Stress Evaluation of Mouse Husbandry Environments for Improving Laboratory Animal Welfare

SIMPLE SUMMARY: It is well recognized that companionship is important to animals and that they need to be provided with an environment accompanied by materials for enrichment, such as toys. However, few studies have evaluated whether specific environments actually benefit animals. Therefore, we designed various environments for laboratory animals and scientifically evaluated which environments reduced these animals’ stress. We found that an environment with freer air circulation and the provision of enrichment materials reduced animal stress, and no risk or benefit could be determined for the presence or absence of a companion. We do not consider that our results necessarily indicate the lack of a need for a companion, but, rather, the importance of having a good companion. Our results can serve as a meaningful guideline for the creation of suitable environments for laboratory animals. ABSTRACT: Animal welfare is recognized as essential for the coexistence of humans and animals. Considering the increased demand and interest in animal welfare, many methods for improving animal welfare are being devised, but which method reduces animal stress has not been scientifically verified. Therefore, reducing animal stress by providing a proper breeding environment and environmental enrichment can be the basis for animal study. In this study, stress levels were assessed based on the mouse-breeding environment. We considered that the higher the body weight and the lower the corticosterone concentration, the lower the stress. According to the results, animals in the individual ventilation cages were determined to have lower serum cortisol concentrations, while the body weight of the animals was increased when in individual ventilation cages compared with individual isolated cages and when providing environmental enrichment compared with group breeding or not providing environmental enrichment. The results provide appropriate guidelines for improving laboratory animal welfare.