The aim of this study was to explore the real time changes in the vascularity of growing superovulated
follicles and to establish whether the blood flow of growing follicles can affect superovulation variability. Eight
Holstein-Freisian cows received PGF2α 10 days after spontaneous ovulation. After 36 hours, all follicles larger than
5 mm were aspirated at day 0 (D0). Animals were given 28 Armour units (A.U) FSH 24h after aspiration and for 4
days (twice daily, 12h interval). On day 5, animals received a GnRH analogue. Blood samples were then collected
daily and were used to detect estradiol (E2), progesterone (P4) and insulin like growth factor-1 (IGF-1) using an
enzyme immunoassay (EIA). Results showed that neither the follicular diameter nor the follicle sectional areas (SA)
are reliable parameters to predict the superovulation response. On the other hand, the blood area (BA) and blood
area percentage were significantly (P<0.05) higher for ovulated (OF) than non-ovulated follicles (NOF). The (NOF)
became atretic or continued to form luteal cysts. The P4 level was below 1ng/ml while E2 increased on day 3 to
reach the peak. IGF-1 decreased on day 3 and then started to increase until ovulation. In conclusion, the
haemodynamics of superovulated follicle could be considered a major source of superovulated variability and play a
crucial role in controlling the superovulation result.