Follicular dynamics and changes in plasma estradiol-17β and progesterone concentrations during estrous cycle in beetal goats

Abstract

The study was designed to monitor ovarian follicular dynamics and plasma progesterone and estradiol-17β concentrations in Beetal goats (n=7; age: 3.7±0.2 years). Following ovulation synchronization, two consecutive estrous cycles (n=14) were monitored via ultrasonography during the breeding season (Sep-Nov 2016). The interovulatory interval of Beetal goats averaged 21.2±0.3 d and follicular and luteal phases were 3.9±0.1 and 17.2±0.3 days, respectively. The 4-wave follicular pattern was higher than 3-waves (71% vs. 29%; P>0.05). In 3-wave cycles, follicular waves emerged on Days -0.3±0.3, 8.3±1 and 14.5±0.5 of estrous cycle (Day 0=ovulation), while in 4-wave cycles, waves emerged on Days 0.5±0.2, 7.5±0.5, 11.9±0.4, and 16.1±0.6. The maximum diameter of preovulatory follicle and corpus luteum was 7.2±0.2 mm and 11.8±0.3 mm, respectively. On an average 1.7±0.2 follicles ovulated per cycle and luteolysis began on Day 17.2±0.3 of the cycle. The largest follicles of first and ovulatory wave had greater diameters than those of 2nd and 3rd wave (P<0.05). The peak plasma estradiol-17β concentration was observed 33.6±9.6 h before ovulation. The peak plasma progesterone concentration was attained by Day 12.2±1 and reached <2 ng/mL within 1.6±0.3 d following the onset of luteolysis. The plasma progesterone concentration and diameter of corpora lutea correlated throughout the estrous cycle (r=0.94; P<0.05). In conclusion, seventy-one percent of the cycles in Beetal goats were of 4-wave pattern and overall Beetal goats had tendency of twin ovulations.