Abstract
Potential applications of modern reproductive technologies including monitoring follicular
dynamics, estrus synchronization and superovulation would be a new dimension of research at
the farm level of Bangladesh for improving buffalo's fertility and production. Therefore,
experiments were conducted to bridge the knowledge gap on reproductive, productive and
estrus characters of existed buffaloes, to maximize pregnancy rate by improving feeding and
breeding practices and estrus synchronization and to understand the ovarian dynamics after
induction of superovulation in buffalo cows. In Experiment-1, a survey was conducted to know
the scenario of productive, reproductive performances of Indigenous, Cross, Nilli and Murrah
buffalo cows in selected study areas in Bangladesh. Estrus characters in terms of ovarian
dynamics monitored by trans-rectal ultrasonography, vaginal electrical resistance, estrogen and
progesterone level at the time of AI were also studied in this experiment. Results showed that
milk production in Murrah and lactation length in Nilli cows were significantly (p < 0.05) higher
in comparison to the other breeds. Estrus duration, first calving age, number of services per
conception, calving interval, and voluntary waiting period varied significantly (p < 0.05) among
the breeds. Insignificant (p > 0.05) variation existed in ovarian physiological characteristics such
as vaginal electrical resistance, the average number of follicles, and largest follicular diameter,
estrogen, and progesterone at day 0 of the estrus cycle of local, crossbred, Nilli, and Murrah
buffalo. Experiment-2 was performed to compare the pregnancy rate obtained after following
the feed supplement and administering GnRH hormone at the time of AI in Buffalo cows.
Buffalo cows were inseminated under two groups: single time AI and double-time Al in natural
estrus providing supplemented feed and supplemented + administration of GnRH hormone.
Pregnancies were confirmed by ultrasound scanning on day 35 of post-AI. The highest
pregnancy rate (62.5%) was observed in supplemented feed + GnRH practicing with doubletime AI group and the lowest pregnancy rate (25%) was observed in traditional feeding practice
with single time AI group. Though the effect of the number of AI on the pregnancy rate was not
significant (P>0.05) within groups. The average largest follicular diameter, level of plasma
estrogen (E2) and progesterone (P4) concentration at day 0 of estrus differed very markedly
(p<0.001) between pregnant and non-pregnant buffaloes of the three groups. In Experiment-3,
the efficacy of the OVSYNCH (GnRH+PGF2a+GnRH+TAI), Co-SYNCH (CIDR+GnRH+PGF2a+
GnRH+ TAI) and Pre-SYNCH (PGF2a+AI) protocols for synchronization of estrus and
successful pregnancy after performing TAI with frozen-thawed semen was studied along with
the effects of seasons and the timing of induction of synchronization protocols (AM vs PM) on
pregnancy rate of buffalo cows. The result illustrated that the pregnancy rate was higher in
CoSYNCH (47.5%, 62.5%) protocol than that of OVSYNCH protocol (37.5%, 54.16%) in both off
breeding and breeding seasons, though the difference between pregnancy rates of these two
groups was non-significant (P>0.05). A higher pregnancy rate (66.7%, 16/24) was observed in
AM sub-group, though differences between the percentage of pregnant buffaloes were
statistically non-significant (P>0.05) in AM and PM sub-groups. Whereas, 90.32% buffaloes
were responsive to PreSYNCH protocol and the pregnancy rate was 67.85% (19/28) after AI
with observed heat. All three protocols showed remarked effect on larger follicular size,
estrogen and progesterone levels at the time of AI. In Experiment-4, ovarian activities after
superovulation treatment with FSH were monitored by trans-rectal ultrasonography. The result
showed a significant (P<0.05) effect of superovulation treatment on follicular size, number and
maturation. The result also presented that the ovulation rate was 58.62% and the embryo
recovery rate was very poor (~3%). This study would serve as a basis or reference for further
study on assisted reproductive technologies such as the synchronization of estrus and
superovulation in native buffaloes to improve pregnancy rate.