Effects of Bacitracin and Bacitracin Zinc on In Vitro Fermentation, Methane Production and Microbial Populations of the Rumen

This study was conducted to investigate the effects of bacitracin (B) and bacitracin zinc (BZ) on in vitro fermentation, methane and ammonia production, and select microbial populations of the rumen. Both B and BZ were added at 3 doses, namely 10 (low), 30 (medium), and 90 (high) mg/l of in vitro fermentation medium. Results showed that B and BZ had similar effects on rumen fermentation characteristics and microbial populations. Low dosage of B or BZ addition reduced (P 0.05) on total VFA concentration and feed digestibility. The population of total bacteria was unaffected (P>0.05) by low B and BZ doses, but was significantly (P 0.05) on the populations of protozoa and fungi. Results indicated that optimum B or BZ addition could reduce methane and ammonia production, with no adverse effects on total VFA concentration and feed digestibility. Further, these effects are probably associated with the variation of rumen functional microbial populations.