Bovine somatotropin

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This article is about rBST. For other uses, see RBST.

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.

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[edit] 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.

Somatotropin and somatropin both refer to growth hormone (GH), a protein hormone produced by the mammalian anterior pituitary.

[edit] Recombinant Bovine Somatotropin (rbST) and rBGH

rbST (Recombinant Bovine Somatotropin) or rBGH (Recombinant Bovine Growth Hormone) is a controversial, genetically engineered version of the Bovine Growth Hormone used for increasing milk production in cows.

Monsanto developed a recombinant version of bST (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 generally refer to the same Monsanto product sold under this brand name. Other terms include, rBGH, BGH, rBST, BST and GH.

Injected into dairy cattle, the product can increase milk production by an average of over 10%. [1]

[edit] Controversy

Monsanto's product has been very controversial. Some of the reasons are outlined below.

[edit] Human Health Effects

Many groups claim not enough research has been done into human health effects in consumers of products from rbST injected cows.

Canada's health board, Health Canada, banned rBGH, citing its potential to cause "sterility, infertility, birth defects, cancer and immunological derangements".[citation needed] 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)."[2]

BGH proponents argue that cross-species differences are significant enough to prevent most cross-species effects. (i.e. bST does not "work" in humans.) [3] Monsanto, the largest single producer of rBGH [4], 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, 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. [5]

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". [6]

rBGH has been associated with an increaced risk of mastitis in cows, which may cause milk from cows treated with rBGH to become contaminated with pus and antibiotics used to treat the disease. Milk from mastitic cows is not entered into the human food chain. [7]

[edit] IGF-1

Monsanto's studies show use of rBGH in cows increases insulin growth factor 1 (IGF-1) in milk. [8] 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 [9]. 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 [10], 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 [11], prostate cancer [12], and colorectal cancer. [13].


On 22 may 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. [14]

[edit] FDA Approval

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. [15] 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 its evaluation in the late 1980's. 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." [16]

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."[17]

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."[18]

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."[19]

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."[20]

Demand for organic milk (produced without the use of synthetic hormones) in the US has increased 500% since Monsanto introduced their rbST product, and is the fastest growing sector of the organic food market. [21] Shortages exist, and not enough organic milk is produced to meet demand. [22]

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 it up to separate nations), Australia, and New Zealand.

[edit] Animal Health and Welfare

In 1998, a Canadian committee found that there may be increased risks to animals due to injections of rbST. According to their report, use of rbST increased the risk of mastitis by up to 25%, and infertility by 18%. [citation needed]

Humans who have too much (human) growth hormone can develop a disease called acromegaly; some speculate that it is no more healthy for cows to have too much growth than it is for humans, despite the fact that somatotropin does not noticeably stimulate physiological maturation and was even refined from slaughtered cattle and used in medical attempts to treat dwarfism in humans in the 1930s, to no positive or negative effect [citation needed].

Many animal rights activists oppose factory farming practices because they oppose cruelty to animals. Monsanto claims rBST only has physiological effects on cattle in good health. [citation needed]

[edit] 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.

[edit] National Policies

  • 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.

[edit] See also

[edit] Scientific Studies

  1. Report of the Royal College of Physicians and Surgeons of Canada Expert Panel on Human safety of rbST [23]
  2. Report of the European Commission Scientific Committee on Veterinary Measures relating to Public Health on "Public Health Aspects of the Use of Bovine Somatotrophin" [24]
  3. JC Juskevich and CG Guyer, "Bovine growth hormone: human food safety evaluation," Science, 249, op. 875-884, 1990. [25]

[edit] References

  1. Science and technology: Udder confusion. Anonymous. The Economist. London: Jul 3, 1999.Vol.352, Iss. 8126; pg. 70, 2 pgs.
  2. Big Milk, Big Muscle, Big Money. Fifth Estate - CBC Television. Toronto: Nov 29, 1994.
  3. U. S. Food and Drug Administration Center for Food Safety and Applied Nutrition / Cornell University BST Fact Sheet [26]
  4. IGF-1 and Milk.com (link articles) [27]

[edit] External references

[edit] Regarding Monsanto

[edit] Other external references

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