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 WetWet 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