Live cattle futures surged in overnight trading, boosted apparently by the notification by Tyson Foods to its fed-cattle suppliers on Wednesday that, beginning Sept. 6, it will no longer accept cattle fed with Zilmax, a beta-agonist sold by Merck Animal Health.

The letter, addressed to “cattle feeders” with the subject line of “animal well being,” was signed by John Gerber, director of cattle procurement for Tyson Fresh Meats, Inc. It reads:

“As you know, animal well-being is extremely important to our business. This is why we want to express our continued concerns about the receipt of cattle that become non-ambulatory or lame at some of our beef plants.

“There have been recent instances of cattle delivered for processing that have difficulty walking or are unable to move. We do not know the specific cause of these problems, but some animal health experts have suggested that the use of the feed supplement Zilmax, also known as zilpaterol is one possible cause. Our evaluation of these problems is ongoing but as an interim measure we plan to suspend our purchases of cattle that have been fed Zilmax.

“The purpose of this letter is to provide notice that within 30 days – or as of September 6 – we will no longer purchase cattle that have been fed Zilmax. This suspension will remain in effect until further notice.

“This is not a food safety issue. It is about animal well-being and ensuring the proper treatment of the livestock we depend on to operate. If you have any questions, please contact your Tyson Fresh Meats cattle buyer.”

Merck says safety, animal welfare is well-demonstrated

In the wake of the Tyson announcement, Merck Animal Health also released a statement stressing that animal well-being is a priority for the company.

“The facts are clear. The benefits and safety of Zilmax are well documented. Zilmax has a 30+ year history of research and development and rigorous testing. Worldwide regulatory agencies have reviewed extensive data on Zilmax and have concluded that use of Zilmax according to the label is safe in cattle. It is important to understand these data included rigorous animal health safety and well-being studies – conducted by University experts – that found the behavior and movement of cattle fed Zilmax is normal.

“Merck Animal Health has offered technical assistance, both internal and external experts, to help Tyson to understand what is behind the instances at its facility. Merck Animal Health is confident in the extensive research and data behind the product and the fact that its safety has been well demonstrated.”