This past year, horse racing regulators worldwide have turned their attention to a seemingly innocuous substance: cobalt. Every horse needs this important element to survive, but some horsemen believe that supplementing the substance will help their horses gain a competitive advantage on the race track.

At the 2015 University of Kentucky (UK) Equine Showcase, held Jan. 23 in Lexington, Kentucky, Cynthia Gaskill, DVM, PhD, Dip. ABVT, reviewed cobalt, its use in racehorses, and recent research on the topic. Gaskill is a veterinary toxicologist at the UK Veterinary Diagnostic Laboratory (UKVDL), also in Lexington.

Cobalt is a trace mineral found in B vitamins that horses require in tiny amounts for correct functioning of their physiology. As a result, all horses will have trace amounts of the substance in their systems.

Gaskill explained that doctors used cobalt to treat anemia (essentially by increasing the blood's oxygen-carrying capacity) in humans for decades. However, it was associated with a variety of adverse effects, including gastrointestinal, neurologic, cardiovascular, and thyroid problems. As a result, doctors have largely ceased using it. Some athletes, however, continue using it as a doping agent, she said.

Until recently, she added, researchers had not evaluated cobalt supplementation's beneficial or adverse effects in horses. Since racing regulators' interest in the element has increased, however, the amount of research into it has, as well.

In 2014, Gaskill said, Heather Knych, DVM, PhD, of the University of California, Davis, and colleagues carried out a study evaluating how cobalt distributes and works within horses' bodies following a single intravenous dose comparable to what's reportedly used on the racetrack. Some key findings included:

• Horses' baseline serum cobalt levels were less than 1 part per billion (ppb), which is extremely low, Gaskill said;
• Peak serum concentrations following cobalt administration were extremely high, she said;
• The substance's half-life (the time required for the drug's blood concentration to decrease by 50%) was about six-and-a-half days, which is longer than previous studies suggested, Gaskill noted—this is beneficial for drug testing purposes;
• Serum concentrations 10 days following administrations were still elevated—about 20 to 50 ppb—which is also good for testing purposes; and
• The team found that administration had no effects on horses' erythropoietin levels or red blood cell counts (both of which could improve oxygen-carrying capacity and, thus, performance) or any adverse effects at the administered dose.

Also in 2014, Emmie N. M. Ho, PhD, a racing chemist at the Hong Kong Jockey Club's Racing Laboratory, in China, worked with colleagues on developing cobalt testing thresholds. Gaskill said the research team proposed a threshold of 2 ppb on race day and 10 ppb for out-of-competition testing. She noted that laboratories in Hong Kong use a different testing method than U.S. labs use, which detects much smaller concentrations and, thus, results in a lower threshold.

Last October, Indiana set a race-day cobalt threshold of 25 ppb for horses in that state. Gaskill said that prior to the threshold's implementation, 6 to 7% of horses tested had increased cobalt levels. Since implementation, less than 1% of horses tested have had increased cobalt levels.

Kentucky is currently doing cobalt surveillance. The Racing Medication and Testing Consortium had not yet recommended a threshold value at the time of this presentation, but should soon, she said.

Gaskill said several additional studies evaluating cobalt's adverse effects, the administration of cobalt-containing supplements, and blood samples from nonracing Standardbreds are underway. She also said there's work underway evaluating different cobalt testing methods, which can result in different test results.

In closing, Gaskill stressed that while illicit cobalt use appears to be prevalent, it's effects—negative or positive—aren't currently well-understood: "No one has documented any beneficial effects scientifically yet in horses."