The effects of a rabbit eating moldy dry feed depend on the amount and type of mold, the rabbit's health, and individual sensitivity. Possible consequences include gastrointestinal upset, respiratory problems, liver or kidney damage, immune suppression, and in severe cases, death.
What to Do
Remove any moldy food immediately. Monitor your rabbit closely for lethargy, loss of appetite, diarrhea, or breathing difficulties. Contact your veterinarian right away if you notice any signs of illness.
Prevention
Store dry food in a cool, dry place, clean feeding bowls regularly, and always inspect food for mold before offering it to your rabbit. When it comes to mold, prevention is far safer than treatment.