Thanks very much Peggysue, I always have problems because I don't know what to look for when I'm buying vitamins.
He's not obese. Anymore...
Before we bought him he was getting tones of oats (more than some horses that compete) and free choice very quality hay. His hooves weren't trimmed for ages and time to time owners drag him out and sat on him and kick him until he moved. He has 550Ibs and the rider had 190Ibs. He was ridden with awful hooves on roads, which also could be the cause.
But the main cause I think it was wrong food.
What does cushings mean? Sorry, my english is not good :(
Thanks for advices :)