Equine Chorionic Gonadotropin Treatment 11 Days After Artificial Insemination Reduces Pregnancy and Lambing Rates in Creole Ewes

This study evaluated the effects of equine chorionic gonadotropin (eCG), 11 days after artificial insemination (AI) on pregnancy and lambing rates in Creole ewes. After laparoscopic insemination, ewes were randomly assigned to either eCG (nulliparous, n=14 and multiparous, n=16) or no eCG (nulliparous, n=13 and multiparous, n=15) treatment. On day 11 (day zero=AI) 330 IU of eCG was administered IM to eCG treatment ewes. Blood samples were taken on day 11 and 15 to determine the estradiol and progesterone concentrations. The presence or absence of large follicle and large corpus luteum were evaluated on day 15, pregnancy on day 35 by ultrasound, then the lambing rate. In ewes, treatment with eCG increased the number of large follicles (eCG, 11/30 vs. No eCG, 4/28; p=0.041), turgid uteruses (eCG, 13/30 vs. No eCG, 1/28; p=0.005) and large corpora lutea (eCG, 15/30 vs No eCG, 6/28; p=0.013). There were higher concentrations of estradiol-17 ß (10.43±0.42 vs. 6.24±0.25 pg mL^-1; p=0.0001) and serum progesterone (8.22±0.21 vs. 5.28±0.19 ng mL^-1; p=0.0001) in eCG treated ewes. However, eCG reduced the pregnancy rate (eCG, 13/30 vs. no eCG, 23/28; p=0.003) and the lambing rate (eCG, 9/30 vs. no eCG, 20/28; p=0.002). In conclusion, treatment with eCG 11 days after AI reduced pregnancy and lambing rates in Creole ewes.