Ovsynch plus CIDR-based fixed-time AI protocol as a therapeutic strategy in repeat-breeder crossbred dairy cattle

Cattle(18) were administered GnRH analogue (20 µg buserelin) on day 0 and day 9 and PGF2á (500 µg cloprostenol) on day 7. A controlled internal drug release (CIDR, 1.38 g progesterone) device was inserted from day 0 till day 7. On day 10, AI was carried out in all the cattle. In response to day 0 GnRH, all the cattle ovulated within 24 h with subsequent development of corpus luteum (CL). All the cattle responded to PGF 2á 2á on day 7. All the cattle exhibited synchronous ovulation between 72–96 h after CIDR and removal on day 7 (or 24 and 48 h after day 9 GnRH). First service conception rate was appreciably higher (61%) than 0% conception rate of all the cattle during their previous AIs (4.06±0.29). It is inferred that Ovsynch plus CIDR-based fixed-time AI protocol is highly successful for inducing synchronized ovulation in repeat-breeder cattle, and yields an appreciably high conception rate.