EL RETORNO AL ANESTRO, LAS PÉRDIDAS EMBRIONARIAS Y LOS ABORTOS COMO PRINCIPALES CAUSAS QUE REDUCEN LA FERTILIDAD DE LAS CABRAS SOMETIDAS AL EFECTO MACHO

Background. In anestrous goats exposed to sexually active male goats ("male effect"), more than 90% display estrus and ovulate, but only 70% give birth. Objective. To determine the causes that reduce fertility at birth of goats exposed to the male effect. Methodology. Twenty-nine goats in seasonal anestrus that had a body condition of 1.3 ± 0.05 were used. Three adult male goats were exposed from November 1 to January 15 to artificial long days (16 h of light per day) followed by natural photoperiod. The three males were introduced into the group of goats on March 29, remaining with them for 15 days. Subsequently, from day 16 (April 13), only one male provided with a ventral harness to prevent copulation remained with the females until the end of the observations. Estrus, ovulations, pregnancies and their evolution over time were determined. Results. All goats were detected in estrus, and 28 of 29 ovulated. Most of the goats (23/29) were diagnosed pregnant 38 days after the introduction of males, and this proportion did not differ from that registered at 72 days (18/29; P = 0.09). Of the 23 females diagnosed pregnant at 38 days, 16 gave birth. Of the 13 goats that did not give birth, six returned to the anestrus after having presented estrus behavior associated or not with ovulations; four lost the embryo between days 45 and 58; one was diagnosed as pseudopregnant at 58 days and two aborted at 95 and 129 days of pregnancy. Implications. These results show that fertility at kidding is reduced in goats exposed to sexually active male goats, most likely due to the low body condition of the females. A nutritional supplementation could improve the fertility of females exposed to the male effect. Conclusion. The results obtained in this study allow us to conclude that returning to anestrus, embryo losses and abortions reduce the fertility of goats subjected to the male effect during the seasonal anestrus.