The effect of different production systems and practices on the environmental impact, quality and safety of products from ruminant livestock: 2. Dairy products.

Technological advances often are viewed with scepticism and suspicion, with activists taking the lead in the media. Consumers, being largely uninformed then follow suit, resulting in retailers and supermarkets rejecting products that have been developed through technological innovative means. The genetically modification (GMO) technologies in particular have found it difficult to penetrate the market, because of perceived health and safety concerns. One such technology in the dairy industry is the use of recombinant bovine somatotropin (r-bST) to enhance milk yields and efficiency in cows. Activist and consumer pressure managed to get the use of r-bST banned in many parts of the world. The question however remains: Was this justified? The facts regarding the safety and health implications of r-bST were highlighted in a review by Drs Erasmus and Webb published in the South African Journal of Animal Science, Volume 43, Issue no 3 of 2013. The title of the review is: The effect of different production systems and practices on the environmental impact, quality and safety of products from ruminant livestock: 2. Dairy products.

Some of the claims by activists are that r-bST will cause cancer, increase the amount of antibiotics in milk, lower the quality and nutritional value of milk, result in mad cow disease, catastrophically increase mastitis and result in hyper metabolic stress in cows (animal welfare issue). To evaluate these claims, it is maybe important to understand the role of bovine somatotropin (bST) (also referred to as growth hormone) in the dairy cow.

Bovine somatotropin is a naturally occurring hormone produced in the pituitary gland which influences and controls milk production. This is noticeable by the high correlation of bST level in the blood and the level of milk produced and how the bST level increases or decreases depending on stage of lactation. The recombinant form (r-bST) has exactly the same composition and action, and therefore milk yields, efficiency of milk production and persistence of lactation can be increased if the cow is injected post-peak with r-bST when the endemic bovine somatotropin level begins to decline. If this practice is followed, milk yield of the cow is increased by 10 to 15% and feed efficiency by about 12%, and there is no evidence of increased mastitis (and therefore increased antibiotic use) or more metabolic stress than non – r-bST treated cows with the same milk yield.

So, what about the safety concerns for humans? At least four reasons can be advanced why the application of r-bST is safe and why the Food and Drug Administration (FDA) in the USA, which is the registration body of new products, approved the use thereof: (1) Bovine somatotropin (and therefore r-bST) is a protein which is digested in the digestive tract to amino acids like any other plant or animal protein. Amino acids have no hormonal activity and therefore no hormonal residue remains after digestion. (2) Bovine somatotropin is specific to cattle (bovine) and does not have biological effects in humans because the amino acid sequence of human somatotropin and bST differs vastly. This means that bST cannot bind to the human receptor which is necessary to initiate biological functions. (3) Most bST in milk is denatured by pasteurization and also when processed as part of baby liquid-food formulae. (4) The fourth reason is associated with the hormone insulin-like growth factor-1 (IGF-1). Since bST stimulates the production of IGF-1 and IGF-1 is present in milk, and since the structure of bovine and human IGF-1 is identical, the concern is that the increased levels of IGF-1 as a result of r-bST injections may cause the growth of tumours in humans. The increase in IGF-1 levels due to r-bST treatment is however lower than the average of what is normally found in human milk and minute compared to human plasma levels and the daily secretion of IGF-1 into the human digestive tract. To illustrate how minute: one would need to consume 270 glasses of milk per day to equal the normal level of IGF-1 in human saliva and digestive secretions!

The r-bST example by activist intervention is an important reason why technological advances sometimes do not find application in industry, to the detriment of farmers and everybody in the value chain. Activist campaigns have significant influence as in particular fields they dominate the media and internet, which are the sources of popular and non-scientific articles normally consulted by the man in the street. My advice is that people should not rely on these channels if unsure, but rather to consult science journals which are also easily accessible from the internet.