The present invention is a pet cage having a upper cage member and a lower base member. The lower base member has a bottom that is partially cut out. An exchangeable plate or tray is provided and adapted to engage with the opening in the bottom of the lower base member. When an exchangeable plate or tray with access points, such as through-holes, are used, the pet can graze on fresh grass in a safe environment. When an exchangeable plate or tray without access points are used, the cage is restored to a conventional cage with closed bottom surface.