The Changes Of The Ovarian,Estradiol And Progesterone Concentration Of The Young Cows In The Estrous Cycle

The studies were conducted to investigate the ovarian dynamics development by B-mode ultrasonography and such two reproductive hormones as estradiol (E2) and progesterone (P4) were assayed by RIA during the Natural estrous cycle in young cows.and it was the changes in the follicular wave and the changes of reproductive hormones as follows:(1) In the estrus cycle, the average diameter of one day after estrus cycle was the smallest, with a mean of 18.24mm, 21.94mm the day of estrus cycle, 21.63mm two days after estrus cycle; the average circumference of one day after estrus cycle was the smallest, with a mean of 68.43mm, 79.85mm the day of estrus cycle, 68.85mm two days after estrus cycle; the average area of one day after estrus cycle was the smallest, with a mean of 1.02mm~2, 1.49 mm~2 the day of estrus cycle, 1.08 mm~2 two days after estrus cycle.(2) In natural estrus cycle, the ovulation rate of the right side was higher than the left; after synchronization estrus, the ovulation rate of the right side was also higher than the left.(3) In natural estrus cycle, the number of young cows ovulating within 24h were more than 24h later.(4) The average diameter of dominant follicle (13.09+1.94 mm) in right ovary was bigger than the left (11.85+0.82 mm), but the difference was not significant (P> 0.05); when the follicular wave occurred, the number of the left edge dominant follicle was 3.18+0.40, slightly bigger than the right edge follicles (3.09+0.30), but the difference was not significant (P> 0.05); the size of mature follicles are basically the same between left(14.76+0.94 mm) and right side(14.34 +1.30 mm),no significant difference between them(P> 0.05).(5)In natural estrus cycle, follicular development appears the form of follicular wave, there are 3-4 follicular waves in this study, mainly is the 3 follicular waves, accounting for 81.82%, percentage of four follicular wave is 18.18%. The average estrus cycle time of those young cows with 3 follicular wave was 20.8d.the time of first follicle wave is the 2.11d,and the duration was approximately 6.1d; the time of second follicle wave is the 8.22d,and the duration was approximately 5.2d;the time of third follicle wave is the 13.44d,and the duration was approximately 6.4d;however, The average estrus cycle time of those young cows with 4 follicular wave was 22d.the time of first follicle wave is the 1d,and the duration was approximately 3.5d; the time of second follicle wave is the 4.5d,and the duration was approximately 5d;the time of third follicle wave is the 9.5d,and the duration was approximately 4d; the time of forth follicle wave is the 13.5d,and the duration was approximately 6.5d;(6) Throughout the whole estrous cycle, the E2 level reached the maximum in the estrus day, and the average was 6.23+0.85pg/ml, then it was rapidly declined down to the minimum(3.5+0.01pg/ml)on the third day in the estrous cycle, and later,it had been maintained a low level to the sixth day, and then it had two small peaks on the ninth,twelveth day.(7) Throughout the whole estrous cycle, P4 level reached the minimum in the estrus day, and the average was 0.37+0.97ng/ml, continuing to maintain this low level to the third day (both <1ng/ml). P4 level began with rising more than 1ng/ml from the third day, continuing to rise after that in the first estrous cycle, but declining from the sixth day to the ninth day in the second estrous cycle. After that it showed raising.It reached the maximum value(3.9+2.22ng/ml) on the 15 day.(8) Throughout the whole estrous cycle, the young cow level of E2 and P4 was negatively correlated (r =- 0.240 *)(9) Throughout the whole estrous cycle, except for the sixth to twelveth day, the E2 level of young cows with 4-wave was higher than those with 3-wave, however, all other times, the states was opposition, and the difference between them was not significant (P> 0.05)(10) Throughout the whole estrous cycle, the P4 lever of the 4-wave young cows was all higher than the 3-wave ones, and the whole curve was same. However, the P4 level was significant difference (P <0.05) between the two waves young cows on the fifteenth day, other time periods no significant differences (P> 0.05) yet.