EFFECTS OF DIETARY PALYGORSKITE SUPPLEMENTATION ON CECAL MICROBIAL COMMUNITY STRUCTURE AND THE ABUNDANCE OF ANTIBIOTIC-RESISTANT GENES IN BROILER CHICKENS FED WITH CHLORTETRACYCLINE

Antibiotic-resistant genes (ARGs) have been regarded as emerging contaminants that threaten public health worldwide. Poultry excreta, often used as a fertilizer in agriculture, are a major route for the proliferation and dissemination of ARGs in the environment. The aim of the present study was to assess the potential of dietary palygorskite (Plg) supplementation as nutritional manipulation for the modulation of microbial community structure and the attenuation of ARGs in the cecal contents of broilers fed with chlortetracycline (CTC). In total, 256 one-day-old, mixed-sex, broiler chicks were allocated randomly into a 2 × 2 factorial design of four treatments, which consisted of two levels of CTC (0 or 50 mg/kg) and Plg (0 or 10 g/kg). By employing in vivo feeding and slaughter experiments, after collecting the cecal contents and extracting the total genomic DNA, 16S rRNA V3-V4 hypervariable amplicon pyrosequencing and quantitative PCR-based approaches were used to address the impact of Plg on microbiota and the abundance of ARGs in broilers. The results showed that broilers given a diet supplemented with Plg had greater α-diversity indices including Chao1, phylogenetic diversity tree, and observed-species index calculations, when compared with those without Plg supplementation. Birds given a diet supplemented with Plg had fewer Firmicutes at the phylum level, but a greater abundance of Alistipes at the bacterial genus level. Dietary Plg counteracted the CTC-induced increased abundance of ARGs, among which tet(K) had a pronounced decrease, along with a similar decreased tendency for other measured ARGs and intI1. Overall, the results indicated that Plg supplementation caused pronounced changes in cecal microbial diversity and microbiota community composition of broilers, and effectively reduced ARGs, indicating that Plg supplementation is a potential alternative measure for the attenuation of ARGs in the cecal contents of broilers.