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.

This experiment examined the efficacy of a single dose of �-tocopherol acetate (2000 IU) in either an aqueous or oily formulation, given as an intraperitoneal (i.p.) or subcutaneous (s.c.) injection or orally as an aqueous formulation, at raising a-tocopherol concentrations in blood plasma and liver of young sheep with low vitamin E. Maximum plasma concentrations (Cmax) were greatest in sheep supplemented by the s.c.-aqueous method or orally (4.83 and 3.49 mg/L respectively). These values were 3.0-5.7 times the C, values of the other treatment groups. Also, the time taken to reach Cmax (Tmax) was far shorter in these 2 treatments than in the other treatments (Tmax values were 0.70 and 0.65 days respectively). Tmax values were greatest for the oily formulation (42 and 73 days for the i.p. and S.C. injections, respectively). The area under the plasma a-tocopherol concentration-time curve (AUC(0-85d)), was greatest for the s.c.-aqueous group (median of 2066 mg.h/L). Six of the sheep in the i.p.-aqueous group had AUC(0-85d) values similar to the controls whereas the rest were similar to the s.c.-aqueous group. Plasma �-tocopherol acetate was only consistently detected in sheep in the s.c.-aqueous group (Cmax of 25.25 � 3.14 mg/L and Tmax of 0.24 � 0.03 days). Pharmacokinetic modelling of the plasma data obtained from sheep in the s.c.-aqueous group was helpful in understanding the factors which controlled the appearance and disappearance rates of plasma �-tocopherol in this group. In contrast to plasma data, liver concentrations of �-tocopherol at days 24 and 57 were greatest in sheep supplemented by the i.p.-oily method. The s.c.-aqueous was the second most effective method at raising concentrations in the liver. The results suggest that supplementation by s.c. injection of an aqueous formulation may be an effective means of administering vitamin E to sheep.

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