To evaluate the comparative efficacy of
Ovsynch and Heatsynch protocols with respect
to ovarian response, estrus, pregnancy rate and
progesterone concentrations, 29 cyclic buffalo
heifers were assigned randomly to one of four
treatments: G-P-G treatment (n=8) received
two GnRH doses, one seven days before and
the other two days after a single dose of PGF2á;
G-P-EB1 treatment (n=8) was given estradiol
benzoate (EB) one day after PGF2á treatment
instead of the second GnRH dose; G-P-EB2
(n=8) and G-P-ECP (n=5) treatments received
EB or estradiol cypionate instead of second
GnRH in G-P-G protocol, respectively.
Ovarian ultrasonography and expression of
estrus signs were monitored twice daily until
the fifth day after the last hormone dose. Our
findings indicated a more obvious estrus
response to estradiol than the second GnRH
dose. The longer estrus duration observed in
response to estradiol (32 to 34 h) could provide
more time for estrus detection and
insemination in these animals. The pregnancy rates to first insemination recorded for the
different estradiol-based protocols (20.0 to
37.5%) indicate that estradiol esters may be
used to replace the second GnRH injection of
the Ovsynch protocol to induce ovulation and
obtain a satisfactory reproductive outcome.