The Gut Microbiota of Broilers Reared with and without Antibiotic Treatment

The aim of this study was to examine the microbiota in broilers reared with and without antibiotics and to investigate differences between the upper, middle and lower sections of the gastrointestinal tract (GIT). One of two commercial flocks was treated with an antibiotic (T) (20 mg trimethoprim and 100 mg sulfamethoxazole per ml in the drinking water for 3 days) and the other was left untreated (UT). The GIT contents of 51 treated and untreated birds were aseptically removed from the upper (U), middle (M) and lower (L) sections. These were pooled in triplicate (n = 17 per section per flock), the DNA extracted and purified, 16S amplicon metagenomic sequencing performed and the resultant data analysed using a range of bioinformatics software. There were significant differences in the microbiota of the upper, middle and lower GIT, and treatment with the antibiotic significantly affected the microbiota in each of these sections. This study provides new data on broiler GIT microbiota and suggests that GIT location is a more important determinant of the constituent bacterial flora rather than the use or otherwise of antimicrobial treatments, at least when applied early in the production cycle.