A CIDR-based AI protocol establishes pregnancy in repeat-breeder dairy cattle

The objectives of this study were to document ovarian and endocrine responses as well as pregnancy establishment following the treatment of repeat-breeder crossbred dairy cattle with a progesterone-releasing controlled internal drug release (CIDR) -based artificial insemination (AI) protocol. Cattle (25) received prostaglandin F2a (PGF2a , 500ìg) on day 0, concurrent with the intravaginal placement of CIDR (1.38 g progesterone) for 15 days, followed by gonadotropin releasing hormone (GnRH) analogue (20ìg) administration at the spontaneous onset of estrus (day 17, 18 or 19). About 10 h after GnRH, AI was carried out in all the cattle. On day 0, a corpus luteum (CL, 13.7±1.4 mm) and a large follicle (11.1±0.6 mm) were detectable in all the cattle. On day 15, the former was regressed (P0.05), whereas the latter disappeared completely in all the animals. Estrus detection was carried out daily subsequent to CIDR removal. All the cattle exhibited onset of estrus between 48–96 h after CIDR removal. The preovulatory follicle observed at the time of AI (15.0±0.5 mm) ovulated in all the cattle (P0.05) between 72–120 h after CIDR removal (or 24–48 h after GnRH). First service conception rate was appreciably greater (52%, P0.05) in comparison to 0% conception rate of all the cattle during their previous AIs (4.2±0.2). Retrospective analysis suggested that cattle failing to conceive had persistently higher (P0.05) luteal activity on the day of AI compared to their conceiving counterparts. In conclusion, a CIDR-based (PGF2a +CIDR-GnRH) based AI protocol is highly successful for inducing ovulation in the repeat-breeder (due to endocrine dysfunctions) cattle, and resulted in an acceptable conception rate.