Proteome and microbiota analysis reveals alterations of liver-gut axis under different stocking density of Peking ducks
The aim of this study was to determine the impact of stocking density on the liver proteome and cecal microbiota of Peking ducks. A total of 1,200 ducks with 21-day old were randomly allotted into 5 stocking density groups of 5, 6, 7, 8 and 9 ducks/m2, with 6 replicates for each group. At 40 days of age, duck serum and pectorals were collected for biochemical tests; liver and cecal contents of ducks were gathered for proteome and microbiota analysis, respectively. Serum MDA increased while pectorals T-AOC reduced linearly with enhancing stocking density. Duck lipid metabolism was altered under different stocking density as well. Serum LDL-C increased linearly with increasing stocking density. Proteome analysis revealed fatty acid biosynthesis proteins such as acyl-CoA synthetase family member 2 and fatty acid oxidation related proteins including acyl-CoA dehydrogenase long chain and acyl-coenzyme A oxidase were enriched in high stocking density group. Additionally, high stocking density increased oxidative response related proteins such as DDRGK domain containing 1 while diminished anti-oxidant capacity related proteins including regucalcin and catalase. 16S rDNA analysis revealed that higher stocking density was accompanied with decreased microbial diversity, as well as depletion of anti-inflammatory bacterial taxa, including Bacteroidales, Butyricimonas and Alistipe. In addition, decreased bile acid metabolism-associated bacteria such as Ruminococcaceae, Clostridiales and Desulfovibrionaceae were found in the high-density group. Both proteome and 16S rDNA results showed inflammation and chronic liver disease trend in the high-density group, which suggests the involvement of the liver-gut axis in oxidative stress.