I like the idea, but think it would be stronger if the horse was more connected to the viewer -- head up and alert. As it is, it seems more about the gate than the horse.
I have to agree that the gate and fence dominates the image. Which is unfortunate, since to me those are the least interesting components to me. It looks like there is some great atmosphere going on in the background, as well as some nice rolling hills. If the fence were more picturesque like a split rail, and not so dominant, it might work as a foreground element. But in this case I'd enjoy just seeing the horse, perhaps not so centered, with the nice background.