Mouse cage change criteria

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Mouse cage change criteria

• Goals
• Provide healthy environment
• Reduce animal stress
• Minimize care costs
• Minimize odors

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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

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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

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Mouse behavior

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

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Mouse poop is not the problem

• Mice like feces
• It is normal for mice to EAT feces

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Movie
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Urine is the problem

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

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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
  (dont count a fresh drip from bottle)
• If you see any mold on the bedding or food

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Five mice in a cage
3 days
7 days
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M4 D7
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M5 D5
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M1 D10
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M1 D12
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