Maintaining Welfare While Extending Cage-Change Intervals: A Performance-Based Study in IVC-Housed Mice.

Area of Science:

• Laboratory animal science
• Animal welfare and husbandry
• Microenvironment management

Background:

• Standard 2-week cage changes in individually ventilated cages (IVCs) are labor-intensive and can increase animal stress.
• Extending cage change intervals is crucial for specific research, such as viral studies, but must maintain animal welfare and microenvironmental quality.

Purpose of the Study:

• To determine the maximum acceptable interval for full cage changes in IVCs for pair-housed mice.
• To evaluate the efficacy of biweekly partial bedding changes in extending cage-change intervals.
• To assess the impact of extended intervals on microenvironmental parameters and animal health.

Main Methods:

• Wild-type C57BL/6J mice (8-week-old) were housed in IVCs under various conditions: no bedding change (up to 42 days), biweekly partial bedding changes (up to 84 days).
• Microenvironmental parameters (ammonia, humidity, temperature), visual cleanliness, daily health, and nasal histopathology were monitored.
• Different cage densities and sexes (2 males, 2 females, 4 females) were tested.

Main Results:

• Pair-housed male and female mice tolerated 42 days without cage changes, limited by soiled bedding, not ammonia levels or health concerns.
• Biweekly partial bedding changes allowed housing for 84 days (2 males/females) and 62 days (4 females) without exceeding microenvironmental thresholds.
• No significant histopathologic evidence of ammonia-induced injury or other diseases was observed in any group.

Conclusions:

• Extending full cage change intervals to 42 days is possible for pair-housed mice.
• Partial bedding changes can extend housing periods significantly, up to 84 days for some densities.
• Reduced cage density and partial bedding changes support extended housing without compromising animal welfare or microenvironment in IVCs.