Virginiamycin reduces acidosis in hungry sheep fed wheat grain

Lactic acidosis can occur when cereal grains are fed in large quantities or without an adequate introduction. Feed additives, such as monensin and lasalocid, have been shown to prevent lactic acid accumulation in the rumen of cattle following infusion of readily fermentable carbohdrates (Nagaraja et 0” al. 1981). The aim of this experiment was to determine if virginiamycin (StafacK 20, 2 kg/t) would prevent acidosis in hungry sheep fed wheat, barley or oat grain without any introductory period. Merino wethers were penned individually and fed wheaten chaff (300 g/day for 9 day) before being offered 2.1 kg of wheat, barley or oat grain, with or without virginiamycin (3 x 2 factorial design, n = 20, N = 120). Rumen fluid and blood were sampled prior to grain feeding and at 24 hours following grain feeding. All animals were monitored by a veterinarian not involved in the allocation of animals to treatment groups. Any animal which was depressed, showed severe laminitis, evidence of discomfort or failure to eat was euthanased or removed from the experiment. The number of animals removed from each treatment in the week following grain feeding was analysed using analysis of deviance. Means of other measurements were compared using analysis of variance and Fishers protected LSD at the 5% level of significance. Rumen lactate concentrations were transformed to log values prior to analysis. Twenty four hours followin g access to grain the rumen pH was higher (P c 0.05) and the rumen Llactate and plasma protein concentrations were lower (P c 0.05) in sheep fed wheat plus virginiamycin compared to sheep fed wheat alone (Table 1). There was no effect (P > 0.05) of virginiamycin on grain intake, although intake of sheep fed oat grain was lower (P c 0.05) than intake of sheep fed wheat or barley. The number of sheep withdrawn from the experiment following grain feeding was lower (P c 0.05) when wheat was fed with virginiamycin compared to untreated wheat grain.