I rarely shoot horses, because I don't usually see a composition there. In this case, I did see a composition. Very simple, but a very strong contrast between horses, pasture, and background trees. I liked the contrasting colors of the two horses, the different flow lines in the pasture (some going up, some down, and some level), and the way the small splash of foreground leaves (1/3 in from the left) contrast with the background forestation. It's an unusual look that makes this composition unique for me.
I see. I throught about it a bit and came to the conclusion I would have actually zoomed out to show more from the surrounding. Small horse-dots in the big landscape, I imagine. This version doesnt provides enough context for me. Of course I dont know the place so maybe it is not an option.
//edit: now that I saw the small icon of it again I guess I can imagine what you was seeing and thats indeed beautiful. I would have not zoomed out very much contrary to my above suggestion. I would have give the horses a bit more room at the left and bottom, with the consequence of zooming out, to preserve them both standing more to the left side. If they where standing nearer to each other, the actual framing would fit better. I think finding just the right spot for shooting is critical here.