FERTILITY FOLLOWING OESTRUS INDUCTION USING PGF2a AND TREATMENT WITH GnRH AND hCG IN REPEAT BREEDING CATTLE SHOWING PROLONGED OESTRUS

Abstract

The trial was conducted to evaluate the fertility o; repeat breeding cattle showing prolonged oestrus after induction using dinoprost and further treatment with GnRH and hCG. Results revealed that prostaglandin alone was highly effective with a reasonable Improved conception rate in prostaglandin induced oestrum in cows was reported by Plunkett et al. (1984) and Leeba (2003). In group II and III in which GnRH and hCG was administered during induced oestrus, a lower conception rate was obtained as compared to group I repeat breeding animals. lyer and Sreekumaran (1992) and Velayudakumar (2003) obtained a higher conception rate when GnRH was administered to repeat breeding cattle having ovulatory disturbances. Similarly, higher conception rate in hCG treated repeat breeding cattle was reported by Mehta et al. (1986), Goley and Kadu (1995) and Selvaraju et al. (2004). However, Archbald et al. (1993) reported that treatment with GnRH at or prior to insemination did not improve the conception rate in repeat breeding dairy cows. Similarly, Swanson and Young (1990) observed that hCG administration at the time of insemination failed to improve conception rate. Mialot et al. (1999) recommended AI at the observed oestrus in PGF2r induced animals when the oestrus detection was conducted most satisfactorily. However, herds in which oestrus detection was poor, they recommended the sequence of GnRH plus PGF2~ protocol and fixed time AI. conception rate. Administration of GnRH and hCG during induced oestrus was not beneficial in improving the conception rate. It can be recommended that induction of oestrus using prostaglandin could be employed for enhancing the conception rate in repeat breeding animals with the history ofi prolonged oestrus.