The hay troughs below are only about twelve inches deep. You can buy them with taller sidewalls. Why would a shallow trough be better for the horses?

Western Horse Watchers Association
Exposing the Hypocrisy, Lies and Incompetence of the Wild Horse Advocates
The hay troughs below are only about twelve inches deep. You can buy them with taller sidewalls. Why would a shallow trough be better for the horses?
