Long History of Antibiotic Misuse in Livestock

It is now illegal to give livestock antibiotics to gain weight

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In the 1950s, farmers made a game-changing discovery: Healthy livestock that were given antibiotics gained weight. Although the amount of weight gained—about three percent—may seem insubstantial, 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 cited this increased superbug prevalence as a call to ban the practice of giving healthy livestock antibiotics. On January 3, 2017, it finally became illegal to administer antibiotics to cattle for the sole purpose of gaining weight (an off-label use).

Why Are Livestock 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 four 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 arisen or spreading. However, constant prophylactic or subtherapeutic use of antibiotics among livestock is very contentious.

Why Is Antibiotic Administration in Livestock Potentially Dangerous?

With the routine use of antibiotics in livestock, we've seen a bump in the number of antibiotic-resistant germs in the global population. For example, although once rare, fluoroquinolone resistance became much more common after the FDA allowed farmers to put fluoroquinolones like Baytril in animal feed and water. (Currently, federal law prohibits the extralabel use of Baytril. In other words, this drug can only be used to treat infection in animals.)

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 in livestock 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. However in 2013, the FDA proposed Guidance For Industry #213, or GFI #213, a voluntary proposal for the judicious use of antibiotics in livestock. In December 2016, the FDA updated this guidance. Also in 2016, manufacturers of animal antibiotics agreed to change or remove labels that promote the use of human antibiotics to fatten livestock. Consequently, off-label use of antibiotics in livestock is now illegal.

Looking back, GFI #213 encouraged the makers of veterinary antibiotics to switch antibiotics from over-the-counter to prescription and required that a veterinarian administer these drugs.The hope was that by making antibiotics less accessible and more tightly controlled, farmers would use these drugs only for disease and disease prevention.

In time, Elanco and Zoetis, two of the biggest manufacturers of animal antibiotics, agreed to comply with Guidance #213. Furthermore, Tyson, Purdue and Foster Farms all agreed to curb their practice of administering subtherapeutic antibiotics to livestock. Meanwhile, McDonald's, Popeye's and Wendy's no longer wanted to buy meat from producers that use antibiotics for subtherapeutic uses. Eventually, all industry producers of livestock antibiotics agreed to remove information from labels promoting the use of antibiotics for weight gain in cattle. Finally, much like in Canada, some European countries, and South Korea, this practice is now illegal in the United States.

Bottom Line

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. It's a very good thing that the practice of giving livestock antibiotics for weight gain is now banned in the United States.

Sources

 

Kuehn BM. FDA Moves to Curb Antibiotic Use in Livestock. JAMA. 2014.

Mathew AG. Antibiotic Resistance in Bacteria Associated with Food Animals: A United States Perspective of Livestock Production. Foodborne Pathogens and Disease. 2007.

Update on Implementation of FDA's Guidance for Industry #213. December 23, 2016. www.fda.gov.

 

 

 

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