The aim of this study was to investigate superovulatory responses of cows according to the status of various follicular classes on day 0 (day of initiation of the superovulatory treatment). One hundred and two superovulation cycles were selected. The animals were superstimulated between days 8 and 12 of oestrous cycle with 400 mg of Folltropin-v given in decreasing doses over a 4 d period and luteolysis was induced with two intramuscular injections of cloprostenol. The ovaries of all cows were examined by ultrasonography on day 0, at oestrus, and on day 7 after oestrus. The results showed that the follicular and ovulatory responses were higher (P<0.0l ) in cows that were superovulated in the presence of a high (≥6) number of follicles than in the presence of a low (≤5) number of follicles 4 to 6 mm in diameter. Follicular and ovulatory responses did not differ according to the status of the three other follicular classes studied. Additionally, the mean numbers of fertilised structures and unfertilised ova were not influenced by the status of any of the follicular classes studied. In conclusion, the follicular and ovulatory responses were influenced by the status at initiation day of the superovulatorv treatment.
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