Effectiveness of alpha-tocopherol and selenium supplements in preventing lupinosis-associated myopathy in sheep.

Objective: To compare the effectiveness of combined selenium and alpha-tocopherol acetate treatments in preventing lupinosis-associated myopathy in sheep.

Design: Measurement of plasma muscle and liver enzymes, and histopathological examination of muscle and liver in the treatment groups.

Procedure: The treatments were: subcutaneous injections of selenomethionine and vitamin E (sc(SeM+E)), an intraruminal selenium pellet and oral doses of vitamin E and intramuscular injections of selenomethionine combined with either oral doses of vitamin E (imSeM+orE) or intramuscular injections of vitamin E in an oily carrier. Another group received no supplements, while a control group was given selenium pellets on day 0 and fortnightly oral doses of vitamin E from day 0 to 72. To produce lupinosis-associated myopathy, the sheep were fed a diet low in vitamin E and given repeated injections of a crude extract of Diaphorthe toxica. Groups sc(SeM+E) and imSeM+orE were stressed by dosing with protected polyunsaturated fatty acids from day 56 onwards.

Results: Lupinosis-associated myopathy was induced in all unsupplemented sheep. In these sheep the storage of Se increased and that of vitamin E decreased. The subcutaneous treatment was highly effective in preventing lupinosis-associated myopathy and also produced the highest vitamin E concentrations in plasma and liver. Supplemental vitamin E was more efficacious than supplemental Se. Concentrations of vitamin E in the livers of sheep given intramuscular vitamin E were higher than expected based on plasma concentrations. Oral doses of vitamin E proved the least effective method of increasing concentrations in liver. Lupinosis did not affect Se concentrations in liver or muscle.

Conclusion: The sc(SeM+E) treatment is highly effective in preventing lupinosis-associated myopathy but needs to be further assessed when selenium and vitamin E are both limiting in the diet.