Partially divided caging reduces overall aggression and anxiety which may indicate improved welfare in group housed male C57BL/6J mice

Abstract

Deciding which environmental enrichment is used in mouse caging is often subjective, with cost frequently prevailing over welfare benefits, including aggression and anxiety. While many devices introduced to encourage natural behaviors and reduce aggression show mixed results, we have previously demonstrated significant reductions in aggressive behavior between group-housed male mice housed in partially divided caging. To further assess behavior, we have raised male C57BL/6J mice in either partially divided caging or in standard caging with no divider. Animal behavior was tested on rotarod, open field, novel object recognition, elevated plus maze, and Y maze. Body weights were taken weekly beginning at weaning and bite wounds were counted weekly beginning at 133 days old. Aggressive behavior was recorded weekly beginning at 133 days old. Results indicated significantly less anxiety in the elevated-plus maze, statistically fewer bite wounds, and a statistically significant decrease in aggressive behaviors of mice in partially divided caging compared to mice in standard cages. We conclude that reductions in anxiety, aggressive behavior, and bite wounds may indicate improved overall welfare for non-sibling, group housed male mice.