OTTAWA, Ontario – Health Canada's Veterinary Drugs Directorate recently approved an expanded product label for Zilmax.

The updated label allows for component feeding, an alternative method of administering Zilmax using a targeted lower dose, according Merck Animal Health, Summit, NJ. Merck also included a maximum rate in complete feed.

Feeding directions for component feed state Zilmax should be “fed continuously to cattle during the last 20 to 40 days on feed, in a feed containing no less than 6.8 g/ton and no more than 24 g/ton zilpaterol (90 percent dry matter basis), to provide 60 mg zilpaterol hydrochloride per head per day.”

The label also includes an updated caution label that states Zilmax should not be fed to cattle in excess of 90 mg per head per day in complete feed. Also, Zilmax should not be fed in complete feed if pen consumption exceeds 26.5 lbs. per head per day, the company said.

Merck temporarily suspended sales of Zilmax in the United States and Canada to conduct a scientific audit that monitored the process of feeding Zilmax to cattle. The audit came after Springdale, Arkansas-based Tyson Foods, Inc. and several other meat processors announced plans to stop using the feed additive and refuse cattle that had been fed Zilmax. The beta-agonist drug promotes “increased rate of weight gain, improved feed efficiency and increased carcass leanness in cattle,” according to Merck.