What's wrong with this horse?

IMO it is messy - bits of saddle, bits of fence, bits if hills in the background, you cannot see all of the head, a blue rope cutting across the head etc.

Suggest you do some reading about composition:

Have a look at these:

http://digital-photography-school.com/5-elements-of-composition-in-photography

http://digital-photography-school.com/5-more-elements-of-composition-in-photography

Also for that shot your aperture is to small (f22) - you could safely open it to f8 which would increase your speed which currently is a bit slow for the focal length (Speed should be about 2 x focal length ie 100 focal length should  = 1/200 speed)

keep shooting