Don’t give a horse on ulcer treatment free choice hay.
You’re probably thinking… What?!?! I know! I agree… this sounds CRAZY! And goes against everything you might think is going to help a horse with ulcers.
If you have had a horse you have treated, unsuccessfully, for ulcers, keep reading!
Because here is the thing… horses on ad libitum hay have poor absorption of omeprazole (the drug of choice in treating equine gastric ulcer syndrome; EGUS). And if they don’t absorb it, it simply will not do its job of suppressing acid production. And if it doesn’t suppress acid, ulcers won’t heal.
In a study by Sykes et al (2017) it was shown that 3 out of 6 horses on ad libitum hay diets had minimal if any acid suppression (i.e. medication was totally useless).
Sykes 2019 suggests instead that horses are medicated after an overnight fast. THEN, withhold feed for 60 to 90 minutes after administration. Then feed a large feed of forage, which will stimulate gastrin which then makes omeprazole more effective. After the horse has eaten the hay it can be fed any concentrate it may require in its diet.
So overnight fast, then dose, then wait an hour, then feed lots of hay or allow access to pasture.
To be honest this goes against instinct and messes with my head a bit. BUT the research into this seems conclusive so I am going to trust and go with it.
Once the horse has finished its course of omeprazole treatment you should immediately revert back to ad libitum access to hay and minimise and periods of time off feed.