One of my dogs hates snow. So I shovel paths for him to run out and potty in. I don't see why you couldn't do something similar for your horses. You could just shovel the top layer, low enough for them to be able to walk. Like in a large random shape, they would soon enough stomp the snow down and make the trail easier for themselves. It's not much, but it might help, plus the work out is always a good thing.
We had 17in here in December. Not sure how much this time since it keeps coming down. Already tore one pine 3 ways, we will have to cut it the rest of the way. Fell on a wood fence, but this is a real fence, not a factory puzzle. Built by hand, withstood 20 years and now a tree falling on it, still as solid as a rock!