Vitamin E treatment of weaner sheep. I. The effect of vitamin E supplements on plasma α-tocopherol concentrations, liveweight and wool production in penned or grazing sheep

Abstract

Effect of vitamin E supplements on liveweight gain and wool production, and their effectiveness in increasing plasma alpha -tocopherol concentrations and preventing nutritional myopathy was investigated. Commercial preparations were compared in pen and grazing experiments in the first part of the study. In a pen experiment, 3 different treatments, intramuscular oily injection, oral drench and dried supplement added to feed, were compared; in grazing sheep, intramuscular oily injection and oral drench were compared. The intramuscular oily injection was slow to increase the plasma concentrations of alpha -tocopherol in pen experiments and did not prevent vitamin E deficiency and development of subclinical myopathy in grazing experiments. Oral treatments increased plasma alpha -tocopherol concentrations in the pen experiment; though repeated oral drench did not increase plasma alpha -tocopherol in the grazing experiment, the development of subclinical nutritional myopathy was prevented. Aqueous preparations of vitamin E and the effect of selenium supplements in grazing sheep were studied in the second part of the study. Aqueous injections of 2000 mg of vitamin E acetate by intramuscular and subcutaneous routes in December and February were successful in rapidly increasing and maintaining plasma alpha -tocopherol concentrations in grazing weaner sheep. Injections of aqueous emulsions of vitamin E acetate could be the most useful preventative treatment for nutritional myopathy if problems of tissue damage can be overcome. None of the vitamin E supplements increased liveweight gain in any of the experiments, and there was no increase in wool quantity or quality in any of the grazing experiments. When selenium and vitamin E supplementation were compared, selenium-supplemented sheep had greater wool length and fibre diameter over summer-autumn than vitamin E-treated or control sheep. Vitamin E supplements are expensive; unless flocks are susceptible to vitamin E-responsive myopathy, it is suggested that there is little economic justification for using vitamin E as a supplement over the summer.