Fifteen minutes of daily contact with sexually active male induces ovulation, but delays it’s timing in seasonally anestrous goats
Résumé
The present experiment was conducted to determine i) whether the sexually active bucks are able to stimulate the ovulatory activity of seasonal anestrous goats when the daily contact is reduced to 15 min per day during 15 days; and ii) the exact ovulatory activity in anestrous goats exposed to bucks for 2 h or less than 2 h per day during 15 days. One group of goats (n=15) was isolated from bucks. The other six groups (n= 15 each) were exposed to sexually active bucks (n= 1 each) for 15 min, 30 min, 1 h, 2 h, 4 h, or 24 h during 15 days. Goats with plasma concentrations of progesterone > 0.5 ng/mL were considered to have ovulated. More than 93% of females exposed to bucks ovulated throughout the experiment regardless the duration of contact with males, whereas none of them ovulated in the isolated group (P < 0.0001). The proportions of females that ovulated at least once did not differ among groups, as well as the proportions of goats that displayed normal or short ovulatory cycles. The interval between the introduction of males and the first ovulation did not differ among groups of goats in contact with bucks for 15 min, 30 min, 1 h or 2 h. However, in these groups, this ovulation occurred about 2 days later than in females in contact with males during 4 h or 24 h (6.3 vs. 4.4 days; P < 0.05). We conclude that 15 min of daily contact with sexually active bucks is sufficient to stimulate the ovulatory activity in seasonally anestrous goats, but the first ovulation is delayed in goats exposed to males for 2 h per day or less during 15 days in comparison with those in contact with males for 4 h or 24 h per day.