Controlled breeding in dairy cows. Part 1: bovine oestrus cycle and synchronisation

Background: Timed artificial insemination (TAI) as part of a controlled breeding programme is a reproductive strategy that eliminates the requirement for oestrus detection, guarantees the submission of enrolled cows and attempts to optimise the timing of insemination relative to ovulation. However, the success of TAI requires careful cow selection, diligent herd management and the selection of an appropriate synchronisation protocol. Aim of the article: This article, the first in a two-part series, outlines the key ovarian follicular wave dynamics in the bovine oestrous cycle and the key goals of any synchronisation protocol. It describes the most commonly used drugs, their actions and how they can be combined into effective synchronisation protocols. The second part of the series, to be published in a subsequent issue of In Practice, discusses how to implement controlled breeding strategies on farms and considers factors aside from the TAI protocol that are essential for the success of any programme.