EFFECTS OF SUPPLEMENTATION WITH FETAL CALF SERUM ON DEVELOPMENT OF BOVINE EMBRYOS IN SYNTHETIC OVIDUCT FLUID MEDIUM

The effects of fetal calf serum (FCS) or serum fractions on the develo pment of bovine embryos was investigated. Bovine zygotes were produced in vitro and were cultured in a semi-defined culture medium (mSOF). I n the first experiment, blastocysts produced in mSOF supplemented with 10% whole heat-treated FCS or desalted FCS appeared about I day earli er, their proportion was significantly (P < 0.05) higher (whole: 30%, desalted: 29%) and they had significantly (P < 0.05) more cells at day 8 (119 cells, 127 cells) than did blastocysts produced in mSOF withou t any supplement (16%, 98 cells) or mSOF supplemented with a glucose c oncentration equivalent to that of serum (15%, 88 cells). Our results indicate that high molecular mass components (> 5 kDa) of serum are re sponsible for the effects of FCS on the kinetics of development, on th e percentage of blastocysts obtained and the total number of cells in blastocysts. A further analysis using time-lapse microcinematography s howed that the acceleration of development induced by serum occurred b etween the 9-16-cell and morula stages. Finally, in an experiment desi gned to analyse by microcinematography the effect of the addition of F CS using semen from a different bull to inseminate the oocytes, a diff erent batch of serum and adding mSOF at a different time (42 h after i nsemination), acceleration was similarly observed between these two st ages. Our microcinematographic studies demonstrate that the addition o f FCS at two developmental stages (three-four-cell and five-eight-cell ) before the 8-16-cell stage accelerates development just after this c ritical blocking stage.