STUDIES ON MODULATION OF FOLLICULAR DYNAMICS AND SUPEROVULATORY RESPONSES IN POST PARTUM ONGOLE COWS
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Date
2007-08
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SRI VENKATESWARA VETERINARY UNIVERSITY TIRUPATI - 517 502. (A.P.) INDIA
Abstract
ABSTRACT:
A study was conducted to test the hypothesis that sychronising the
follicular wave emergence by hormonal and non hormonal methods and delaying
the exposure of follicles to LH would increase the ovulation rate embryo recovery
in Bos indicia cattle. Fifty eight parous Ongole breed cows were used as donors
and were randomly divided into four groups. Group I cows were treated uith
conventional superowlation protocol on day 10 of their natural cycle. In Group 11
the dominant follicle was ablated between day 6-8 of the cycle and superovulation
was initiated 48 h later. Group 111 and Group IV cows received a NORimplant +
EV 4 days before the start of the superovulation treatment. The implant was
removed 12 and 60 h after PGF injection in Group 111 and Group IV respectively
with the latter group receiving 25 mg LlI. Cow were superovulated by
administering 200 mg NIH-FSH-PI in divided and decreasing doses for 4 days.
Embryos were collected non surgically 7-7.5 days after superestrus and were
morphologicaly evaluated based on the stage of development and quality.
A total of 94.83% cows responded to superovulation treatment without
any significant difference between groups. The mean ovulation rates in the four
treatment groups (13.53 f 1.80, 15.08 f 1.5, 10.37 * 0.82 and 16.17 f 1.99
respecively) were significantly (P<0.05) different. The mean number of total
ova/embryo, viable embryos, fertilized embryos, unfertilized embryos and empty
zona did not differ significantly between treatment groups. The rate of
fertilization of recovered ova varied from 91.56 - 100% in different Groups.
Compact morula comprised the highest number (63.22 - 79.41%) in all the
treatment groups. No significant differences were observed in the mean number of
Grade I, Grade I1 and Grade I11 embryos between groups.
Overall data revealed that 25.45% 40.00% and 34.54% of cows flushed
were poor, average and good embryo donors respectively. One cow in each of the
treatment groups 1 (7.14%), I11 (6.25%) and IV (8.33%) produced all non viable
embryos. Collectively 5.56, 42.59, 25.42 and 24.07 per cent cows produced zero,
1-5,6-10 and >10 viable embryos.
As the CL number increased, the mean number of total ovalembryos
increased progressively and significantly (P<0.01) with in the groups consequent
to increase in ovulation number from 2-10 and >10 respectively. The overall
mean viable embryo recovery also increased progressively and significantly
(Pc0.0 1 ) as the overall total ova/embryo recovery increased from 1 -5 to 6- 10 and
> 10 embryos per collection. The number of calvings had no significant (P>0.05) effect on
suerovulatory responses. The total ova/embryo recovery was lower in winter
compared to summer and rainy seasons. The ovulation rate, total ovalembryo and
viable embryo recovery was significantly higher in dry cows compared to
lactating cows. Pregnancy rate with transfer of fresh embryos (52.94%) was significantly
influenced by transfer site and transfer quality. The pregnancy rates did not differ
significantly between embryos frozen thawed either in glycerol (37.5%) or in
ethylene glycol (13.64%). Cumulatively frozen-thawed embryo transfers resulted
in significantly @<0.01) lower pregnancy rates than those achieved with fresh
embryo transfers. The ovulation rate and embryo recovery were negatively correlated to
concentrations of P4 on day 0 but positively correlated to concentrations of P4 on
day 3 and day 718. A significant positive correlation was observed between
ovulation rate and E2 concentration and between viable embryo recovery and E2
concentration on day 0. The occurrence of standing heat and the mean time of
LH peak were significantly delayed in Group IV cows compared to the other three
groups. The p4 concentration was significantly higher on days 7, 14 and 21 in
recipients conceived following ET. On the contrary significant differences were
not observed in the E2 concentration between pregnant and non pregnant
recipients at different days of the cycle.
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