Why are antibiotics given to healthy farm animals?

Just as with humans, antibiotics are a crucial tool for treating infections and diseases in farm animals. This is especially true for animals raised in large numbers and in close contact with each other, where diseases can spread quickly. That’s why farmers sometimes give drugs to healthy animals as a preventive measure. Over time, farmers have noticed that animals that were constantly ingesting antibiotics grew bigger and faster. “The problem is that this rather liberal use of antibiotics increases the risk of antimicrobial resistance, which is a major problem not only for livestock, but also for humans,” says Greta Reintjes, a marine biologist and microbial ecologist who heads the Microbial-Carbohydrate Interactions Group at the University of Bremen. This risk is what led the European Union (EU) to ban the prophylactic use of antibiotics in 2022. “This legislation prohibits all routine use of antimicrobials, meaning they can only be used to treat an infected or sick animal,” explains Reintjes.

Although antibiotics are banned in Europe for healthy farm animals, it is still an established practice outside the EU. For example, in Canada, where intensive fattening is the dominant method of livestock farming, antibiotic use is more than three times higher than in the EU. “As it can be difficult and expensive to remove a sick animal from such a large herd, many farmers give antibiotics to the entire herd as a preventive measure,” says Reintjes. However, do the benefits of this approach outweigh the risks? Reintjes thinks not. “Personally, I don’t see any benefit,” he adds. “I think these practices are the result of prioritising production over health and safety.”

Having investigated alternatives to prophylactic antibiotic use within the RUMIC project, funded by the Marie Skłodowska-Curie Actions, Reintjes says that one of the easiest ways to keep animals healthy and prevent disease is through diet. For example, in Canada cattle are often fed concentrates to increase overall weight gain and thus be able to produce more meat. However, such a monotonous diet is not good for the cattle’s microbiome, making the animal – and therefore the herd – more susceptible to disease. “If cattle are fed a varied diet that includes fresh grass, mixed silage and hay, among other feeds, their microbiome will be diverse and healthy and ready to naturally combat harmful microbes should they try to develop, all without the need for antibiotics,” Reintjes explains. Reintjes also recommends feeding complex carbohydrates, which act as prebiotics. Prebiotics have been shown to support and improve animal performance and health by increasing the abundance of beneficial bacteria in the gut. “A healthy animal is less likely to suffer from disease, which reduces the need for antimicrobials at the source,” Reintjes concludes. You can read more about Reintjes’ research here .