Fetal bovine serum:

Fetal bovine serum is a character, appearance light yellow clarification, no hemolysis, no foreign body slightly viscous liquid. Fetal bovine serum should be taken from fetal bovine by caesarean section. New bovine serum from newborn cattle within 24 hours of birth; Calf serum is taken from calves 10-30 days old.

Obviously, fetal bovine serum is the highest quality, because fetal bovine has not been exposed to the outside world, the serum contains the least amount of antibodies, complement and other components harmful to cells.