Determination of the reproductive performance of Holstein cows in Uruguay

Trials to determine the onset of post-partum (pp) ovarian activity in a Holstein herd were carried out in 1985 and repeated during the same time of the year in 1987. In each, 20 recently calved adult cows and first-calf heifers were randomly selected and sampled for milk progesterone (MP4) determination twice a week between days 10 and 90 pp. Climatic conditions and availability of high quality fodder were better in 1987 than 1985. Results showed differences both in pregnancy rate (40% vs. 65%), as well as in the percentage of anoestrous cows (60% vs. 15%) between 1985 and 1987, respectively. In the second trial, not all cows in physiological oestrus (according to MP4 measurements) were identified in heat by observation of behavioural signs. It was concluded that nutritional levels greatly influence the reproductive efficiency of the herd on this farm, and that poor oestrus detection was a further contributory factor. Another trial conducted on a dairy herd in order to compare the efficiency of oestrus synchronization by PGF2α with manual enucleation of the corpus luteum (CL) showed no differences between treatment groups. Ovarian palpation to assess the presence of a CL was accurate in 69% of cases while the use of MP4 estimations proved to be 100% efficent. (author). 13 refs, 1 fig., 2 tabs