Effect of rates and extent of ruminal barley grain dry matter and starch disappearance on bloat, liver abscesses, and performance of feedlot steers

Abstract

The objective was to test the hypothesis that differences in ruminal solubility and degradation of barley grain affects health and rate and efficiency of gain in feedlot steers. Ten barley grains were fed to 200 steer calves (365±27 kg) in diets containing 85.5% barley grain. Overall, 14% of the steers bloated at least once in the experiment and 16% had abscessed livers. Incidences of bloat and liver abscesses did not differ ( P>0.15) between barleys with two- versus six-row head-type morphology. The percentage of animals which bloated at least once was negatively related to the percentage of barley dry matter (DM; r=−0.60; P<0.1) and starch ( r=−0.73; P<0.05) which slowly disappeared in the rumen. Similarly, the percentage of slowly disappearing DM was correlated to the percentage of animals with liver abscesses ( r=−0.82; P<0.01). No differences in DM intake (9.7–10.9 kg per day), daily gain (1.46–1.61 kg per day), kg gain per kg feed DM consumed (0.146–0.157), or carcass characteristics were detected between steers fed the barleys. Dry matter intake, daily gain and feed efficiency of the steers were not related to starch or DM in ground barley which initially washed out of the bags or slowly disappeared in the rumen. Also, rate of disappearance of starch and DM were not related to rate or efficiency of liveweight gain. Daily gain was, however, positively related ( r=0.70; P<0.05) to the percentage of DM which slowly disappeared when rolled grain was incubated in the rumen. Similarly, the estimated degradability of rolled barley in the rumen at a ruminal passage rate of 5% per h was positively related ( r=0.66; P<0.05) to liveweight gain per feed DM consumed. In conclusion, bloat and liver abscesses increased when barley grain was rapidly solubilized and degraded in the rumen. Further, although rate and extent of ruminal disappearance of starch and DM from ground barley grain have important implications with respect to health of cattle, the effect of intrinsic differences in ruminal degradability on rate and efficiency of gain cannot be evaluated in isolation from the effects of grain processing.