Extended Sanitization Frequency for Bottles: Using Volume as an Alternative to Time-Scheduled Replacements for Mice in Disposable Individually Ventilated Caging Systems

The Guide for the Care and Use of Laboratory Animals specifies that sipper tubes require weekly sanitization, although reduced frequency for sterile, disposable caging components may be justified with performance-based assessments; therefore, extending bottle duration beyond 1 week, and replacing instead at a lower volume limit, may be acceptable if it does not compromise mouse health or water quality. Weekly bottle change for sterile, disposable bottles results in excessive waste of both water and plastic-bottles are typically more than half full at 7 days. A volume-based replacement schedule is a visual alternative to weekly changes for systems using sterile, disposable bottles, reducing the number of bottles processed and facilitating operations by allowing spot changes without the need to date or track bottles. Furthermore, the gravity-drip design of Innovive's Aquavive bottle minimizes contamination, suggesting that water quality and cleanliness may be maintained for longer durations. To assess the impact of a volume-based replacement schedule on mouse health and water quality, C57BL/6NCrl mice at varying housing densities were monitored for changes in animal weight and mean water consumption. At bottle replacement, packed cell volume was collected from individual mice as a marker of hydration status, and water quality was assessed by visual inspection, culture for Escherichia coli and coliform bacteria, and total microbial count. Baseline measurements were collected over 7 days, followed by a volume-based replacement period, where bottles remained on the cage until they reached 100 mL (13-47 days). No significant differences were observed in animal body weight, body condition, water consumption, or packed cell volume, regardless of cage density or the amount of time the bottle was deployed. Microbial analysis showed no bacterial growth in any bottle, and visual inspection showed no turbidity or cloudiness. Based on this information, our institution allowed prefilled disposable, acidified water bottles to be maintained well beyond 7 days, using a volume-based replacement at 100 mL.