Is there anything medically that can cause it? I am talking the entire ride - every rock, stump, tree, cow, puddle, sign, bag, BARREL... this is a barrel horse that has been hauled for several years now. He is 12 years old. He was a cutting horse until he was 6 so he’s been hauled and exposed his entire life. His previous owner is a good friend of mine who spent years working on desensitizing. You would never know it... he literally spooks at the barrels sometimes while running them. Practice and competition. He’s truly a dog gentle horse and when you kick him forward towards whatever is that spooks him he will go over or on or into it without refusal, but will spook at it the next time you walk near it. 

Any ideas?? We have ridden a lot of horses and never seen anything like it. 

Maybe he's having vision problems? I always wonder if spookiness, espeically in a horse that never used to have that issue, is from poor eyesight? 

He was sold to my friend a few years ago with his spookiness being disclosed. They did a prepurchase on him so checked his basic eye sight. I’m tempted to track down the cutting trainer and see if he was like this when he was younger too. I’ve read little things on EPM and Lymes causing spookiness but I don’t know if they were credible. 

I would have him tested for EPM and it can cause issues of spookiness. I would have EPM ruled out at least. 

Sometimes when a horse has pain/tension, they will get very spooky and not be themselves, or they will get heavy on the bit and lean on a rein.

That's like my white horse.. I can walk by and sneeze and he will jump. Hes always been that way, he actually looks for things to spook at... but, I will say hes pretty much all business in the pen or when actually out moving cows or working .. I know him so well I know hes going to spook before he does lol! Nothing is wrong with him health wise, he's just a big ol chicken $hit! 

I had a Mr. San Peppy bred gelding that was just like yours, You could be brushing him and kinda pitch the brush out of the way after you were finished brushing him off and as soon as the brush hit the ground he would jump and snort, he droved me coo-coo

Hes a big ol goof but hes mine so I deal with his cowardly ways lol! 

Selenium, magnesium, calcium- a deficiency or lack of ratio can cause spooky nerves. 

How does one go about getting this "ratio" back in order??

I've always been told that cutting-bred horses will usually be spooky since they are bred to be REACTIVE in order to do their job (cutting).

I second this. My mare is a totally different animal after being treated for EPM. 

You may want to have him tested for PSSM.  I'm going through this with mine now.  It can cause alot of behavior issues.

I've been reading the PSSM forum on facebook and alot of people report spookiness.

Basic lab work showed my horse being deficient in several things that may point to PSSM.  He is PSSM1 neg so we'll test him for PSSM2.

HIs symptoms and gentetics point to PSSM2.

EPM & Lymes can cause spookiness but if this horse has had the problem pretty much it's whole life, I do doubt that's what you are dealing with.  I second the PSSM1 or PSSM2 possibility.  My one mare was horribly spooky, would bolt, buck, etc when she was symptomatic.  (of course, it's only one of many possible symptoms & they do not have to have ALL of the symptoms that some have experienced.)

We have cutting and cow breds - they are watchy, but not stupid spooky like this sounds.  They may not be the best horse to choose for a relaxing trail ride, because they are looking for work - but they won’t run away from everything either.

i second some of the testing suggested.

I was told by a vet friend that every horse in the state of Texas would test positive for EPM.  The treatment for EPM may be  cheaper than the test.

Ask your vet if s/he will prescribe some fluoxetine (Prozac). I'm not big on drugs but it may help an extremely spooky horse. 

When my vet diagnosed my mare, he did not sent off spinal fluid or blood work - he was positive she had it based on tail pull and the other test they do (what it is called is escaping me at the moment...) She's a little over 30 days into treatment and a completely different horse. 

But that's basically what he said, the testing is expensive, all signs pointed toward EPM, so he suggested we just treat and save myself several hundred in testing.

Just curious, how's he bred? I know there are a few cow horse lines that have repuations for being a little....

Check his eyes, put him on MagRestore and Focus, 10 Day course of toltrazuril.