Rodents are the most widely utilized animal model for disease in the world of biomedical research. Despite their essential role, the range of behavior and behavioral needs of these animals is repeatedly under-recognized and underdeveloped. Providing animals with artificial and natural objects can be considered enriching. Enrichment activities are designed to improve the welfare of animals by reducing the levels of abnormal/injurious behavior while maintaining natural and instinctual behaviors. Understanding the species-specific behaviors in depth will improve animal welfare during captivity or limited environments.
The primary goal is to provide enrichment that benefits the animals and science alike. The implementation of a proactive enrichment/ socialization program can reduce atypical convalescence issues and discomfort/distress while facilitating quality care.
In the field of laboratory medicine, federal regulations exist requiring institutions to provide for the psychological well being of many laboratory animals. Enrichment is an outstanding channel of achieving these objectives. Animal enrichment is not mandated for all animals but animal welfare is emphasized by regulatory agencies.1 Proper enrichment can reduce stereotypies and other undesirable behaviors while increasing species-typical postures, activities and behavior.2
In Europe, the “Convention For The Protection Of Vertebrate Animals Used For Experimental And Other Scientific Purposes” provides guidelines for creating lab environments that allow some freedom of movement, as well as a supply of food, water, and care appropriate to animals’ health and well-being. The guidelines, which must be ratified, also state that researchers should check environmental conditions daily and monitor the animals’ emotional well being.1
With a proper understanding of animal enrichment, researchers will be able to enrich laboratory animals without affecting results or compromising experimental design. Since animals respond differently to social and environmental interaction, a consistent program is essential. Accordingly, the physical and social environment requires evaluation.
Indications—Why We Did It
We sought to provide a proactive enrichment program to reduce stress and facilitate quality care due to two principal distressing conditions our animals were experiencing:
1. atypical convalescence issues
2. administration of chemical restraint to perform non-invasive procedures. Devising a comprehensive program allowed us to:
a. provide enrichment that did not alter, compromise or impose a variable to our animal studies and
b. challenge the rats with enrichment to improve their ability to cope with new situations.
The goals were to:
1. return the animal to homeostasis as rapidly as possible
2. reduce atypical convalescence issues post-operatively
3. replace the use of chemical restraint with socialization and enrichment to perform non-invasive procedures such as, but not limited to, bandage changes, infra-red/ caliper measurements and per os (not gavage) oral medication dosing.
Design—How We Did It
All of our studies were approved and performed according to IACUC and regulatory guidelines. The preliminary step focused on education. Education was fundamental towards devising a comprehensive enrichment program for our rodents. After our education sessions, we were furnished with the foundation—or “fundation” as we refer to it—of enrichment facts and information. Now it was up to us to envision and create it—and we did.
The introduction of various food treats and devices was the initial step for phase I. Treats and devices (Bio-Serv, Frenchtown, NJ) were first implemented for our surgical patients. Typically, animals have to rear on their hindquarters to reach the food pellets and water. After an abdominal invasive procedure, it was not sensible to have our rats stretching and struggling to reach their food. By repetitive motion, the animals experienced increased discomfort thus resulting in decreased appetite and hydration. The solution was to temporarily provide floor feeding with enrichment treats, which were certified and nutritionally fortified to support post-operative convalescence and encourage the appetite. We also supplied a re-hydration oral solution in bowls in addition to the water bottle. We offered an array of treats of foraging crumbles, black oiled sunflower seeds, bacon flavored treats, dehydrated fruit and vegetables. We also enhanced the cage environment with hiding retreats, wood blocks and crumble fruit discs to encourage typical psychological behaviors. Treats were extended for 72 hours post-operatively, then twice weekly until the study completion; devices were extended continuously. With remarkable results, 98% of animals experienced substantial decreased complications, such as weight loss, dehydration, lethargy and dull mentation. Because of these results, all current and forthcoming protocols include this new comprehensive enrichment program for any animal undergoing a surgical procedure.
The second phase was to implement a socialization and agility program to replace the use of chemical restraint to perform non-invasive procedures such as bandage changes and applications, oral dosing and performing various methods of measurements of the affected surgical sites. Each time an animal would undergo chemical restraint, which could range from two to three times per week, regardless of method (gas anesthesia, injectable anesthesia), the risk of morbidity and mortality greatly increased. In addition, animals were experiencing persistent complications: weight loss, dehydration, decreased appetite, lethargy, increased discomfort, increased nervousness/fear and fatality from this type of restraint. In addition to the treat and device regimen, a socialization and agility program was implemented. Socialization occurred at 10-15 minute intervals/per rat three times per week, and included tolerant handling, holding, petting and positive reinforcement food training. The agility course was prepared differently for each set up on an enclosed cart or extra large caging unit. The agility course could include dumbbells, hiding retreats, tubes, crumpled blankets, wood blocks and stuffed animals. Any item could be used for agility as long as it did not impose any physical harm to the animal. The course was set up so the animal could explore and have the space to roam and indulge its curiosity along with physical exercise and mental stimulation. Animals either participated in agility twice weekly for 20-30 minute intervals singly or partnered. Again, the results were significant—100% of the animals responded and we were able to eliminate chemical restraint for non-invasive procedures to date. Animals exhibited and experienced less stress, less fear, increased comfort and became highly sociable. This program has been implemented in current and forthcoming protocols for any animal undergoing a non-invasive procedure.
Due to inadequate assessment, there are many opportunities for research in the field of enrichment. Addressing the psychological and physical needs of our research animals created less variability in our results. Most importantly, it improved quality and humane animal welfare. This lessened the need to repeat our experiments and thus allowed the use of fewer animals. Implementing a comprehensive enrichment program and discovering an alternative to chemical restraint decreased atypical convalescence and complications while adding a ‘fun’ element for our animals.
The most humane habitat possible for all research animals should be provided. With a proper understanding of enrichment, animals can be enriched without affecting results or compromising experimental design. GO ENRICHMENT!
The author would like to express sincere appreciation to Bio-Serv of Frenchtown, NJ, for laying the groundwork for our enrichment program.
The Law on Animal Care
The Animal Welfare Act (AWA), America’s foremost animal protection law, covers some lab animals, such as primates, dogs, and guinea pigs. But in 1972, the US Department of Agriculture declared that mice, rats, and birds were exempt from AWA protections. An updated version of the AWA, enacted in 1985, bolsters the standards of care for all laboratory animals, and specifically promotes “the psychological well-being of primates.” Though an estimated 25 million lab rats and mice are still exempt from AWA,1 most major US research institutions receive money from the Public Health Service and must have their animal welfare guidelines approved by the National Institutes of Health Office for Laboratory AnimalWelfare.1
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.