Effects of Compressed Paper Bedding on Mouse Breeding Performance and Recognition of Animal Health Concerns

The combination of bedding substrate and nesting material within the microenvironment of mice is an important consideration for animal care programs in regard to optimizing animal wellbeing. We used 3 general or breeding mouse colonies in our institution to evaluate the effects of bedding substrate on nest building, breeding performance, and recognition of animal health concerns. A scoring system was developed to assess the incorporation of bedding into the nest cup base and walls (nest base incorporation, NBI) in a controlled study with mice bedded on either compressed paper (CP) or corncob (CC) bedding. Compared with CC cages, CP cages had higher NBI scores. To determine the influence of bedding type on the recognition of animal health concerns in an animal facility, cages bedded with CC followed by CP were evaluated for the overall frequency of health-concern reports during a 2-mo time frame for each bedding type in a single-subject A-B study design. The frequency of animal health-concern reports was similar in cages using CC or CP bedding. The animal health condition, rather than bedding type, was associated with the severity of the health problem at the initial report. Breeding performance was compared for 6 mo in matched CC and CP cages containing one of 13 genetically modified mouse lines. NBI scores were higher for breeders housed on CP compared with CC bedding. Monogamous breeder pairs housed on CP had significantly higher indexes of breeding performance (measured as the number of pups per dam per week on study) than did CC cages. This report supports the use of CP bedding in the mouse microenvironment to improve general wellbeing by supporting nesting behavior and reproductive performance without hindering the detection of animal health concerns.