The Effects of Short or Long Term FGA Treatment with or without eCG on Reproductive Performance of Ewes Bred Out-of-season

Abstract

The objective was to evaluate the effects of intravaginal FGA sponges inserted for 4 or 12 days with or without eCG on reproductive performance of ewes out-of-season. Forty-eight anestrous ewes were assigned in equal numbers to four treatments in a 2x2 factorial design. Ewes were administered with FGA sponges on May 17 for 12 days (12-day-FGA-eCG and 12-day-FGA groups, n= 12 each) and on May 25 for 4 days (4-day-FGA-eCG and 4-day-FGA groups, n= 12 each). All treatments were timed to end together on May 29 (day 0, 0 h) at which time sponges were withdrawn and eCG or saline was injected. Five fertile rams which had been isolated from ewes were joined at 0 h for breeding and estrus detection. Blood samples were collected to compare progesterone (P4) concentrations and for pregnancy diagnosis. Overall estrus expression occurred in 40/48 ewes which differed only between 12-day-FGA-eCG and 4-day-FGA (p<0.05) groups. Intervals from 0 h to onset of estrus were shorter (p<0.05) in 12-day-FGA-eCG than those in 12-day-FGA and 4-day-FGA groups with no differences between 12-day-FGA-eCG and 4-day-FGA-eCG or between 12-day-FGA and 4-day-FGA groups. Progesterone levels were basal from day -12 through day 4 (p>0.1) and increased gradually thereafter until day 15. Progesterone remained elevated through day 19 in 11/12, 8/12, 9/12 and 6/12 ewes, respectively, which were diagnosed pregnant on day 30 by ultrasonography. Of the 34 ewes that became pregnant, 31 lambed 150 days following day 0. Pregnancy loss occurred only in 3 ewes from the two groups that did not have eCG treatment No differences in pregnancy and lambing rates and the number of lambs born were found between 12-day-FGA-eCG and 4-day-FGA eCG. The overall pregnancy and lambing rates obtained from mating at first service were 70.8 and 64.6%, respectively. In conclusion, the 4-day-FGA and eCG regimen could adequately replace the 12-day-FGA out-of-season. Application of such a 4-day-FGA protocol must be accompanied by eCG treatment upon sponge removal.