A conversion kit for an enclosed trailer forms at least one animal stall in a storage compartment of the trailer. The conversion kit includes separable vertical stanchions and stall dividers which are removably mountable in the trailer storage compartment to form one or more stalls. A breastplate, a front wall and a feed tray may be mounted at a front end of the stall dividers. A manger door opens to a storage compartment below the feed tray. A saddle hanger may be mounted at a forward end of the front wall. Openable rear doors close one end of the stalls.