Influence of the permanent presence of rams on the resumption of sexual activity in postpartum Barbarine ewes

The influence of the ram effect, starting at lambing, on the resumption of ovarian activity (determined by repeated laparoscopy observations) and oestrous behaviour of autumn-lambing Barbarine ewes was evaluated in 64 multiparous Barbarine ewes in the permanent presence (R; n = 32) or totally isolated (NR; n = 32) from rams. In the R treatment group, all ewes (100%) ovulated at least once before the 100-day postpartum period, compared to only 50% (P < 0.05) in the NR ewes. The first postpartum ovulation occurred 20.3 ± 9.7 days after lambing in ewes of the R treatment being shorter (P < 0.05) than the mean interval of 50.4 ± 28.7 days for ewes in the NR treatment. Resumption of postpartum ovarian activity was associated with abnormal ovarian cycles. Ewes (R) exposed to rams had a higher frequency of long cycles and tended to yield a reduced ovulation rate than ewes (NR) in isolation from rams (1.07 ± 0.26% versus 1.20 ± 0.40%). In the R treatment group, only 22 ewes of the 30 that ovulated (73%) displayed oestrus with a peak occurrence between days 30 and 40 after parturition. It is concluded that the continuous presence of rams could substantially hasten rebreeding in autumn postpartum Barbarine ewes. © 2003 Elsevier B.V. All rights reserved