Reproductive performance of postpartum ewes treated with insulin or progesterone hormones in association with ram effect

Contents The reproductive performance of postpartum Santa Ines (SI) and Morada Nova (MN) ewes treated with insulin or progesterone hormones in association with ram effect was evaluated. Ewes from SI (n=69) and MN (n=69) breeds were randomly allocated to three groups of each breed (T1ram effect only; T2ram effect+insulin; T3ram effect+progesterone). Progesterone concentrations (g/ml; mean +/- SD) before and after introduction of rams (n=6) were 0.51 +/- 0.22 and 3.78 +/- 0.68 (T1), 0.65 +/- 0.21 and 3.77 +/- 0.78 (T2) and 0.52 +/- 0.21 and 3.84 +/- 0.84 (T3) in SI ewes and 0.74 +/- 0.19 and 3.71 +/- 0.56 (T1), 0.70 +/- 0.21 and 3.79 +/- 0.75 (T2) and 0.81 +/- 0.14 and 3.87 +/- 0.80 (T3) in MN ewes, respectively. Thus, lower progesterone concentrations were found before the introduction of rams (p<.05). After the introduction of rams, preovulatory peaks of LH (g/ml) occurred at 28 (T1), 44 (T2) and 48 (T3) hr in SI ewes and at 64 (T1), 40 (T2) and 44 (T3) hr in MN ewes. The mean number of ovulations was similar between groups (p>.05), was 1.3 +/- 0.51 (T1), 1.5 +/- 0.54 (T2) and 1.6 +/- 0.51 (T3) in SI ewes and 1.3 +/- 0.51 (T1), 1.6 +/- 0.51 (T2) and 1.6 +/- 0.51 (T3) in MN ewes. In conclusion, the ram effect alone is effective at inducing and synchronizing oestrus in sheep under postpartum anoestrus, irrespective of hormone treatments.