Enhanced intestinal barrier function as the mechanism of antibiotic growth promoters in feed additives

Antibiotic growth promoters (AGPs) are a cost-effective tool for improving livestock productivity. However, antimicrobial-resistant bacteria have emerged, and the search for alternatives to AGPs has consequently intensified. To identify these alternatives without the risk of the emergence of antimicrobial resistance, it is important to determine the mechanism of action of AGPs and, subsequently, search for compounds with similar properties. We investigated the antimicrobial and anti-inflammatory activities and intestinal barrier function of several AGPs using epithelial and immune cells. At the minimum administered dose of antibiotics, which effectively function as a growth promoter, the mechanism of action is to enhance the intestinal barrier function, but not the antimicrobial activity as determined using Dunnett's test (n = 3, P < .05). Inflammatory response was dependent on the combination of antibiotics (100 µmol/L) and immune cells. The results suggest that future studies should screen for nonantibiotic compounds that ameliorate intestinal barrier function.