The principal benefit of the mash is to encourage the horse to ingest an important quantity of water, wich will encourage his recovery. If the mash have beet pulp, he also have emollients functions on the dygestif system. Also, It's recommend to distribute a mash afetr intensives exercices (competitions, race …) or only to share a special moment with his horse !
In terms of frequency, it's recommend to distribute one or two mash per week. In fact, the mash is constitute r most part of cereals, and constitue high energy food who in excess may adverce consequences on the health of horses.