That’s all true as far as the need to graze constantly, but not so much the “pain” associated with saliva production, and it’s not necessarily related to wood chewing/cribbing/wind-sucking and other idiosyncratic behaviors. My horses are on 24/7 turnout with lots of grass and free-choice hay, yet I have a wood chewer who came with that habit and has been impossible to cure in the 8 years I’ve owned him. He’s 22 now and it’s unlikely I’ll ever get him to give up the bizarre habit. He lips (it’s more a cupping with his tongue than a chewing) his water bucket, feed bucket, metal gates….anything horizontal. And he eats the edge of the top fence board, but only in one area of the farm. He’s never without hay or grass in front of him, and it’s all good quality. There’s lots of research to suggest that a horse who is left standing in a stall for long periods without hay is more likely to develop ulcers because his gut is digesting itself rather than to have pain from lack of saliva. Interesting point of view, but you might want to do more research on it.
Horses In the Yard