Merck said the review supported that Zilmax (zilpaterol hydrochloride) is safe when used according to the product label and in combination with sound animal husbandry practices.
"The research results and industry data showed that cattle weights, and thus feed consumption rates, have been steadily increasing over time," Merck said. "This 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 added that enhanced product labels along with certification requirements and a best practices program will ensure that usage of Zilmax remains compliant with the label.
Merck temporarily suspended sales of Zilmax in the United States and Canada to provide sufficient time to conduct a scientific audit that monitored the process of feeding Zilmax to cattle. The audit came after Springdale, Arkansas-based Tyson Foods, Inc. announced plans to stop using the feed additive and refuse cattle that had been fed Zilmax.
Merck updated the Zilmax label to include component feeding, an alternative method of administering Zilmax using a targeted lower dose. The company submitted the updated label to the Food and Drug Administration which approved the label.
Other steps the company is taking to ensure proper use of Zilmax includes a certification program. Feedyard team members, distributors, feed manufacturers, nutritionists and veterinarians who use Zilmax or provides consultative services on feeding Zilmax to cattle, must complete a Zilmax training program, as well as annual retraining, which addresses proper use of the product.
“The training will focus on best practices, product handling, mixing protocols, cattle management, product inventory, record keeping and clean-out procedures,” the company said. “Completion and adherence to the program will be a prerequisite for the use of Zilmax.”
In addition to the certification program, Merck has developed Best Management Practices that include the best regimens for feeding Zilmax to cattle.
“Emphasizing best management practices illustrates our commitment to our industry partners by helping set benchmarks for animal mobility, mitigating risk factors, and reinforcing the significant role of nutrition and handling in animal performance,” said KJ Varma, BVSc, Ph.D., Diplomate ACVCP, senior vice president Global R&D, Merck Animal Health. “We remain committed to working closely with our customers to maintain the highest standards of care for the health and well-being of cattle.”
Finally, Merck will conduct in-field use studies that will focus on observing cattle throughout the production system; evaluating the mobility of cattle and reviewing “potential confounding factors”, such as nutrition, transportation and other factors. An independent third-party will oversee the studies which will extend into the high heat months.
“Zilmax will be made available only to cattle feeders that can meet and maintain all conditions of the Best Management Practices initiative and the Certification Program, as well as fully comply with all protocols of the In-Field Use Studies,” the company said. “We believe the results of the In-Field Use Studies will help support the return of Zilmax to the market place in the future.”