Seminal plasma does not advance ovulation in hCG-treated sows

In gilts, seminal plasma treatment before or during the LH-surge has been found to advance ovulation in all animals by as much as 8 to 14 h. Two experiments were performed to assess whether such an advancement occurs in multiparous sows in which ovulation is induced by 750 i.u. hCG at 68 h after weaning. In both experiments, seminal plasma was inseminated at 4, 5 and 6 h after hCG (7 and 6 sows, respectively) and control sows (6 and 6 sows, respectively) were not inseminated. In Experiment 1, using Meishan semen, all sows ovulated between 38 and 44 h after hCG; no advancement of ovulation was seen due to treatment. In Experiment 2, using GY seminal plasma, 3 and 4 sows, respectively had started ovulation at 44 h after hCG. Again, no advancement of ovulation was seen due to treatment. Therefore, in both experiments, seminal plasma treatment within 4–6 h after hCG failed to advance ovulation to a similar extent as found in spontaneously ovulating gilts. It is unclear what causes this lack of effect. Maybe seminal plasma treatment does not advance hCG-induced ovulation or batches of seminal plasma differ in their ovulation-advancing properties.