The California Horse Racing Board (CHRB) has started evaluating cobalt levels in racehorses competing at tracks in that state and in certain necropsy scenarios, according to a March 4 memo from CHRB Equine Medical Director Rick Arthur, DVM.

In the memo, sent to California horsemen and veterinarians, Arthur said, "Cobalt toxicity has been associated with myocardial (heart muscle) and other organ pathology in humans and other animals. High cobalt levels have been associated with the parenteral or oral administration of cobalt salts. While there is no documented evidence of cobalt toxicity in racehorses, the CHRB considers the administration of cobalt salts a potential equine health and safety issue."

In live horses, cobalt levels higher than 5 parts per billion (ppb) in serum or 25 ppb in urine will prompt an investigation to determine where the element came from, the memo states. In necropsy samples, "until specific criteria are determined, the top 10% cobalt levels from … tissue specimens will trigger an investigation to determine the source of the cobalt."

Cobalt is an essential element present in vitamin B-12. "There is no evidence that vitamin B-12 injections will produce abnormally high cobalt readings," Arthur's memo relayed. "Nor will normal equine vitamin and mineral supplements. Low concentrations of cobalt salts found in routine feed and vitamin/mineral supplements are legal and not found to be harmful