Preovulatory LH peak and time of ovulation in nulliparous and primiparous goats after male effect

Simões, João
Azevedo, Jorge Manuel Teixeira de
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The aim of the present study was to determine the time of preovulatory LH peak and ovulation in anoestrous goats, after stimulation by male effect. Seven nulliparous and eight primiparous Serrana goats were isolated from bucks during nonbreeding season. Anoestrus was confirmed by circulating progesterone levels. A 6-day progestagen treatment (Chronogest® 45 mg FGA, Intervet, Holland) was performed to synchronize oestrus on early May. Vaginal sponges were removed at the time of buck introduction (BI). Plasma LH levels were determined (ELISA), every 4 h, through 24 h after onset of oestrus and total number of ovulations were detected by transrectal ultrasonography, every 8 h, until 44 h. No significant differences (P > 0.05) were observed between nulliparous and primiparous goats for the interval between BI and onset of oestrus (50.6 ± 3.6 h vs 45.6 ± 2.9 h), preovulatory LH peak (54.9 ± 3.2 h vs 55.5 ± 3.8 h) or ovulation (77.7 ± 3.0 h vs 78.3 ± 3.6 h). However, the interval between the onset of oestrus and preovulatory LH peak was lower in nulliparous (4.3 ± 0.8 h) than in primiparous (10.5 ± 2.4 h; P < 0.05) goats. The interval between the onset of oestrus and ovulation was also lower in nulliparous (27.1 ± 1.4 h) than primiparous (33.3 ± 2.3 h; P < 0.05) goats. The interval between preovulatory LH peak and ovulation was constant between nulliparous (22.9 ± 1.5 h) and primiparous goats (22.8 ± 1.7 h; P > 0.05). In conclusion, these results showed that nulliparous ovulate, in average, early than primiparous goats regarding the onset of oestrus.
Goats , LH , Ovulation