Oregon State University Research on the effects of PG-600® on ovulations, pregnancy and lambing rates

Abstract

Our objective was to evaluate reproductive effects of varying gonadotropin dosages on anestrous ewes pretreated with progesterone and then exposed to a novel ram. Hypothesis was that a lower dosage of P.G. 600® (equine chorionic gonadotropin 80 IU/ml and human chorionic gonadotropin 40 IU/ml) induces estrus in anestrous ewes. Twenty-four anestrous ewes were treated with intravaginal progesterone-releasing devices for 9 days and given prostaglandin F2α 2 days prior to device withdrawal. On the day of progesterone withdrawal (day 0), ewes were given 5 ml of P.G. 600® (T1; n = 8), 1.5 ml of P.G. 600® (T2; n = 8) or 5 ml saline (control group, C; n = 8). Three rams were rotated every 4 hours through each group of ewes for 4 days. Venous blood samples were collected on day 0 prior to treatment (0 hour) and at 2, 4, 6, 8, 12, 24, 48, 72, 96, 120, 144, 168, and 336 hours. Serum estradiol-17β and progesterone concentrations were determined by chemiluminescence. Ovulation and pregnancy rates were determined using transrectal ultrasonography on days 9 – 11 and on days 21 and 28. Serum progesterone concentrations increased (p < 0.00001) in T1 compared to T2 and C groups. Serum estradiol concentrations, ovulation, pregnancy, and fecundity rates, and weaning weights were not significantly different among groups. We concluded that gonadotropin treatment neither enhanced nor diminished reproductive productivity.