Lactic acidosis and its effect on wool tensile strength

An experiment was conducted to test the effect of the feed additive virginiamycin (VM) on lactic acidosis and wool tensile strength in sheep given wheat. The ground wheat grain was given in a slurry by stomach tube in increasing amounts each day up to a maximum of 1 kg per dose or until rumen pH dropped below 5.20. Sixty mature Merino wethers were all fed wheat chaff ad libitum and given the following treatments: 10 control sheep were only fed the basal diet; 10 were given intra-ruminal doses of VM; 20 sheep were given wheat grain intra-ruminally; and 20 sheep were given wheat grain containing VM. Virginiarnycin was given at a rate equivalent to 80 mg/day. All animals were fed chaff for 83 days prior to and for 120 days following the wheat and VM treatments. Rumen pH and L-lactic acid concentration were measured in all 60 sheep from the day that wheat was first given until 3 days after the last wheat drench. Lactic acidosis, defined by a rumen pH of less than 5.2 and rumen lactic acid concentration of greater than 20 mmol/L, significantly decreased staple strength of wool in sheep given the wheat drenches. Inclusion of VM with the wheat grain significantly increased (P < 0.05) the tensile strength of the wool compared with the effect of wheat on its own. Reduction in wool strength was more closely correlated with a reduction in feed intake in the days following the lactic acidosis than with either rumen pH or the concentration of rumen lactic acid.