Try to find a chain harrow... Two pasture areas would be good for the horses - and the pasture. When one pasture has been eaten down by the horses, move them to the second one where the grass is longer, giving the grass in the previous pasture time to recover. Continue to rotate the horses between the two pastures over the season to keep both the horses and pastures happy.

You could drag a lot of items behind your tractor. The spring out of a mattress. Some boards cut to about the width of the tractor. Perhaps someone on here will decide they'd like manure in their gardens and come get it.

If you could keep chickens and run them in the pasture after the horses etc, the chickens would likely break up the manure looking for bugs and undigested grains. It makes a lovely pasture and you get to harvest the eggs or the chickens.

Fence post, etc. couple of screw in eye bolts/lag screws and a piece of rope, chain, etc. will make an adequate drag to spread things around. Two horses on one acre?!?!?! You ain't doing them any favors as they can't exercise and obviously you're feeding them hay year round as there's no grazing available. Sorry, pet peeve.

do you have a good sized tractor to drag the mentioned solutions???

^^ Yes

I'm fortunate to be in Oregon, so my problem is less with poopsicles and more with poop soup, but...
The consensus among those on Chronicle of the Horse Around the Farm forum is that frozen manure stuck to frozen ground is a lost cause and best left until spring.
One great (although not cheap) option is to create a sacrifice area separate from your pasture(s), laying down geotextile and then several inches of gravel to create drainage, prevent mud and ice, and allow manure removal, even in the icy cold. (Of course, with snow, you'll still have poopsicles, but it's better than icy mud.) You do have to remove manure every day, or you will be back to square one.

My method of breaking up manure piles is, each morning I walk around the pasture and kick the piles apart. For only 2 horses this would not take long. In the past when I had 4 horses I invested in a manure spreader which I pulled behind my garden tractor.

Invest in a good quality chain harrow with 5/8 tines. One that is both wide enough to get through the gates and the the longer the length the more efficient a job it will do. This will be heavy so make sure your tractor can handle it.

Oh wow, how odd that this old post got resurrected. Sad to report that my last horse had to be put down last week. I am now horseless.