Beyond Comfort: A Review of the Critical Role of Bedding Selection in Rodent Welfare, Microenvironment, and Research...

This review addresses the critical but often underappreciated influence of bedding selection on rodent welfare, cage microenvironment, occupational health, and research outcomes in biomedical studies. Although contact bedding is widely preferred by mice and rats and is the current industry standard, there is considerable variation in bedding type, volume, sterility, and manufacturer practices, with no established universal protocols. We synthesize over 150 publications, evaluating corncob, wood, and cellulose-based beddings with respect to their physical attributes, absorbency, ammonia management, dust and contaminant control, and support of species-typical behaviors. The review highlights methodological challenges and inconsistent results across studies, with absorbency and ammonia accumulation particularly affected by bedding mass, volume, and microbial contamination, rather than material type alone. Occupational health risks, including ergonomic strain and allergen exposure, are impacted by bedding handling frequency and composition. Animal health is generally not strongly influenced by bedding type, although pine shavings and certain corncob products present toxicity and reproductive risks in some studies. Bedding also has documented impacts on hepatic enzyme induction, neurobehavioral development, pain sensitivity assays, and gut microbiome composition, posing substantial risks for experimental confounding and compromised reproducibility. Based on the evidence, cellulose bedding is recommended for minimizing negative outcomes, but the complexity and variability inherent in bedding selection necessitate careful documentation and transparent reporting. We advocate for standardized detail in publications to ensure comparability and rigor across rodent-based research.