Authors : H. Kohram , G. Mohammadi and E. Dirandeh
Abstract: The objective of the present study was to evaluate the ovarian response of buffaloes to GnRH injections given at different moments of the estrous cycle. The estrous cycles of 15 buffaloes were synchronized with 2 iM injections of prostaglandin F2 given 11 day apart. The buffalos were randomly assigned to 1 of 3 groups. Buffaloes in the control group received no treatment, whereas GnRH6 buffaloes received a GnRH injection between day 5 and 7 and GnRH16 buffaloes received a GnRH injection between day 15 and 17 of the estrous cycle (estrus = day 0). Daily, from estrous cycle day 0 to the next estrous cycle day 23, cows had their ovaries scanned by ultrasound. All follicles were classified in to 4-6 mm and 7 mm follicles. Data were analyzed using the GLM procedure of SAS. In the 3 treatments, the number of 4-6 mm follicles had a decline trend from day 1 and reached their least amount on day 4 and 5 (p<0.05). Thereafter, the number of this class of follicles in the control, GnRH6 and GnRH16 treatments increased until day 8, 10 and 6, respectively (p<0.05). In response to an injection of GnRH, the number of small follicles in GnRH6 and GnRH16 treatments increased on day 9 and 18 respectively. Again, the number of small follicles increased in the control and GnRH6 groups from day 15 and 19, respectively, to day 21 of the estrous cycle. The number of 7 mm follicles had an increase (p<0.05) until day 3 in the control and 5 in the GnRH6 and GnRH16 groups. In the GnRH6 treatment of buffaloes, GnRH injection on day 6 increased (p<0.05) the number of large follicles on day 10. The number of 7 mm follicles in the two groups (control and GnRH6) increased between day 17 and 19 of the estrous cycle. An increase the number of small and medium sized follicles 2 day after GnRH injection showed that an injection of GnRH at the beginning or later days of the estrous cycle could promote the emergence of a new follicular wave in buffaloes.
H. Kohram , G. Mohammadi and E. Dirandeh , 2008. Alteration of Follicular Dynamics by GnRH at Two Different Stages of the Estrous Cycle in Water Buffalo. Journal of Animal and Veterinary Advances, 7: 996-1001.