Thanks Bloo. If you don't mind my asking what high fat/low protein pellets do you use and what were his symptoms when he was double with the protein?
It's called 'the black bag' it's 10-12% protein and 14-16% fat.
Normal senior feeds are between 14-18% protein and 2-10% fat and when I fed him one of those he would act like a sugar high child in a straight jacket, he'd quiver and flinch away from touches but he'd almost never move. When I'd take him out just to check him over and get him moving he'd walk like he had no control over his legs, collapsing in the back or wobbling around. There was also a lot of swelling in his legs but it wasn't hot.
He's always been on 24 hour turn out so I thought he'd eaten some poisonous plant and it was neurological the way it presented itself but he was coherent and when I changed his feed to hay saver he was a completely different horse. I tried a few different senior feeds but every time I put him on one he'd revert back so my vet checked the brand's I'd used and she told me that his problem was that there was a lot more pepsin in his stomach than there should have been at his age, which was digesting the protein faster than his body could use it. The build up of it was poisoning him.
He's a hard keeper so he was getting 4 qts of grain twice a day to keep the weight on but he dropped weight and I honestly thought I was going to have to put him down. I went through a few vets to see what the general consensus of his condition was but none of them said they same thing and nothing any of the suggested helped until I went to my current vet.
Now he gets 1 qt of grain twice a day and rice bran oil, which is a fat supplement, to compensate for the lack of grain. He essentially gets all his energy now from fat now. I also have to watch out about what kind of hay I give him, he can't have alfalfa or clover hay but I've found that timothy, orchard grass, Bermuda grass or mixes of the three are fine on most occasions.