Hope you don't mind me making a few suggestions / comments. They are meant only as 'things you might want to think about' - feel free to ignore them completely.
I really like 44 + 46. On those shots, the horse stands out against the background and help reinforce the horse as the subject. On some of the others, the backgrounds are a bit busy - particularly the fencing, with strong lines that distract the eye and cut across the subject.
Exposures seem good too, very little blowing out of highlights on the horse.
Some of the shots seem a bit 'soft' too - it can be very difficult to capture quickly moving objects in focus and it is normally a balance between getting a fast enough shutter speed (to avoid subject blur) and a small enough aperture to get the depth of focus. Opening up the aperture could have helped to increase the shutter speed, and reduce the depth of focus to help isolate the horse against a blurred background- but of course your focusing would then get tricker.
I'd be interested to know what shutter/ap/iso settings you used - and also what lens.
