Better to go slow he didn't get this way over night and you can't get him in shape over night.Be careful worming one that is really thin you can kill all the worms and kill him too,I have seen that happen.Give him half the wormer.And maby watch him a week or two give the other half.You kinda have to get em on their feet to a certain degree.I had a vet call me once and he had already called the owner of the horse,I knew the owner he had let a kid break a horse for him and was furnishing all feed just go to feed store get all you want well he was but was feeding theres not his horse.I have never seen but one other in my life this bad still on his feet.The vet called me said go get Johnny's horse and I'll get him to your place today.I go over kid says he lays down when I try to get on I said no !!!! hes almost starved.He almost can't get in trailer his dad kept saying he was a bronc and was bad.I started him out on a flake of grass hay,and 1/3 can of grain,in a.m and p.m.and gave him 1/3 of the wormer.Had to be really carefull.Two weeks later next third wormer,and had him up to half can of grain and kept hay out all time just grass hay.At end of mo. last of wormer.and almost full can of grain and this was mixed about half with bran.beet pulp.It took me two mo.finally got a couple hundred lbs.on him he still looked ruff but could do a little riding.He was not a bronc.He layed down with the kid cause he couldn't hold him and the saddle up together.Long story don't mean nothing just be careful and go slow.We feed bran and beet pulp mixed even and or grain,in a three lb.can half bran,beetpulp mix other half grain.more we ride add both in even amounts,I have a friend that has an old calf horse hes 34 now no teeth,feeds strait beet pulp soaked in water for an hour pours off loose water and feeds like that.keeps alfalfa hay out and Black will chew on it till its all gone.Chews on the hay till gets all the juice out spits it out like chewing tobacco goes get another mouth full.Is fat as a tick and shines like new money.I have fed every thing made.I ride for the public and have too keep em looking good and this has been the best Most cost effective mix i have used.We ride barrel and calf horses In Ok.and Tx if you are going to win better have a good one.This is a long winded deal but might give some ideas from examples.Its like riding one go one step at a time let the horse tell you when to step it up,watch and listen, they don't go by a calender or a watch.Good luck,Ronny