Some Relationships Between Trichostrongylid Infestation and Cobalt Status in Lambs: II. Trichostrongylus Axei Infestation * *Extracted from a thesis presented to Dublin University for the degree of Ph.D. Pt. 1 appeared in Br. vet. J., 121, 362 (August), 1965

SUMMARY Forty-four lambs were reared under worm-free conditions and fed on a diet low in cobalt. When their average age was 11 weeks they were randomly divided into four groups, two of which were fed a cobalt-supplemented diet. Five weeks later the lambs of one supplemented and of one non-supplemented group were given 3,000 Trichostrongylus axei infective larvae until a total of 51,000 had been given. Serum vitamin B12 levels were indicative of pronounced cobalt deficiency in non-supplemented lambs. Parasitic infestation did not bring about any fall in serum vitamin BI2 in either cobalt-supplemented or cobalt-deficient lambs. Cobalt deficiency caused a highly significant reduction in growth. Infestation in cobalt-deficient lambs, however, caused no significant depression of live-weight at a time when a similar infestation was causing a highly significant decrease in the weight gain of cobalt-supplemented lambs. This result may mean that either a low cobalt status in the host or general malnutrition as a result of cobalt deficiency had the effect of reducing the pathogenicity of T.axei. Infestation, by causing dehydration and concomitant haemoconcentration tended to mask the anaemia due to cobalt deficiency.