Thinking of breeding your mare this spring? The recent outbreak of contagious equine metritis (CEM, which is caused by bacterium Taylorella equigenitalis) in the United States and the previous outbreak of equine viral arteritis (EVA) have underscored the importance of doing your homework when lining up a stallion. While not all diseases are avoidable without intensive testing, there are questions you might ask prior to contracting to breed your mare by either live cover or artificial insemination (AI).

Liz Scott, DVM, of Idaho Equine Hospital in Nampa, Idaho, has a special interest in equine reproductive medicine. She suggested a number of questions to pose to the owner of a prospective stallion for your mare:

  • Was the stallion tested initially for EVA and then vaccinated yearly? If not, then you might request that the horse be tested and then vaccinated.
  • Is the stallion a new import into the United States, and if so, what is his CEM status? Has the stallion been re-tested following the import quarantine?
  • Has the stallion been fertility tested, and what were the results? Typically this is done yearly to check semen quality, quantity, and motility.
  • How well does the semen ship, and do motility percentages persist with transport?
  • How well does the stallion's semen freeze and sustain fertility upon thawing?
  • What percentage of mares does he get in foal when bred in-house and how does this compare with percentage conception of shipped semen?
  • Has the stallion been used exclusively for AI breeding, or does he also do live cover? With live cover or AI with improper hygiene practices, the stallion is at risk of contracting venereal diseases, like CEM and EVA, as well as being infected with Pseudomonas sp., Klebsiella sp., and other bacterial pathogens.
  • Have any breeding horses on the premises been identified with a venereal disease, and if so, when and how was this resolved?

Scott emphasized the value of working with an experienced reproductive veterinarian who can guide you through the process of preparing your mare for breeding and consult about specific concerns to address to the stallion farm before finalizing a breeding contract.

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About the Author

Nancy S. Loving, DVM

Nancy S. Loving, DVM, owns Loving Equine Clinic in Boulder, Colorado, and has a special interest in managing the care of sport horses. Her recent book, All Horse Systems Go, is a comprehensive veterinary care and conditioning resource in full color that covers all facets of horse care (available at or by calling 800/582-5604). She has also authored the books Go the Distance as a resource for endurance horse owners, Conformation and Performance, and First Aid for Horse and Rider in addition to many veterinary articles for both horse owner and professional audiences.

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