Mouse cage change criteriaMouse cage change criteria

Goals:Goals:

Provide healthy environmentProvide healthy environment

Reduce animal stressReduce animal stress

Minimize care costsMinimize care costs

Minimize odorsMinimize odors

Special ConsiderationsSpecial 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

More biology than you expectedMore 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

Mouse behaviorMouse behavior

• How do mice feel about a new, clean cage?

Mouse poop is not the problemMouse poop is not the problem

• Mice like feces

• It is normal for mice to EAT feces

MovieMovie

UrineUrine is the problem is the problem

• WetWet urine is the problem

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

When do you need to change the When do you need to change the cage?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

Five mice in a cageFive mice in a cage3 days 7 days

M4 D7M4 D7

M5 D5M5 D5

M1 D10M1 D10

M1 D12M1 D12