Development of bovine oocytes matured, fertilized and cultured in a serum-free, chemically defined medium

Abstract

This experiment was conducted to determine if bovine embryos derived from in vitro maturation, fertilization and culture could develop in serum-free medium. Oocytes were matured and cultured in TCM199 supplemented with or without fetal calf serum (FCS), and in TCM199 supplemented with growth factors (GF-TCM199), namely epidermal growth factor, insulin and transferrin. The proliferation of cumulus cells co-cultured with embryos was also examined. The highest rate of embryo cleavage (48%; 2-cell/total) and blastocyst formation (30%; blastocyst/2-cell) was obtained in serum-supplemented medium, and the extensive cumulus cells proliferation formed a monolayer within 3 d of culture. In TCM199 alone, no cleaved embryos developed to the blastocyst stage, and very limited cell proliferation was observed. In GF-TCM199, 3% of cleaved embryos developed to the blastocyst stage. The collagen-coated dish improved cumulus cell growth, and the rate of blastocyst formation was 8%. The viability of these embryos was judged by transfer, with one of the three recipients becoming pregnant and delivering one calf. In conclusion, the results indicated that collagen-coating and growth factors-supplementation can support embryonic development in serum-free TCM199; however, development in vitro was significantly less extensiver than that in serum-supplemented TCM199.