Experimental Guidelines

Selecting Appropriate Animals

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. The goal in selecting experimental animals is to minimize the variability. Reducing variability will translate to fewer animals and less work to produce significant results.

Within a line of inbred animals, all are virtually genetically identical and when used in experimental procedures greatly reduce variability in results.

Factors that can increase variability in experimental results:

• Infection with pathogenic microorganisms.
  
• Inflammation or infection associated with wounds.
  
• Extravasation of irritating substances such as chemotherapeutics.
  
• Animals with severe 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.

Recommendations:

• Do not use animals with bite wounds.
  
• 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. Alcohol used alone is not recommended for sterilization of instruments.