Older, pregnant mares will soon teach manners even to a rank stallion. Such an experience can be good for younger stallions that have become unruly or difficult to handle, but there is risk of injury. The stallion can stay with the mares through the next breeding season or be removed. It is not advisable to turn an inexperienced stallion in with a band of mares in the spring. Some mares, especially shy ones, seem to have a higher probability of conceiving in a natural environment.
Some stallions also have a higher conception rate in a pasture mating program.
So, pasture mating often results in higher conception rates. While little research exists on the various mating programs, management intensity, skill and knowledge of the handler, the value and behavior of the stallion and mares are probably major deciding factors for or against pasture mating. Today, most stallions are used in a hand-mating program. Actually, stallions used in an Al program are handled by hand. Hand mating requires more labor and facilities than pasture mating.