Effects of 2-methylbutyrate on rumen fermentation, ruminal enzyme activities, urinary excretion of purine derivatives and feed digestibility in steers

Abstract

The objective of this study was to evaluate the effects of 2-methylbutyrate (2MB) supplementation on rumen fermentation, ruminal enzyme activities, urinary excretion of purine derivatives and feed digestibility in the total tract of steers. Eight ruminally cannulated Simmental steers were used in a replicated 4×4 Latin square experiment. The treatments were: control (without 2MB), L2MB, M2MB and H2MB with 8.4, 16.8 and 25.2g 2MB per steer per day, respectively. 2-methylbutyrate was hand-mixed into the concentrate portion. Diet consisted of 60% corn stover and 40% concentrate (dry matter [DM] basis). Dry matter intake (averaged 9kg/d) was restricted to a maximum of 90% of ad libitum intake. Ruminal pH was linearly decreased, whereas total VFA concentration (range of 64.19–71.06mM) was linearly (p<0.01) and quadratically (p<0.01) increased with increasing 2MB supplementation. Ratio of acetate to propionate increased linearly (p<0.01) from 2.53 to 3.80 as 2MB supplementation increased due to the increased in acetate production and decreased in propionate production. Activities of CMCase and xylanase were linearly increased, whereas that of protease was linearly reduced with increasing 2-methylbutyric supplementation. In situ ruminal NDF degradation of corn stover was improved but the CP degradability of soybean meal was decreased with increasing 2MB supplementation. Urinary excretion of purine derivatives was quadratically (p<0.01) changed with altering 2MB supplementation (52.74, 58.50, 59.17 and 54.36mmol/d for control, low, medium and high 2MB supplementation, respectively). Similarly, digestibilities of DM, NDF and CP in the total tract were also linearly and quadratically increased with increasing 2MB supplementation. The present results indicate that supplementation of diet with 2MB improved rumen fermentation and feed digestion in beef cattle. It was suggested that the 2MB stimulated the digestive microorganisms or enzymes in a dose-dependent manner. In the experimental conditions of this trial, the optimum 2MB dose was about 16.8g 2MB per steer per day.