Simple, clean, nice pose and energy from the colt. The foreground looks a bit odd to me, but can't really explain why - looks a bit fake/plastic maybe, though that's due to the DOF and/or processing I suppose.
I like the contrast between light and dark, and the sepia toning is nice. The composition seems a tad awkward, as if it needs to be perfectly centered, or cropped in a way that allows negetive space on one side or the other(these really are just nit picks though :))