The impacts of feeding milk with antibiotics on the fecal microbiome and antibiotic resistance genes in dairy calves

Abstract

The effects of ingestion of antibiotics on the microbiome of the young calf are not well understood. The objective of this study was to evaluate the effect of feeding milk containing pirlimycin on the prevalence of antibiotic resistance genes in the fecal microbiome of dairy calves using a metagenomic approach. In this study calves were assigned to either pasteurized whole milk (control; n = 5) or pasteurized whole milk containing 0.2 mg L−1 of pirlimycin (treatment; n = 5). Fecal samples were collected on days 1, 42, and 84. Functional analysis of DNA via metagenomic rapid annotations using subsystems technology revealed that pirlimycin had no effects on abundance of sequences coding for different cell functions except in the “phage, prophage, and transposable elements” category. Evaluation of the major antibiotic resistance types in samples via annotation against the Comprehensive Antibiotic Resistance Database analysis showed no difference between the two groups. The results of this study will help assess the risk of use of antibiotics in animal agriculture and increase our understanding of how antibiotics present in waste milk affects both calves and their manure, and will lay the groundwork for future research on manure treatment or other strategies to minimize any negative impacts.