Follicular dynamics in Zebu cattle

The aim of this study was to investigate the follicular dynamics during est rous cycle in Gir breed (Bos indicus) cows. Follicular growth and atresia d uring estrous cycle were evaluated using a portable ultrasound device. Lute al activity was evaluated by serum progesterone levels. Cycles with two (6. 67%), three (60.00%), four (26.67%) and five (6.67%) follicular waves were observed. There was no difference (P >0.05) in dominant or subordinate foll icles growth or atresia rates among follicular waves. The maximum diameter of the ovulatory follicle was higher than the diameter of the other dominan t follicles in cycles with four waves, and higher than the diameter of the second dominant follicle in cycles with three waves (P <0.05). There was no difference (P >0.05) in estrous cycle length (21.11+/-1.76 and 22.25+/-1.7 1 days) or progesterone levels during diestrous (4.48+/-1.45 and 5.08+/-1.4 0 ng/mL) between cycles with three or four waves. Follicular dynamics in Gi r cattle is characterized by a higher incidence of cycles with three or fou r waves, associated with a low persistence of the dominant follicle.