Zilmax cleared for component feeding in Canada

(Canada Beef Inc. photo)

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.

“Enhanced language”

Merck in 2013 suspended sales of the drug, nicknamed “Vitamin Z” in some feedlots, in both Canada and the U.S. after packers Tyson Foods and Cargill stopped accepting Zilmax-treated cattle.

Tyson said at the time its decision followed observations that some animals arriving at its packing plants were having trouble walking or moving.

A Reuters news agency review in late 2013 of reports submitted by Merck and others to the U.S. Food and Drug Administration (FDA) showed at least 285 cattle to have died unexpectedly or been destroyed in the U.S. after being fed Zilmax since the drug was introduced in 2007.

Reuters said the reports showed at least 75 animals lost hooves and were euthanized after being fed Zilmax over the past two years. The reports show pneumonia was a factor in 94 cases and listed bloat as a cause in 41.

Of the animals that died, 113 were fed either an antibiotic, a different growth-promoting drug or both, along with Zilmax, Reuters said. Some experts have said there is no proof Zilmax was the chief cause of any cattle deaths.

Merck said at the time it would retrain and certify beef producers in administering the drug to cattle, and run a “scientific audit,” following Zilmax-fed cattle from feed yards to packing plants, to determine potential causes of lameness and other mobility issues.

Merck said Friday it has run “an extensive assessment and analysis of existing as well as new product data” and sought input from industry experts, business partners and customers about Zilmax and its use.

“The totality of the comprehensive review supported that (Zilmax) is safe when used according to the product label and in conjunction with sound animal husbandry practices,” the company said Friday.

Merck said in November its research results and industry data showed “cattle weights, and thus feed consumption rates, have been steadily increasing over time.”

That fact, Merck said, “created the possibility that certain cattle could consume feed quantities that result in ingestion of Zilmax in an amount that exceeds the approved dose.”

Merck said its review also found “enhanced label language” along with certification requirements for the drug’s users and a “thorough best practices program” would make sure Zilmax use “remains compliant with the label.”

Under the certification rules, every feedlot worker, distributor, feed mill, nutritionist and veterinarian using Zilmax or consulting on its use must complete the Zilmax training program and yearly retraining on its use. — AGCanada.com Network

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