You should not center you subject like that. Try to use the rule of third for instance.

I really like this shoot, but agree that having the horse off center may have helped the photo. You have a nice leading line with the fence that could have been better taken advantage of if you framed the image so the fence was in each corner. But I know these shots are fast, and you did a great job.

I like that you shot at the horses eye level and framed tight. I take in that the lower quality is do to poor lighting in the barn.

Overall this shot is technically correct, but there could be more emotion is the man was looking at the camera or connecting more with the horse.