A cattle feed additive that is widely used by Cargill and other big U.S. beef producers was temporarily taken off the market Friday by its maker after a controversy over its effect on animal health.

New Jersey-based drugmaker Merck said it would temporarily halt sales of Zilmax in this country and Canada, just over a week after Tyson Foods said it would stop buying cattle that had ingested the additive. Zilmax is mixed into feed to bulk up cattle before slaughter, resulting in more meat for processors like Tyson and Cargill.

Arkansas-based Tyson told cattle feeders that a side effect of Zilmax might be causing animals to have difficulty walking.

However, Minnetonka-based Cargill and the few other giant U.S. beef producers have stood by Zilmax. Cargill says it has experienced no "animal well-being incident" that it could directly link to Zilmax.

Merck has maintained that Zilmax is safe for cattle and continued to do so Friday, but said in a news release it would temporarily suspend sales to "ensure effective implementation" of a previously announced scientific audit of the additive.

The company gave no indication when Zilmax would be back on the market.

Cargill said it supports Merck's move. "We think it's prudent," Cargill spokesman Mike Martin said. "It's always a good thing to conduct additional research when questions arise about a product like this."

Cargill's head of animal welfare will participate in a third-party group that Merck is establishing to oversee its Zilmax audit.

The additive's animal welfare issues pose no food safety concerns for people.

Zilmax is mixed into cattle feed 20 to 40 days before slaughter, aimed at adding roughly 25 pounds of muscle to each animal.

The additive has been available for six years, but Cargill was the last major meatpacker to adopt it, doing so in June 2012. The company had been wary of Zilmax's effect on beef quality. "There were some Zilmax concerns about the tenderness of beef," Martin said.

But after much research on how to effectively apply Zilmax, Cargill figured out ways to use the additive without sacrificing quality, he said. For instance, the company ages beef longer to offset any possible Zilmax effect on tenderness, Martin said.

The temporary halt to Zilmax sales will have no effect on Cargill's production, Martin said.

Adding heft to cattle has become a bigger industry concern over the past couple of years as drought has shrunk the U.S. cattle herd to its lowest level since at least 1952. A dwindling cattle supply was the key reason for Cargill's closing of a huge slaughterhouse and beef processing plant in Plainview, Texas, earlier this year.

Animals with more meat courtesy of Zilmax and additives like it help make up for the shortfall of cattle.

Merck's decision to halt Zilmax sales and conduct an audit is aimed at reaffirming confidence in the additive, the company said in a statement.

Zilmax generated $159 million in sales in 2012 for Merck, which had $47 billion in total revenue last year.