Meat processing giant Tyson Fresh Meats will no longer accept cattle fed the supplement Zilmax as of Sept. 6.
The United States based company sent a letter to cattle feeding operations citing recent problems where cattle entering processing plants were lame or could not move.
It based its decision on some information that the feed additive containing zilpaterol could cause lameness and so decided to stop its use as an interim measure even though the product has been approved for use since 2004.
“It is not about a food safety issue,” the company said in the letter.
“It is about animal well being and ensuring the proper treatment of livestock we depend on to operate.”
Tyson processes about 25 percent of the beef in the United States and it is estimated about 75 percent of American beef cattle are fed products like Zilmax.
Merck manufactures Zilmax and its research has shown positive results with higher red meat yield and better weight gain when fed for the last couple weeks of finishing.
In a statement, Merck said it does not believe the product is responsible for the problems Tyson has observed.
“Tyson itself points to the fact that there are other possible causes and that it does not know the specific cause of the issues it recently experienced. We will continue to work with Tyson to help it identify those other causes,” said the company.
Cargill Meats has accepted beef cattle fed Zilmax since the late spring of 2012 even though it had some past concerns about decreased tenderness resulting from use of this product.
“It’s taken us a few years to accept cattle fed Zilmax because we wanted to be certain that best practices were being followed to ensure beef quality was not being adversely impacted,” said a statement from Cargill’s corporate communications division.
It has no plans to change its cattle procurement practices.
JBS did not respond to requests for comment.
There has been little specific research on the animal welfare connections but considerable work has been conducted on weight gain and economic benefits, said Reynold Bergen of the Beef Cattle Research Council.
When these products are approved, manufacturers are obliged to look at concerns from producers or veterinarians and identify possible causes. However, a major field study with huge data sets is required to determine whether the product causes lameness or other side effects.
“These anecdotal reports are coming in and they are getting maybe more consistent that the lameness thing needs to be looked at the most closely,” he said.
The impacts on Canadian producers are likely minimal because few cattle are going to Tyson, however it could have a larger impact on the industry because of the uncertainty over what is really happening with these products.
“There don’t seem to be many implications on the quality side but things like welfare concerns can cause real public confidence issues,” Bergen said.
“When things like this come up we have got to get real answers to them.”
Numerous independent studies in Canada and the U.S. have found average daily gain and feed efficiency are improved by about 20 percent for grain-finished cattle but few researchers have found lameness to be an issue.
A study from the University of Wisconsin found Zilmax and Optaflexx, produced by Elanco Animal Health, had positive effects on gain but suggested cattle with poor skeletal structure could have lameness problems due to the added muscle growth. There have also been some complaints about tougher beef.
“There is conflicting results in the literature about what it does to meat quality. The consensus has become that it does toughen the meat ever so slightly,” said carcass quality researcher Heather Burns of the University of Alberta agriculture faculty.
Her research on the effect of beta agonists and growth hormone implants was published in 2011 and 2012 with further research examining the effect of increased connective tissue in muscles.
However, more research is needed because there is worldwide concern over ractopamine and products like Zilmax.
She has learned the product has the greatest effect on cattle with lighter muscle like Holstein steers or cows. The growth hormones and beta agonists may work against each other in the body, but the net benefits make using them worthwhile.
“There is still a net advantage in the use of them in terms of the ability of the cows to gain a lot of weight in a short period of time,” she said.
However there is growing consumer backlash against such products.
“There are two sides to the story, what the consumer wants, which the meat industry tries to deliver, but then there is also consumer education so you can indicate to the consumers groups that we are not hurting animals or we are not compromising the safety of your product,” she said.
Her research did not turn up reports of lameness but there are plenty of anecdotes that the condition seems to occur among some cattle and pigs fed beta agonists.
“Every time they look for it in a scientific study, they can’t find it but there are anecdotes,” she said.
Animal behaviorist Temple Grandin of Colorado State University has also observed problems in market-ready cattle fed zilpaterol when they arrived at slaughter plants.
In a paper titled Effects of Economics on the Welfare of Cattle, Pigs, Sheep and Poultry, she said the effects in fat cattle were uneven. The problems appeared in various breeds.
“A few animals were severely affected, 20 to 50 percent were sore footed lame, and the rest of the group were normal,” she wrote.
She also reported monitoring steers that seemed to be reluctant to move quickly down unloading ramps when normal animals usually trot or run up ramps. She also observed stiffness in some cattle.
“They act like they have muscle cramps,” she wrote.
Grandin regularly audits slaughter plants for animal welfare concerns and said cattle arriving at a plant should be evaluated for lameness, heat stress, open-mouth breathing and stiffness.
She also advocates more research on genetic interaction and beta agonists, suggesting cattle with greater natural potential for muscle growth suffer more side effects.