Heated Nipple Waterer
This design uses a plastic, insulated drink cooler with spigot removed. There is then a valve attached to PVC pipe and fittings, where the nipples are then attached.
Ball valve to shut off water:
Electric fish tank heater, 50 watt, good for up to 15 gallons of water. Auto temperature control, 78 degrees.
Installed nipple, screw-in style with silicone caulk around the base: