While sterility of the birds' environment is not possible, or even desirable, basic cleanliness is important to health. The bedding should not be allowed to become wet. Wet bedding and manure build-up can lead to sore feet. Wet bedding can also become moldy which is harmful to the birds. Wet bedding should be removed from the pens and replaced with dry material.
Good ventilation is probably the most important factor in keeping indoor pens dry.
For instance, if a pen of birds have become old enough to be moved to larger pens, all the birds should be moved at once. This allows pens to periodically become empty, and ready for thorough clean-out and disinfection. After the clean-out is complete, new birds may be placed. This procedure allows for a break in the disease cycle. Besides breaking the disease transmission cycle, it is frequently observed that overall bird quality improves if a house can stay empty for a while.