The Hong Kong Jockey Club has determined that the banned substance zilpaterol found in tests taken from 12 horses trained by P.F. Yiu was the result of contaminated feed and has determined that a second feed product used by trainers has similarly been contaminated.
Zilpaterol is a beta-2 agonist used to promote weight gain in livestock and is prohibited in racing. In North America, the Association of Racing Commissioners International classifies zilpaterol as a Class 3 drug with a Category A penalty.
Following the positives for horses trained by Yiu that had raced June 2 at Sha Tin Racecourse and at Happy Valley June 5, stewards "immediately undertook an exhaustive testing regime of all products used by Mr. Yiu which may have been administered to horses trained by him."
Those tests revealed the presence of zilpaterol in feed used by Yiu, and subsequent tests detected the prohibited substance in another feed used by trainers in Hong Kong. Neither manufacturer was identified.
The HKJC announced June 13 that alternative feeds were being made available to all trainers who previously used feed that could be contaminated. Officials also are testing urine samples from about 80 horses that are scheduled to race at Sha Tin June 16 that have previously been exposed to the two contaminated products.
Earlier this year the California Horse Racing Board dismissed 48 positive tests for zilpaterol after it was determined that the source of the drug was a contaminated sweet feed produced by the Purina company. Most of the positive tests were from horses training at the Cal Expo harness track and resulted in temporary restrictions on food vendors delivering certain types of Purina feed at California tracks.
The prohibitions were lifted after Purina provided feed that tested negative for any contamination.