A new study confirms what Joseph Garner, PhD, and his colleagues have long suspected – that laboratory mice are healthier, more fertile and have better welfare when they have the means to build a nest, which reduces stress and helps them naturally warm themselves.
Garner has done a series of studies in these mice not only to enhance their living conditions and well-being, but also to improve the results of research studies. Laboratory mice now are routinely housed in cold conditions, so the animals expend much of their energy trying to keep warm. This changes their physiology and may compromise the outcome of research studies, says Garner, an associate professor of comparative medicine at Stanford. But given the means to build a nest, the mice will thrive, producing more pups that are healthier and more likely to survive, he and his colleagues report in a study out this week.
In the study, the researchers gave pairs of mice from three of the most commonly used strains a few different living options. Some got a bed alone, while others got a bed, plus a choice of one of two different materials for building nests. The nest-builders proved to be healthier in many respects – good news for the mice, as well as for the research labs that maintain them. Garner told me:
This is a great example of how ‘good welfare is good business.’ The mice with nesting material produced more pups per litter, the pups reached a healthy weight faster, the mortality of the pups is reduced, and the mice used less food.
Providing mice with nesting material is very cost-effective for commercial mouse breeders, he says. For the most commonly used mouse strain, laboratories that invest 60 cents in nesting material over six months will gain an additional $273 on average in pups, he calculates. But it’s not just mice and mouse breeders that stand to benefit:
For a scientist on campus, this means that you can reduce the cost of breeding mice because you need fewer breeding pairs to produce the mice you need, and those mice will be healthier, better quality mice. So this is a great incentive for all of us to do the right thing and invest in enrichment for our mice.
The study, a collaboration with Brianna Gaskill and researchers at the Charles River laboratory, appears online in PLoS One.