Use of antibiotics in livestock has been surrounded by controversy since the practice began in the 1940s. The primary target has been the low-level, or sub-therapeutic, use of antibiotics, primarily to promote growth in livestock.

There are two reasons the practice concerns some health officials. First, residues may remain in the end product, though the breakdown of active ingredients in the drug, and specific withdrawal times before harvest, limit this threat. Second, some bacteria become resistant to antimicrobial drugs.

The latter concern is why the debate over antibiotic use in animals continues. In July, the Food and Drug Administration (FDA), for the first time since banning chloramphenicol in food animals, pulled approval for another antibiotic previously okayed for use in food-animal production. The ban on enrofloxacin use in poultry to treat important diseases was driven by concerns its therapeutic use in poultry could cause bacterial resistance to the human form of the antibiotic, Cipro.

According to FDA: “Enrofloxacin does not completely eliminate Campylobacter from the birds' intestinal tracts, and those Campylobacter bacteria that survive are resistant to fluoroquinoline drugs. These resistant bacteria multiply in the digestive tracts of poultry and persist and spread through transportation and slaughter, and are found on chicken carcasses in slaughter plants and retail poultry meats.”

This decision has many folks concerned it portends a wider government crackdown on antibiotic use in livestock production.

Antibiotic use in livestock

Antibiotics are an important tool for cattle producers to ensure the health of their animals, says the Animal Health Institute (AHI), a trade association for animal health product manufacturers. All antibiotics used in food-animal production undergo stringent review by FDA to ensure a safe food supply for the end consumer, AHI says, adding that these products have three basic purposes for use in livestock — disease treatment, disease prevention and performance enhancement.

“We typically think of antibiotics used as performance enhancers as being fed at a somewhat lower dosage and for a longer period of time than for disease treatment,” says Gay Miller, a University of Illinois veterinarian who has studied the impacts of antibiotic use in swine production.

This technology has improved beef cattle's overall efficiency to utilize feed and other resources, has enhanced the health and reproduction of cattle, and improved their welfare, states the report “Fifty Years of Pharmaceutical Technology,” by Tom Elam and Rod Preston.

Miller adds the benefits also include lower costs to consumers as a result of the improved efficiency.

But, antibiotic resistance has become an issue of increasing global concern in food animal production — especially in regard to resistant strains of Campylobacter, E. coli and Salmonella.

“Of course, it raises concerns about resistance issues… but from my perspective the most important thing to reflect on with regard to antibiotic resistance is from a benefit/cost perspective,” Miller says.

“And to date, science has not found a link between the use of antibiotics in food animals and development of resistant bacteria that might compromise the efficacy of related antibiotics in human medicine,” according to the National Cattlemen's Beef Association Web site, www.beefusa.org.

Even so, this fear has caused international urgings to limit or ban the use of antibiotics as growth promotants (AGPs). In fact, several countries in the European Union (EU) have banned AGP use in livestock production. In January, all such use in livestock will be banned in EU member countries.

And, in June 2003, McDonald's Corp. announced its direct suppliers would be prohibited from using antibiotics that are important to human medicine as AGPs in animals after 2004. The firm also says it intends to create purchasing preferences for companies that work to minimize antibiotic use, according to a report from the Center for Agriculture and Rural Development (CARD) at Iowa State University (ISU) in Ames.

The Denmark experience

To offer some insight on how an industry-wide ban on AGPs could affect the U.S. food animal production, a look at Denmark's AGP ban in swine production provides some comparable evidence. The world's leader in pork exports, Denmark's swine industry is at least as sophisticated as that of the U.S.

Denmark first banned AGPs in swine finishing in 1998. After the ban, few health problems were reported and total antibiotic use was cut by more than 50%.

The reason for the ban, says Scott Hurd, associate professor of epidemiology and risk assessment at ISU, was because: “They felt there was a human health risk for using antibiotics in swine.

“Their concern is they are seeing increased levels of resistance in humans to certain drugs like avoparcin and fluoroquinolines. So that's what they were responding to,” he adds.

Hurd says the ban was a precautionary measure, and only blocked the usage of AGPs. Danish producers can still use antibiotics for disease treatment following diagnosis.

In 2000, Denmark extended the ban on AGPs into the weaning phase of production. That's when farmers ran into trouble, reporting significant health problems and a rise in mortality rates among piglets. Therapeutic use of antibiotics rose dramatically.

Now, five years after the ban was first enacted, swine producers are still feeling the effects. Hurd, and a group of practitioners and producers, recently visited Denmark to speak with producers, veterinarians and health officials to measure the economic impact and animal health impact of the ban.

From his visit, he learned several things about the impact the ban has had on pork production.

“We saw that the ban on AGPs did have a significant impact on animal health. So, that meant what we thought was just growth promotion was apparently preventing a lot of disease,” Hurd says.

“And, related to that, the effect on animal health still remains in Denmark. They haven't been able to manage their way out of it,” he adds.

A second, more interesting fact Hurd uncovered is that based on the data so far, Denmark's AGP policy has done nothing to improve human health. Resistance levels in humans haven't decreased, nor have human rates of food-borne illness.

“Instead, Danish officials claim their strategy is successful because they reduced the number of antibiotics used,” Hurd says. “They never pegged any predictions on reducing antibiotic resistance.”

Reducing antibiotic use?

Since the ban only targets AGPs, antibiotics are still used in disease treatment, and the numbers of animals requiring antibiotics for such therapeutic treatment has increased dramatically, Hurd says. In fact, the actual amount of drugs used for treatment purposes has gone up more than 100%.

But overall, the tons of antibiotics used in Danish swine production has been halved. Hurd says about 150 tons of antibiotics/year were used before the ban — the last five years have averaged about 70 tons/year.

In its report, CARD estimates that if the U.S. implemented a similar ban, first-year costs would increase by $4.50/animal. During a 10-year period, losses would be estimated to exceed $700 million.

“The take-home message is everyone has to remember Denmark is a very small country — they don't have that many pigs or that many people. Take that small change and multiply it by 100 to compare it to the U.S., and the impacts are much bigger,” Hurd says. “And, there has been no demonstrated human health impact, but there has been a significant animal health impact. Those are the tradeoffs we are measuring right now.”