OESTRUS detection is the keystone to the survival of any dairy enterprise. Accurate oestrus detection will provide the most appropriate timing of artificial insemination (AI) to produce the maximum conception rate possible (Anon 1984). Suboptimal oestrus detection and conception rates lead to lost opportunities in maximising profits in the dairy industry by decreasing milk yields per day of a cow's life, coupled with increased culling due to failure to conceive (Esslemont and Kossaibati 2002). Oestrus detection in dairy herds where stock bulls are used is vital, as bulls may be sub- or infertile. If a problem is not diagnosed and corrective measures such as changing the bull and/or beginning AI are not taken the result will be extended calving intervals and increased barren rate percentage. In a paper summarised in this week's issue of Veterinary Record , Holman and others (2011) compare various oestrus detection methods in a commercial UK dairy herd. Staff simply …