Animal and Veterinary Sciences

The aim of the present study was to determine follicle development and resumption of ovarian activity in Bulgarian Murrah buffaloes by transrectal ultrasonographic monitoring of the ovaries during the first 50 days after after calving throughout the breeding season. The investigation included 18 clinically healthy Bulgarian Murrah buffaloes divided into two groups: Group I (n=8, primiparous buffaloes) and Group II (n=10, multiparous buffaloes). A transrectal ultrasonography was made at 3-day intervals between 1 st and the 50 th postpartum days. The evaluation of follicular development was based on the visualization of small, medium or large follicles. Ovulation was recorded when the first detected large follicle disappeared during the followed examinations and a corpus luteum in the same place was observed. After data processing, the mean diameter (mm) of small, medium and large follicles was determined. The average intervals (days) from parturition to the first identification of medium, large follicles and corpus luteum were also estimated and cumulative percentage of animals in both groups, according to the ovarian structures, and the time of their detection was calculated. The obtained results showed presence of small follicles during the experimental period. The mean diameters of medium and large follicles in multiparous animals were greater (P<0.05) than respective sizes in primiparous animals. The mean interval between calving and first ovulation trended to be shorter in multiparous in comparison with primiparous buffaloes. On postpartum day 46 cumulative percentage of multiparous animals with detected corpus luteum was higher (P<0.05) than estimated in primiparous animals. In conclusion, the follicular growth between clinically healthy primiparous and multiparous Bulgarian Murrah buffaloes during the first fifty days after calving throughout breeding season was different. The faster development of ovulatory follicles followed by ovulation and corpus luteum formation in multiparous than in primiparous bufaloes indicated an earlier resumption of the ovarian activity after calving. The obtained data could be used in development of different schedules for reproductive optimization in dairy buffaloes.