Seventy-five Thoroughbred mares were submit-ted to echographic and clinical examination during oestrus to evaluate follicular growth. A Scanner with a 5Mhz linear-array transdutor was used. Follicular growth control can be carried out by ultrasonography. A follicular diameter of 41 mm (77% of mares), follicular shape-changes (60% of mares) and the variations in uterine image (70% of mares) were the findings which permitted ovulation prognosis with accuracy (P < 0.01).
mare; ultrasound; follicular growth
