Nearly all large ranches keep a sizeable herd of horses for use by the cowboys in gathering and moving the cattle.  These ranches will often have their own horse breeding programs with each year's foal crop destined to become either mounts for use on the ranch or brood mares.

Typically, when a new cowboy first arrives for work on the ranch he is "strung" with a group of horses, usually unbroken 3 - 4 year olds that have lived out on the open range.  This string of horses will be his and only his for use while he remains on the outfit.  Real ranch-broke horses are highly prized for their versatility and broad range of experience.  One oft cited reason by cowboys for leaving a ranch job is that the horses have become too broke, making the job less exciting and challenging.