To determine the relationship between plasma and tissue a-tocopherol concentrations during vitamin E depletion, weaned lambs were placed on a vitamin E-deficient diet for 0, 1, 2, 4, 8 and 12 weeks. aTocopherol was measured in plasma, erythrocytes, liver, adrenal, adipose tissue, three different skeletal muscles and heart muscle. The a-tocopherol concentration in plasma fell at the same rate as the atocopherol concentration in skeletal muscles, heart muscle, adrenal and adipose tissue. The a-tocopherol concentration in liver and erythrocytes fell at a faster rate than that of plasma and all muscle tissues. There were significant correlations between a-tocopherol concentration in plasma and a-tocopherol concentrations in all the tissues measured. Different skeletal muscles had significantly different concentrations of a-tocopherol which may relate to their differing susceptibility to nutritional myopathy. The increase in malondialdehyde in oxidatively-stressed muscle tissue and the correlation with atocopherol concentration in most muscle tissues indicated that the muscles had reduced antioxidant capacity in vitro as a result of vitamin E depletion. It was concluded that during vitamin E depletion in sheep a-tocopherol concentration in plasma was a good index of vitamin E status under the experimental conditions employed. a-Tocopherol : Vitamin E : Nutritional myopathy : Sheep
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.
Nutritional myopathy occurs as both a clinical and subclinical disease in weaner sheep in Western Australia during summer and autumn. The effect of subclinical nutritional myopathy (SCNM), caused by vitamin E deficiency or combined vitamin E and selenium deficiency, on liveweight and wool was investigated. During the period of SCNM there was no significant difference in liveweight gain in sheep with and without the disease in any of the experiments. Initial liveweight in one experiment was significantly (P < 0.05) higher in sheep that were to develop SCNM during the course of the experiment. In vitamin E deficient-selenium adequate SCNM, there was no difference in wool growth over the period of the disease and no differences in any of the wool measurements at shearing. At 2 sites, the greasy and clean fleece weights were significantly (P < 0.05) greater in a group of sheep diagnosed with more severe SCNM compared with sheep without SCNM. It was concluded that unlike the clinical disease, SCNM was unlikely to cause any economic loss.
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