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Factors Affecting the Ruminal Characteristics of Cattle Fed All-Concentrate Rations

U. S. Department of Agriculture

Abstract

Two finishing trials and a fistulated steer study were conducted to determine the effects of various factors on the ruminal characteristics of cattle consuming all-concentrate rations. The first trial studied urea vs. soybean meal, mineral buffers vs. none and supplemental zinc vs. none in a 2³ factorial design. Buffers significantly increased the level of ruminal bicarbonate and the incidence of bloat. Urea significantly decreased both molar percent of acetic acid and the A/P ratio. In steers fed soybean meal the rumen epithelium was significantly darkened and the papillae were significantly more clumped. Significant interactions were observed between nitrogen source and buffers for ruminal pH and A/P ratio and also between buffers and zinc for ruminal ammonia, ruminal bicarbonate, and papillae clumping. Studies using a fistulated steer consuming these rations characterized the buffering capacity of the ruminal fluid. The ruminal fill was 11% greater on buffered rations. The second trial tested the effects of stilbestrol, pelleting and supplemental magnesium and zinc. Pelleting the ration caused a significant increase in ruminal ammonia and darker ruminal epithelium. Bloat caused no difficulty in this trial.

¹ ARS, Animal Husbandry Research Division, Beef Cattle Research Branch, Agricultural Research Center, Beltsville, Md.