Effects of halving intravaginal sponges and eCG dose on estrus response and fertility in Tahirova ewes during the breeding season

Abstract

The aim of this study was to compare the effect of halving the intravaginal sponges impregnated with 20 mg of flugestone acetate (FGA; 20 or 10 mg) and a dose of equine chorionic gonadotropin (eCG; 600 or 300 IU) on fertility in Tahirova ewes. A total of 200 Tahirova ewes were randomly assigned to 1 of 2 groups during the breeding season. Half of the ewes (n = 100) were treated with whole intravaginal sponges (WS, 20 mg of FGA) and the other half (n = 100) with halved sponges (HS, 20 mg of FGA) for 14 days. The ewes in both groups were further randomly divided into 2 subgroups (of 50 ewes each). Half of the ewes in each group received a 600 IU dose and the other half received a 300 IU dose of eCG at sponge withdrawal via IM route. As a result, 4 treatment groups, WS 600, WS 300, HS 600, and HS 300 were established. All the ewes were injected with PGF(2)alpha (0.294 mg, IM) a day prior to sponge withdrawal. Blood samples were collected from 40 randomly selected ewes (20 from the WS group and 20 from the HS group) on the 1st, 4th, 7th, 10th, and 13th day aft er sponge insertion. Serum progesterone profiles of ewes treated with whole and halved FGA sponges were similar on all sampling days. The FGA dose (whole or halved sponge) affected the pregnancy rate and the dose of eCG (600 or 300 IU) affected the fecundity significantly, while it did not affect the pregnancy rate. The data also demonstrate that FGA dose x eCG dose interaction affects estrus and lambing rates significantly. In the whole sponge groups, ewes treated with 600 IU of eCG had significantly lower lambing rates, but a significantly higher fecundity rate compared to the ewes injected with 300 IU of eCG. While the fecundity rates were similar in the 600 IU eCG groups (WS600 and HS600), estrus, pregnancy, and lambing rates were significantly higher in the HS600 group compared to the WS600 group. It was concluded from the study that the sponges containing 20 mg of FGA can be halved for a more economical estrus synchronization at the farm level in Tahirova ewes, resulting in higher pregnancy rates, but halving the recommended dose of eCG (600 IU) could decrease the fecundity rate.