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The effect of the extent of vascular perfusion of the wall of the preovulatory follicle on in vitro cleavage rate of the recovered oocyte and embryo development to >8 cells was studied in 52 heifers. Heifers received a luteolytic dose of prostaglandin F2α (PGF2α) when the largest follicle was ≥11 mm. An ovulation-inducing injection of GnRH was given 36 h later (hour 0), and collection of follicular fluid and the oocyte was done at hour 26. Vascular perfusion of the follicular wall was assessed by colour Doppler ultrasonography at hours 0 and 26. Each of the recovered oocytes (41/52; 79%) was mature (extruded polar body). Cleavage and embryo development were assessed at 48 h and 120 h respectively, after in vitro fertilisation (IVF). The percentage of cleaved oocytes and >8 cell embryos was 80% (31/39) and 55% (17/31) respectively. Vascular perfusion of the follicular wall was greater (lower pulsatility index; P<0.001) for follicles that produced cleaved versus non-cleaved oocytes and greater (P<0.04) for follicles that produced >8 cell versus ≤8 cell embryos. Percentage of follicular wall with Doppler signals of blood flow was greater (P<0.001) for >8 cell versus ≤8 cell embryos. Follicular-fluid concentration of free IGF1 was lower for cleaved oocytes (P<0.001) and >8 cell embryos (P<0.05), and oestradiol was lower (P<0.05) for >8 cell embryos. Results supported the hypothesis that greater vascular perfusion of the wall of the preovulatory follicle was positively associated with IVF and embryo development.

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