The Man Who Turned Antibiotics Into Animal Feed–Post Script
Posted by Richard Conniff on March 10, 2014
In 2007, researchers at Johns Hopkins University analyzed industry data and found that, while antibiotics produced a slight weight gain in chickens, the cost exceeded the resulting commercial benefit. A 2010 study by the US Department of Agriculture likewise found “no statistically significant impact on production” in broiler chickens, and another USDA study in 2011 found significant gains in nursery pigs, but none in animals close to market size.
Data from Denmark and Sweden, where the use of antibiotics in food animals is restricted, clearly show that tight control of the practice “does not lead to long-term negative effects on industry”, says Tyler Smith, a researcher at The Johns Hopkins Center for a Livable Future. “We are squandering a medical miracle on the basis of very limited evidence that it is necessary to produce animals,” he says.
If antibiotics do boost weight gain, even temporarily, how might it happen? Do they inhibit “bad” bacteria that would otherwise impair growth? Do they slow microbial metabolism, freeing up more nutrients for the host animal? Do they thin the intestinal walls or otherwise make it easier for the animal to absorb nutrients? Nobody knows for sure.
One promising development for livestock producers and health advocates alike is that new genetic insights into an animal’s “microbiome” – the microbes that colonize its gut and other niches – may provide far more exact answers to these questions. Livestock producers are already testing beneficial bacteria and other mechanisms to tweak the bacterial processes in an animal’s gut. In one case, using “good” bacteria to crowd out “bad” ones, a strategy called competitive exclusion, reduced the salmonella load in factory-reared turkeys by 90%. That kind of precise control could soon render subtherapeutic antibiotics in animal feed irrelevant.