My 7-year old Tennessee Walker gelding has stopped shedding out. I was feeding him Southern States 10-T feed with alfalfa cubes dissolved in warm water, which is what the other 3 horses are eating. They are shedding well. I am gradually switching him back to Equitech 10, which is 10 percent fat as opposed to the protein content in the other feed, although he will get protein from the alfalfa cubes.
I can't remember why horses don't shed other than Cushings Disease -- but he isn't patchy. Just hairy.