I think we get a pretty effective impression of the partnership[ there, especially with the timing and the way you've caught them in the moment. It's quite a beautiful shot in that sense. I think it's great how you've positioned and shot this from this particular point of view, as we get to see a bit of the expression but not too much...
I'm not too fond of the way the background feels like it's angled diagonally, and I feel as if the horse itself is pretty dark. It's interesting how you've outlined the equine beauty, but I feel it's a shame we miss out on the details.
You could crop out the let side a bit and maybe the top too... if only to make it somewhat more tidy and such.
I really like this photo, and I love the pose - it's clear to see the connection between horse and owner. I think the vintage-like style and colours work really well with the empathetic feel of the piece too. The only thing I would say is perhaps (I know I am guilty of this too) be a little more careful with your framing? A few things (such as the flag on the left, which could very easily be cropped out) distract my attention from what is otherwise a very beautiful image.