A SINGLE DRENCH OF VIRGINIAMYCIN TO INCREASE SAFETY OF FEEDING GRAIN TO SHEEP

Two experiments tested the efficacy of a single drench of virginiamyci n for protecting sheep against grain poisoning (lactic acidosis). In E xpt 1, 80 penned sheep (30+/-0.4 kg) were drenched with 0, 40, 80, or 160 mg of virginiamycin in 10 mt of water, then fed wheat ad libitum. Eleven sheep that received no virginiamycin and one receiving 40 mg vi rginiamycin were withdrawn from the trial due to inappetence after eat ing wheat. Sheep drenched with 80 or 60 mg virginiamycin were heavier (P < 0.05) than control sheep at 20 days after drenching, and none was withdrawn, Rumen pH was higher (P < 0.05) in sheep drenched with virg iniamycin than in control sheep. In Expt 2, 100 sheep (62+/-0.7 kg) we re either gradually introduced to a standing wheat crop by restricting the length of time they had access to the crop, or drenched with 160 mg of virginiamycin then given unlimited access to the crop. Sheep rec eiving virginiamycin lost more weight in the first week of the experim ent, but thereafter gained weight faster than the sheep gradually intr oduced to wheat. There was no difference between groups in wool streng th. These trials indicate that a single drench of virginiamycin can ef fectively prevent lactic acidosis in sheep.