In vitro developmental competence of in vitro-matured bovine oocytes fertilized and cultured in completely defined media.

The objective was to establish an in vitro system in which bovine oocytes can be matured, fertilized, and cultured up to the blastocyst stage without support of serum, BSA, or somatic cells. Media consisted of modified tissue culture medium 199 (mTCM 199) with ovine LH (oLH) for maturation (IVM), experimental alterations of modified defined medium (mDM) for sperm selection and insemination (IVF), and citrate+synthetic oviductal fluid+nonessential amino acids (c-SOF+NEA) for zygote/embryo culture (IVC). Effects of heparin, BSA, polyvinyl alcohol (PVA), penicillamine (P), Hepes, and sodium bicarbonate (NaHCO3) were studied. Results included proportions of oocytes that cleaved by 48 h and that reached morulae by 120 h, blastocysts by 168 h, and expanded blastocysts by 216 h postinsemination (pi). Best results were obtained when the IVF medium included 0.5 mg P+1.0 mg PVA per milliliter with no more than 10 mM Hepes, and when 3.0 mg PVA/ml and 10 mM Hepes were present for IVC. Different concentrations of NaHCO3, up to 50 mM from 25 mM, during IVF did not alter results. Embryos produced in defined conditions yielding the best results remained viable after vitrification as evidenced by continued development in vitro for 96 h postthawing. Bovine oocytes matured in defined medium supplemented with LH were fertilized and cultured up to the blastocyst stage in chemically defined conditions that afforded results comparable to those reported earlier after inclusion of serum, BSA, and/or somatic cells.