Itchy horse.

It depends on where you are located as to what feed is available.  I use ADM Senior Glo on all my horses, including the filly.  Their web site has a TON of valuable advice.  If you google ADM Alliance you'll find it.

The Senior Glo is a bit higher in price but it keeps them healthy on less.  (Zag is FAT)  Anyway, I hope you find something and get him off the sweet feed!

thank you for the advice.  He is a really sweet boy and I have had him for four years.  I hate to see him suffer and the vet is puzzled, too.  I will see if the feed is available around here.  I live near a race track so there might be a chance to get a special feed.  Thanks again.

  With your horse's age, if he can maintain his weight without concentrates, just feed him hay and a vitamin/mineral supplement.  If the diet is grass, look for a vit/mineral that is higher in Ca than P.  I'd look for something around 20% Ca, 10% P, no more than 20% salt and at least 100,000 IU/# Vit A.  Don't worry about the others unless Se is indicated for your area.  All the other values will fall into an appropriate level but these will give you a good value to look for.  Offer it free choice.  If he thinks he will die without some grain, give him just enough oats to keep him happy.  Add some flax to the oats.  It will help improve his skin and it has anti itch properties.
 
  To know for sure what's bothering him, do an allergy test on him.  I spent 2 summers trying to figure out what was eating one of my mares only to have it come back that she is allergic to grass!

thanks for the tips.  I am sure he would report me to the humane society if he didn't get some kind of feed so he gets his oats.  My local store didn't have the correct ratio for vitamins and minerals so I settled for a mineral block.  I will keep looking.  He is very definately not underweight.  He stands about 15.3 and he weighs over 1200lbs.  I sure hope he doesn't itch this summer, but with the nearby racetrack, I can get a blood allergy test done by a vet there if my vet isn't able to do it.
He did have a sheath problem.  I cleaned him a lot and got "beans".  I  finally called the vet and she told me what to try.  It helped, but, thankfully, I still had her come out and tranquilize him and do a more thorough cleaning.  What a bunch of junk she got out, and after I had gotten so much over a period of several weeks.  She told me and I will pass this on, use baby shampoo, it lubricates and is not apt to irritate.  Use bath hot water.  I bought an oral calf feeder to use to flush and it worked super.

  Trace mineral blocks are nothing more than colored salt blocks.  Read the tag.  Most are 98%+ salt.  They have none to very very little Ca, P and Vit A.&nbspurina and Manna Pro make a loose mineral product called 12-12.  It's 12% Ca and 12% P and 100,000 IU vit A.  Not ideal as you would like 2X the Ca to P in the total diet but it's a start. Every feed manufacterer makes some type of dry loose mineral blend.  Your feedstore will get anything in you ask for if it's in their product line.  Your local mill will market something.  They have it to mix in with all their feeds.  As long as it's non medicated, you can use cattle Vit/minerals (not sheep).  Most of the time the locally milled stuff is better because it's formulated for your region.   EquiPride makes a quality product but it's a little pricey.  I use Progressive nutrition minerals.  I would stay away from ration balancers as many of them have grain and forage products in them.  They will probably trigger the itching like the sweet feed.

For what it's worthy, my horses started rubbing their tails and manes off this summer. It drove me nuts. I tried different feeds, I treated them for lice, wormed them regularly and switched out wormers, checked for ticks (sometimes ticks under their bellies will make them scratch and/or roll), brushed them religiously thinking maybe it was just a build up of dead skin (and indeed the mare with the thicker tail does get pretty scaly). Nothing worked. Purdy, poor thing, had a bald spot at the top of her tail, and they both had lovely short hair at the base of their tails which made everyone think they had worms (if they did they were superworms because I was obsessive about worming them).
 
Finally I was in the barn cleaning out the feed room when I realized there were flattened nails all over the doors...nails pounded through from the inside that had been flattened down, and there was my horses' tails, in big long strangs and hanks. They'd been standing in the shade of the barn with t heir butts against the wall, and those flattened nails caught their tails and pulled them out. I put bought tarps and tarped two layers over all the inside where they leaned. Then I started looking around the pasture, and found their manes hanging from the fence wherever they would reach through the fence to eat on the other side.
 
I'd check your paddock, barn, stall,whatever, THOROUGHLY (it took me 6 months to figure this out) to see if the horse doesn't have a favorite place where they're just incidentally pulling out the hair.
 
Also rule out fungal  infection. They can get mild fungal infections in their manes that can result in hair loss, and it can be super difficult to diagnose, even for vets who often don't know a lot more than we do about our horses, unless they just happen to have run across it before. I think I'd try a weekly (or more often) vinegar wash for the mane, work it in there, for some reason that's pretty effective for some fungi. It will also make the mane really shiny and pretty. And just in case, dust for lice. Those buggers can be really hard to see, in fact I've never actually seen one on a horse, but I've treated for them many times and in fact it's a regular part of our yearly regimen to treat for it twice in the spring/sumer. (Lice is pretty common  here).
 
If you find a dietary supplement that helps, let me know. My mares' manes are relatively thing, too, and I have no idea why. Purdy always used to have a thick mane. They receive supplemented senior feed, corn, alfalfa pellets, salt and mineral blocks. I know there are products specifically for growing manes and tails but I generally assume they're basicaly hype. But if anyone knows of stuff that works, I'll give it a whirl.
 
BTW, my girls no longer have short hair sticking up from their tails, the tarps did the trick for that. They still have thin areas on their manes where they reach through the fence. Aside from new fencing all around, there's not a lot I can do about that. I'm fairly certain if I start braiding them instead of pulling out a few strands at a time they'll just pull out entire sections.

I have a gelding with fly allergies who rubs his shoulders, chews his legs bare in the summer.  Luckily in the winter he's OK.  I ordered spirulina wafers and garlic off the Springtime catalog and fed him those things until the cows came home, didn't do a lick of good!  About the only thing I could do is to keep the poor thing inside electric fencing where he couldn't rub but felt really bad.  Tried every brand of fly spray, etc.  I did buy an antihistimine from the feedstore, didn't seem to help, tried a cortisone shot, didn't touch his itch.  Not food related like yours though.  Goodluck finding your answers.

2 many horses;  Actually, I used the wrong term.  This is a 'high performance horse block, extruded"  It has a maximum of 16% salt.  It has more Ca than P and has Vitamin A.  It was more to make me feel less like I wasted a trip to the feed store.  Sure did read a lot of labels.  Thanks for getting back to me.

AllieBaba, thank you.  I have seen the locust tree he rubs on and he does so with great vigor.  It is shaped so he can rub his sides, back, and mane.  I will try vinegar on his mane, but I used vinegar last summer and it didn't seem to stop or slow down the itching.  Thank you for taking the time to share with me.
 
Danastark, I used to go past a horse vet's place five days a week as part of my job.  They had one horse turned out with a full body fly sheet, neck included, full face fly mask, and bandages around on his legs.  Looked strange but I figured it was to keep the flies away.  He is always turned out this way in the summer.  I did read that if you can figure out what time of day the flies are pestering, you can keep the horse in and keep a fan on it to discourage the flies.  Thank you for sharing.  It is great to have someplace to turn to for advice.