چکیده (انگلیسی):

Objective: To evaluate the return of ovarian cyclicity with four hormone based protocols
during non-breeding season in infertile Corriedale sheep.
Methods: The return to ovarian cyclicity was considered in terms of percent estrus
response rate (ERR). The time of exhibition of estrus after either sponge removal or last
PGF2a injection, was considered as time to onset of estrus. Infertile Corriedale ewes were
randomly selected and distributed into four groups corresponding to four hormonal
protocols such as PsE (intravaginal progesterone sponges for 12 days and eCG (equine
chorionic gonadotropin) at 24 h before sponge removal; n = 6), GP (GnRH on day 0 and
PGF2a on day 5; n = 7), GPG (GnRH on day 0, PGF2a on day 5 and second injection of
GnRH on day 7; n = 7) and PsPG (Intravaginal progesterone sponges for 12 days, PGF2a
and gonadotropin-releasing hormone (GnRH) respectively, at 24 h before and after
sponge removal; n = 8).
Results: PsPG protocol produced significantly (P < 0.05) higher ERR (87.5%) in ewes
as compared to GPG (28.57%) but non-significantly (P > 0.05) higher than GP (85.71%)
and PsE (66%). Estrus was compact and more synchronized in PsPG group because 75%
of ewes exhibited estrus during the first 48 h. The collective incidence of estrus (78.94%)
was also maximum during the first 48 h.
Conclusion: PsPG estrus induction strategy has a potential to replace eCG based protocols
for returning of ovarian cyclicity in infertile Corriedale sheep.