Many hormone and drug treatments could have a negative impact on the endocrine system, so it’s best to avoid using them altogether in the breeding stallion. However, there are some stallions and situations where carefully selected and monitored hormone and drug therapies can be helpful, according to Sue M. McDonnell, PhD, Certified AAB, of the University of Pennsylvania’s School of Veterinary Medicine. She described these scenarios at the Hagyard Bluegrass Equine Reproduction Symposium, which was held Oct. 18-21 in Lexington, Ky. However, she recommended that horse owners contact their veterinarians to determine the best treatment methods for their animals.

"We see hormones and drug treatment as a last-stitch or emergency approach," said McDonnell, who is the founding head of the veterinary school’s Equine Behavior Program. "Wherever possible, we can identify several simple management changes that should be made in addition to these treatments. That would include turnout, good exercise, natural day length (they aren’t kept under artificial light), and diet.

"A large portion of our caseload involves breeding behavior problems, including slow-starting novice breeding stallions; overenthusiastic or aggressive stallions or stallions with particular breeding misbehaviors; and stallions with ‘special needs’ such as erection and ejaculation dysfunction, musculoskeletal discomfort, or neurologic disabilities that impair breeding ability," continued McDonnell, who emphasized again that horse owners should rely on the judgments of their veterinarians on what treatment routes to take.

McDonnell described a variety of ways to pharmacologically induce ejaculation. She made an observation about stallion physiology; ejaculations occur as the stallion drops his head and as the head comes back upbut always when the head and neck are in the same posture. She pointed out this could reflect the exact neck angle at which the horse ejaculates when mounting the mare. Thus, she encouraged those who study acupuncture (or other disciplines that tie certain points of the body together) to investigate why this particular neck angle is adopted and whether there are other ways to induce ejaculation using methods that don’t involve drugs or hormones