Functional Foods - The truth on r-BST

May 2007

Prof Lourens Erasmus of the Department of Animal and Wildlife Sciences, University of Pretoria, lays out the scientific facts and exposes the misconceptions on this controversial topic.

THE use of recombinant bovine somatotropin (r-BST) sometimes referred to as recombinant bovine growth hormone (r-BGH), was approved by the FDA in the US in 1994 for use in dairy cattle to increase milk production and feed efficiency. Even before that, in 1988, r-BST was first registered for use in South Africa by Monsanto, the US-based food biotechnology company.

Unfortunately, r-BST has been, and remains, a controversial subject locally and internationally. Here are some examples of headlines on r-BST related articles that were published recently:

• Bovine somatotropin: curse or blessing? THE DAIRY MAIL, February 2005
• Crack for cows could be bad for you too. THE STAR, September 2005
• Cancer link to SA milk. CAPE ARGUS, September 2005
• What’s in your milk? THE SCIENTIST, February 2007

Over the past few years, selling of r-BST-free milk and dairy products has become an effective marketing tool for many dairy outlets in South Africa and its labelling as such is probably contributing to the controversy. In a recent article published in Feedstuffs, major food corporations were openly accused of creating a fear in the public’s mind that there is a dangerous difference between r-BST free and generic milk, thereby having a way to differentiate their product, capture market share and charge more for the same milk, as this extract illustrates:

‘The word "hormone" is really handy if you want to scare the average consumer. Never mind that such campaigns undermine the consumers’ confidence in the generic product and add to consumers doubts about all food production. Never mind that in the case of r-BST there is no way to actually verify that the claim you make is actually true. Never mind that the decision hurts the dairy producers that were profitably using an approved, well-established technology in their herds.

‘The dairy industry needs to understand that this is not really about r-BST. It is just this moment’s convenient target. This is about who will control the production and distribution of food. It is about whether determined and well-funded dominant corporate entities can partner with each other to push out competition and charge more for what is really the same food.’

The purpose of this article, therefore, is to clear all misunderstandings and provide readers with the scientific facts regarding naturally-produced BST and r-BST so they can make well-informed decisions when purchasing dairy products.

What is BST?

Bovine somatotropin is a naturally-occurring protein hormone produced in the pituitary gland, which directs nutrients to the mammary gland for increased milk production. It is well known that higher producing cows have elevated circulating levels of BST. As early as the 1930s it was discovered that by injecting BST into lactating cows a significant increase in milk production occurred. Bovine somatotropin is present in trace amounts in all milk.

How is r-BST produced?

r-BST is produced in commercial quantities using recombinant DNA technology. The gene in cattle that controls BST production has been identified, isolated and inserted into an E coli bacterium, found in the intestinal tract of humans and animals, and which acts like a tiny factory and produces large amounts of r-BST in controlled laboratory conditions. The r-BST produced by the bacteria is purified and then injected into cattle.

Why give additional r-BST to cows?

r-BST must be injected into the cows on a regular basis (every 14 days) to affect milk production. In general, milk production is increased by 10 – 25% with r-BST administration and feed intake increases on average by 5 – 15%. Feed efficiency (kg milk produced/kg feed consumed) is improved because a higher proportion of nutrients are used for milk production and less for body maintenance. In short, r-BST only supplements a cow’s naturally-produced BST to bring it up to a level found in genetically superior cows. Only good managers should use r-BST.

r-BST is not a magic bullet that will allow all cows in all situations to produce more milk. It must be used correctly and only in well-managed herds. r-BST should be used selectively only on healthy cows in proper body condition and administration should only start around 10 weeks in lactation or when the cow has been confirmed pregnant. It is also extremely valuable as a management tool to reduce body weight in over fat cows later in lactation or prolonged lactations (>300 days) of cull cows or cows with reproductive problems.

r-BST: misconceptions and concerns

Objective assessment by consumers has been clouded by media-amplified fears generated by organisations and individuals opposed to any use of modern biotechnology, and confusion caused by trade-motivated use of selectively emphasised evidence. Expressed concerns have centred on four main aspects; human welfare, animal health and welfare, labelling and socio-economic aspects.

Human health concerns: Chances are pretty good that anyone would think twice about drinking milk again when reading the following in your daily newspaper: ‘The next time you pour some milk into your coffee, you could be taking a gulp of a cancer-causing hormone. The hormone r-BST – known as crack for cows – is being injected into cattle whose milk could contain lethal hormones responsible for cancerous cell growth in human tissue.’ (THE STAR, September 21, 2005)

Or this from the website milksucks.com: ‘Have some . . . pus with your cookies? If you down a glass of cow’s milk, you will. It may be white but every cupful contains somatic cells, ie pus. One culprit causing hundreds of millions of pus cells in every litre of milk may be bovine growth hormone. This isn’t just disgusting – it can be dangerous. Pus can contain paratuberculosis bacteria which is believed to cause Crohn’s disease in humans.’

Milk is perceived as nature’s most perfect food, and the nutritional value of milk supports this claim. It is, therefore, understandable that some milk processors and consumers might feel uneasy about administering r-BST to cows and any potential carry-over effect that might detract from the purity of milk. It is, therefore, important to understand all the relevant facts regarding the safety of r-BST milk.

Trace amounts of BST occurs naturally in all cows’ milk at variable levels, generally less than 2ppb but occasionally ranging up to 10ppb. Numerous studies have shown no significant difference in BST levels of milk from r-BST treated cows when compared to control cows.

Both natural BST produced by the cow and r-BST are immediately digested and broken down into inactive amino acids and peptides in the human digestive trace, ie digested like all other milk proteins. In contrast, steroid hormones like estrogens, progesterone and anabolic steroids are smaller ring-like structures that are absorbed from the digestive tract and are biologically active in humans. Additional assurance of safety is that heating, such as pasteurisation, inactivates BST that may be present in milk.

Even if injected into humans, BST has no effect since it is species specific. In the 1950s, studies looking at natural BST as a possible treatment for human dwarfism found that it had no effect, the reason being that the amino acid sequence of BST, which gives it its three-dimensional shape, differs by about 35% from that of human somatotropin (HST).

Milk composition from r-BST treated cows has been thoroughly investigated. Numerous studies report no effect of r-BST on the percentages of milk fat, protein, lactose, total solids, solids-non-fat as well as the dairy product manufacturing characteristics of milk. Regulatory and scientific bodies such as the FDA, American Medical Association, National Institutes of Health, and others in at least 50 countries, including the UK, Canada, France and Germany, have authorised milk and meat from cows supplemented with r-BST as safe for people of all ages.

Recently, activist attention has turned to insulin growth factor–1 (IGF-1) since BST, whether natural or injected, causes increased milk production by promoting the production of the hormone IGF-1, and IGF-1 is present in milk. Bovine IGF-1 and human IGF-1 are identical in structure, is a normal component in human gastrointestinal secretions and plays a role in normal cell division. Concerns have been expressed that increased levels of IGF-1 in milk of r-BST treated cows might lead to increased cell division and growth of tumours in humans. Looking at the normal concentrations of IGF-1 in cow and human milk as well as in human body fluids, however, puts everything in perspective (Table 1).

From Table 1 it is clear that IGF-1 concentrations in milk varies according to stage of lactation and during a lactation period a typical IGF-1 profile in cow-s milk varies from 150ng/ml after calving up to 25ng/ml one week after calving to 1-5ng/ml at day 200 of lactation. Some studies indicated no difference in the level of IGF-1 when labelled (r-BST free) or unlabelled milk were compared. Other studies showed a two to five-fold increase of IGF-1 as a consequence of r-BST treatment. A joint FAO/WHO expert committee on food additives (JECFA) cites average control values of IGF-1 in milk of 3,7ng/ml for untreated cows and a significant increase to 5,9mg/ml as a consequence of r-BST treatment. However, this is lower than the average for human milk and minute when compared to human plasma levels of IGF-1 and daily IGF-1 gastrointestinal secretions.

The FAO/WHO committee concluded that any increase in IGF-1 from milk from r-BST treated cows is orders of magnitude lower than the physiological amounts produced in humans. Consequently, the potential for IGF-1 to promote tumour growth will not increase when consuming milk from r-BST treated cows resulting in no appreciable risk for consumers.

Animal welfare concerns: Concerns have been expressed regarding the potential effect of r-BST on the incidence of mastitis (infection of the mammary gland), increased use of antibiotics, negative effects on reproduction and higher stress levels in cows.

The EU Committee on Veterinary Medical Products (CVMP) concluded that there was no evidence of a significant direct treatment related effect of r-BST on mastitis. The incidence of mastitis is linked to level of milk production. r-BST treated cows have higher incidence of mastitis and more somatic calls in milk than lower yielding controls, but these levels are comparable with untreated cows with a similar yield.

Other means of increasing milk yield, such as selective breeding has also been seen to increase the incidence of mastitis. There is even evidence that BST may reduce the severity of mastitis in treated animals. The effect of r-BST on the incidence of mastitis is much less than other factors such as climatic conditions, hygiene, milking procedures and herd to herd variation. Furthermore, around 50% of mastitis cases occur in the first 60 days after calving, a period when r-BST is not even used.

Discussions about potential increases in mastitis due to r-BST use have fuelled concerns of increased use of antibiotics and of an increase of their residues in milk. The FAO/WHO expert committee on food additives concluded there is no higher risk and the increased potential for drug residues in milk could be managed by practices currently in use by the dairy industry and by following label directions for antibiotic use.

As expected, cows administered with r-BST show tendencies towards longer calving intervals, decreased pregnancy rates and increased services per conception. These changes are associated with increases in milk yield and the resulting prolonged negative energy balance and occur regardless of whether or not the high milk yields are achieved using r-BST.

It’s often claimed that r-BST-supplemented cows are ‘stressed’. But how do we actually measure stress? Various studies have reported no change in the basal metabolic rate, no activation of the hypothalamic adrenal axis, no decline in productive efficiency and no depressed immune system in r-BST treated cows when compared to control cows. There is no basis to support the contention that r-BST treated cows are stressed.

Socio-economic concerns: r-BST is a technology involving no capital cost and therefore readily utilised equally by large and small dairy producers. In situations where supply outstrips demand or is restricted by quotas (as in the EU), farmers would be likely to use the technology to improve productivity rather than productive volume, ie the same volume of milk produced by fewer cows. This also has a positive impact on the environment through less methane production and faecal nitrogen and phosphorus secretion.

In South Africa the number of dairy producers has declined from 7 077 in December 1997 to 4 039 in October 2007. Currently around 30 primary producers per month are leaving the dairy industry and in many stores daily fresh milk supply is no longer guaranteed. Shouldn’t we allow dairy producers to use any environmentally-friendly technology available to enable them to produce milk economically and keep them on their farms? After all, r-BST is just another dairy technology advance, similar to genetic improvements, electronic identification, embryo transfer, semen sexing, robotic milking and others.

Labelling r-BST milk

The following is printed on a milk container of an US milk producer, so judge for yourself. ‘Hillcrest Dairy Milk is produced on our farm in Central New York. We are a family farm dedicated to providing our customers with the highest quality dairy products available.

‘We treat our cows kindly and never inject them with artificial growth hormones (r-BST or r-BHG) to increase their milk production. Our cows graze freely on lush natural pasture as nature intended.

‘We pasturize our milk slowly and gently to preserve the natural flavour , then pack them in these cartons, fresh the same day!

We hope that you appreciate the extra effort that goes into the fresh wholesome Hillcrest Dairy Milk from our family to yours.’

When reading a statement like this (as far as I know pasturization is a standardised procedure, how gentle can it be?) one cannot blame the uninformed consumer considering that there might be a difference between ‘natural milk’ and r-BST milk, where there is, in fact, no difference. The expressed position of the US, FDA and many other government and independent organisations is that milk from cows given r-BST is no different than milk from cows not given r-BST. It is fact that some retail stores advertising ‘hormone free’ milk are charging more for milk that is of no more nutritional value or safer, than milk that costs less. Not only does this practice impose a needless financial burden on low income consumers, it is generating unnecessary confusion and producers shall not be permitted to attract potential customers with a blanket ‘hormone free’ label. It is important that labels clarify that no significant difference has been found between milk from r-BST treated and non r-BST treated cattle.

The bottom line

Milk from r-BST treated cows is similar to non-supplemented cows. It poses no threat to animal welfare and it is completely safe for human consumption. Let us all stand together and promote milk as a safe wholesome and healthy food and take care that we do not, through biased reporting and labelling, deny dairy producers the use of just another management tool that can help improve the efficiency of South African dairy farmers.