INCREASED TOLERANCE TO ANNUAL RYEGRASS TOXICITY IN SHEEP GIVEN A SUPPLEMENT OF COBALT

To determine whether oral cobalt supplements could modify the clinical onset of annual ryegrass toxicity, groups (n = 5) of sheep were dosed orally with 0, 4 or 16 mg cobalt/day. After 3 weeks on this treatment , toxic ryegrass seed was added to their feed to provide 0, 0.15 and 0 .30 mg corynetoxins/kg body weight, daily. Sheep receiving cobalt inge sted 30% more toxin than did unsupplemented sheep before clinical sign s developed (P = 0.03). There was no significant difference between gr oups receiving 4 and 16 mg cobalt. The results showed that cobalt dela yed, but did not prevent, the onset of clinical signs of annual ryegra ss toxicity.