Animal Selection for Research

The goal of any experiment is to determine the effects of defined experimental variables in a controlled environment. When working with biologic systems variability between experimental animals can confound the interpretation of results. By selecting appropriate animals an investigator will reduce experimental variability. This will result in the use of fewer animals and less work to produce significant results.

Factors that can increase variability in experimental results:

• Use of outbred animals or animals from varying backgrounds or sources.
• Infection with pathogenic microorganisms.
• Inflammation or infection associated with wounds.
• Extravasation of irritating substances such as chemotherapeutics.
• Animals with ulceration, necrosis and or infection of a tumor.
• Behavioral changes in animals can signal a difference. For example the mouse that constantly runs in circles in its cage is not the same as the one who does not.

To reduce experimental variability:

• Use inbred animals from the same source when possible.

• Do not use animals with open wounds or other signs of illness or injury.
• Do not use animals that display abnormal behavior.
• Protect animals from infection with potential pathogenic microorganisms.
• Select endpoints that will not introduce additional variables. Complete the study before animals become moribund or develop ulcerated, necrotic or infected tumors.
• Use aseptic technique when preparing for and performing surgery. Shave the fur and scrub the surgery site. Select an appropriate method of sterilizing instruments for surgery.