Maintaining cells in vitro in a healthy condition and over time is a complex task. They will only survive, grow and multiply if they are well fed and provided with an appropriate and protective environment. Complex mixtures of substances ("media") are used to bathe the cells in order to both feed and protect them. Different cells have different requirements. In many instances the presence of serum in the mixture is essential if the cells are to grow adequately and normally. Bovine serum is much the most widely used, because high quality bovine serum is available in sufficient volume and has been found to support cell growth very well indeed.
Serum is the centrifuged fluid component extracted from either clotted or defibrinated whole blood. Bovine serum comes from blood taken from domestic cattle.
Whilst the procedure of making serum may seem to be straightforward, the processing of serum takes place under very tightly controlled conditions. The process has been carefully developed and uses sophisticated facilities and equipment, and is accompanied by extensive testing particularly stringent when processed bovine serum is intended for use in the production of medicinal products.
Fetal Bovine Serum (FBS) comes from the blood drawn from a bovine fetus via a closed system of collection at the slaughterhouse. Fetal Bovine serum is the most widely used serum supplement for the in vitro cell growth factors because of its high content of embryonic growth promoting factors.
Bovine serum is a by-product of the meat industry. Bovine blood may be taken at the time of slaughter, from adult cattle, calves, very young calves or (when cows that are slaughtered are subsequently found to be pregnant) from bovine fetuses. It is also obtained from what are called "donor" animals which give blood more than once.