The answer to this also depends a lot on the ambient outdoors temperature. Horses can stay warm through the winter outside in almost any weather (down to single

The answer to this also depends a lot on the ambient outdoors temperature. Horses can stay warm through the winter outside in almost any weather (down to single digits F easily). But in order to do so, they use their GI system like a furnace. So they basically are CONSTANTLY eating and pooping. So the colder it gets the more they eat.