Superovulation following follicular synchronization with GnRH at random stages of the oestrous cycle in heifers
2011
Kohram, H.,University of Tehran, Karaj (Iran Islamic Republic). Dept. of Animal Science | Vahedi, V.,University of Tehran, Karaj (Iran Islamic Republic). Dept. of Animal Science | Nasrollahi, S.,University of Tehran, Karaj (Iran Islamic Republic). Dept. of Animal Science | Farahavar, A.,University of Tehran, Karaj (Iran Islamic Republic). Dept. of Animal Science
The objective of this study was to develop a superovulatory programme based on synchronization of follicular waves with GnRH which could be applied regardless of the stage of the oestrous cycle. Thirty-six heifers were applied GnRH (Cystorelin, 200 microg) between Days 0 and 7 (n = 15), 8 and 12 (n = 8) or 13 and 20 (n = 13) of the oestrous cycle. Four days after GnRH treatment, all follicles equal or bigger than 6 mm were either punctured (n = 21) or left intact (n = 15). All heifers were superstimulated from Day 6 to Day 10 after GnRH treatment with 320 mg Folltropin-V. In parallel, 21 heifers were superstimulated in a conventional manner (Days 8 to 12) and were used as controls. The homogeneity of follicular inventories among Stage-groups occurred within 4 days of GnRH treatment for follicles equal or bigger than 7 mm but only 2 days after follicular puncture for follicles 4 to 6 mm. In response to the follicular puncture, the mean number of follicles 4 to 6 mm increased in heifers of the punctured group (P less than 0.01). Following the superstimulation, the follicular (P less than 0.01) and ovulatory (P less than 0.01) responses were higher in the punctured group than in the nonpunctured group. The in vivo production of transferable embryos in the punctured group was similar to that of the nonpunctured group but it was lower (P less than 0.01) than in control heifers. In conclusion, our results indicate that regardless of the stage of the oestrous cycle, the homogeneity of follicular inventories following the follicular synchronization is obtained using GnRH treatment and follicular puncture. Nevertheless, the in vivo production of embryos was severely compromised in our study for unknown reasons.
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