Label also to mark upper limit for use in complete feed.

Canada has granted the makers of cattle feed additive Zilmax an expanded product label that allows for component feeding at the lower end of its dosage range — and draws the line for a maximum rate in complete feed.

Merck Animal Health on Friday announced approval from Health Canada’s Veterinary Drugs Directorate (VDD) to update the growth-promoting additive’s label to include component feeding.

The update allows for a lower targeted dose of 60 milligrams of the drug’s active ingredient, zilpaterol hydrochloride, per head per day through “one of multiple daily feedings,” such as in a morning or evening feeding, Merck said.

The new method, which the U.S. Food and Drug Administration approved for Zilmax last fall, gives Canadian cattle feeders “an alternative option to deliver the appropriate dose of Zilmax to cattle every day,” the company said.

Merck said the VDD has also approved a revision to the “complete feed” information on the Zilmax label.

The complete feed label dose for zilpaterol is 8.3 grams per tonne (100 per cent dry matter basis) to provide 60 to 90 mg of active ingredient per head per day, Merck said.

The label will now include an “updated caution statement” that emphasizes cattle shouldn’t be fed Zilmax beyond a 90 mg dose per head per day.

If pen consumption of complete feed exceeds 10.8 kilograms per head per day (100 per cent dry matter basis), Zilmax “should not be fed in complete feed,” the company said.

Zilpaterol, a beta-agonist drug, is prescribed for “increased carcass leanness, increased dressing percent, improved rate of body weight grain and improved feed efficiency” in feedlot cattle during the animal’s last 20-40 days on feed.

The drug’s label specifies it should be used only in feedlots and only in cattle weighing at least 450 kg (992 pounds). The label requires it be thoroughly mixed into manufactured feeds, and never used undiluted or as top-dressing on feed.

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