Triglyceride content of bovine oocytes and early embryos

A microfluorescence technique was used to measure the triglyceride content of a minimum of two bovine oocytes or preimplantation embryos up to the hatched blastocyst stage. Embryos were produced in vitro from abattoir-derived ovaries and grown in medium containing synthetic oviductal fluid, amino acids and BSA (SOFaaBSA medium); 10% fetal calf serum was added to some of the embryos at the four-cell stage. Before maturation, the triglyceride content of oocytes was 59 +/- 1.37 ng and it decreased (P < 0.05) after maturation to 46 +/- 0.85 ng. A decrease in triglyceride content (P < 0.05) was also observed after fertilization with the formation of the two-cell embryo (34 +/- 1.80 ng). In the absence of serum, the triglyceride content remained relatively constant from the two-cell to the hatched blastocyst stage. The triglyceride content of blastocysts produced in vivo was similar (33 +/- 0.70 ng) to that of blastocysts produced in vitro in the absence of serum. In contrast, the triglyceride content of embryos grown with 10% fetal calf serum increased steadily from the 9-16-cell stage to a value in hatched blastocysts (62 +/- 1.14 ng) almost double that in serum-free conditions. These results indicate that triglyceride may act as energy source during bovine oocyte maturation and fertilization and that the presence of serum causes excessive synthesis or accumulation of triglyceride in early embryos.