Follicular development in Pelibuey ewes in different seasons determined by ultrasonography

Abstract

The aim of the present study was to evaluate estrous behavior and follicular development in Pelibuey ewes at different seasons of the year. One hundred and twenty ewes were synchronized with intravaginal progestogen sponges maintained for 12 days. The day 0 (day sponges were removed), the onset and interval to estrus were detected and follicular development was measured over four consecutive days. The variables evaluated were: the time of onset of estrus, interval to estrus and number of follicles. To determine the effect of the season on the response variables, a Chi-square test and an analysis of variance were performed for a randomized complete block design. The results indicate that season affected (P < 0.01) the incidence of estrus; it was the highest in autumn and winter (100 %) and lowest in spring (70 %). Season also influenced (P < 0.01) the number of small (class 1) follicles on Day 1 and the number of large (class 3) follicles on Day 3. In each case, follicle number was higher (P < 0.01) in spring compared with the other seasons. It is concluded that the estrous activity and follicular dynamics in Pelibuey sheep is manifested largely during the winter season. Furthermore, onset of estrus and follicle class number are significantly related to seasonal effects. The reproductive activity is observed in Pelibuey ewes during all the year.