Be aware of the horse-per-acre ratio. You must be aware of how many acres are needed to provide your horse will enough pasture. The ratio is highly variable though. It depends on the type of grass in the pasture, the soil, the expected amount of hours grazed, pasture management, and the weather. In some cases, one horse only requires 1 acre, if the pasture is good. Yet if the pasture is poor, one horse might need 2.5 acres.