Since Georg Brandt discovered cobalt in 1793, people have exploited its virtues for a wide range of uses, from paint pigmentation with its rich blue color to enhancing human athletic performance. Because some racehorse trainers in the United States and Australia have abused cobalt in horses, an Australian research team recently investigated cobalt concentrations in urine and blood after chronic cobalt administration to determine whether current regulatory drug detection thresholds proved useful for this purpose.
“Cobalt is an essential trace element required to synthesize vitamin B12, which plays a vital role in cellular metabolism and DNA synthesis,” said Ross Wenzel, GradDip (ClinBiochem), MAppSc (Thesis) of the Trace Elements Laboratory at the Royal North Shore Hospital, in New South Wales.
An average 500-kg (roughly 1,100-lb) working horse, fed approximately 2% of its body weight in forage per day, requires 0.1-0.15 mg cobalt/kg/dry feed daily. These levels typically can be met through diet alone and, because no known reports of cobalt deficiency exist, equine nutritionists advise a maximum of 25 mg/kg dry matter intake.
“The rationale for supplementing horses with cobalt pertains to a presumptive increase in red blood cell production in response to cobalt indirectly inducing hypoxia,” Wenzel said. In turn, more oxygen will be delivered to exercising muscles to maximize energy production and enhance performance.”
In other words, some people believe that giving cobalt indirectly diminishes the amount of oxygen reaching the muscles, causing the body to compensate, producing more red blood cells to deliver more oxygen to the muscles.
“Research has failed to support this presumption,” he added. “There is no evidence to suggest that cobalt will stimulate a hypoxic response in excess of that naturally achieved in training.”
“With the range of unnecessary cobalt-containing supplements on the market, the need to develop a testing regime capable of differentiating cobalt misuse from regular supplementary intake is apparent,” said Wenzel.
He explained that his group pursued the study “on the initiative of study co-author and equine veterinarian Derek Major in response to a high rate of racing cobalt infringements where anecdotally, up to 500 mg of cobalt chloride were being administered intravenously.
To better understand how horses metabolize cobalt, Wenzel and coworkers administered 25-50 mg cobalt chloride intravenously once to twice weekly for 10 weeks. They assessed both urine and blood cobalt concentrations routinely during the study period and again 81, 106, and 127 days after its commencement.
“We found marked cobalt accumulation throughout the study, with increasing cobalt concentrations in collected samples as the study progressed. Cobalt levels in red blood cells remained elevated for at least 12 weeks after intravenous administration, which is consistent with the lifespan of red blood cells,” said Wenzel.
Throughout the study the researchers found that only blood analysis, not urine testing, identified cobalt levels exceeding the respective international thresholds and, therefore, appeared to be a better means of assessing cobalt misuse in horses.
“Urine samples collected on race day from horses suspected of cobalt doping may no longer exhibit elevated levels from cobalt administered in the previous weeks,” he said, explaining that any perceived hypoxic benefit attained from cobalt administration would take several days to be realized, and they were only able to detect very recent exposure to cobalt in urine. “Hence, only those jurisdictions determining blood cobalt levels are effectively screening for nefarious cobalt use,” he said.
He said urine cobalt determinations are disadvantaged for other reasons: Urine cobalt concentrations vary markedly with hydration levels, urine can potentially be contaminated with environmental sources of cobalt during collection. Also, urine “can return elevated cobalt levels from the innocuous cobalt contained in vitamin B12, with excess amounts of this compound excreted in urine,” he said.
“Considering that cobalt does not actually have any documented performance-enhancing effects and does not appear to stimulate the production of red blood cells in racehorses, the misuse of cobalt is ill-conceived,” said Wenzel, adding, “Excess cobalt is neither useful nor necessary. Public education is needed on this topic.”
You can find the study, “Cobalt accumulation in horses following repeated administration of cobalt chloride,” in the Australian Veterinary Journal, Volume 97, No. 11, November 2019, p 465-472. The abstract is available online.