Effect of follicle size on fertility in cattle. Academic Article uri icon

abstract

  • Abstract Procedures that control the timing of ovulation are of enormous value in advancing the use of reproductive technologies in all species. Among cattle, most protocols that control the timing of ovulation utilize gonadotrophin-releasing hormone (GnRH) around the time of insemination. A luteinizing hormone (LH) surge and ovulation are induced with an injection of GnRH. However, GnRH results in the ovulation of a wide range of follicle sizes regardless of whether or not standing oestrus had been initiated. Among both heifers and cows, the relationship between follicle size and pregnancy success following a fixed-time insemination protocol was quadratic. Small follicles induced to ovulate resulted in lower pregnancy rates, increased embryonic/ foetal mortality, and a slower rise in subsequent concentrations of progesterone compared with cows induced to ovulate larger follicles. Among postpartum cows, there was no relationship between ovulatory follicle size and pregnancy status when cows spontaneously initiated standing oestrus and ovulated. Furthermore, animals that exhibited standing oestrus within 24 h of fixed-time insemination had greater pregnancy success compared with animals that did not exhibit standing oestrus, and cows that exhibited standing oestrus had greater circulating concentrations of estradiol compared with cows that did not. Therefore, follicular maturity at time of GnRH-induced ovulation can influence pregnancy success following a fixed-time insemination protocol.

published proceedings

  • CABI Reviews

author list (cited authors)

  • Perry, G.

citation count

  • 1

complete list of authors

  • Perry, G

publication date

  • January 2007