Follicular Dynamics during Estrous Cycle of Pubertal, Mature and Postpartum Crossbred (Nili Ravi × Jianghan) Buffaloes

SIMPLE SUMMARY: The objective of this study was to observe the follicle dynamics and its relationship with different physiological (pubertal, sexual mature and postpartum) conditions of buffaloes. These data could be beneficial in establishing best reproductive model for future studies and enhancing the efficiency of advanced reproductive technologies (ARTs) in buffalo industry. The present study describes the estrous cycle characteristics (follicular wave pattern, ovulation, follicle growth, regression or atresia) in Chinese crossbred buffaloes during pubertal, sexual maturity and postpartum stages. This study would be helpful to provide the theoretical insight to overcome the poor reproductive performance by employing the ARTs to enhance fertility in crossbred buffaloes. ABSTRACT: The follicular dynamics is used as a reliable indicator for reproductive management in livestock. However, the follicular dynamics (follicle wave emergence, estrus cycle length, diameter of dominant follicle, follicular growth and atretic phases) during the estrous cycle of crossbred (Nili Ravi-Jianghan) buffalo is still unexplored. Therefore, the present study aimed to observe the follicular dynamics in estrous cycle of crossbred buffaloes at different physiological stages (pubertal; n = 28, sexual mature; n = 22 and postpartum; n = 18). In the present study, the follicular dynamics were ultrasonically examined at 12 h intervals throughout an estrous cycle during the breeding season. The results indicate that about 86.76% (59/68) crossbred buffaloes, irrespective of physiological stage, exhibited two follicular waves in estrous cycle with an average estrus cycle length was 20.7 ± 0.4 days. The estrus cycle length was significantly shorter (p < 0.05) in pubertal buffaloes (19.4 ± 0.4 days) compared with sexual mature (21.5 ± 0.3 days) and postpartum (21.9 ± 0.4 days) buffaloes. The first follicular wave emerged on same day during one- (pubertal vs. postpartum), two- (pubertal vs. mature vs. postpartum) or three-wave (mature vs. postpartum) estrous cycle buffaloes. The maximum diameter of dominant follicle (DF) in pubertal, sexually mature and postpartum crossbred buffaloes was 9.6 ± 2.0 mm, 10.6 ± 0.5 mm and 12.6 ± 0.7 mm with growth rate of 1.08 ± 0.04 mm/day, 0.92 ± 0.04 mm/day, and 0.9 ± 0.07 mm/day, respectively. In conclusion, similar to other buffalo breeds, Nili Ravi-Jianghan crossbred buffaloes showed the two-wave follicular pattern dominantly with an average duration of ~20 days estrous cycle. The observed follicular dynamics can be used as a reliable indicator for synchronization and fixed-time artificial insemination (FTAI) programs to improve the fertility of crossbred buffaloes.