The accuracy of several aids in detecting oestrus in dairy cattle

The accuracy and efficiency of oestrus detection using behavioural observations only, or in combination with hormone-treated steers or tail paint, was assessed on a large commercial dairy herd of 120 cows. The oestrus detection rate was 50, 88 and 80%, respectively, with no significant difference in conception rate between methods following artificial insemination. Continual observation for 12 h during the day detected 83% of oestrous cows over the 3-week period.

Progesterone analysis of fore-milk confirmed oestrus in all cows detected except for 5 cows detected with steers and 4 with tail paint. As all except 2 of these animals conceived at that oestrus, the accuracy of the 3 methods was considered to be the same.

Oestrous activity in cows was high at morning milking, then rose again to reach a peak in early afternoon. Mean number of mounts/oestrous cow, observed during the 12 h of continual daily observation, was 14.6 +- 1.8.

The implication of these results on dairy herd management are discussed.