A single drench of virginiamycin to control acidosis in sheep and cattle

SUMMARY Previous studies have shown that a single drench of virginiamycin (2.6 mg/kg liveweight) can prevent mortalities due to lactic acidosis in sheep. It was proposed that the most important feature of a successful drench of virginiamycin is the length of time that lactate production in the rumen is suppressed. The aim of this study was to examine the likely effective dose prior to testing the technique on cattle exposed to grain feeding and therefore prevent mortalities. This was achieved by drenching both sheep and cattle with equivalent doses of virginiamycin and taking periodic rumen samples which were incubated with glucose in vitro to determine potential lactate production. Drenching with virginiamycin decreased L-lactate in both sheep and cattle. D-lactate was increased in sheep but was variable in cattle. Rumen L-lactate levels were suppressed for 4-5 days in sheep when they were drenched with virginiamycin at 2.6 mg/kg and twice that dose did not appear to increase the period of L-lactate suppression. L-lactate was suppressed for only 3 days in cattle drenched with virginiamycin at 5.2 mg/kg, indicating that cattle require larger doses of virginiamycin than sheep to achieve similar levels of protection against lactic acidosis.