Post–Mating Mefepronic acid treatment has no effect on Progesterone levels and fertility in early lactating ewes during the non–breeding season

This study aimed to assess the effects of post–mating treatment with mefepronic acid on serum P4 concentrations and reproductive parameters in early lactating Merino ewes during the non–breeding season. A total of 92 Merino ewes, 40-50 days (d) postpartum, were treated with an intravaginal sponge containing 60 mg of medroxyprogesterone acetate for duration of 7 d during the non–breeding season. On the day the sponge was removed (d 7), an injection of 500 IU eCG was administered. The mated ewes were then randomly divided into two groups: a control group and a treatment group. In the treatment group (MA) (n=28), ewes received an intramuscular injection of 10 mg·kg-1 mefepronic acid on d 9 post–mating. In the control group (n=27), the ewes did not receive any drug treatment on d 9 post–mating. The results showed that there were no statistically significant differences (P>0.05) between the Control Group and MA Group in pregnancy rates (33.3% and 39.2%), early fetal mortality rates (22.2% and 18.2), lambing rates (77.8 and 81.8%), twin rates (0 and 33.4%) and litter sizes (1.0 and 1.44). The P4 concentration on d 11 post–mating in the MA group (2.74 ng·mL-1) was not significantly different from that of the control group (3.16 ng·mL-1) (P>0.05). It is concluded that post–mating mefepronic acid treatment did not improve the P4 and fertility in early lactating Merino ewes during the non–breeding season.