Colostrum (known colloquially as beestings, bisnings or first milk) is a form of milk produced by the mammary glands of mammals (including humans) in late pregnancy. Most species will generate colostrum just prior to giving birth. Colostrum contains antibodies to protect the newborn against disease. In general, protein concentration in colostrum is substantially higher than in milk. Fat concentration is substantially higher in colostrum than in milk in some species, e.g. sheep and horses, but lower in colostrum than in milk in some other species, e.g. camels and humans. In swine, fat concentration of milk at 48 to 72 hours after parturition may be higher than in colostrum or in late-lactation milk. Fat concentration in bovine colostrum is extremely variable.