INFLUENCE OF EXOGENOUS PROGESTERONE CONTRIBUTION (CIDR) POST-ARTIFICIAL INSEMINATION IN PRIMIPAROUS EWES

Abstract

The aim of the present investigation was to evaluate the effect of the exogenous contribution of progesterone (P4) during 35 d postinsemination
in primiparous ewes on the percentage of gestation and embryonic mortality. Forty ewes were synchronized with the CIDR device, for a period of 9 d. Two d before the device was removed, 15 mg of prostaglandin F₂a v.i was applied. All the ewes were inseminated by laparoscopic (laparoscopic artificial insemination, AI) with frozen semen (straws of 0.25 mL, with 90x10⁶ spermatozoa). Subsequently to AI, the ewes were completely randomized into two experimental groups: the IASP group (n=20) inseminated ewes that did not receive additional P₄; and the IACP group (n=20) inseminated ewes that received exogenous P₄ for 35 d post-insemination. The gestation rate was evaluated by ultrasonography on d 25, 35 and 50 post-insemination and confirmed with the concentration of P₄ in serum. The presentation of estrus in response to synchronization with hormonal treatment was 100% in
ewes. The onset of estrus reports an average of 37±4.25 h, after the removing of the CIDR device. No differences were found between treatments (P>0.05) in the concentrations of P4 in serum during the estrus synchronization process (IASP: 7.66±1.6, IACP: 8.17±1.8). The percentage of pregnant between treatments until d 25 was not different (P>0.05, IASP: 60%, IACP: 55%); however, in the second diagnosis of pregnancy at 35 d post-insemination, the pregnancy rate in the IASP group was reduced by 15% compared to its initial diagnosis (P<0.05, IASP: 45%, IACP: 55%). In conclusion, the exogenous contribution of P4 in primiparous ewes during 35 d post-insemination maintains the pregnancy and reduces up to 25% the embryonic mortality.