Breeders willing to risk disease or injury for the traits they desire are at the heart of the problems we face today.

We've had bad news following bad news lately with the loss of some of the top horses in equestrian sports. The only silver lining to emerge in this dark storm of fatal injuries in Thoroughbred racing and eventing is that these incidents have heightened awareness throughout the equestrian world, and it takes that spotlight shining on a problem for a solution to be found. That's not because no one cared before, but it takes money to do research, and research is how we will develop equine sports with fewer catastrophic injuries. But not all the recent losses came during competitions; a freak barn accident took the life of the beloved event pony Theodore O'Connor. Anyone who rides knows horses can spook and run off like Teddy did. It is the nature of the beast to flee when scared by something real or imagined. But with horses who suffer injuries at the prime of their athletic careers, there has to be a better way to protect them. That way (or maybe ways) will be found through research.

We asked veterinarian and freelance writer Stacey Oke, DVM, MSc, to delve into the topic of catastrophic injuries for this month's cover story (page 26). She interviewed top researchers and veterinarians, specifically those working with Thoroughbred racehorses.

Among topics she covers are the rates of catastrophic injuries in racehorses based on research from around the world. We also asked her for updates on research that could help us protect horses from injury.

A point some of her sources made is that Thoroughbreds have, perhaps, been bred for traits that don't include the ability to withstand catastrophic injury.

Not Just Thoroughbreds, Not Just Injuries

The problem of selective breeding that leads to undesirable traits is arising in other breeds of competition horses. This point was raised at the 2008 International Equine Summit when breed representatives participated in a discussion on genetic concentration and, specifically, an overreliance on specific bloodlines in an attempt to reproduce known traits.

When you concentrate bloodlines, you can concentrate good traits, but you can also multiply undesirable traits. For example, Quarter Horse breeders have been rewarded in the show ring for having heavily muscled horses. Unfortunately, one of the top sires that passes that body type also passed a genetic disease called hyperkalemic periodic paralysis (HYPP).

University of California, Davis, research on Quarter Horses for HYPP in 1992-1996 found 1.1% had the H/H homozygous genotype, indicative of disease, while 35% were heterozygous affected (N/H; these horses have the disease and have a 50% chance of producing a foal that is HYPP positive). Results of testing in 2005 showed 2.2% of horses tested had the H/H genotype, and 37% were N/H.

What is particularly striking is that in those intervening years of genetic testing and disease awareness, the HYPP gene frequency did not decrease, and there was a two-fold increase in the number of horses with the homozygous gene frequency!

With 4% of Quarter Horses affected based on the 2005 numbers, it means about 160,000 horses at that time had HYPP. This happened despite mandated testing and refusal of the registry to allow H/H horses.

What it comes down to is that as long as breeders are willing to risk disease or injury for the competitive traits they desire, we will continue to produce horses with physiological problems.

About the Author

Kimberly S. Brown

Kimberly S. Brown was the Publisher/Editor of The Horse: Your Guide To Equine Health Care from June 2008 to March 2010, and she served in various positions at Blood-Horse Publications since 1980.

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