Horse Health Research Continues at 2016 Tevis Cup

When the 61st Tevis Ride commences early on July 23, about 170 horse and rider teams will head down the historic Western States Trail across the rugged Sierra Nevada mountains in a challenging 100-mile journey. It will also allow equine researchers another opportunity to study elite endurance horses in a field setting.

Since 2012, and in addition to the required hands-on horse evaluations during the ride, researchers Greg Fellers, DVM; Langdon Fielding, DVM, Dipl. ACVECC; and Gary Magdesian, DVM, Dipl. ACVIM, ACVECC, ACVCP, have drawn and analyzed equine blood samples at Mile 36. They’ve been trying to uncover data that would objectively identify horses unlikely to finish the course within the allotted 24 hours.

Also since 2012, the researchers have reviewed the data after the ride and compared them with actual completion rates. They focused on potassium and chloride levels, which decrease as a horse sweats and serve as an indirect marker of hydration. In the first year, the team found that horses with specific potassium and chloride levels had a 25% event completion rate compared to a general completion rate of around 50%.

The blood-draw protocol continued in 2013 to gather more data, and in 2014 the decision was made to “red flag” horses whose blood test results indicated they could be at risk of not finishing. The researchers informed the riders and crew of the results and rechecked the horses before they left the one-hour hold at Mile 36. Unexpectedly, the team said, the 18 horses flagged at Mile 36 had an 80% completion rate.

The unexpected results continued in 2015 when, using the same protocol as in 2014, 40 red-flagged horses had a 60% completion rate compared with the field’s overall 46% completion rate.

Why the jump from 25% predicted success to 60% or greater?

“I have a theory,” said Fellers, “that perhaps riders and crew adjust ride pace, allow more time for the horse to eat and drink, and generally alter ride strategy based upon our test results.”

This year researchers will return to the protocol of 2012 and 2013, in which neither ride veterinarians nor riders and crew will know blood test results until after the event completion. Further, about 15 riders have agreed to have their horses’ blood drawn at home before leaving for Tevis and at three other locations before Mile 36. With this exercise, the researchers hope to determine when during the ride dehydration starts.

The 2016 Tevis Cup kicks off at 5:15 a.m. on July 24 from the Robie Equestrian Park, near Lake Tahoe, California. The race will wrap up at the Auburn Gold Country Fairgrounds in Auburn, California.

About the Author

Marsha Hayes

Marsha Hayes has been covering endurance, trail, and other equine topics since 2005. She believes every horse has a story.

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