Effect Of Synchronization Of Follicular Wave Emeregence On Superovulation And Embryo Yield In Crossbred Cows

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Date
2009
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Tamil Nadu Veterinary and Animal Sciences University
Abstract
The present study was aimed at assessing the effect of GnRH analogue in synchronizing the follicular wave emergence in Jersey crossbred cattle and to study the effect of initiating FSH treatment (normal and reduced doses) after synchronizing the emergence of follicular wave on superovulatory response and embryo yield. Six healthy, non-lactating and regularly cycling Jersey crossbred cows aged between 5-6 yrs were utilized for the study. Initially, as a control study, the normal follicular wave pattern was ultrasonographically investigated in all the six cows. In experimental group, all the animals were injected with GnRH analogue (Buserelin acetate; 10 μg i.m.) on Day 6 of the cycle (Day 0 – oestrum) and follicular wave pattern was studied. All the six animals were subjected for four superovulatory treatments. Treatment1-Conventional: FSH (400 mg - Folltropin-V) treatment was initiated on Day 10; Treatment II – Gn-D8-400: FSH treatment (400 mg) was initiated on the day of GnRH synchronized follicular wave emergence (Day 8); Treatment III – Gn-D10-400: FSH treatment (400 mg) was initiated two days after synchronized follicular wave emergence (Day 10) and Treatment IV- Gn-D10-200: Similar to Gn-D10-400 group, but superstimulated with 200 mg. Monitoring the normal follicular wave pattern revealed that 77.8, 16.7 and 5.6 per cent of oestrous cycles exhibited three, two and four follicular waves respectively. The first wave dominant follicles (DF) were in a growth phase during Days 0.8 – 6.67 of the oestrous cycle and got deviated from the subordinate follicles by 3.30 – 3.67 days after emergence irrespective of the number of follicular waves succeeding the first one. Thus characteristics of the first wave DF was much predictable than that of the subsequent waves. Three peaks of FSH levels could be appreciated in three-wavecycles preceding the emergence of each follicular wave. When GnRH was administered on Day 6 of the cycle, the DF (10.83 + 0.38 mm) ovulated in all the animals (100 %) in a mean interval of 27.67 + 0.21 h and a synchronized homogenous group of follicles emerged after two days (Day of 8.00 + 0.0). With the formation of an additional luteal structure (ACL), the progesterone concentration (10.57 + 0.61 ng / ml) was significantly (P<0.01) increased than normal cycle (5.58 + 0.45 ng / ml) during the mid luteal phase. In Conventional group, all the animals (100%) responded for FSH, with 13.67 + 1.80 CL and 2.00 + 0.37 AF. However, the superovulatory response varied widely (9 - 21ovulations). In Gn-D10-400 group, the animals responded with 11.00 + 0.63 (10 – 14) CL and 3.50 + 0.22 (3 – 4) AF comparable to the Conventional group. In both Conventional and Gn-D10-400 groups, almost all the Class III follicles on the day of superovulatory oestrus ovulated indicating that these follicles were healthy enough to respond to endogenous LH surge. In Gn-D8-400 group, the mean number of CL and AFs were 5.00 + 1.77 (1 – 11) and 12.83 + 4.65 (2 - 30) respectively. More number of Class II follicles and suprabasal progesterone levels (due to incomplete luteolysis) on the day of oestrus was correlated positively with increased number of AFs. The embryo recovery rate (53.89 %) in Gn-D10-400 was comparable to that of Conventional group (55.49 + 9.70 %), but the recovery rate (36.57 + 16.44 %) was substantially affected in Gn-D8-400 group. In Gn-D10-400 group, a higher percentage (87.24 %) of transferable quality (Grade 1 and 2) embryos and lower incidence of arrested / degenerated embryos (3.33 %) and UFO (1.85 %) was recorded than the Conventional (79.49%, 6.72 % and 6.25 % respectively) group. However, in Gn-D8- 400 group, arrested/degenerated and UFO (62.50%) and Grade 4 embryos (20.84%) constituted the major proportion of ova recovered and transferable quality embryos accounted for only 8.34 per cent. Increased anovulatory follicular population from the day of oestrus to the day of embryo collection and thus an increased concentration of oestradiol would have resulted in a poor embryo recovery / quality in Gn-D8 group. With the reduced dose of FSH (200 mg) in Gn-D10 group, all the animals responded with a mean superovulatory response of 6.33 + 0.99 CL (4-11) and an average of 44.24 per cent embryos / ova were recovered. When compared with Gn- D8-400 group, a non-significant increase in superovulatory response and embryo recovery rate was recorded in Gn-D10-200 group.
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Keywords
GnRH, Follicular wave synchronization, Superovulation, Embryo yield, crossbred cows
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