The phrase "cage floor" refers to the bottom part of a cage where animals are kept. It is the flooring or surface on which they walk or rest. Full definition
The wire cage floors are meant to allow feces to drop through, but when cages are stacked, it falls onto the animals below. (animalrescuecorps.org)
In their review of Smith's Kennel, inspection reports detailed one or more dogs with cherry eye, cysts from walking on cage floors, overgrown nails, bloody feces, infectious matter in their eyes and hair loss. (shelterme.tv)
Campbell's need a lot of cage floor space — particularly on the main level of the hamster cage. (smallanimalchanel.com)