Endocrine manipulation--toxicological frontiers

A variety of hormonal products has been developed for use in food animal production. Applications include therapy, particularly for fertility problems, zootechnical purposes comprising mainly the management of reproduction, for example the synchronization of oestrus, and the improvement of performance such as increased growth rate or increased milk yield. Although there is well established legislation both domestically and internationally for the registration of veterinary pharmaceutical products, hormones have become a special case at least to the public. This is particularly true when hormones are used to improve animal performance. The two notable issues to date have been the use of anabolic steroids as growth promoters and of bovine somatotrophin (BST) to increase milk yield in dairy cows. The high public profiles of these two issues have separately forced the introduction of new legislation in the EC, which will continue to have far-reaching implications for research and development in animal health and production for many years. This paper interprets recent developments in legislation concerning veterinary products and hormonal products in particular, giving examples of the toxicological assessment of four specific molecules and speculating upon the likely implications for the future practical exploitation of endocrine mechanisms in food animal production.