Seasonal influence on follicular and luteal dynamics in dairy cows

The objective of study was to investigate the influence of season, viz. summer, winter, and isothermic (spring and autumn season), on follicular and luteal dynamics in dairy cows. Thirty dairy cows (n=10 in each season) were subjected to the ultrasonographic examination of ovarian structures, i.e. follicle and corpus luteum, during two- and three-follicular waves in an estrous cycle using B-mode and colour doppler mode of ultrasonography. The daily temperature-humidity index (THI) was recorded to envisage its variation among different seasons. In results, the size of the dominant follicle was recorded to be significantly different in all seasons during the second follicular wave. However, all other parameters for follicle, i.e. day of wave onset, length of growth phase, duration of dominance, the maximum diameter of the largest sub-ordinate follicle, as well as luteal morphometric analysis had no significant difference among different seasons. On the other part, the THI varied significantly in different seasons with maximum THI in the summer (72.54), followed by the isothermic (64.7) and lowest in the winter season (54.12). As a part of summation, the seasonal impact was barely noteworthy on different aspects of follicular and luteal dynamics except for the size of dominant and sub-ordinate follicle in dairy cows.