Newborn bovine serum is a serum made from the blood of calves within 24 hours of birth.
The definition of newborn bovine serum varies among pharmacopoeias of different countries. The United States Pharmacopeia specifies that newborn calf serum, abbreviated as NBCS, is obtained from cows under 20 days old. The European Pharmacopoeia stipulates that the donor calf for newborn bovine serum is a cow under 1 year old. The 2020 edition of the Pharmacopoeia of the People's Republic of China defines newborn bovine serum as: serum collected from newborn cows that have not eaten within 14 hours of birth, separated, sterilized, and filtered before production.