Test results showed that the animals had 10 to 15 times the amount of selenium in their blood than normal and 10-20 times the normal amount in their liver, according to Dr. John Harvey, executive associate dean at the University of Florida College of Veterinary Medicine.
The college's Florida Racing Lab conducted several tests in the investigation, which began after the horses began dying prior to the start of the U.S. Open polo match on April 19. Tests included necropsy, histopathology and toxicology.
While it was determined there was hemorrhaging in various body parts of the various animals, it was not significant enough to have caused the deaths, according to Harvey.
The Venezuelan Lechuza Caracas Polo team, which owned the horses, previously issued a release stating: "A Florida-licensed veterinarian wrote a prescription for a compounded substitute vitamin supplement for BIODYL containing vitamin B, potassium, magnesium and selenium. This compound was prepared in the State of Florida by a compounding pharmacy. Only the horses treated with the compound became sick and died within 3 hours of treatment. The horses that were not treated remain healthy and normal."
Franck's Pharmacy of Ocala, Fla. admitted last week "the strength of an ingredient in the medication was incorrect."
The pharmacy, which prepared medication for the animals, did not name the medication or the ingredient.
The horses reportedly appeared dizzy and disoriented while being unloaded from their trailers Sunday afternoon just prior to a 3 p.m. match. Seven died at the scene, and the others during treatment elsewhere or while being moved to a medical facility.
Aside from the high levels of selenium, Harvey says all of the other drugs found in the horses were normal.