The Birds and the Bees; What Happens at the Breeding Shed?

Busily crisscrossing the rural roads of Central Kentucky are a fleet of Stonestreet horse trailers carrying very precious cargo. These are the broodmares on their way to their dates with stallions.

All Thoroughbreds have the same official birthday – January 1st – therefore the breeding sheds open around February 14th each year. This allows 11 months for gestation plus a  ‘just in case’ two weeks – any foal born before January 1st will officially turn one-year-old at the start of the year, even if they are just a few hours old. As races are classified by age, this would be disastrous for their future racing career.

In order to be eligible to compete in races, a Thoroughbred must be registered with the Jockey Club. One of the requirements for registration is that a foal must be the result of a live cover; foals produced by artificial insemination, embryo transfer or any other form of genetic manipulation are not eligible for registration. Learn more here American Stud Book Principal Rules

Stallions remain at their homes, the stallion farms, and the broodmares visit them on a date determined by our reproductive veterinarian. The breeding shed at a stallion farm offers a controlled environment for the mating ensuring the safety of the stallion, the broodmare, and the attendants.

Some central Kentucky stallion barns are beautiful. Check out Hill N Dale, home of Curlin.

Upon arrival, the broodmare enters the waiting area. An attendant confirms her identity by checking the name on the halter or neck strap, that she has received the appropriate vaccinations and, if applicable, has proof of a clean uterine culture. The broodmare is teased to ensure that she will be receptive to the stallion and her tail is wrapped and washed to prevent any debris being introduced to the uterus during the cover.

The broodmare then leaves the waiting area for the breeding shed itself. If she is a maiden, or has never been bred before, the teaser will jump her; he mounts the broodmare but cannot penetrate her due to the cape he wears across his underside. This gives the Stallion Manager a good indication of how a maiden will react to being mounted by a stallion, and he will prepare accordingly.

The teaser leaves the breeding shed, and the stallion enters from the opposite side of the building. All breeding sheds have two points of access as a biosecurity measure. The broodmare is positioned facing away from the stallion. One handler holds her lead shank and two others stand nearby. The broodmare wears a thick leather neck shield for the stallion to bite onto and steady himself when mounted. It prevents any injury to the broodmare from his teeth.  She also wears thick leather booties on her hind feet to prevent injury to the stallion if she kicks out. The stallion will approach the broodmare and sniff her, and the flehmen response may follow. Once the stallion is ready to mount the broodmare, one handler lifts the broodmares foreleg with a leather strap and holds it (in the same position as when a hoof is picked), and the other handler holds the tail to one side. The stallion and his handler step forward and the stallion mounts the broodmare. As soon as his weight is on her back, the broodmares foreleg is released as kicking is no longer a danger to him.

The stallion penetrates the broodmare until the flagging of his tail indicates ejaculation. As the stallion dismounts, a ‘dismount sample’ of semen is collected in a cup, and its morphology, motility, and volume are viewed under a microscope.

The stallion and broodmare part ways, and she will return to Stonestreet. The following day, our reproductive veterinarian will perform an ultrasound to ensure she has ovulated. 15 days later, he will return to check for pregnancy!