Bovine somatotropin

Bovine somatotropin (bST), or bovine growth hormone (BGH), is a protein hormone that occurs naturally in the pituitary gland of cattle. It is a factor controlling the amount of milk produced by a dairy cow. Bovine somatotropin is naturally in the milk extracted from a cow. Recombinant bovine growth hormone (rBGH), however, is a synthetic version of BGH that is injected into a cow to artificially increase her milk production.

Semantics and Abbreviations

Somatotropin (ST) is a protein hormone produced in the pituitary gland of all animals^[1]," including cattle. Bovine somatotropin is abbreviated bST or BST. It is also called bovine growth hormone, or BGH.

BST can be produced synthetically, using recombinant DNA technology. This is called "recombinant bovine somatotropin" rBST or "recombinant bovine growth hormone" rBGH. The current tradename of rBST produced by Monsanto is Posilac^[2].

For consistency, this article will use BST or rBST when possible.

Human growth hormone is abbreviated hGH or HGH. The word somatropin refers to synthetically produced human growth hormone, rHGH.

Physiology

Because of protein homology, Bovine Growth Hormone (GH) cross-reacts with the receptors of prolactin and placental lactogen — two hormones that stimulate the mammary tissue of a mature lactating cow in good health to produce more milk.

Protein hormones are large. The hormone does not pass through the placenta to fetal calves. It does not pass through the lining of the digestive system, and is broken down in the digestive system.

The sequence and 3D structure of the bovine growth hormone protein are different from the human growth hormone protein. Protein hormones require a "lock and key" type interaction with other compounds in the body to function, so any changes in sequence or structure would inhibit function. In other words, BGH will probably not function as a human growth hormone.

Uses in Agriculture

"In 1937 scientists observed that milk yield increased when BST was administered to lactating cows. From the '30s through the early '80s, knowledge on chemical structure, function and activity of ST from several animal species increased. Supplies of ST were limited during this period to what could be extracted from the pituitary glands of slaughtered animals^[3]."

Monsanto developed a recombinant version of rBST, which goes by the brand name POSILAC®. Growth hormones associated with injections given to dairy cows to increase milk production are known under an assortment of terms, but these terms generally refer to the same Monsanto product sold under this brand name.

Injected into dairy cattle, the product can increase milk production by an average of more than 10%.^[4]

Production of rBST

While specific information about the production of rBST is proprietary, the technology is commonly used to produce other proteins such as human insulin.

In short, the gene for a protein of interest is cloned into a bacterial plasmid. Bacteria, usually a non-virulent type of E. coli, undergo Transformation. Bacteria that receive the plasmid will produce the protein product of the gene. The protein can then be purified from bacterial extract. The bacteria are technically genetically engineered, but the term is somewhat stretched in this case. The bacteria are being used to produce a product, but they are not fundamentally changed.

Cows that receive rBGH are not genetically engineered. rBGH is the same as other treatments such as insulin that are used in humans.

Controversy About rBST

Use of rBST has been held in controversy for a variety of reasons, including: animal health concerns, human health concerns, and the encroachment on small farmers by large corporations.

Animal Health Concerns

In 2003, a meta-analysis on rBGH's effects on bovine health was published in The Canadian Journal of Veterinary Research. The article states that rBGH "was found to increase the risk of clinical mastitis by approximately 25% during the treatment period." "Use of rBST increased the risk of a cow failing to conceive by approximately 40%." Treated cows had a "an estimated 55% increase in the risk of developing clinical signs of lameness^[5]."

The movie The Corporation has a segment on rBGH. This includes video of cows suffering from mastitis. According to The Corporation's website: "Because of the increased production, the cows suffer from mastitis, a painful infection of the udders. Antibiotics must then be injected, which find their way into the milk, and ultimately reduce people's resistance to disease^[6]."

"Dairy records demonstrate an association between milk yield and incidence of mastitis. This association suggests that incidence of mastitis would increase in BST-treated cows because they produce more milk. This has been observed in some BST studies. However, BST does not appear to increase the incidence of mastitis above that expected from the greater milk yield^[7]."

"Although increased milk yield is associated with an increased incidence of mastitis, proper management practices can minimize the frequency and impact of mastitis. Not every mastitis case requires treatment of the cow with antibiotics. All milk is tested for the presence of antibiotics before it is marketed and dairy producers realize they must not ship milk contaminated with antibiotics. Producers incur significant financial penalties if they ship antibiotic-contaminated milk. Dairy producers have considerable incentive to follow established guidelines for antibiotic use. Use of BST will not increase the incidence of antibiotic contamination of the milk supply if producers use antibiotics as directed^[8]."

In other words, mastitis is not caused specifically by treatment with BGH or rBGH, but is caused in general by the increased levels of milk production, whether promoted by rBGH or other methods. Cows that naturally produce more milk are more likely to experience mastitis. Similarly, cows that produce more milk require more services (fertilization attempts) than cows that produce less milk. Selective breeding of dairy cows has greatly improved milk yield over the years, but has also increased incidence of mastitis and other health problems in dairy cattle.

Human Health Concerns

Several countries, including Canada and most of the European Union, have not approved rbST for use due to trade, economic, political and animal welfare concerns; however, dairy products from rbST-supplemented cows are imported and approved as safe by all countries.

BGH proponents argue that cross-species differences are significant enough to prevent most cross-species effects. (i.e. bST does not "work" in humans.)^[9] Monsanto, the largest single producer of rBGH has repeatedly claimed that the amounts are too small and digestion too complete for them to have any direct effect in humans. They claim that there is no scientifically verifiable difference between milk from treated versus untreated cattle.

According to Monsanto and the various government regulatory bodies which have reviewed rbST, milk and meat from cattle supplemented with rbST are safe. Monsanto also states that the only difference between milk from supplemented cattle and unsupplemented cattle is the amount of insulin growth factor 1 (IGF-1) — and that there is not even a difference in the concentration of bST.^[10]

Opponents counter that indeed there are differences aside from the higher rate of IGF-1, most importantly that BGH and rBGH (rbST) have a different chain of amino acids. This difference "can markedly change the immunogenic characteristics of a protein".^[11] Whether the change in immunogenic characteristics brought about by rBGH actually poses a threat to consumer health has yet to be demonstrated.

Canada's health board, Health Canada, commissioned a study which found "no biologically plausible reason for concern about human safety if rbST were to be approved for sale in Canada. The only exception to this statement is (possible hypersensitivity)."^[12]

rBGH has been associated with an increased risk of mastitis in cows. The warning label on Monsanto’s Posilac explicitly states, "Cows injected with Posilac are at increased risk for clinical mastitis."^[13] The EU Scientific Committee on Animal Health and Animal Welfare (SCAHAW)was asked to report on the incidence of mastitis and other disorders in dairy cows and on other aspects of the welfare of dairy cows.^[14] The Committee stated

"bST (Bovine somatotropin) use substantially increases foot problems, mastitis and injection site reactions in dairy cows. These conditions are painful and debilitating, leading to significantly poorer welfare of the animals. bST also causes reproductive disorders. Therefore, from the point of view of animal welfare and health, this substance should not be used."

Health Canada, like the SCAHAW, banned rBST because of its effects on cows ^[15]. Health Canada cited this reason for its ban

"The veterinary experts cited an increased risk of mastitis of up to 25%, of infertility by 18%, and of lameness by up to 50%. These increased risks and overall reduced body condition lead to a 20-25% increased risk of culling from the herd."

Yet the U.S. Food and Drug Administration (located in the same country as Monsanto) post-approval monitoring programs tracking animal health of rbST supplemented cows for more than ten years found that cows from supplemented herds had no increased incidents of mastitis or any other health concerns and were as healthy as cows in herds not receiving rbST supplements.^{[citation needed]}

IGF-1

Monsanto's studies show use of rBGH in cows increases insulin growth factor 1 (IGF-1) in milk.^[16] Although IGF-1 is important for normal development, some studies found that IGF-1 levels in the human blood stream are elevated in patients with breast, prostate or colorectal cancer.^[17] In 1994, the American Cancer Society asserted "Extensive testing and research has shown that rBST is indistinguishable from natural bovine growth hormone and thus entails no health risks for consumers. There are no valid scientific findings to indicate a risk of human carcinogenisis" regarding rbST,^[18] though they did not specifically mention the effects of IGF-1. In 1998, the American Cancer Society reported a correlation between human blood levels of IGF-1 (often associated with obesity) and breast cancer,^[19] prostate cancer,^[20] and colorectal cancer.^[21]

On May 22, 2006, Scientific American reported that Dr Gary Steinman of the Long Island Jewish Medical Centre published a paper in the Journal of Reproductive Medicine proposing a link between IGF and the incidence of twin births. He cites the May 6 issue of The Lancet which compared the relative increase of twinning rates in the USA and UK.^[22]

Milk economy

Milk production in North America, Europe, and Australia is already plentiful and milk is generally inexpensive. Those opposing the use of the drug have expressed concerns that using the drug to increase milk production (hence depressing prices) primarily benefits large scale producers and will narrow the margins that small dairy farms receive for their products. However, considering that organic milk can be sold at a premium and is in short supply, it seems contradictory that farmers would be "forced" into using growth hormones.

Consumer resistance

As of February 2007, Safeway in the Northwestern United States stopped buying from dairy farmers that use rBGH. The two Safeway plants produce milk for all of Oregon, Southwest Washington, and parts of northern California. Safeway's plant in San Leandro, CA had already been rBGH-free for two years. Another company going rBGH free is Chipotle Mexican Grill that has also announced it will only serve rBGH-free sour cream at its more than 530 restaurants.^[23]

Regulation

Banned outside the United States

The sale of Posilac is illegal in virtually every developed country with the exception of the United States. In the United States, the use of rbST has been approved by the FDA.

In Japan, Australia, New Zealand, and Canada, rbST is not approved for use.

The European Union declared the use of rbST as safe in 1990, but in 1993, a moratorium was placed on its sale by all 25 member nations.

Canada's health board, Health Canada, refused to approve rBGH for use on Canadian dairies, citing concerns over animal health. The study they had commissioned, however, found "no biologically plausible reason for concern about human safety if rbST were to be approved for sale in Canada. The only exception to this statement is (possible hypersensitivity)."^[24]

Regulation inside the United States

In November 1993, the product was approved for use in the U.S. by the FDA, and its use began in February 1994. The product is now sold in all 50 states. According to Monsanto, approximately one third of dairy cattle in the U.S. are injected with Posilac; approximately 8,000 dairy producers use the product.^[25] It is now the top selling dairy cattle pharmaceutical product in the U.S.^{[citation needed]}

A great deal of controversy within the FDA surrounded Posilac's evaluation in the late 1980s. Richard Burroughs, who had a lead role in the review process, was shocked at how few tests the agency was requiring. Burroughs ordered more tests but was soon fired. He said, “I was told that I was slowing down the approval process.” Alexander Apostolou, director of the FDA's Division of Toxicology, says, “Sound scientific procedures for evaluating human food safety of veterinary drugs have been disregarded.” When he expressed his concerns at the agency, he was pressured to leave.

Chemist Joseph Settepani testified at a public hearing about “a systematic human food-safety breakdown at the Center for Veterinary Medicine.” Prior to his testimony, he was in charge of quality control for veterinary drug approvals. Soon after, he was stripped of his duties as a supervisor and sent to work in a trailer at an experimental farm. On March 16, 1994, others at the FDA resorted to writing an anonymous letter to members of Congress, saying they were “afraid to speak openly about the situation because of retribution."^[26]

The Food and Drug Administration (FDA) does not require special labels for products produced from cows given rbST. Monsanto sued the Oakhurst Dairy over their use of a label which read: "Our Farmers' Pledge: No Artificial Growth Hormone."

Monsanto stated: "We believe Oakhurst labels deceive consumers; they're marketing a perception that one milk product is safer or of higher quality than other milk. Numerous scientific and regulatory reviews throughout the world demonstrate that that's unfounded. The milk is the same, and the amount of protein, fats, nutrients, etc., are all the same."^[27]

Oakhurst's President stated: "We have said from the beginning that we make no claims to understand the science involved with artificial growth hormones. We're in the business of marketing milk, not Monsanto's drugs."^[27]

The suit was settled when Oakhurst agreed to add a qualifying statement to their previous label, reading: "FDA states: No significant difference in milk from cows treated with artificial growth hormone."^[27]

The FDA has charged several dairies with selling "misbranded" products, based on labels stating that their milk was "hormone free" or contained "no hormones". The FDA states that all milk contains hormones and "milk cannot be produced in a way that renders it free of hormones."^[28]

Demand for organic milk (produced without the use of synthetic hormones) in the US has increased 500% since Monsanto introduced their rbST product; organic milk is the fastest growing sector of the organic food market.^[29] Shortages exist, and not enough organic milk is produced to meet demand.^[30]

Use of the recombinant supplement has been controversial. While it is used in the United States, it is banned in Canada, parts of the EU (The EU's stance leaves the decision up to individual nations, though none have allowed it^[31]), Australia, and New Zealand.

Voluntary removal of rBGH from the milk supply

As of February 2007, Safeway in the Northwestern United States stopped buying from dairy farmers that use rBGH. The two Safeway plants produce milk for all of Oregon, Southwest Washington, and parts of northern California. Safeway's plant in San Leandro, CA had already been rBGH-free for two years. Another company going rBGH free is Chipotle Mexican Grill that has also announced it will only serve rBGH-free sour cream at its more than 530 restaurants.^[32]