Description
The aim of this study was to characterize the ovulation parameters in nulliparous (n=24) and multiparous (n=14) Serrana goats during the breeding season. Oestrus was synchronised with two cloprostenol injections (50 µg, 10 days apart). Transrectal ovarian ultrasonographic scanning was performed daily, during 2 consecutive oestrous cycles. Day of ovulation was considered when large follicles disappeared and the number of ovulations was confirmed by posterior corpora lutea counting. The mean ovulation rate was 1.47 ± 0.06 (n=91); no differences were observed between induced and natural oestrus. However, ovulation rate was lower in nulliparous goats than in multiparous goats, either after induced oestrus (1.25 ± 0.09, n=24 versus 2.00 ± 0.18, n=14, P<0.001) or natural oestrus (1.19 ± 0.07, n=32 versus 1.81 ± 0.09, n=21, P<0.001). 44.8% (64/134) of total ovulations were observed in left ovary and 55.2% (70/134) in the right ovary (P>0.05). Single ovulations were observed in 78.6% (44/56) of the oestrous cycles in nulliparous goats and in 20% (7/35) of the oestrous cycles in multiparous goats (P<0.01). Double ovulations occurred in both ovaries (73%; 27/37), only in the right ovary (24.3%; 9/37) or in the left ovary (2.7%; 1/37). Ovulations observed in two consecutive oestrous cycles were both single in 36.5% (19/52) of the cycles, alternatively single and multiple in 34.6% (18/52) and both multiple in 28.9% (15/52). The correlation coefficient between the number of ovulations in two consecutive oestrus was very low (r=0.31, P<0.05, n=52). In conclusion, nulliparous goats have lower ovulation rates, due mainly to a higher number of single ovulations, when compared with multiparous goats.
; Azevedo, Jorge Manuel Teixeira de 
