Antibiotic Misuse in Livestock

Misuse of antibiotics in livestock leads to antibiotic resistance

In the 1950s, farmers made a game-changing discovery: Healthy livestock that was given antibiotics gained weight.  Although the amount of weight gained--about 3 percent--may seem insignificant, in a large-scale industry where every ounce counts, even a weight gain of a few pounds per cow could mean tens of millions of dollars. 

In 1995, the FDA approved the addition of antibiotics to livestock feed and water.

Ever since that time, we've seen a dramatic increase in the prevalence of drug-resistant bacteria (antibiotic resistance). For example, 20 percent of all ground meat contains salmonella that is drug resistant. Many people cite this increased superbug prevalence as a call to ban the practice of giving livestock without disease antibiotics. 

Why are livestock animals given antibiotics?

Although the exact number is hard to gauge, it's estimated that between 15 and 17 million pounds of antibiotics are administered to livestock every year. Another estimate pegs the number at 18 percent of the 22.7 million kilograms of antibiotics produced in the United States per annum

Livestock animals are given antibiotics for 4 reasons:

  • therapeutic uses to treat sick animals;
  • metaphylaxis or when one animal in a herd or flock gets sick and all the animals are given short-term antibiotic treatment to prevent the spread of disease;
  • prophylaxis to prevent disease from occurring in livestock;
  • subtherapeutic uses where antibiotics are used for weight gain or improved meat quality in livestock.

Sometimes farmers need to give their animals antibiotics like when they get sick (therapeutic uses) or when serious infection threatens the farm (metaphylaxis).

Such administration is short term and intended to battle infection that has already reared its ugly head. However, constant prophylactic or subtherapeutic use of antibiotics among livestock is contentious.

Why is antibiotic administration to livestock potentially dangerous?

With the routine use of antibiotics in livestock, we've seen a bump in the number of antibiotic-resistant bugs in the global population. For example, although once rare, fluoroquinolone resistance has become much more common after the FDA allowed farmers to put fluoroquinolones like Baytril in animal feed and water.

Researchers believe that antibiotics given to livestock at subtherapeutic levels kill off some normal bacteria flora. By killing off this normal flora, animals can digest their food better, less food is required to feed them and less excrement is produced. However, some drug-resistant bacteria flora manage to survive the antibiotics onslaught and make their way into the food supply.  When people consume improperly cooked food, this bacteria infects humans.

Furthermore, some studies show that handlers of these animals can be infected by these drug-resistant bacteria merely by touching the livestock.

Even though subtherapeutic antibiotic administration likely contributes to increased prevalence in drug-resistant strains of salmonella, E. coli and so forth in human populations, actual proof that an increased prevalence of these superbugs has lead to disease is elusive. Moreover, increased prevalence of drug-resistant bacteria is by no means solely attributable to livestock antibiotic use alone.  Antibiotic misuse and overprescription also contribute to the problem. Along with warnings of increased cost caused by the discontinuation of subtherapeutic antibiotic administration, meat producers also cite these other reasons in their argument to maintain the practice.

What's the FDA doing about antibiotic misuse in livestock?

Meat lobbies are powerful forces. A mandatory move by the FDA to control the use of subtherapeutic antibiotics in livestock would be met with protracted and costly legal battles. Fearing these repercussions, in 2013, the FDA proposed Guidance #213, a voluntary proposal for the judicious use of antibiotics in livestock.

Guidance #213 encourages the makers of veterinary antibiotics to switch antibiotics from over the counter to prescription and require that a veterinarian administers these drugs.The hope being that by making antibiotics less accessible and more tightly controlled, farmers will use these drugs only for disease and disease prevention.

So far, Elanco and Zoetis, two of the biggest manufacturers of animal antibiotics, have agreed to comply with Guidance #213. Furthermore, Tyson, Purdue and Foster Farms have all agreed to curb their practice of administering subtherapeutic antibiotics to livestock. Meanwhile, McDonald's, Popeye's and Wendy's no longer want to buy meat from producers that use antibiotics for subtherapeutic uses. Nevertheless, we're far from ridding the food chain of antibiotic misuse altogether--something Canada, some European countries, and South Korea have all done.

Without a doubt, it's disquieting to think that ever mouthful of your medium-rare Porterhouse steak could be loaded with drug-resistant bacteria. (This disgusting thought likely underlies the PR-fueled decision for fast-food giants like Mickey D's to slash such meat from their menus.) Keep in mind, however, that some antibiotics are needed to keep our meat clean and healthy.  Instead, it's the misuse of antibiotics that's the problem and reflects a larger pattern of antibiotic misuse and overprescription that plagues every facet of the healthcare system.

Increased antibiotic resistance--especially in our last-resort antibiotics like fluoroquinolones--may someday mean that these drugs will no longer work. We will no longer be protected by our medicines!  With animals taking the same antibiotics that we do, the fear of antibiotic resistance is particularly salient. Animals like hogs serve as perfect incubators for the selection and recombination of drug-resistant bacterial strains. In fact, when these bacteria recombine in livestock, islands of genetic material (called integrins) are usually exchanged which confer multi- (not single) drug resistance. 


Selected Sources

Article titled "Antibiotic Resistance in Bacteria Associated with Food Animals: A United States Perspective of Livestock Production" by AG Mathew and co-authors from Foodborne Pathogens and Disease published in 2007.  Accessed on 5/13/2015.

Article titled "FDA Moves to Curb Antibiotic Use in Livestock" by BM Kuehn from JAMA published in 2014.  Accessed on 5/12/2015.



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