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Unintended Effects of Genetic Manipulation
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Transgenic pigs expressing bovine growth hormone had lower appetites, enlarged organs, gastric ulcers, and other health problems.

Manipulated Organism: Pig (Sus domesticus).

Inserted Transgenes: Bovine growth hormone (bGH) gene, with expression controlled by the mouse metallothionein promoter.

Goal of This Study: Compare the growth and overall health of pigs expressing bovine growth hormone with their non-transgenic siblings.

Intended Effect: The transgenic animals gained weight 10-15% more quickly than their non-transgenic siblings.

Unintended Effects:
  • Despite their faster growth rate, the transgenic pigs ate 10-20% less. According to the authors, appetite suppression is also observed in pigs receiving growth hormone by injection.

  • The weights of the heart, liver, kidneys, and adrenals in the transgenic pigs all increased relative to their total body weight.

  • Autopsies were conducted on 5 transgenic and 3 non-transgenic pigs. Five out of 5 transgenic pigs had gastric ulcers, 4 out of 5 suffered from joint inflammation, and 4 out of 5 had enlarged nuclei in cardiac cells. None of the 3 non-transgenic pigs displayed these symptoms.

  • The authors noted that the transgenic pigs were lethargic and uncoordinated, and the boars lacked libido.

Source: Pursel, V. G., C. A. Pinkert, K. F. Miller, D. J. Bolt et al. (1989). "Genetic Engineering of Livestock," Science vol. 244, pp. 1281-8.

Author Affiliations: USDA Agricultural Research Service, Beltsville, MD; University of Pennsylvania, Philadelphia; University of Washington, Seattle.

Funding: National Institutes of Health, U.S.

Product Status: Not on the market as of 2009.

Copyright 2009 The Nature Institute.

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