Timna Wyckoff knows more about bacterial organisms than 99.99 percent of the American public. So, when she suggests prudent use of antibiotics in farm animals, people really ought to listen.

Her graduate and post-doctorate research was devoted to finding the weakness in bacterial organisms — the proverbial Achilles heel — that would make them more susceptible to antimicrobial therapies. But the more she came to understand these organisms, the more she learned about their ability to adapt, evolve, mutate, exchange genes and even resist the effects of antibiotics.

A paradox exists in that the more antibiotics are used, the more likely it is that resistant bacteria will develop, says Wyckoff, assistant professor of biology at the University of Minnesota-Morris.  So, it would be wise to use the antibiotics judiciously, she adds, “because the paradox will exist every time we use them.”

As more and more consumers catch wind of this, you may find yourself having to defend the use of antibiotics in farm animals. Here is pertinent background, along with some of the answers you might provide. 

No smoking gun

Wyckoff and her students surveyed eight organic dairies and eight conventional dairies within a 100-mile radius of Morris, Minn. (The dairies were generally in the 20- to 100-cow range.) They gathered milk samples from the farms and took them back to the lab, looking for one type of bacteria in particular -— Staphylococcus — and the bacteria’s resistance to antibiotics.

“Our preliminary results suggest that bacteria on conventional farms are more resistant (to antibiotics) than those on organic farms,” Wyckoff says. 

One would reasonably expect this to occur because the selection pressure is greater on farms that use antibiotics — in the face of antimicrobial agents, some bacterial organisms will die or be placed at a competitive disadvantage, while others will adapt and survive. This has been borne out by other studies, including one in the January 2005 Journal of Antimicrobial Chemotherapy in which researchers cited higher antibiotic-resistance among enterococci bacteria found on farms using antimicrobial agents. 

What does this mean for human health? According to the book, “The Antibiotic Paradox” by Stuart Levy, farm workers can pick up resistant bacteria in the course of everyday contact with animals. “Farm workers who are in contact with animals have high levels of resistant bacteria in their normal intestinal flora,” Levy writes. 

But Levy stops short of suggesting these farm workers have more health problems than the normal population. “There is no evidence that these workers have more disease than their counterparts working without antibiotics,” he writes.

Levy’s book leads the reader to believe there’s some sort of threat or presumptive risk that must be addressed. But no one knows for certain if the use of antibiotics in farm animals does, indeed, present a human-health risk. 

“There’s still no smoking-gun study to show a link between human antibiotic resistance and the use of low-level antibiotics on farm,” says Steve Kopperud, senior vice president of Policy Directions, Inc., a Washington D.C., government-affairs firm that specializes in agriculture, food and health-related issues.

Often necessary

Kopperud agrees that consumers have every right to be concerned about antibiotic use. But it’s an issue that should also be placed in the proper context.

He says the livestock industry has shown responsibility and professionalism in the use of antibiotics. For instance:

  • In the late 1990s, the American Veterinary Medical Association adopted guidelines for the judicious use of antimicrobials. The guidelines encourage preventative measures, such as good animal husbandry, to ward off health problems. But if veterinarians must intervene with therapy, they are encouraged to consider other therapeutic options before using antimicrobials. 
  • The AVMA guidelines have been embraced by producer groups.
  • The livestock industry is using more and more antibiotics labeled for animal use  only. In fact, an entire class of antibiotics, known as ionophores, is devoted to this purpose.  

Furthermore, a comprehensive review of the scientific literature led several American and European researchers to write in the January 2004 Journal of Antimicrobial Chemotherapy that the actual danger to human health (from the use of antibiotics in food animals) is small. “Although some antibiotics are used both in animals and humans, most of the resistance problem in humans has arisen from human use,” they wrote.

In other words, before anyone points a finger at the use of antibiotics on farms, they ought to be looking at the overuse of antibiotics in human medicine. 

For instance, a mother takes her child to a doctor’s office for a cold or flu. Antibiotics are not what she needs since the problem is viral in nature. Yet, how many times will she ask for them anyway? How many times will a doctor prescribe them just to keep her happy?

“Despite physicians’ advice to the contrary, a person searching long enough will eventually find a physician who will prescribe an antibiotic, even when one is not indicated,” Levy, a medical doctor, writes in his book, “The Antibiotic Paradox.”  

As Kopperud alluded to earlier, the issue needs to be placed in proper context. Without a definitive link between the use of antibiotics in farm animals and resistance problems in humans, everything else is simply based on supposition or hearsay.

The next time a person expresses concern to you about the use of antibiotics in farm animals, point these things out to them.


For more information

be sure to look for quarterly inserts in dairy herd management known as “For the Record.” Past issues of “For the Record” may be found at the Web site  www.alpharma.com/newahd/pages/default.aspx


Fewer and fewer residues found on tankers

since 1996, the percentage of bulk tank samples found positive for animal-drug residues has declined. These samples are from tanker trucks. They constitute the vast majority of samples reported each year in the Food and Drug Administration’s National Milk Drug Residue Data Base.

 Year  % positive for drug residues
 2005  0.038 
 2004 0.044
 2003  0.053
 2002  0.061 
 2001 0.067
 2000  0.073
1999 0.085
1998 0.088
1997 0.093
1996 0.104

Reported on a fiscal-year basis. Fiscal year 2005 began on Oct. 1, 2004 and ended on Sept. 30, 2005.


Talking points

1.  Do cows receive antibiotics like people do?

  • Yes, sometimes cows get pneumonia or infections. Without antibiotic treatment, the cows could die or become seriously ill.  So, it is simply humane to treat them — and make them well again.
  • Growth-promoting antibiotics are not used on milk cows. Only therapeutic and prophylactic antibiotics are used — and, again, very sparingly. 
  • If a cow is treated with antibiotics, the milk from that cow is disposed of and does not reach the food supply.

2.  Are there antibiotics in milk?

  • No, every tanker load that arrives at a milk-processing plant is tested for antibiotics. Any tanker that tests positive is disposed of immediately, never reaching the public. In addition, milk is tested several times during processing.