Characterization of different bedding materials for laboratory mice

Bedding may be one of the most important elements of the microenvironment because it is continuously in direct contact with laboratory mice. Determining the most suitable bedding for each experiment will improve animal welfare. Ammonia levels, absorption, particle size, thermal diffusivity, microbial growth, and stools dropping to the cage floor were determined using four different commercial bedding materials (cellulose, corncob, and two different poplar). The ammonia levels over 21 days were lower for the cellulose and corncob than for poplar bedding. Both poplar beddings showed more variability in particle size than the other two types of bedding. The cellulose bedding showed the highest absorption ability and maintained more stable temperatures during unexpected heating and cooling conditions. It was also the only one that allowed stools to drop through to the cage floor. All bedding materials maintained a steady number of microorganisms for the first 14 days, although the corncob showed less microbial growth. While certain materials may be more suitable for typical experimental settings, overall, our findings highlight that bedding choice should be considered an important experimental variable when designing research studies, depending on the aim, procedures, established parameters, and specific characteristics of each research project.