Virginiamycin to protect sheep fed wheat, barley or oats from grain poisoning under simulated drought feeding conditions

Abstract

Lactic acidosis can occur when large amounts of cereal grains are given to sheep without adequate adaptation. Virginiamycin has been shown to reduce lactic acid accumulation in vitro and in the rumen of sheep following ingestion of readily fermentable carbohydrates. The aim of this experiment was to determine if virginiamycin would prevent acidosis in hungry sheep given wheat, barley or oat grain without any adaptation. Merino wethers, penned individually and given wheat chaff 300 g/day for 9 days, were offered 2.1 kg of wheat, barley or oat grain, with or without virginiamycin. Rumen fluid was collected before and 6 and 24 h after grain feeding. Blood samples were obtained before and 24 and 48 h after grain feeding. 24 h after grain feeding, rumen pH was lower (P0.001) and rumen L-lactate higher (P0.05) in sheep given wheat without than with virginiamycin. D- and L-lactate were produced in equal proportions in sheep given grain plus virginiamycin, while sheep fed on grain without virginiamycin produced more of the L-lactate isomer 24 h after grain feeding. There was no effect of virginiamycin on grain intake, although intake of sheep given oat grain was lower (P0.01) than intake of sheep given wheat or barley. The number of sheep withdrawn from the experiment after grain feeding was lower (P0.05) when wheat was given to sheep with virginiamycin compared with untreated wheat grain. Feeding virginiamycin with grain did not reduce grain intake, but reduced the severity of acidosis in sheep given wheat grain.