Biology / Health / Microbiology / Science

Antibiotic use in lifestock: surely it’s a good thing! Spoiler: it really isn’t

When I saw the first news piece about McDonald’s reducing the amounts of antibiotics used in their beef production, I was hardly surprised to see people panicking. “Surely antibiotics are a good thing! Reducing them means that livestock will be less healthy and humans could get sick! McDonald’s are just trying to skimp on health and safety to increase profits!”

So, a quick fact check! Antibiotics are fed to livestock to prevent the animals getting sick, yes. That’s not actually a good idea, for the exact same reason as humans don’t take antibiotics preventatively: antibiotics are best used in a targeted and concentrated dose to kill vulnerable bacteria. They kill beneficial bacteria (such as bacteria in the gut) as well, which can cause illness and discomfort on its own, and they enable antibiotic-resistant bacteria to multiply unchecked by the presence of other benign bacteria. It’s a breeding ground for resistance: only the resistant will survive, and then what are you going to treat the associated illnesses with?

But actually, antibiotics in animal husbandry are typically used for their properties as growth stimulants, not to keep the animals healthy. Low, sub-therapeutic doses — doses that wouldn’t be good at killing bacteria anyway — are given in food, and are thought to affect the gut flora of the animal, allowing it to take up more of the nutrients it has been fed. Regardless of the mechanism, it’s proven that animals given low levels of antibiotics grow faster on the same amount of food.

At the same time, the animals’ feed and excrement are chock-full of sub-therapeutic doses of antibiotics, and a barn is not a closed system. Other animals (mice, etc) consume bits of the feed, the excrement is used as manure, etc. More and more antibiotics get into the general environment, and again, foster resistance in bacteria, some of them harmful. The animals can harbour drug-resistant infections which can infect farm workers, and these infections will be untreatable by the antibiotics already used in the animal feed. At the same time, when the animal is slaughtered, the meat may be contaminated with drug-resistant bacteria. Humans who eat and particularly those who prepare it can then contract drug-resistant infections, untreatable by any of the antibiotics to which the original animal was exposed.

So McDonald’s reducing the levels of antibiotics used in their livestock is unequivocally a good thing. In principle, the practices of prophylactic use of antibiotics and the use of antibiotics to promote growth need to be eliminated from animal husbandry. There are counter-arguments — some experts feel that the impact on human health and the environment is actually negligible, particularly compared to the benefits of the increased livestock growth, and particularly in countries with food insecurity.

For my part, though, I applaud McDonald’s in taking a first and necessary step. We need to preserve the potency of the antibiotics (and antifungals, a similar and critical issue found in crop-based farming) that we have, and even small gains are important. We don’t have a limitless supply of options ready to implement.


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