Hormones [in milk and milk products]

A number of hormones and hormonal active substances are occurring naturally in milk. They are also used worldwide in the production of food animals to promote growth, to increase the efficiency of feed utilization and milk production, or in the area of reproduction and fertility. The natural hormone content of cow's milk, both glandular and tissue hormones, is generally in the sub-milligram range, typically between 40 and 500 microg per kg for the steroids. Under the hormones, administered for therapeutic use, the prostaglandins and oxytocin are given to individual cows to treat malfunctions of the reproductive organs or to treat hard milking. For more management stimulated reasons, oestrogens are used in herds to synchronize the oestrus and in the following calving and lactation. A special case and evaluated contrary is the administration of bovine somatotropin (BST) derived from genetically engineered bacteria as a drug to increase the efficiency of feed utilization and milk production. The genetically engineered BST is practically identical to the natural BST produced by the pituitary gland and both compounds cannot be distinguished from each other. Natural BST occurs in all milk at levels of approximately 1-3 nanog per ml. The administration of artificial BST leaves the milk content unaffected but leads to an elevation of the insuline-like growth factor (IGF-1), a protein which is absorbed from the gut in primates and which causes glucose intolerance. However, the concentrations in milk remain within physiological levels for both BST and IGF-1, and are similar to the levels found in human milk. Pasteurization eliminates 85-90 per cent of immunoreactive BST in milk. Beyond this, BST is not active in primates including humans, even at provocative doses. Numerous medical and scientific groups worldwide have documented their conclusions that food products from BST-treated animals are safe for human consumption including the evaluation of secretory IGF-1 in milk. The use of BST for lactating dairy cows is therefore not a matter of food safety or public health from the scientific point of view, but a matter of political decisions under socioeconomic considerations.