Mouse cage change criteria

1. Mouse cage change criteria Goals: Provide healthy environment Reduce animal stress Minimize care costs Minimize odors

2. Special Considerations • Microisolator cage tops hold in waste gases and moisture • Small amounts of bedding dry out- excessively deep bedding stays damp • Moisture from the water bottle is as bad as moisture from urine

3. More biology than you expected • Ammonia (NH3) is the gas of most concern- it irritates eyes, damages lungs. • Urine, NOT feces, is the source of ammonia • FRESH urine contains no ammonia • Over time, bacteria convert the urea in urine to ammonia • The urine needs to be wet for this to happen

4. Mouse behavior • How do mice feel about a new, clean cage?

5. Mouse poop is not the problem • Mice like feces • It is normal for mice to EAT feces

6. Movie

7. Urine is the problem • Wet urine is the problem • Water (from the water bottle) is also a problem if it rehydrates dried urine

8. When do you need to change the cage? • When more than 25% of the bedding, as viewed from the bottom, is wet • When the bedding, as viewed from the top, is wet (don’t count a fresh drip from bottle) • If you see any mold on the bedding or food

9. Five mice in a cage 3 days 7 days

13. M4 D7

14. M5 D5

15. M1 D10

16. M1 D12