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Low doses of antibiotics are commonly added to animal feed in the U.S. to prevent disease and promote growth. However, there is widespread concern that this practice is contributing to the problem of antibiotic resistance.
To evaluate the effect of in-feed antibiotics on the intestinal microbiome of swine, researchers studied six pig littermates that were born to a sow with no prior antibiotic exposure and were housed in a highly controlled environment. Beginning at age 18 weeks, three of the piglets ate a feed containing low doses of chlortetracycline, sulfamethazine, and penicillin, and three ate the same feed without antibiotics. Fecal samples for analysis were obtained at baseline and on day 14 of medicated feed.
In the medicated piglets,…