1918
Effect of prostaglandin F2α on fertility of ewes treated with a short-term progesterone-based estrous synchronization protocol
Previous studies have shown either no effect or a lower fertility in ewes treated with PGF2α at the end of a short-term progesterone-based estrous synchronization (STPBES) protocol. The objective of this study was to further evaluate the effects of PGF2α when used as a component of STPBES treatments in ewes. Ewes (n=423) from 4 farms located in WV and PA were randomly assigned to receive controlled internal drug releasing devices (CIDR-g, 0.3g progesterone) for 5 (n=243) or 7 (n=180) days. At insert removal, approximately half of the ewes in each treatment group were randomly assigned to received either 0 (n=203) or 4 (n=220) mL Lutalyse (20 mg dinoprost; PGF2α) and were joined with sexually mature rams. Data were analyzed using analysis of variance with the model consisting of the main effects of duration of treatment with CIDR devices, injection with PGF2α, farms, and their interactions and additionally, least square means for treatment effects were determined. The mean estrous response was 82.2 ± 36.9% and was not affected by treatments. Conception rate (P=0.01; 67.1 ± 4.0% vs 52.9 ± 4.0%), pregnancy rate (P<.01; 58.1 ± 3.5% vs. 44.0 ± 3.3%) and proportion of ewes lambing to the first service (P<.0001, 45.8 ± 3.8% vs. 33.9 ± 3.9%) were higher in ewes that did not receive PGF2α (CIDR devices alone) than in ewes treated with CIDR devices and PGF2α. Conception (P=0.01; 67.1 ± 4.1% vs 52.9 ± 3.9%) and pregnancy rates (P<.0001; 56.0 ± 3.1% vs. 46.2 ± 3.9%) were higher, and proportion of ewes lambing to the first service period (P = 0.07, 44.3 ± 3.9% vs 35.4 ± 3.8%) tended to be higher in ewes treated with CIDR devices for 5 days compared to those treated for 7 days. In conclusion, injection of PGF2α at insert removal in STPBES protocols did not increase estrous response and decreased fertility at the synchronized estrus.
Keywords:
prostaglandin, ewes, fertility, progesterone