I have not tried the heat-boxes, but they look interesting and seem to work well once the piglets find them.
I have also seen old futon bed frames used to block off a area where piglets can go but mom cannot.
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I raise smaller breed pigs, sows up to 200lbs with piglets the size of soda pop cans at birth.
We are always in attendance at birth, the one time I wasn't we lost a piglet due to crushing. But sometimes, like in the middle of the night, you just can't be there and newborns are not yet as mobile as they will be in a few hours.
I find the best I can do is to create a area where mom will go to easily get away from the piglets once she has given birth to all. I use heat lamps with standard
light bulbs for this purpose.
In winter this means two
lights, apart from each other, mom ends up under the one that the piglets are not under. Usually closer to the door and her food, piglets end up at the far back of the house.
In spring, this means one light in a corner at the back, mom doesn't want the extra heat and avoids the light area.
Once mom gets up after feeding - the piglets get cold (if not summer time) and will move toward a heat light, place this off to one side and when mom comes back she will have lots of room to flop on the other side before the piglets are on her for another feeding.