Abstract
•The effects of CIDR treatment durations on ewe reproductive performance were investigated.•Ewes were treated by CIDR for 3, 6, 9, or 12 successive days.•CIDR use for 6 days provided higher return and net profit than that for 9 or 12 d.•CIDR use for 3 days is inefficient for estrus synchronization in ewes.
This study was conducted using 80 multiparous Awassi ewes during the breeding season to compare the effects of controlled internal drug release (CIDR) treatment durations on ewe reproductive performance, hormone profiles, and economic production measures. Ewes were evenly allotted to one of various CIDR treatment durations (3, 6, 9, or 12 d) in four groups (CIDR3, CIDR6, CIDR9, and CIDR12 (control), respectively). The ewes in all groups were injected with 300 IU of equine Chorionic Gonadotropin (eCG) at the time of withdrawal. Blood samples were collected at the time of CIDR insertion and withdrawal, as well as at the time of insemination to measure serum estradiol (E2) and progesterone (P4) concentrations. Timed insemination was performed at 48 h post CIDR withdrawal. The heat detection rate was significantly (P < 0.05) highest in CIDR12 and CIDR9 (100% and 84.21%, respectively). The total pregnancy rate was significantly (P < 0.05) higher in CIDR9 and CIDR6 (68.4% and 60%, respectively) than in CIDR3. Additionally, fecundity was significantly (P < 0.05) lowest in CIDR3. At insemination, the P4 level was significantly (P < 0.05) lower in CIDR9 and CIDR12 than in the other groups. At insemination, the E2 level was higher (P < 0.05) in CIDR6 followed by that in CIDR3 and CIDR9, and then in CIDR12. The total variable cost, total cost, the return and net profit were higher in CIDR6 than in other groups. In conclusion, although use of CIDR for 6, 9, and 12 d is efficient to synchronize estrus in ewes with similar reproductive performance, CIDR use for 6 d provided higher return and net profit than that for 9 or 12 d. CIDR use for 3 d is inefficient for estrus synchronization in ewes.