The effect of sub-clinical Johne's disease on milk production, fertility and milk quality in Israel

The aim of this study was to assess the effect of sub-clinical Johne's disease (indicated by comparing anti-Mycobacterium avium subsp. paratuberculosis (Map) antibodies, detected by commercial IDEXX ELISA test kit) on milk production, intercalving interval and somatic cell counts. Prevalence of Map test-positive animals in the three herds was 7 %; 1.5 % for the first lactation, 7 % for the second, 14 % for the third and 10 % for the fourth and higher lactation. Animals that tested negative in the ELISA test during one month of study produced significantly more milk than those tested positive (p = 0.01). The comparison of the previous milk recordings among the positive cows, showed more production of milk during their first, second and third lactations and less throughout later periods in. None of these differences, however, were statistically significant. Comparison of between partum interval and somatic cell counts among the two groups showed no significant differences. It is therefore concluded that sub-clinical Johne's disease according to the factors evaluated in this study did not pose a significant herd problem.