Genetically Modified Laboratory Animals – What Welfare Problems Do They Face?

Buer M, Hjorth J, and Hansen A. (2003). Genetically Modified Laboratory Animals – What Welfare Problems Do They Face?. Journal of Applied Animal Welfare Science, (6-4): 319-338.

Research question:  The purpose of genetic modification (GM) in lab animals is to theoretically design a genetic mutation and predict its effects.  This article discusses the welfare problems associated with genetically modified (GM) lab animals.

Methodology:  The authors review situations that may cause welfare problems specific to GM rodents.  They discuss principles of animal welfare, the problems with animal suffering, the specific types of GM that will likely cause welfare problems, and the role that GM animals have in improving the welfare of all animals in research.  Animal suffering is defined as “intense physical or mental states felt by the animal” that the animal cannot resolve on its own.

The authors define “GM” as organisms generated by 1 of 4 ways:

  1. pronuclear injection of a DNA construct (transgenics)
  2. gene targeting techniques (knockouts and knock-ins)
  3. transfection with episomal vectors
  4. genetic modification by similar procedures distinct from conventional breeding and mutagens

Important Points on Lab Animal Welfare: 

  • Welfare concerns for all lab mice whether they are GM or not include: pain or discomfort, shortened life expectancy, inability to eat, inability to mate, sensory deprivation, and any other restrictions to normal behavior.
  • One way to assess an animal’s welfare to consider how a human would react under the same conditions. This works well for painful stimuli, but not as well for psychological states.


Welfare Concerns Specific for GM mice:

  • GM can lead to unexpected genome rearrangements which can cause severe health problems, death, or it can have no noticeable effect at all.
  • Procedures are invasive and tissue samples are often taken from tail tips or ear punches.
  • Cloned mice often have abnormal placentas and many don’t survive to birth or die prematurely.
  • Some mice are bred to express harmful mutations which damage their health.
  • It is common for some lines of GM mice to develop gastrointestinal issues.
  • Not all mutations that would cause pain or disease in humans appear to cause the same pain or the same symptoms in mice. An example is a line of mice that were bred to use as a model for cystic fibrosis, but showed no pulmonary symptoms.  They showed other symptoms such as ulcers instead.



  • No specific differences can be defined between GM mice and other lab animals in regards to welfare. Welfare issues are very similar for both groups.  Normal lab animals can often develop the same diseases and problems naturally; however, in GM mice welfare concerns are more predictable.
  • GM lines are often given test treatments before symptoms develop, and in these cases their welfare is likely to be much better than other lab animals.
  • Three goals of animal welfare are to reduce the number of animals used in research, replace them with other systems when possible, and refine experiments to improve focus. Because GM mice are bred for specific purposes, they can often help to meet these goals.
  • GM lines of mice usually require fewer animals to establish and fewer animals to complete a research project. In this way, GM mice help to reduce the overall number of animals needed to complete a project.
  • Addressing welfare issues in GM animals is important for scientists to gain public support for the use of GM animals in research.


Summary by Traci Raley, MS

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