U.S. sales of antibiotics for food-animal production, which had been rising steadily for years, dropped 30 percent, by weight, from 2015 to 2017 - potentially affecting livestock producers and consumers, a new government report finds.

The decline reflects U.S. restrictions, enacted in 2017, on the use of growth-promoting antibiotics, as well as rising U.S. consumer demand for products raised without antibiotics, according to the report from the Economic Research Service, an arm of the U.S. Department of Agriculture.

The Euoprean Union, for similar reasons, also saw a sizable drop in the use of antibiotics for food-animal production: a decline of 31 percent from 2010 to 2015, according to the report, "The U.S. and EU Animal Pharmaceutical Industries in the Age of Antibiotic Resistance."

Food animals refer to animals used to generate food, including meat, dairy, eggs and animal byproducts.

Antibiotics save lives, both human and animal. But microbes and genes can develop resistance to antibiotic drugs, raising worldwide concern, said the report, written by Stacy Sneeringer, Maria Bowman and Matthew Clancy.

As the report notes, rising foreign demand for U.S. and EU meat exports - reflecting economic growth in many developing countries - had pushed up U.S. and EU sales of antibiotics for food-animal production for many years.

But U.S. domestic demand for meat raised without any antibiotics has increased, at least partially offsetting increased antibiotics linked to foreign sales. For instance, in 2017, 44 percent of U.S. broilers (poultry) were raised without antibiotics, up from just 2.7 percent in 2012, the report notes.

Among other findings of the report, which the Economic Research Service said is based on information from a wide range of sources:

• Although more research and development money is being spent in what the report calls "the animal pharma industry," the number of new animal drugs approved in the U.S. is dropping. That means more money is being spent to research and develop, on average, each newly approved animal drug.

• Approvals of food-animal antibiotics have declined both in number and as a share of approvals of all food-animal pharmaceuticals. (Drug companies make products other than antibiotics that are used in food animals.) Further, since 1992, most new antibiotic approvals for use in food animals have been generic drugs that are also used in human medicine.

• The number of new drug approvals for companion-animal (pet) products account for an increasing share of all new animal drug approvals in the United States. "Because most drugs are not approved for both food and companion-animal use, this finding suggests the increasing share of animal pharma R&D devoted to companion-animal pharmaceuticals comes at the expense of food-animal pharmaceuticals," the report said.

Livestock producers and others in agriculture are concerned that fewer antibiotics are being developed for use in food products. With fewer new drugs available, agriculturalists worry their ability to respond to livestock diseases will be hampered, the report said.

If that worry is true, the industry would be affected economically, and consumers would be hit with higher food prices, the report said.