Reproductive responses and progesterone levels of postpartum oestrus synchronization in goats with different body reserves

Thirty adult goats were classified at parturition into two body condition score (BCS) groups: BCI (n=16) with a score of 2.7 and BCII (n=14) with a score of 2.0. On the fiftieth day postpartum, oestrus was synchronized by CIDR for 5 days. Upon CIDR removal (Day 0), they received 1 mL of PGF2 alpha IM and mated for 72 hours. Kids were kept with does and weaned at 40 days of age. Blood samples were taken at 0, 1, 4, 8 and 21 days after CIDR removal for progesterone assay. The BCI group showed a greater weight loss compared to the BCII group, and BCS before synchronization was 1.9 +/- 0.08 and 1.6 +/- 0.07 for the BCI and BCII groups, respectively (P<0.05). The weaning weight of BCI kids was greater when compared to BCII (P<0.001). After CIDR removal, all females were marked and mated. Pregnancy rate was higher in BCI goats (87% vs 36%; P<0.05), as well as prolificacy (1.65 vs 1.25; P<0.05) and twinning rate (0.62 vs 0.25; P<0.05). Progesterone concentration was higher in pregnant does in BCI. A positive relationship was found between progesterone level at CIDR removal and BCS at parturition (0.57; P<0.01), also between progesterone level at 21 days after CIDR removal and BCS at parturition (0.47; P<0.05), or BCS before synchronization (0.51; P<0.05). We conclude that oestrus response to postpartum CIDR synchronization appeared to be slightly dependent on BCS. However, goats with low BCS at oestrus synchronization exhibited a reduction in pregnancy rate.