A door assembly (13) for an animal enclosure, the door assembly comprising: a frame (23) for mounting over an aperture (21) in a wall of the enclosure; a door (19) moveably mounted in the frame (23), the door (19) being moveable between a position where the aperture in the wall is open for the passage of an animal and a position where the aperture in the wall is closed thereby to prevent the passage of an animal; and a motor (37) for driving the door (19) between the closed and open positions.