Beloved Kentucky Derby winner Barbaro was euthanized Monday after an eight-month struggle to recover from the broken hind leg he suffered at the Preakness Stakes last year. Barbaro's owners stressed soon after his injury that they wanted him to live whether or not he could breed. How healthy does a horse have to be to sire a foal?
In theory, Barbaro could still get a mare pregnant. A stallion can father foals through artificial insemination or embryo transfer even after he's dead. But Barbaro was a special kind of racing horse called a Thoroughbred. (Only a Thoroughbred can compete for horse racing's triple crown.) According to the rules of the Jockey Club, which sets the standards for Thoroughbred breeding in the United States, no offspring that results from artificial insemination or embryo transfer can have the coveted designation. The only way a thoroughbred is allowed to reproduce is by "live cover"; i.e., horse-to-horse sexual intercourse. Barbaro was never able to become a father; his nagging leg injuries made it dangerous for him to even attempt mounting a mare.
The Jockey Club has never allowed artificial insemination, or AI. Vials of frozen sperm are easier to transport and dilute and can impregnate more mares than live cover, so AI could produce a glut of thoroughbreds born from popular studs and mares. Some breeders believe this could result in the overproliferation of offspring from particularly desirable studs, and limit genetic diversity. If too much of a thoroughbred's sperm were available, it would be less rare, and perhaps less valuable. (It was estimated that Barbaro, who was 4 years old when he died, could have commanded $1 million a year had he recovered enough to mate. His virility was so valuable that his owners had it insured.)
The breeding registries for other equines, like Standardbred horses * and quarter horses, do permit artificial insemination. AI is less physically dangerous for both the male and female than natural breeding, and can be done in a couple of ways. Handlers have a stallion mount a "breeding phantom," which resembles a pommel horse and comes outfitted with a rubber-lined vagina that can be adjusted to match the temperature, pressure, and lubrication level of the real thing. Breeders can also use a female in heat or one who has been given hormones as a "mount mare," to attract the stallion for mounting and semen collection in an artificial vagina. The deposit can be chilled to around 39 degrees Fahrenheit and refrigerated for up to 70 hours before use. For longer storage, horse semen can be frozen, but this doesn't always work.
Meanwhile, Barbaro's bloodline lives on, even though he wasn't able to breed. His parents, Dynaformer and La Ville Rouge, have produced about 1,000 thoroughbreds combined.
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Explainer thanks Dan Metzger of the Thoroughbred Owners and Breeders Association and Dan Fick and John Cooney of the Jockey Club.