Elizabeth Dodemaide, B.V.Sc., M.A., MACVSc, Associate Director, Laboratory Animal Services, Rutgers, The State University of New Jersey

The Guide for the Care and Use of  Laboratory Animals (the Guide) is an internationally accepted primary reference on animal care and use, and its use is required in the United States of America by the Public Health Service Policy. It was first published in 1963, and has been revised a number of times since then. The most recent edition was published in January, 2011.

The purpose of the Guide is to assist institutions and investigators in caring for and using animals in ways judged to be scientifically, technically, and humanely appropriate. Recommendations in the Guide are based on scientific principles, published data, expert opinion, and experience with methods and practices shown to be consistent with both high quality research and humane animal care and use. The recommendations are intended to be used as the basis for development of a comprehensive animal care and use program, in the context of applying performance standards to the implementation of the program.

The most recent edition of the Guide has additions and changes that institutions have to incorporate into their animal care and use programs. One addition is a specific section on Environmental Enrichment (p.52).  The 1996 version discussed the use of environmental enrichment devices in determining appropriate cage size, and provision of an environment that encouraged species- specific behaviors. For social species, environmental enrichment was suggested as a method to compensate for the lack of social interactions with conspecifics when animals must be housed alone. Most references listed were for non-human primates (NHPs).

The 2011 Guide expands on the discussion of environmental enrichment, citing many references covering a larger range of species. The Guide says:

“The primary aim of environmental enrichment is to enhance animal well-being by providing animals with sensory and motor stimulation through structures and resources that facilitate the expression of species-specific behaviors and promote psychological well-being through physical exercise, manipulative activities, and cognitive challenges according to species-specific characteristics.” —p. 52-53.

The main points in this section include:

• Examples given of structural additions include perches and visual barriers for NHPs, elevated shelves for cats and rabbits and shelters for guinea pigs. Manipulable resource examples include novel objects, foraging devices for NHPs, manipulable toys for NHPs, dogs, cats and swine, wooden chew sticks for  some rodents and nesting materials for mice.

•   The Guide further states: “Well- conceived enrichment provides animals with choices and a degree of control over their environment, allowing them to better cope with environmental stressors.”—p. 53. A stated caution is that not every item added to the animal’s environment necessarily benefits its well-being, an example being the addition of marbles to a mouse cage where it has been found to be a stressor rather than an enrichment.

• When enrichment items are used, the rotation of the items should be a consideration. However, changing the environment too often may be stressful.

• The IACUC, researchers and veterinarians should regularly review the enrichment programs to ensure they are beneficial to animal well-being and consistent with the goals of animal use. Programs should be updated to reflect new knowledge as needed.

• Animal care personnel should be trained in behavioral biology of the species they work with to appropriately monitor the effects of enrichment.

• Enrichment affects phenotype and may impact experimental outcome (independent variable).

• It is recommended to read and/or conduct research before updating a local Environmental Enrichment Plan.

Application of Guide standards in an animal facility should take into consideration the desired outcome—benefiting or enhancing animal welfare. Engineering standards are prescriptive and provide limited flexibility for implementation. However, they can be useful for establishing a baseline and aid in evaluating compliance.

A more advantageous approach is to apply performance and practice standards. Describe a desired outcome and provide flexibility in achieving this outcome by allowing those responsible for managing the animal care and use program, the researcher, and the IACUC, the discretion to apply methodology to achieve the outcome. The intent of the Guide is to provide flexibility for institutions to develop and modify practices and procedures when new information becomes available and changes in conditions occur. The new Guide places great emphasis on social environment which is intimately tied to enrichment, and must always be considered as part of a comprehensive enrichment program.

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