Ultrasonographic Study of Ovarian Cyclicity in Zebu Cows of Bangladesh

Abstract

A study was undertaken to examine the cyclicity in (N=10) zebu cows by transrectal-ultrasonography. Ultrasonography was done daily for two consecutive inter-ovulatory cycles of each cow. Follicles 4 mm or greater than that were measured, follicular dynamics, maximum sizes of the dominant follicles and corpus luteum, days of attaining maximum diameters were recorded. Changes in the uterus were also evaluated. The inter-ovulatory cycle length was 21.8±0.8 days. All ten cows had two waves of follicular growth. The first wave emerged on Day 3.3±1.0. The maximum diameter of the first wave dominant follicle was 12.1±1.1 mm on Day 9.3±1.0 of the cycle. Onset of atresia of first wave dominant follicle began on Day 12.3±1.0, while the second wave (ovulatory) emerged on day 12.3±1.0. The maximum diameter of second wave dominant follicle (ovulatory follicle) was 18.1±0.6 mm on Day 18.7±1.3. The diameter of corpus luteum was 23.2±1.6 mm on Day 13.1±1.5. The mean number of medium sized follicles (6-8 mm) was higher than that of small sized follicles (4-5 mm) throughout the inter-ovulatory cycle. The corpus luteum reached maximal diameter of 23.2±1.6 mm at 13.1±1.5 days. Edematous fluid in the lumen of uterus appeared dark in colour with increased uterine diameter in all ten cows during Day 0 (Day of oestrus) to Day 3. Maximal uterine diameter was observed on Day 0 resulting from edematous anechoic fluid in the lumen in all cows. But from Day 6-15, the uterine diameter decreased and showed comparatively less darkness. The results indicated that indigenous zebu cows of Bangladesh seem to have follicular dynamics and cyclicity similar to other breeds of cattle.