Over 150 horses were banned from racing in Japan over the weekend after the emergence of a possible prohibited substance in a popular feed additive.
The unprecedented decision by the Japan Racing Association (JRA) involved 156 horses entered to run at Tokyo, Hanshin and Hakodate racecourses on Saturday and Sunday.
The JRA had been alerted to the potential contamination of feed products with theobromine, a substance similar to caffeine, after a number of trainers had contacted them on Friday about a recall of the Green Cal supplement.
With no time to test the product before racing, the JRA removed the horses entered from 22 stables in the Ritto Training Centre and six stables at the Miho Training Centre.
Shinobu Ito of the JRA said: "We have been telling feed vendors to only ship products that have been tested but the products that were delivered this time contained additives that were not tested yet. We have to decide it to ensure the fairness of the competition."
In a statement, Nosan Corp, the manufacturer of Green Cal, said: "We would like to investigate the causes. The product does not use theobromine and it is not yet known how the substance got into the product."
The JRA announced it would be conducting tests on horses who may have taken the supplement, with those clear of contamination able to participate in races.