The California Horse Racing Board, citing feed contamination, has dismissed 48 positive tests for zilpaterol, which is used in cattle.
The contamination of the feed appears to have occurred in mid-February, with the first positive detected from a race run March 1. The CHRB ruled that the cases from March 1 to March 26 have or will be dismissed.
The CHRB said the contaminated feed has been identified, as described in a March 22 advisory, and horsemen are or should be aware of the contaminated feed. If trainers have removed the feed, residues of zilpaterol in horses should be eliminated by the end of March.
Most of the positive tests were from horses at the Cal Expo harness track.
In a follow-up directive, the CHRB instructed all licensed feed vendors to remove Purina sweet feed products from the company's Turlock, Calif. plant from state racing facilities until Purina can show that the feed does not contain the prohibited drug zilpaterol, which is used to promote weight gain in cattle.
Purina has notified horsemen that they may return the products to their distributor, according to the CHRB statement.
"Horsemen who have not already done so are advised to return any Purina or Country Acres sweet feed they have from Purina’s Turlock plant to their feed vendor. The Turlock plant is designated TRL on the lot number on each bag of feed," the CHRB statement said.