PARENT SESSION

(M670) EFFECT OF FSH STARVATION ON THE DEVELOPMENTAL COMPETENCE OF BOVINE OOCYTES IN VITRO.

Durairaj, Saravanan¹, Mayes, Mario¹, Adams, Gregg¹, Singh, Jaswant¹, ¹ Western College of Veterinary Medicine, Saskatoon, SK, Canada

ABSTRACT- The objectives of this study were to determine the effect of in vivo FSH starvation on the competence of bovine oocytes to develop in vitro, and to determine the optimum time interval between FSH stimulation and oocyte collection. A follicular wave was induced during the mid-luteal phase in Hereford-cross heifers (n=40) by ablation of all follicles ≥5 mm in diameter. Heifers were given a total dose of 150 IU of purified bovine FSH (NIH S1 units) im, divided bid for 3 days (i.e. 6 treatments of 25 IU each). Cumulus-oocyte-complexes (COC) were collected by transvaginal ultrasound-guided follicle aspiration at 12, 48, 84 and 120 hours after the last FSH injection (n = 10/group). The COC were matured and fertilized in vitro, and embryos were cultured in vitro for 7 days. Blastocyst development was compared among groups by Fisher Exact test. A total of 976 follicles were aspirated and 550 COC were obtained from 40 heifers. The proportion of oocytes that developed into blastocysts tended to be greater (P<0.1) in the 48 hr (13%) and 84 hr groups (16%) than in the 12 hr (8%) and 120 hr groups (8%). A greater proportion (P<0.05) of 8- and 16-cell embryos was obtained from the 120 hr group (25%) than in the 12 hr (12%) and 84 hr groups (14%). In conclusion, the study supports the hypothesis that FSH starvation influences oocyte competence and optimum time for oocyte collection appears to be 48 and 84 hours after the last FSH injection.

KEY WORDS: developmental competence, oocyte, superstimulation, bovine