The Journal of Research ANGRAU

RAMANA et al
RESULTS AND DISCUSSION
In Ovsynch protocol the first injection of
GnRH is designed to induce ovulation and formation
of a new or accessory corpus luteum and a new
follicular wave. In the present investigation
ultrasound scanning of ovaries was done every day
after injection of GnRH induced ovulation and till the
formation of corpus luteum. However, follicular wave
emerge was noticed in all the six cows on day
1.33+0.21. The dominant follicle resulted from this
wave emergence grew up to 12.48+0.57 mm by day
7.6 with a growth rate of 1.66+0.26 mm per day. This
is in agreement with the reports of Mishra et al.(2002)
and Souza et al. (2006) in Sahiwal cows with GnRH.
However, Krishna Mohan et al. (2010) reported much
lesser size (9.17 + 0.27 mm) dominant follicle in
Sahiwal cows.
All the cows with a corpus luteum which were
administered with luteolytic dose (25 mg of Dinoprost
Tromethamine) on day 7 were in estrus within
2.33+0.21 days. The dominant follicle of all the six
cows was ovulated with the second dose of GnRH
on day 9 of the luteal phase. The ovulation recorded
was 100 per cent with GnRH treatment which is in
agreement with Gumen et al. (2003). This could be
due to larger size of the dominant follicle measuring
more than 9 mm will potentially ovulate in the GnRH
treatment animals (Adams 1992). Ultrasound
monitoring of the ovulated cows had shown a corpus
luteum of 16.50+0.30 mm on day 10 following the
induced estrus. Out of 22 postpartum lactating cows,
8 cows showed estrus after 1 st GnRH injection and
the cows exhibited normal estrus except two which
had weak estrus following PGF 2 α administration on
day 7 of the treatment. Second dose of GnRH was
administered on day 9 and all the cows inseminated
at the observed estrus. The estrus response recorded
in this study was in agreement with Mialot et al.
(1998) and Vasconcelos et al. (1999). In the present
study the conception rate found to be 54.54+0.36
per cent.
The ultrasound scanning of PGF 2 α treated
cows revealed a dominant follicle of 10.00 + 0.78
mm within 3-4 days after the PGF 2 α administration,
which is in agreement with Alan et al. (2003) and
Naidu et al. (2010) in Nelore cows. Out of 22 cows
treated with double injections of prostaglandins 18
exhibited estrus within 3.66+0.21 days. The time of
onset of estrus following PGF 2 α injection recorded in
this study is corroborating to the findings of Alves et
al. (2002) in Gir cows.
In the present study the conception rate
found to be 67.00 +0.26 per cent. Naidu et al. (2006)
has reported higher conception rate (90.0%) than the
present findings in Ongole cows, which might be due
to better synchrony of ovulation and fertilization as
the existing follicles were influenced the next wave
of follicles during induction. All the treated postpartum
lactating ongole cows in Ovsynch and double PG
groups exhibited 100 and 82.5 per cent of estrus,
respectively. The reason for varied estrus response
rate between different treatment groups might be due
to the difference in the treatment protocols and due
to, presence of too small dominant follicles (< 9 mm)
at the time of second PGF 2
injection (Rivera et al.
1998).
In the control group the mean time required
for conception after calving was recorded as
163.60+10.72 (95-397) days, which is less than the
previous studies (Venkateswarulu, 1971; Rao et al,
1985; Acharya & Bhat 1990; Ravi Kiran et al. 1995;
Rao et al. 2001and Naidu et.al,.,.2010). The service
period of cows in the treatment groups resulted a
reduction of approximately 85 days compared to
control group cows.
Hence, it is concluded that the estrus
synchronization with GnRH and PGF2 gives better
results and would reduce the calving to service period
drastically and beneficial to the farmers in dairy
industry.
ACKNOWLEDGEMENT
The authors express their sincere gratitude to the
SVVU, Tirupati for providing facilities to carry out
the research work at Cattle Project, Live Stock
Research Station, Lam Farm, Guntur.A.P.
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