Study of follicular dynamic by real-time ultrasound in prepubertal Gir heifers
The objective of this research was to contribute for knowledge of reproduction physiology of Gir breed, throughout ultrasound study of follicular dynamic in prepubertal heifers. Follicular growth was monitored on 13 heifers during 42 consecutively days. It was identified a process of successive anovulatory follicular growth waves, with each wave showing a dominant follicle and a variable number of other smaller in size (subordinates). Those waves were variables in length and, for purpose of analysis, they were classified in three categories as follows: length waves class 1 (CO1: <12 days), class 2 (CO2: 13-16 days) and class 3 (CO3: >17 days). Forty-nine waves were analyzed: 6 CO1 (12.2%), 31 CO2 (63.3%) and 12 CO3 (24.5%). Differences among length of waves were observed, inclusive between those from the same female. In the CO1 class the average maximum diameter of dominant follicle was (P<0.05) shorter (9.4±0.3 mm) than CO2 (10.4±0.2 mm) and CO3 (11.6±0.4 mm). The plateau and rates of growing and athrepsia of follicles were not different (P<0.05) between CO classes. However, the CO3 plateau (2.9±0.5 days) was greater than CO1 (2.0±0.5 days) and CO2 (2.6±0.2 days). Similar characteristics on subordinate follicles were not different (P<0.05) among CO classes.