Ovarian follicular dynamics and conception rate in Boran cows previously subjected to repeated ovum pick up
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Date
2021
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Addis Ababa University
Abstract
The study was conducted to investigate the effect of repeated ovum pick-up on ovarian follicular dynamics, serum estrogen and progesterone pattern, and the conception rate of Boran cows. Eight Boran cows were estrous synchronized by 500μg PGF2α at 11 days intervals. After the second PGF2α injection ovaries were scanned by transrectal ultrasonography every 12 hrs for the first two days and then every 6 hrs until ovulation. From the day of ovulation onwards, the ovaries were examined twice daily (at 12 hrs interval) to characterize the growth and regression pattern of ovarian follicles during two consecutive estrous cycles. A blood sample was collected every other day to evaluate estrogen and progesterone concentrations. The mean (±SEM) IOI was 21.1±1.19 days for cows with two waves and 22.66±0.57 days for cows with three waves. The length of the IOI was not significant (P>0.05) by follicular waves. The mean (±SEM) number of days from the emergence of cohort follicles to ovulation of dominant follicle of the ovulatory wave was significantly (P<0.05) greater (10.80±1.03 days) for two wave cows than three-wave cows (7.50±0.70 days). The mean (±SEM) diameter of the preovulatory follicle was significantly (P<0.05) larger for cows with two waves (14.29±1.36mm) than for cows with three waves (12.30±1.01mm). The mean (±SEM) growth rate of the dominant follicle that finally ovulated was significantly (P<0.05) higher (1.16±1.2mm/day) in the three-wave cycle than in two-wave cycles (0.85±0.1mm/day). The mean (±SEM) serum concentrations of estrogen and progesterone were 28.73±6.56 pg/ml and 0.88±0.40 ng/ml, respectively during the proestrous and estrous. While during the late diestrous cycle, serum estrogen and progesterone were 11.01±1.61pg/ml and 2.67±0.12 ng/ml, respectively. 87.5 % of cows were found conceived on ultrasound 32 days after insemination. In conclusion, based on ovarian follicular dynamics, serum estrogen and progesterone pattern, and conception rate repeated ovum pick does not significantly affect the fertility of Boran cows. Boran cows were characterized by a higher incidence of two-wave cycles.
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Boran cows, estrous cycle, follicular wave, hormones, ovum pick-up