Effects of breed and progestin source on estrus synchronization and rates of fertility and fecundity in Iranian Sanjabi and Lori ewes.

ABSTRACT

A trial was conducted to evaluate the effects of FGA (Fluorogestone acetate) and CIDR (Controlled internal drug release) on the induction of estrus and pregnancy and fecundity rates of the Sanjabi and Lori sheep. A total of 360 Sanjabi and Lori sheep were randomly grouped into two treatments with intravaginal devices inserted for 13 days Group FGA (40 mg FGA, n = 180) and Group CIDR (n = 180). All ewes received an i.m. injection of 400 IU eCG (equine chorionic gonadotrophin) at devices removal. Estrous was assessed by exposing all ewes to vasectomized rams at 12 h intervals. Cervical artificial insemination was performed 12 h after estrus onset. The overall estrus response was 72.5%. The source of progestin did not influence the efficiency of estrus response but a significant difference (p<0.05) was found between the breed groups (Lori 88.6%, Sanjabi 58.3%). Among the sheep that received either CIDR or FGA, estrus response was significantly (p<0.05) higher in the Lori (CIDR 82.2%, FGA 91.1%) than in the Sanjabi (CIDR 64.4%, FGA 52.2%) breed. The lambing and fecundity rates for all groups were 60.2% and 1.2 +/- 0.03, respectively. No significant differences in term of the lambing and fecundity rates were recorded between CIDR and FGA groups and among Lori and Sanjabi breed. The results of this study indicate the source of progestin or sheep breed did not influence the pregnancy and fecundity rates. The sheep breed influences the estrous response rate while the source of progestin did not affect the estrous response.