Full-length 16S rRNA gene amplicon analysis of gut microbiota in pigs fed with different diets in growing and finishing stages

The present study utilized full-length 16S rRNA gene sequencing to investigate the impact of dietary protein content on the composition and function of gut microbiota, and to analyze the gut microbiota of pigs in the growing (30 kg) and finishing (120 kg) stages under different feeding conditions. The results indicated that the gut microbiota was significantly different between pigs fed high- and low-protein diets. Comparing fecal samples from pigs at 30 and 120 kg, pigs at 30 kg showed a significant increase in the relative abundance of <i>Clostridium butyricum</i>, whereas at 120 kg, the abundance of <i>Lactobacillus reuteri</i> and <i>Lactobacillus johnsonii</i> decreased. To access the functional profiles and metabolic pathways based on amplicon sequence variants (ASVs), the microbiome of the 120 kg exhibited significant enrichments in Kyoto Encyclopedia of Genes and Genomes (KEGG) pathways related to metabolism-related category, including Alanine, aspartate and glutamate metabolism, Tyrosine and Thiamin metabolism, and Inositol phosphate metabolism. Meanwhile, analysis using the MetaCyc database showed that the metabolic pathways of the 30 kg group were significantly distinct when compared to the 120 kg of fecal samples. Overall, the findings indicated that the gut microbiota composition and function in the 30 and 120 kg fecal samples were markedly shaped by different dietary protein levels.