The type and depth of bedding provided to laboratory mice and rats significantly affects their ability to thermoregulate, nest, burrow, and engage in natural behaviors.
Bedding quality has measurable effects on laboratory rodent welfare. Mice provided with insufficient nesting material show higher stress hormone levels, reduced immune function, and impaired thermoregulation. The standard of providing a few grams of nesting material in shallow bedding trays fails to meet the burrowing and nesting needs of these animals. Research shows that providing ample nesting material and burrowing substrate improves rodent welfare without compromising experimental outcomes in most study types. Progressive refinement of husbandry standards represents a readily achievable welfare improvement for hundreds of millions of laboratory rodents worldwide.