Never fed anything except barley. No advantage to cooking it- I buy it micronised so it is already cooked, but if you put hot water on it it makes a wonderful porridge for a cold day! My feed mix consists of a base of barley, mixed with peas, beans soya (also micronised)and flax (as a top dressing. The barley is three times by volume the amounts of the other ingredients, which are also micronised. Maybe the Irish are feeding "raw" barley, and boiling it used to be a traditional way of releasing all the nutrients the horse cannot utilise form raw grain but with the advent of micronised feeds this is unnecessary.