We have our horses on a diet supplied by a equine nutritionist, and while the products are amazing, they are extremely expensive. For horses who are prone to colic, wether it be gas colic, or an impaction, you should look into getting some kind of enzyme or probiotic to aid him to digest better. You can also give him 1-2 oz of oil, which helps with gas. We feed flax oil or soybean oil, and stay away from corn as it is too high of an energy source and fat source.
If you want to check out what we are giving the horses, go to kamanimalservices.com
The liquid "KLPP" is a super potent probiotic type supplement that balances the PH in the horse's gut and relieves them of gas. If we have a horse that has a belly ache, you can give the KLPP to them and if often suppresses whatever is going on.
We feed 1/2-2 oz/day to the horses to maintain healthy gut actions.
Also, the enzyme they carry, like I said, help them digest better to the risk of impaction reduces. People feed diff. Kind of probiotics but the stuff this woman carries is a ton more potent and works faster with using 1/3 of the amount.
Also, your horse might have ulcers, which is pretty common in performance horses. The senior feed you are giving him (with the molasses and oats, etc) could be causing pain in his stomach if it were to be ulcers. Kam Animal Services has an ulcer formula, but its, like I said before, is not cheap and I think you could get something cheaper.
Make sure your guys is drinking enough water. We had a horse given to us because she kept colicing over and over. She's on the enzymes, KLPP, and a few other things and we monitered her water intake and she has only had 1 extremely mild case of gas since she's been here.
The Safe Choice is good, we used to feed that to our guys. Although, not that it matters, but we heard the protein in that feed comes from pig hair. Eww! Haha, I don't think it really matters. Just kind of funny. Haha.
I hope that help at all. If you choose to look into those products, I'd be happy to answer any questions. They've done miracles for us so I feel like I should always spread the word.