Horses with urinary tract issues usually pee less, and you will see them stretch out to pee and then they won't.
I had a gelding that was having issues peeing, and when the vet came out, discovered his urethra was lined with crystals. Surgically shoved a catheter up there to clear the tract. That is normally diet-related, from too much calcium, although the horse was a yearling and on mostly timothy hay so it was just a fluke maybe.
At any rate, my colt drinks a lot of water and has since he was a youngster. So did his mom and sister. I had the vet take two different simultaneous blood and urine tests to determine if it was something metabolic or organ related. Nope. My horse was just bored or a "water cribber" purely behavioral. Per the vet, he has his water rationed. One bucket with each hay feeding.
Some horses urinate a lot, at the barn I work at we have four or five out of thirty that really pee a lot. It's just the horse.
Too much protein in the diet can also cause some horses to urinate more, same with too much salt.
Cushings, pre-laminitic horses, and other metabolic propensities can cause it.
It's probably a good idea to have your vet come out to determine what it is. He could just like drinking a lot of water! Maybe it makes him feel "full."
Andrea
