The World Health Organization (WHO) says the farm sector consumes around 80 percent of all medically important antibiotics in some countries.

Meat producers around the world have used such drugs to prevent disease in healthy animals and to speed up their growth.

WHO last week recommended eliminating both of those practices, saying they contribute to the rise of antibiotic-resistant bacteria.

The European Union has banned farms from administering antibiotics to livestock without a veterinarian's prescription or to boost growth. Denmark, Norway and the Netherlands go further by discouraging routine antibiotic use for disease prevention.

The United States only restricts the use of antibiotics for growth promotion.

Four U.K. companies, including restaurant and hotel operator Whitbread PLC (>> Whitbread) and Domino's Pizza Group U.K. (>> Domino's Pizza Group PLC.), have committed to phasing out the routine use of antibiotics in beef, pork and poultry, according to the Farm Animal Investment Risk & Return (FAIRR) network, a coalition of 62 investment groups that manage $2.3 trillion in assets.

U.S. companies ranging from fast-food chain McDonald's Corp (>> McDonald's Corporation) to poultry producer Tyson Foods Inc (>> Tyson Foods, Inc.) have moved to reduce or eliminate medically important antibiotics from their poultry supply chains, but have yet to make similar commitments on beef and pork.

"As investors, we should be urging all U.S. food companies to adopt a comprehensive best practice antibiotics stewardship policy which reduces the use of these medically crucial drugs," said Jagdeep Singh Bachher, chief investment officer for the University of California's Board of Regents.

The U.S. Department of Agriculture last week criticised the new WHO antibiotic guidelines for farmers, saying they "are not in alignment with U.S. policy and are not supported by sound science."

Meanwhile, the states of California and Maryland on Jan. 1 will enact antibiotic laws that go further than the U.S. government's by phasing out the regular use of medically important antibiotics for disease prevention.

Additionally, San Francisco in October became the first U.S. city to require large grocery stores to report on antibiotic use by their meat suppliers.

(Reporting by Lisa Baertlein in Los Angeles)

By Lisa Baertlein