SUMMIT, NJ – Field evaluations of cattle fed Zilmax and control cattle are set to begin in the first quarter of 2014. Merck Animal Health released details about the evaluation protocols.

Cattle will be observed throughout the system — at the feedyard and at the packing plant, before and after receiving Zilmax. Third-party experts will evaluate the mobility of cattle using an established scoring system. The field evaluations will also include compounding factors such as nutrition, transportation, receiving facilities, flooring surfaces, and cattle management and handling practices. A well-known independent epidemiologist and veterinarian will serve as principal investigator and collect all data, analyze results and publicly communicate the results.

While the field evaluations represent progress toward verifying the safety of Zilmax, (zilpaterol hydrochloride), Merck Animal Health said it's too early to determine when the feed additive will be sold in the United States and Canada. Merck Animal Health pulled the drug from the US and Canada after Springdale, Ark.-based Tyson Foods, Inc. notified its cattle suppliers in August the company would stop accepting cattle fed with Zilmax after receiving animals at some of its beef plants that had difficulty walking, or were unable to move. Zilmax sales in the US and Canada totaled $159 million in 2012.

The field evaluation protocols are part of a larger effort to ensure the safety of the Zilmax. Merck Animal Health noted that the company and its advisory board have spent at least three months implementing what Merck Animal Health calls its Five-Step Plan to Ensuring Responsible Beef.

"At Merck Animal Health, we continually evaluate our processes and procedures across the entire company to ensure that we maintain the best science-based practices and procedures for the health and well-being of animals," said KJ Varma, BVSc, Ph.D., senior vice president Global R&D, Merck Animal Health. "Our five-step plan is a direct reflection of that commitment to science. It also reflects our commitment to working with our industry partners to maintain the highest standards of care for the health and well-being of cattle. We are pleased to be able to tap into the vast knowledge and expertise of professionals from throughout the industry to help us carry out this significant undertaking."

In addition to the field evaluation protocols, Merck Animal Health developed a training program linked to a formal certification process. Feed yard workers, nutritionists and veterinarians who uses Zilmax or provides consultative service on feeding Zilmax to cattle must receive annual training on the proper use of the feed additive to receive a certification.

The training will emphasize safety practices, product handling, mixing protocols, cattle management, product inventory, record keeping and clean-out procedures, the company said. Certified operations must also pass an initial homogeneity test to ensure proper mixing practices, as well as four additional feed mix tests throughout the year. Before a feed yard can participate in the Zilmax Field Evaluations, the operation must be certified, the company said.

"We at Merck Animal Health remain highly confident in the safety of Zilmax, which is supported by the results of more than 30 studies, totaling 65,000 cattle that were conducted by well-respected universities and third-party experts," Dr. Varma said. "We believe the field evaluations we are conducting as part of the five-step plan will support the results of previous studies and the safety of the product, and we are confident that they will help create a greater understanding of the best management practices that are so vital to helping ensure the well-being of cattle."