Oestrous synchronisation in cattle--current options following the EU regulations restricting use of oestrogenic compounds in food-producing animals: a review.

Oestrous synchronisation is an important strategy to improve reproductive management of cattle. The use of oestradiol-17beta, and its related ester derivatives, in food-producing cattle for the purposes of oestrous synchronisation is prohibited in the European Union since October 2006; a serious limitation in the implementation of large-scale use of cost effective synchronisation regimens in both dairy and beef herds. This has obvious consequences within the EU and also in other countries that have restricted the use of oestradiol following the EU ban. Oestrous synchronisation is an important facilitator for the use of artificial insemination, a necessary part of any national herd genetic improvement scheme. Presently, only 35% of the Irish dairy herd is bred by artificial insemination; and facilitation rather than restriction is required to increase this percentage. Ideally synchronisation of oestrus should increase submission rates, improve or at least not affect conception rates, and thus, increase overall pregnancy rate at the end of the breeding season. This should reduce the proportion of cows to be culled. This paper aims to review the oestrous synchrony options available in EU countries and other countries affected by the European ban on oestrogenic compounds being used for oestrous synchrony protocols. Currently, the options available for oestrous synchronisation are generally not as effective, efficient or cost effective as those that incorporated use of oestrogenic compounds.