Reproductive performance of seasonally anovular mixed‐bred dairy goats induced to ovulate with a combination of progesterone and eCG or estradiol

Adult goats (n = 32) were randomly assigned to one of four treatments (n = 8, each): (i) progesterone (P₄) + equine chorionic gonadotropin (eCG), treated with 25 mg progesterone intramuscularly (i.m.) + 250 IU eCG 24 h later; (ii) cronolone + eCG, treated with vaginal sponges ‐ 20 mg cronolone × 7 days + 250 IU eCG at pessary removal; (ii) P₄ + estradiol (E₂), treated with 25 mg progesterone i.m. + 1 mg estradiol 24 h later; (iv) cronolone + E₂, treated with vaginal sponges ‐ 20 mg cronolone × 7 days + 1 mg of estradiol i.m. at pessary removal. Goats were tested for estrus throughout the presence of a buck. Seven days prior and after treatment, an ovarian ultrasonographic scanning was performed to determine ovarian function and structures. An ultrasonographic pregnancy diagnosis was performed on day 30 post‐service. In all groups, 100% estrus response was observed within 96 h post‐treatment. While ovulation occurred in 100% of P₄ + eCG and cronolone + eCG treated goats, the other groups only depicted 50% ovulatory activity (P < 0.05). Pregnancy rate was higher (P <0.05) in the P₄ + eCG and cronolone + eCG groups (88 and 100%, respectively), compared with 38% in P₄ + E₂ and cronolone + E₂ groups. The best treatments were those in which eCG was applied. The P₄ + eCG treatment was a pessary‐free, cheaper and effective protocol to induce ovulation in goats during the seasonal anovulatory period.