In a move commended by the National Cattlemen's Beef Association, Merck Animal Health is initiating a scientific audit of Zilmax, a leanness additive for cattle, and pledges to remain transparent about the process.
Recently Tyson Foods reported animals struggling to walk or not moving at all as a side effect of Zilmax, and has decided to discontinue purchases of cattle fed with it.
Zilmax, also called zilpaterol, is comparable to another FDA-approved yet controversial beta-agonist used in swine: ractopamine. NCBA points to research showing that cattle metabolize such drugs quickly enough that they're not stored in the body, and not present in meat.
As the world's second largest beef processor after Brazilian company JBS, Tyson's move has also raised suspicion that marketing beef to foreign markets, where additives are less desirable, is behind the decision to discontinue the use of Zilmax. JBS has indicated that it will not change its cattle buying practices.