ANTIBODIES AGAINST NEMATODES IN SERUM, MILK AND BULK MILK SAMPLES AS POSSIBLE ESTIMATORS OF INFECTION IN DAIRY-COWS

Antibodies against Ostertagia spp., Cooperia spp. and Dictyocaulus viv iparus were assessed in serum and individual milk samples of cows and in bulk milk samples from the refrigerating tank. Titres in milk sampl es were related to serum titres, but also influenced by milk yield, la ctation stage and age of the cow. Correlation coefficients between ser um and individual milk samples were highly significant, and varied fro m 0.42 to 0.56. Correlations between herd means of serum titres and he rd means of individual milk titres varied from 0.41 to 0.61, and those between herd means of serum titres and means of bulk milk samples fro m 0.43 to 0.67. Finally, the correlations between herd means of indivi dual milk samples and means of bulk milk samples varied from 0.52 to 0 .82. This variation was dependent upon worm species and whether or not correction for milk yield was applied. The discrimination of herds wa s evaluated by the between/within herd ratio of variances. F values fo r all types of samples were highly significant, and at least as high f or milk samples as for serum samples. If, as has been shown for serum samples, a positive relationship exists between the milk yield respons e to anthelmintic treatment and the mean herd litre of milk samples or bulk milk samples, assessment of these titres could offer a rational basis for treatment of dairy cows.