BOVINE SOMATOTROPIN AND CLINICAL MASTITIS - EPIDEMIOLOGIC ASSESSMENT OF THE WELFARE RISK

Published data on clinical mastitis in BST trials are re-evaluated app lying general epidemiological methods. Results of pooled analyses are used to estimate relative risks and population attributable fractions. The estimates suggest, that BST treatment is associated with 15-45% e xcess incidence of clinical mastitis, which is probably due to an indi rect causal effect through increased milk yield. The increased risk is of concern to the welfare of future populations of dairy cows. It wil l limit the acceptability and usage of BST under common management con ditions, and it should be taken into account in evaluating BST prepara tions for marketing authorization.