In a letter sent to producers on Wednesday, cattle giant Tyson Foods announced it will no longer buy cattle that have been fed the growth-inducing drug Zilmax, produced by Merck. Industry experts fear the decision will cause the availability of beef to dwindle and inflate beef prices, but Tyson's letter explained the company's decision, saying,
"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."