RESUMO
The present experiment was conducted to determine (1) 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/day during 15 days and (2) the exact ovulatory activity in anestrous goats exposed to bucks for 2 hours or less 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 minutes, 30 minutes, 1 hour, 2 hours, 4 hours, or 24 hours during 15 days. Goats with plasma concentrations of progesterone greater than 0.5 ng/mL were considered to have ovulated. More than 93% of females exposed to bucks ovulated throughout the experiment regardless of 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 minutes, 30 minutes, 1 hour, or 2 hours. However, in these groups, this ovulation occurred about 2 days later than in females in contact with males during 4 or 24 hours (6.3 vs. 4.4 days; P < 0.05). We conclude that 15 minutes of daily contact with sexually active buck 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/day or less during 15 days in comparison with those in contact with males for 4 or 24 h/day.
Assuntos
Anestro/fisiologia , Estro/fisiologia , Cabras/fisiologia , Ovulação/fisiologia , Estações do Ano , Animais , Feminino , Masculino , Indução da Ovulação/métodos , Indução da Ovulação/veterinária , Fotoperíodo , Comportamento Sexual Animal , Fatores de TempoRESUMO
Two experiments were conducted to (a) determine whether sexually active males are able to stimulate the sexual activity of anestrous female goats when duration of contact is reduced to an intermittent contact shorter than 4 daily hours and (b) compare the pattern of secretion of LH when anestrous goats are exposed either permanently or intermittently to males. In the first experiment, 4 groups of anovulatory goats were exposed to sexually active males for 24, 4, 2, or 1 h/d during 15 consecutive days, whereas control females remained isolated. More than 89% of females in the groups exposed to the sexually active bucks ovulated, whereas only 5% did so in the control group (P < 0.001). However, the proportion of females ovulating before day 4 was greater in the 2-, 4-, or 24-h contact groups than in the control, whereas it did not differ between the control group and the 1-h contact group (P = 0.02, <0.001, <0.001 and 0.23, respectively). In the second experiment, 3 groups of anovulatory goats were exposed permanently (24 h/d) or intermittently (2 h/d) to bucks during 5 d or remained isolated. We found that pulsatility of luteinizing hormone (LH) increased in the intermittent and permanent contact groups after males were introduced to females (P = 0.05); this pulsatility of LH remained elevated in the permanent-contact group, whereas it decreased in the intermittent-contact group, once the male was removed (P = 0.32 and 0.05, respectively). We conclude that 1 or 2 daily hours of contact with sexually active males is sufficient to stimulate ovulatory activity in anovulatory goats; however, ovulation is obtained through a different pattern of secretion of LH.