Alrighty, these are great! I love the style, its one of my favorites. Anyhow I have a few suggestions.
First thing I noticed is that the horses don't seem to mesh very well and I couldn't figure out why, you got the horses in the same lighting/texture/colors as background, the cutting has been done well. Then I noticed, where are these horses shadows? I don't think any of them do, its most noticeable in the last one. I would suggest you can play around with the burn tool, or my favorite was to duplicate the image, use brightness/contrast to make it black, scrunch it up stretch it, use a high level of blur then bring the transparency down till it works.
Where you have your copywrited info, the credits look almost...idk. But I don't like the font type or the size. I like the font on the first one, but I would suggest a little smaller and maybe white with the layer being an overlay? Then it is too big on the second and third image. It has to be readable, but it doesn't have to take away from the manip.
I would also point out the point where the hoof meets ground but I still have no idea how to pull that off well. Just be careful with the cutting around them and if needed, try and reshape and bury in the background a bit more if that makes sense. But that is merely if I am being nitpicky, otherwise very well done.