The manifestation and detection of oestrous in heifers

Abstract

Observations on the manifestation of the oestrus were made on a group of 18 yearlings, dairy heifers. There was considerable variation in the intensity of oestrus and in the degree of interest aroused by an oestrous heifer in other heifers in the group. Thus usually only a small proportion of the group mounted an oestrous heifer, frequency of mounting varied, and different heifers tended to mount an oestrous heifer at different periods of observations during an oestrous period. Heifers on heat simultaneously were not of equal interest to the rest of the group and repeatability of mounting behaviour at successive heats was low. Mounting behaviour did not appear to be affected by stage of the oestrous cycle except that oestrous heifers were the most active mounters and best indicators of other oestrous heifers. Bunting rating and size of the group did not appear to influence mounting behaviour. The effect of various factors on the detection of oestrus are discussed.