Beltsville, MD

Abstract

Two trials were conducted to test the effect of ronnel, an organophosphate pesticide with insecticidal and anthelmintic activity, on feedlot performance (trials 1 and 2), ruminal pH, ammonia and volatile fatty acids (trials 1 and 2), rumen microbial morphology (trial 2) and blood plasma amino acid patterns (trial 1) of beef steers. In trial 1, 18 Hereford steers (nine steers per ronnel level) were fed either 0 or 4 mg of ronnel/kg of body weight daily with both limited (1.75% of body weight daily) and ad libitum levels of feed intake. In trial 2, 32 Hereford steers (16 steers per ronnel level) were fed either 0 or 4 mg of ronnel/kg of body weight daily with both limited (1.8% of body weight daily) and ad libitum levels of feed intake. In both trials, ronnel increased rate of gain by approximately 12% regardless of the level of feed intake and similarly improved the feed to gain ratio. The positive effect of ronnel on performance was not the result of an alleviation of insect or parasite infestation in the steers, and ronnel did not cause significant changes in ruminal measurements, rumen microbial morphology or plasma amino acid patterns that would explain the improved performance.

¹ Ruminant Nutrition Laboratory, Animal Science Institute, Agricultural Research, Science and Education Administration, Beltsville, MD 20705.

² The assistance of Dr. M. L. Colglazier in obtaining the fecal egg counts and the assistance of Dr. D. L. Kern in obtaining the bacterial morphology data are gratefully acknowledged.