Antimicrobial use in animals increased about 5 percent from 2006 to 2007, according to information from the Animal Health Institute.
Antimicrobials are used in animals for four purposes: disease treatment, disease control, disease prevention, and growth promotion and feed efficiency.
In a statement released in November 2008, the institute noted U.S. meat production increased by more than 2 billion pounds from 2006 to 2007, which may have contributed to the increase in antimicrobial use.
AHI figures also appear to indicate the percentage of antimicrobials used for growth and efficiency rose in 2007 from 5 percent to 13 percent. Ron Phillips, vice president for legislative and public affairs for the AHI, told JAVMA he thinks the actual change in use was smaller, and revisions to manufacturers' figures from previous years account for part of that rise.
Phillips also said it is likely some producers increased use of ionophores in response to dramatic increases in feed costs.
"If you're feeding grain to animals, that's your biggest input cost," Phillips said. "You're looking for any small way to increase efficiency in use."