Fetal bovine serum (FBS) or fetal calf serum is the blood fraction remaining after the natural coagulation of blood. It comes from the blood drawn from a bovine fetus via a closed system of collection at the slaughterhouse. It is the most widely used serum-supplement for the in vitro cell culture of eukaryotic cells.
USDA Approved Sourcing refers to FBS produced from blood collected in countries outside of the United States that have been approved by the USDA (United States Department of Agriculture) for export of beef products into the United States. Eligible countries for export into the U.S. include Australia, Canada, Chile, Costa Rica, Honduras, Iceland, Japan, Mexico, New Zealand, Nicaragua, Uruguay. Foreign serum is tested to ensure the absence of exotic viruses before release by the USDA.