Choosing the proper tools to enrich the laboratory environment isn’t always black and white

Studies show that the average lab rat prefers cages with shelters and coarse materials for nest building. Their bedding should be absorbent and their food pellets placed in hoppers as well as the cage floor to encourage foraging.

But rats immunized with autologous or heterologous type II collagen to induce rheumatoid arthritis are not your typical lab rat, noted Nirah Shomer, Director of Laboratory Animal Resources at New Jersey pharmaceutical giant Merck, during her talk at the Charles River Short Course. Designed to mimic some of the classic symptoms of this autoimmune disease, collagen-induced arthritis (CIA) models are also highly sensitive to stress. They may have different needs and preferences than their fellow rats.

This conundrum represents one of the many challenges vivariums and face when they try to enrich the laboratory animals so crucial science. As well all know, the research environment can be stressful for animals. It’s quite different from their natural habitat, so anything that can be done to enhance the psychological and physiological well-being of the lab animal prevents stereotypy—repetitive, maladaptive behaviors involving self-injury and reduced reproductive success such as self-mutilation, pacing, rocking and barbering.

And not only does environmental enrichment reduce stress in animals, studies have found that when these tools are incorporated into study protocols they do not bias the research outcomes.

But identifying the best enrichment for each species—and the various models within a particular species—is hard. One size does not fit all. The needs and wants of a minipig are different than that of a mouse which is different than that of a rat. Some animals prefer to be socially housed, others may not.

Shomer said it’s best for facilities to evaluate the environmental enrichment first before adding it to the mix. It’s important to also to consider if the enrichment is ergonomically sound and compatible with the particular colony in question. Cost is a factor as well as is the particular scientific characteristics of the research model. For instance, we all crave a food treat now and then, but this popular pick-me-up might not be suitable for your obesity or diabetes models.

The rat model for rheumatoid arthritis, created to study the pathogenesis of disease and evaluate potential therapies, proved to be a challenge for Shomer’s laboratory. The CIA models develop some of the hallmark symptoms of the disease, and laboratory staff worried that the standard living arrangements for lab rats—bedding, plastic shelters, social housing—could hurt the paws of the arthritic animals and create unneeded stress. Staff were also concerned that eating food pellets off the floor would be too unhygienic for the RH rats.

Substituting different environmental enrichments proved to be a challenge, so Merck conducted an internal study to see which approaches would work best. Eventually, the lab went with soft white bedding, fatter rat huts, pair housing and feeding dishes for the pellets and soft food. Shomer said the changes reduced the stress levels in the animals, reduced laboratory costs and ultimately improved the science.

How to cite:

McEnery, R. Learning What Animals Need. Eureka blog. Jun 18, 2015. Available: http://eureka.criver.com/learning-what-animals-need/