Applied biotechnology for improving fertility of herds in Argentina

In an attempt to find methods to shorten the calving to conception interval of dairy cattle in Argentina, three research projects were carried out: (1) use of hormonal treatments in the early post-partum period to increase fertility in non-cycling cows; (2) treatments to increase the fertility of cycling cows; and (3) management systems to improve the efficiency of oestrus detection. In non-cycling cows, fewer services per conception and earlier pregnancies were obtained when a progesterone suppository was placed intravaginally (PRID treatment) 24-31 days post-partum. No statistical reduction in days open was observed, however, because of the great variability in response within groups. GnRH injection given 24 and 25 days post-partum did not improve reproductive indices. In cycling cows, clitoral massage after AI did not enhance fertility, while GnRH 14 days post-service resulted in pregnancy rates of 68.4% compared with 25% in the control group. In an attempt to improve the efficiency of oestrus detection successive periods of either 10 or 14 days of 'heat' observation followed by similar periods of no observation, combined with the systematic use of an oestrus synchronizer (cloprostenol), resulted in the same reproductive performance as in control cows observed continuously but with a saving of 50% in time spent in oestrus detection. In a seasonally bred herd, a reduction of 12 days in interval to conception and subsequent improvement in milk produced in the following season were obtained by synchronizing oestrus at the start of the breeding season with a norgestomet implant followed by a prostaglandin injection one day before implant removal. In repeat breeders, a second implant 9 days and 21 days later was found to be effective. (author). 24 refs, 2 figs, 4 tabs