Successful breeding of horses is not always as easy as presenting a receptive mare to a fertile stallion. There are many things that can go awry with the reproductive process. Broodmares that were once fertile and produced many excellent foals might one day face the realities of repetitive foaling injuries, chronic uterine infections, or simply old age. Stallions also can experience a decrease in sperm number and quality as the years pass. Pain associated with arthritic hocks or chronic back problems can interfere with a stallion’s ability to mate. When a mare or stallion develops any kind of problem that interferes with its ability to perform reproductively, it could be time to investigate the options of assisted reproductive technology (ART). These are the techniques that offer the hope of producing foals from mares or stallions that might no longer be able to pass along their genes to future generations any other way.

The Subfertile Stallion

Research has shown that maximum pregnancy rates are achieved when a stallion’s ejaculate is of sufficient quality to allow a mare to be inseminated with 500 million progressively motile sperm every other day during the five to seven days of heat.¹ Problems arise when semen evaluation reveals either insufficient numbers or decreased quality of sperm, with more abnormal sperm or fewer sperm that can swim vigorously in one direction (progressively motile). Therefore, methods have been developed to make the best use of limited numbers of good-quality sperm