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.
Merck withdrew Zilmax from the market last year after several leading meat packers refused to buy cattle raised with the help of the product.
They were concerned about lameness and some cattle deaths.
The upshot of further research was a reduction in the maximum amount of Zilmax an animal was allowed to consume. As feedlots kept cattle longer to bring them to heavier weights, the amount they consumed had gone up.
There has also been advice about limiting the length of time cattle are on Zilmax.