Adaptation to High Concentrate Diets by Beef Cattle. I. Adaptation to Corn and Wheat Diets

Abstract

An in vivo and in vitro fermentation study was conducted in conjunction with a feed intake study to characterize ruminant feed intake and rumen microbial fermentation patterns as steers were adapted to high concentrate corn and wheat diets. Steers fed the wheat based diet consumed less (P<.01) total feed and experienced wider fluctuations in rumen pH values than steers fed the corn based diet (4.60–6.25 vs 5.27–5.97). Lower pH values were observed for the wheat fed steers at all levels as indicated by a diet by concentrate interaction (P<.01). Steers fed the wheat diet markedly shifted their intake patterns from greater consumption in the 0-to 12-hr interval to the 12-to 24-hr interval as percentage concentrate increased and percentage roughage decreased in the diet. Reductions in wheat diet intake compared to corn diet intake in the intervals of hr 0 to 2 and hr 8 to 12 represented the difference in total intake observed between these two diets. Highest in vivo lactate values for both diets occurred on the 35% concentrate level with decreasing amounts (P<.01) of lactate observed as the concentrate level increased. Only small amounts of in vivo and in vitro lactate present at the 90% concentrate level indicate microbial adaptation to high grain diets had occurred, yet reduced intake on the wheat diet compared to the corn diet still existing at this level would indicate animal consumption patterns had not yet adjusted. Only small differences due to diet for individual total volatile fatty acid concentrations were observed in this study. Copyright © 1979. American Society of Animal Science . Copyright 1979 by American Society of Animal Science.