The effect of protein malnourishment and caging on growth and behavior of laboratory mice

Inbred (A/J and C57BL/6J) and hybrid mice were given access to low‐ or normal‐protein diets (4 or 26% casein) at 5 weeks of age and housed 1, 2, or 5 mice per cage. For all groups body weights of mice fed normal‐protein diets were greater for group‐caged than for isolated mice, and body weights of mice fed low‐protein diets were less for group‐caged than for isolated mice. At 15 and 16 weeks of age, mice fed low‐protein diets engaged in more exploratory behavior and were less emotional than mice fed normal‐protein diets. Mice that were group caged engaged in less exploration and were more motional than isolated mice. In addition to the major effects of caging and diet on behavior, mode of inheritance was significantly modified.