Effects of melengestrol acetate and P.G. 600 on fertility in Rambouillet ewes outside the natural breeding season

Influence of short- and long-term administration of Melengestrol acetate on estrus activity and reproductive performance of nulliparous Barki ewes

“…Our results of lambing rate were higher than those obtained in control, MGA and MGA+PG 600 groups (14.8, 40.5 and 41.2%, respectively) according to Safranski et al (1992). But close to those obtained by (Windorski et al, 2008) who found that lambing rate in Rambouillet ewes was 80.4, 77.8 and 80.4% in control, MGA and MGA+PG-600, respectively. On the other side, Powell et al (1996) compared 8, 11 and 14 days of MGA supplementation on lambing rates in out of season breeding programs and they concluded no difference.…”

“…Consequently, the advantage that was obtained in ovulation rate through the use of PG-600 was not realized at lambing, although the number of luteal structures increased when PG-600 was injected on the last day of feeding MGA, the number of lambs born per ewe was not significantly affected. In another work, Windorski et al (2008) reported that no significant differences of lambs born per ewe lambing between treated and untreated groups with MGA, where was 1.82, 1.91 and 1.89 for control, MGA and MGA+PG600, respectively. In that regard, Keefe and Wichtel (2000) reported that no significant differences of lambs born per ewe lambing between treated ewes with MGA with and without eCG and mated naturally, prolificacy rates were 1.46% and 1.66%, respectively.…”

Effect of an Intermediate Dose of Melengestrol Acetate (MGA) on Ovulation Inhibition in Ewes

“…In another study, [15] evaluated the effects of melengestrol acetate and P.G. 600 on the fertility in ninety-nine Rambouillet ewes outside the natural breeding season, finding that after seven days of treatment at doses of 0.3 mg per day the pregnancy rate was 24%.…”

“…However, the fertilization rate in programs induction and synchronization of estrus in ewes when is used MGA vary widely, from 25 to 85% [15]; this variability may be related to the dose used, since doses high, inhibit production LH and affects development follicular [16], while dose low have an effect negative on the frequency of LH pulsatile same that can provoke a development of persistent dominant follicles [17].…”

Efficacy of various five-day estrous synchronization protocols in sheep

“…600 was injected at the end of a 10 d MGA treatment, a 20% increase in conception rate was reported by Morrical et al (1997) in ewes receiving the combination treatment and controls compared with ewes receiving MGA only. Windorski et al (2008) reported an increase in the percentage of ewes mated during the first 6 d of the breeding season in MGA and MGA + P.G.…”