AN EXAMINATION OF THE SELENIUM NUTRITION OF SHEEP IN VICTORIA

Abstract

The Se nutrition of sheep throughout Victoria, Australia, was assessed by a survey of the blood glutathione peroxidase activity in 708 flocks. The blood glutathione peroxidase activity in sheep had a seasonal variation with lowest levels in the spring. The enzyme activity was correlated with the blood Se concentration. Areas where blood Se was < 0.03 .mu.g/ml in spring were defined. Sheep with low Se nutrition were grazing pastures in the high rainfall areas on acid soils, particularly those derived from granite. Se concentrations in pasture samples examined were > 0.02 mg/kg and superphosphate application had no significant effect on the Se content of pasture. Management practices such as high stocking rates and rates of application of superphosphate to pasture were associated with low blood glutathione peroxidase activities in sheep. The Se nutrition of most sheep flocks in Victoria evidently is adequate and the deficient areas are localized. There seems little requirement for supplementation of adult sheep. As the delayed type of white muscle disease in spring lambs appears to be the main Se-responsive disorder, direct supplementation of lambs in the low Se areas would be the most effective method of ensuring adequate Se nutrition.