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VI. Enrichment


A way to ease the stress of a caged existence and promote health and well being is to allow captive animals to carry out the behaviors that are normal for the species. The concept of environmental enrichment involves providing objects, opportunities, or other species members that allow species-appropriate behaviors to be expressed. Although the concept of enrichment has made headway in zoos and other facilities that maintain animals, it also has become a legal requirement for some research animals.

The revised Animal Welfare Act of 1985 mandates a minimum of environmental enrichment1. This legislation requires exercise for dogs and modification of enclosures for nonhuman primates to promote psychological well being. This minimum of change to improve animal housing has led to efforts to enrich the lives of many other kinds of laboratory animals as well2.

Environmental enrichment also can lead to a reduction in the number of animals needed, since fewer animals may be lost during the course of an experiment3.


Enrichment can be defined as the increase in the complexity or naturalness of an enclosure with the goal of improving an animal's well being4.

To provide meaningful enrichment requires materials that enable species to perform relevant behaviors. What suits primates probably would be irrelevant for rodents. For example, the one enrichment that has proved helpful for mice is making available materials for nesting. Indeed, mice given access to cardboard tubes that are meant to simulate burrows will shred them and use the material for nest building instead5.

Caution has to guide enrichment. Efforts to provide enrichment could produce unanticipated health hazards to both the animals and their human caregivers. For instance, animals could injure or even strangle themselves on manipulatives, such as swings or enclosures meant to comfort and amuse. Expanding or changing caging, or providing opportunities for exercise, can also increase the likelihood that handlers will be injured.

Another concern is that enrichment might alter research findings in unpredictable ways6. The converse can also be argued, namely, that animals kept in conditions inappropriate for the species will express abnormal behavior to varying degrees, depending on the individual's temperament, and thereby introduce unrecognized bias into research data. Different practices for housing or enrichment in different labs also might introduce variability into research outcomes due to differences in behavior and stress levels that affect the animals' physiology7. The more variable the data, the more animals must be used, which will end up requiring more animals to be used in research8. The current state of affairs is only the beginning of a debate over how to implement enrichment and to provide research animals with a better life.


Readings and Resources on Enrichment

New ALTEX: 2/2018

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Building a Better Epithelium: Breaking the Barrier to the Next Generation of Toxicity Testing
March 10, 2018
San Antonio, TX

SOT Satellite Meeting: Updates on Activities Related to 21st Century Toxicology and Related Efforts: Invited Presentations and Open Mic
March 15, 2018
San Antonio, TX

Social Housing Workshop
June 4-5, 2018
Beltsville, MD

2nd Pan-American Conference for Alternative Methods
August 23-24, 2018
Rio de Janeiro, Brazil 

Eurotox 2018
September 2-5, 2018
Brussels, Belgium

20th International Congress on In Vitro Toxicology (ESTIV2018)
October 15-18, 2018

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