Age, not feed additives, affects antimicrobial resistance genes in chickens

For many years, antibiotics have been added to animal feed to help control harmful bacteria and improve growth. But amid concerns about antibiotic resistance—when bacteria adapt to survive treatments that would normally kill them—poultry producers are trying alternatives, including probiotics, which contain helpful bacteria, and essential oils, which come from plants and may have antimicrobial properties. Researchers at Penn State have now found that feeding broiler chickens an antibiotic, a probiotic or essential oils did not significantly affect the overall diversity of antimicrobial resistance genes. Instead, the chickens' age had a much stronger effect on the resistome—the collection of antimicrobial resistance genes—as the birds grew.