Comparison of two different times period of FSH therapy on developmental competence of bovine oocytes collected through Transvaginal aspiration

Oocyte quality is one of the most important factors in embryo production through in vitro fertilization (IVF). Developmental competence of an oocyte is highly depended on the follicular microenvironment. In this study, the effect of 2 hormonal superstimulation regimes (2 doses and 6 doses of FSH) on developmental competence of oocytes, obtained by ovum pick up (OPU) procedure, was evaluated in cattle species. A total of 120 Holstein heifers with an average age of 11 months were divided into 2 groups of 60 animals. The animals in each group received either 2 or 6 equal doses of FSH (each dose= 50 mg) at 12h interval. The FSH treatment was started 2 days after dominant follicle ablation. The ablation of dominant follicle (s) was done 6 days after synchronized estrous. After OPU, 48 h after the end of FSH therapy, the aspirated oocytes were evaluated morphologically and considered for in vitro maturation, IVF, and subsequent embryo culture. In days 3 and 7, cleavage and blastocyst rates were evaluated. The mean numbers of aspirated follicles were 6.07±0.3 and 14.9±0.9, and retrieved oocytes were 3.93 ± 0.5 and 7.27 ± 0.6, in treated animal with 2 and 6 doses of FSH, respectively, which was significantly different between two groups (P=0.0001). The difference in proportion of grade A oocytes in 2 (66.97±3.57) and 6 (73.48±3.01) doses of FSH groups was insignificant (P>0.05). The rate of cleavage in animals treated with 2 and 6 doses of FSH was 65.67 ± 3.65 and 74.27 ± 5.38, respectively, which was not significant between two groups (P>0.05). Blastocyst rate in the 6 dose FSH group (50.32±3.57) was significantly higher than that of 2 dose FSH group (38.02 ± 3.18) (P=0.011). The results of this study demonstrated that 6 doses FSH in compare to 2 doses FSH prior to OPU resulted in more aspirable follicles with higher developmental competence oocytes.