Evaluation of oocyte maturation conditions and bull effect on the in vitro bovine embryo production

Abstract

The conditions of in vitro maturation of bovine oocytes (Exp. I) and bull effect (Exp. II) on cleavage (CR) and the in vitro morulae and blastocysts (MO/BL) rates were evaluated. Imatured oocytes were matured in vitro under different conditions: B-199 medium with 5% estrous cow serum (ECS), 5% fetal calf serum (FCS) and granulosa cells (T1/Exp. I) or B-199 medium with 10% FCS, 14 IU/ml PMSG and 7 IU/ml hCG (T2/Exp I). After 24 h culture, the mature oocytes were inseminated with frozen-thawed semen from two bulls (R1 and R2/Exp. II). In the Exp. I, the T1 and T2 oocytes were inseminated with semen from R1/Exp. II and in the exp. II the semen from both bulls inseminated T1/Exp. I oocytes. After 48 h, the 2-4 cells embryos were transferred into embryo culture droplets and were further cultured for 9 days. The CR of T2/Exp I was higher (p<0.01) than T1/Exp. I. There was a significant difference (p<0.05) between bulls on CR and Mo/Bl production. The use of hormones in a maturation medium has no effect on embryo production, however the procedure seems to be simpler than with granulosa cells. The use of semen from different bulls for in vitro fertilization has affected the subsequent in vitro production of embryos.