The effect of ovulation induction of GnRH following a short-term estrous induction protocol in Saanen goats

The current study was to compare the effect on the ovulation time and estrus parameters of a GnRH agonist (buserelin acetate) administered 24 or 36 h following a short-term estrus induction and synchronization treatment in non-lactating Saanen goats during the transitional period. Goats received 20 mg FGA sponges during 6 days plus 300 IU eCG and 125 µg d-cloprostenol 24 h prior to sponge removal. After removal of the sponges, goats were given either 1 ml physiological saline (0.9% NaCI) solution (Group 1 ; n = 9) after 12 h, 0.004 mg GnRH (buserelin acetate, Group 2 ; n = 10) after 24 h or 0.004 mg GnRH (Group 3 ; n = 10) after 36 h. The follicle development and ovulation in the ovaries were monitored by transrectal ultrasonography starting from the sponge application until the fifth day of the estrus cycle. Blood samples were collected on the same days to determine the plasma concentrations of progesterone (P4) and estradiol (E 2 ). As no statistical differences was detected in any synchronization parameters, ultrasonic evaluations and plasma P4 and E 2 concentrations among all groups, thus averages were assessed. The total estrus response, duration of the induced estrus, interval from sponge removal to onset of the induced estrus, time occurrence of ovulation from sponge removal and estrus onset to ovulation were recorded to be 93.10%, 33.66 ± 2.85 h, 27.48 ± 2.71 h, 48.05 ± 1.24 h and 21.51±2.37 h, respectively. The total ovulation rate, total number of ovulations per doe, largest follicle diameter and second largest follicle diameter were recorded to be 93.10%, 2.01±0.22, 6.85 ± 0.26 mm and 6.12 ± 0.24 mm, respectively. Results of this study indicate that administration of GnRH at 24 h or 36 h after sponge removal does not affect plasma P4 and E 2 concentrations, estrus parameters and ovulation time in estrus induction and synchronization in goats during the transition period.