Synchronization of ovulation in cyclic gilts with porcine luteinizing hormone (pLH) and its effects on reproductive function

The overall objective was to evaluate the use of porcine luteinizing hormone (pLH) for synchronization of ovulation in cyclic gilts and its effect on reproductive function. In an initial study, four littermate pairs of cyclic gilts were given altrenogest (15 mg/d for 14 d). Gilts received 500 μg cloprostenol (Day 15), 600 IU equine chorionic gonadotropin (eCG) (Day 16) and either 5 mg pLH or saline (Control) 80 h after eCG. Blood samples were collected every 4 h, from 8 h before pLH/saline treatment to the end of estrus. Following estrus detection, transcutaneous real-time ultrasonography and AI, all gilts were slaughtered 6 d after the estimated time of ovulation. Peak plasma pLH concentrations (during the LH surge), as well as the amplitude of the LH surge, were greater in pLH-treated gilts than in the control (P = 0.01). However, there were no significant differences between treatments in the timing and duration of estrus, or the timing of ovulation within the estrous period. In a second study, 45 cyclic gilts received altrenogest for 14–18 d, 600 IU eCG (24 h after last altrenogest), and 5 mg pLH, 750 IU human chorionic gonadotropin (hCG), or saline, 80 h after eCG. For gilts given pLH or hCG, the diameter of the largest follicle before the onset of ovulation (mean ± S.E.M.; 8.1 ± 0.2 and 8.1 ± 0.2 mm, respectively) was smaller than in control gilts (8.6 ± 0.2 mm, P = 0.05). The pLH and hCG groups ovulated sooner after treatment compared to the saline-treated group (43.2 ± 2.5, 47.6 ± 2.5 and 59.5 ± 2.5 h, respectively; P < 0.01), with the most synchronous ovulation (P < 0.01) in pLH-treated gilts. Embryo quality (total cell counts and embryo diameter) was not significantly different among groups. In conclusion, pLH reliably synchronized ovulation in cyclic gilts without significantly affecting embryo quality.