How are horses raised on horse farms?

I keep my two horses on my home farm, and they are paddocked 100% of the time. They rarely need rugs, as trees and dam banks provide adiquate shelter, and are occasionally fed hay (if the season's bad) They require very little vetinary assistance, as they are not subject to the hazards involved with stabling, and in the 16 years I have had horses, kept permanently in the paddock, they have not been affected by any virus (strangles, flu etc) They often share a paddock with sheep or cattle, and appear to enjoy the open spaces and freedom.