Kimberly A. Wasko, CVT, VTS, RALAT
Department of Surgery Drexel University, College of Medicine, Philadelphia, PA

Background
Animals love enrichment just as much as people do. Enrichment gives animals something to occupy their minds and encourages them to be more active. The goal of enrichment is to increase activity and stimulation levels in the captive or limited environment. It helps animals demonstrate their natural behavior, adds variety to their day, allows them exercise, gives them choices in their environment, and enhances their well-being. Enrichment generally enhances the animal’s life pleasures and should be an integral part of the daily care of laboratory animals. Enrichment also gives us the chance to study and observe the animals’ behavior.

Since animals respond differently to social and environmental interaction, a consistent enrichment program is an outstanding channel for achieving these objectives. However, once a program is instituted—What Next?

Objective
Have fun! That’s what’s next! Re-evaluating your program regularly allows diversity. Enrichment is creative and dynamic. It can be basic, simple to comprehensive, and detailed. After envisioning, creating, and instituting an in-depth program for all of our rodent animals, we could not stop there. We needed to evolve to the next level. The enrichment possibilities were boundless –ideas were whirring a mile a minute. With the new ideas came the Zen of Enrichment.

Design—What We Did—Fresh and Distinctive
The introduction of various food treats and devices was the initial start to our enrichment program. Treats and devices (Bio-Serv, Frenchtown, NJ) were first implemented for our surgical patients. Then we eliminated chemical restraint for noninvasive procedures and introduced a socialization program.

Currently, our expanded physical environment, social environment and the opportunity for physical and mental challenges have brought about new experiences for the rodents and fun for all involved.

Standard Physical Environment
The physical environment entailed a standard cage unit size for a rat at 10.5 x 19 x 8 inches in a polycarbonate cage with typical corncob bedding (approximately 1/2 to 1 inch depth). The enrichment device(s) may vary, but a common device is an easy cardboard tube.

Our Physical Environment
We upgraded our physical environment to IACUC approved caging units size 18 x 14.75 x 8 inches with 1/2 to 1 inch corncob bedding layering the bottom of the unit. In addition, we added 6-8 inches depth of Enviro-dri® bedding (Shepherd Specialty Papers, Watertown, TN) to encourage nesting and burrowing. Another new cage unit we added was the Double-Decker cage unit (Tecniplast, Exton, PA) size 18.2 x 15.9 x 15.9 inches. We fitted the Double-Decker unit with a red divider between the first and second levels to provide a “hiding”, protective area. Corncob bedding also layered the bottom of the bottom of the unit 1/2 to 1 inch in depth. We added 3-4 inches of Enviro-dri® bedding to the first level and 2-3 inches on the divider to the second level. The animals also received their wood gnawing blocks, fleece cozies and food treats 2xs/week.

Standard Social Environment
The social environment included same-sex conspecific housing when applicable. Human interaction involved animal handling during cage changing plus handling for the experiment. Typically, nothing extra was implemented.

Our Social Environment
We also included same-sex conspecific housing at every opportunity. Human interaction involved not only handling during cage changing and during the experiments, but 2xs/week petting, holding, and positive reinforcement at 5-10 minutes/sessions to reduce stress and improve tolerant handling.

Standard Opportunity for Mental and Physical Challenges
Typically, there is none. Other than what is fitted in the cage unit originally as the enrichment (example: cardboard tube), the animal remained unstimulated and unchallenged.

Our Opportunity for Mental and Physical Challenges
We engaged the animals in physical challenges immediately when we introduced the larger cage units and bi-level cage units. We also engaged them directly with the additions of copious amounts of bedding material to encourage their natural behavior modes of nesting and burrowing. Other distinctive methods included placing dried fruit chunks in between the bars of the cage lid to encourage physical activity and mental activity. We added the Enviro-dri® bedding on top of the cage lid to encourage the animals to pull the materials through the bars. We also continued to allow the animals to explore an ever-varied agility course 2xs/week for 10-15 minutes/sessions, stimulating senses, mind, body and spirit. The two new caging units were alternated to offer different experiences to the animals.

Discussion
Expanding our current enrichment program permitted the animals to enjoy and benefit from the new encounters. The fresh additions kept them stimulated and persistently challenged. The response was undoubtedly remarkable. The animals were calm, active, sociable, and simply —HAPPY! They attained their enlightenment. A Zen saying goes…When you get to the top of the mountain, keep climbing. May your enrichment program keep climbing too!

Acknowledgements
The author would like to express sincere appreciation to Bio-Serv of Frenchtown, NJ, for their continued support and dedication to environmental enrichment. The author would also like to express her gratitude to Techniplast of Exton, PA for their generous donation of the Double-Decker caging unit to support environmental enrichment.

References
1. NRC [National Research Council], 1996. Guide for the Care and Use of Laboratory Animals. 7th ed. Washington DC: National Academy Press.
2. Bayne KAL, Beaver BV, Mench JA, Morton DB, 2002. Laboratory Animal Behavior. Laboratory Animal Medicine. 1229-1264.

Issue 4, July 2010

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