Research Information System
JOURNAL OF THE HELLENIC VETERINARY MEDICAL SOCIETY, vol.74, 2024 (SCI-Expanded)
This study aimed
to compare the effect of hCG or GnRH administered 36 h following a short-term
estrus synchronization treatment on the ovulation time and pregnancy rates of
Merino ewes during the breeding season. The estrus cycles of ewes were
synchronized with an intravaginal sponge containing 60 mg of medroxyprogesterone
acetate for 6 days, and an injection of 400 IU of eCG and 125 µg of
d-cloprostenol 24 h before sponge removal. Thirty-six h after the sponge
removal, ewes were injected intramuscularly either 1 ml of physiological saline
solution (control-group; n=14), 100
IU of hCG (hCG-group; n=14) or 0.004
mg of buserelin acetate (GnRH-group;
n=14). The estrus behavior was
observed using teaser rams and the ovulation time was monitored using
transrectal ultrasonography twice daily for 96 h after the sponge removal. Ewes
in estrus were allowed a single mating using fertile rams. Estrus response was
higher (P<0.05) in the control group (92.86%) than in the GnRH group (50.00%). The interval from sponge removal to
ovulation and from hCG to ovulation were shorter in the control group than in
the hCG group (70.55, 80.83 h; 34.55, 44.83 h, respectively, P<0.05). In conclusion, administration of hCG or
GnRH at 36 h following a short-term estrus synchronization protocol did not
affect estrus behavior, ovarian findings and pregnancy rate in ewes during the
breeding season.