He has a ewe neck and it ties in to his chest too low. He's mutton withered and long in the back His croup is a little low but it may be that he's not standing on solid ground. Over all he has a weak topline and I'm not wild about his pasterns either. However is only three and some of these things (but not all) he could possibly straighten out and fill out as he grows. Do you have a pic of your mare?

A strong tree is my best assistant- release and tension are perfect, works in the sun and cold without complaining, does not need a lunch break and I don't have to pay it.
www.thompsonpaintranch.com
trainthehorse.blogspot.com