The Effect of Diet on Ruminal Lactate Accumulation Rates in Acidotic Cattle

Abstract

To maximize feed efficiency for weight gain in cattle, cattlemen feed animals high energy grain diets. A negative consequence of feeding this type of diet is a metabolic and physiological condition called acidosis. The starch present in grains is readily fermented by rumen microbial populations to organic acids, including lactic acid. When cattle consume excess grain, they may experience an acute acidotic condition characterized by a drop in ruminal pH below 5.0 and an accumulation of lactic acid in the rumen. This experiment compared the effect of diet on the ruminal lactate accumulation rates in an acute acidosis animal model for cattle. Diets used for this comparison were: (1) a readily fermented starch source (100% ground com) and (2) a readily fermented starch source plus molasses (10% molasses plus 90% ground com) which contains high levels of small molecular weight sugars. The hypothesis under test in this project was that when molasses is present in the diet, the accumulation of ruminal lactic acid is greater than when only starch is present in the diet. Twelve Hereford X Angus crossbred heifers previously adapted to hay/straw diets were abruptly switched to one of the two diets. Four of the six cattle fed 100% ground com showed a decline in ruminal pH and an accumulation of rumina I lactic add, while all six of the 10% molasses plus 90% ground com fed cattle exhibited a decline in ruminal pH below 5.0 and ruminaI lactate accumulation rates. In vitro incubations of ruminaI contents were collected before the induction of acidosis and four and seven hours post-induction of acidosis. The accumulation of lactic add in these samples was measured. Lines were fit to each in vitro lactate accumulation curve and the slopes were used as summary variables to test for the effect of diet. It was found that no statistically supported diet effect existed (P>0.3). However, the data collected during this limited observation suggest that further experimentation is necessary.

With honors.