Livestock farmers are always looking for ways to keep their animals healthy and help them grow bigger and faster to meet demand. One tried-and-true method of doing this is with antibiotics, which farmers have been using since the 1950′s when intensive farming was first developed. But the overuse of antibiotics in livestock has contributed to the development of antibiotic-resistant bacteria, which cause very difficult-to-treat infections and endanger human lives. This past year, for example, the CDC issued a warning about antibiotic-resistant Salmonella in several raw chicken brands.
More recently, researchers have begun looking for alternatives to antibiotics for livestock farming. They’re turning to a different -biotic: probiotics. Probiotics are beneficial microbes, chiefly bacteria, that have become popular health supplements. They occur naturally in fermented foods (like yogurt, kefir, and sauerkraut) or can be purchased in pill form. Currently, most studies of probiotics focus on human health and wellness; however, the first reference to probiotics as dietary supplements to improve health (in 1974!) described them as a component of animal feed. Scientists have been interested in the application of probiotics to animal husbandry since the 1980′s, and in the 1990′s, scientists began investigating their use in seafood production as well.
As a result, many livestock farmers turned to probiotics to supplement their animals’ diets, but they still use antibiotics in large amounts. The problem is that probiotics do not produce consistently larger or healthier animals when applied on the farm. Since probiotics vary so much in terms of the bacterial species they contain as well how they are used (for example, at what age pigs are initially given probiotics), scientists struggle to draw firm conclusions about their benefits. As such, when farmers’ economic livelihoods are on the line, it is understandable that some may be wary of making radical changes to their farming practice, such as by replacing antibiotics with probiotics wholesale.

Another challenge in switching farmers from using antibiotics to probiotics is that, unlike antibiotics, probiotics interact with bacteria already in the animal’s gut. Since every pig has a slightly different gut bacterial community, the same probiotic might have different effects on each animal. To better tailor probiotics, researchers may one day have to know exactly which microbes are usually found in which animals, as well as how each one contributes to health. With the development of new DNA sequencing technologies, someday farmers may be able to send a sample from each of their animals’ digestive systems to scientists, who will send back an overview of the microbes already in the animals’ bodies and tips for which ones to add to maximize health and growth.
Another option is that scientists might eventually be able to use genetic engineering to improve the bacteria found in the probiotics themselves. Researchers are already exploring genetically-engineered bacteria as a potential treatment for numerous illnesses. Custom-designed probiotic bacteria would eliminate the need to run trial-and-error studies to determine which probiotics work best for which livestock