Anthony,
You can use the scheme that is used for instant hot water. Put a
small plastic tube from your water heater to the chicken house and
back again. Then use a low power circulating pump to circulate hot
water through the tube and the water in the chicken house. You could
lay the tube on top of the ground and run the circulating pump
whenever the outside temperature drops below 32 degrees. If you are
worried about looks bury it slightly under the ground.
This is the scheme used for instant hot water in large hotels, etc.
The small volume of water in the hot water pipes is continuously
recycled through the water heater which holds quite a large volume of
water compared to the volume of water in the pipes.
The increase in energy costs is relatively small and worth it for the
convenience of getting instant hot water.