SUPEROVULATORY RESPONSE IN DAIRY COWS AFTER APPLICATION OF ECG

Abstract

PURPOSE: The aim of the present study was to determine the follicular dynamics and superovulatory response in dairy cows after the administration of eCG. METHODS: The study included 6 Holstein cows bearing CL in the ovaries treated with PGF2α for estrus induction. After estrus detection daily ultrasound scanning to monitor the dominant follicle of the first follicular wave was made. Superovulation treatment (2500 IU eCG and two doses of 500μg PGF2α analog on the 48th and 60th hour after the eCG injection) started at the emergence of the second follicular wave. The number and diameter of the follicles ≥ 5 mm, the number of corpora lutea and anovulatory follicles (AF) and the ovulation rate (OR) were estimated. RESULTS: At the start of the superovulation treatment (SO) the average number and diameter of the medium and large follicles were 2.7±1.2 and 0.67±0.13 cm and 1.6±0.5 and 1.45±0.28 cm, respectively. There were high positive correlations between the days of the treatment and number of large and medium follicles (r = 0.80, P = 0.018 and r = 0.75, P = 0.03). The average number of large follicles on day 5 was greater than those at the start of SO. On day 8 the OR was 55.9% and the difference between anovulatory follicles and corpora lutea was not significant. CONCLUSIONS: The used protocol provided acceptable OR, but the average number of AF (44.1%) remained high. Ultrasonography could be used to monitor the first dominant follicle and the emergence of a new follicular wave.