I just got back in from feeding hogs. It's windy and 18 degrees outside. It's supposed to get into the single digits with high wind tonight. When it's cold like this we haul warm water to all the hogs and poultry. (I guess it's not too big of a deal in Kansas but in Wisconsin we had to worry about dehydration in livestock during prolonged periods of bitter cold weather. Old habits die hard.) The warm water enables them to get a big drink of water without getting chilled or develope a huge brain freeze. The cattle have insulated waterers so we don't worry too much about them.
The hogs are still out in their 6 acre pasture paddock. We made a U shaped line of round bales for the hogs to burrow into for warmth and protection from the wind. Pigs are herd animals and like to sleep in groups. 20 big hogs can generate quite a bit of heat. Hogs are also masters at composting. They will pee in their nest of hay. This sounds gross but the combination of moisture and organic matter will start up the composting process. This generates a lot of additional heat in the pig nest.
Since the pasture is dead and brown right now, we'll feed the hogs alfalfa until things green up again. This is fed in addition to a grain based hog feed and any extra/skimmed milk from the dairy.