Effects of a single oral dose of a commercial selenium cobalt and vitamin preparation on ewe fertility.

The results of a field trial on 18 farms on the effects of dosing ewes with a commercial trace element supplemented to provide 5 mg selenium, 6.5 mg cobalt, 500,000 iu vitamin A, 12,000 iu vitamin D3 and 100 iu vitamin E two weeks before joining the ram showed no beneficial effect on reproductive performance. The mean level of the enzyme glutathione peroxidase (GSH-Px) ranged in control ewes from 8.7 to 58.6 units/ml erythrocytes. Reproductive responses to the treatment varied between farms but the variation was not related to flock selenium status as indicated by the GSH-Px test.