The light on the horse is great, but the sky is kinda dishwater. Maybe you could try this as duotone or b/w? Then I wouldn't be expecting much from the sky.
I think with the white sky, this is screaming for a black and white conversion. Or maybe sepia. Nice stop action. I like how the fence lines pull you right back to the horse.
To out of focus for me. Looks to be a buckskin, he blends in with the footing & grass along the fence. I think if the hue/saturation was adjusted it would bring out his black legs, brighten the background and define his coat.