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Wal-Mart Stores Inc (WMT.N) said its U.S. units were asking meat suppliers to reduce the use of antibiotics in animals, joining the list of U.S. companies that have responded to consumer and government concerns over the excess use of drugs in livestock.

Walmart U.S. and Sam's Club U.S. will also ask suppliers to provide annual reports on antibiotics management and animal welfare, the world's largest retailer said on Friday.

Public health experts and federal regulators are concerned that routine feeding of antibiotics to animals could spur creation of antibiotic-resistant superbugs in humans, creating a health hazard.

Wal-Mart's U.S. units will ask suppliers to limit the use of antibiotics for the treatment of sick animals and not to boost their growth, the company said.

"We have listened to our customers, and are asking our suppliers to engage in improved reporting standards and transparency measures regarding the treatment of farm animals," Kathleen McLaughlin, senior vice president of Walmart sustainability, said in a statement.

Tyson Foods Inc (TSN.N), the largest U.S. poultry producer, said in April that it planned to eliminate the use of human antibiotics in its chicken flocks by September 2017.

McDonald's Corp (MCD.N) also said in March its U.S. restaurants would gradually stop buying chicken raised with human antibiotics over the next two years.

However, Sanderson Farms Inc (SAFM.O), the third largest U.S. poultry producer, said on Wednesday that it planned to continue using antibiotics on its birds, partly because there are no alternatives on the horizon for treating a deadly but common gut disease.

Under its new policy, Wal-Mart will also ask suppliers to address animal welfare concerns related to habitation and slaughter.

Wal-Mart's shares were down slightly at $75.99 in late morning trading on the New York Stock Exchange on Friday.