Effects of Leuconostoc lactis on the antioxidant ability and indole-3-acetaldehyde metabolism via regulating the gut microbiota-liver axis in aged laying hens

Lactobacillus has antioxidant properties that may benefit poultry production. However, there is no systematic research on antioxidant of Lactobacillus strain and its effects on regulating nutrient metabolism in aged laying hens. This study investigated the influence of Leuconostoc lactis on production and antioxidant capacity in aged laying hens and explored the key biomarkers associated with tryptophan-skatole metabolism and its effects on the intestinal microbiota-liver axis. Hens supplemented with L. lactis showed a higher laying rate, reduced hepatic MDA levels, and increased T-AOC in comparison with the control group (CG). Indole-3-acetaldehyde (IAld) levels were elevated in both feces and yolk, and skatole decreased in feces by the L. lactis group compared to CG. The total polyunsaturated fatty acids (PUFAs), C18:3n3, and C18:2n6c in yolk were raised in the L. lactis group relative to CG. In the liver, mRNA levels of AhR, CYP2D6, and CPT-1 were markedly upregulated in the L. lactis group relative to CG. The L. lactis-treated group also exhibited higher alpha diversity in fecal samples at 30 days and in ileal samples at 60 days. Further, we conducted the hepatocyte validation experiment and found that MDA levels were significantly reduced, and T-AOC was increased in both the L. lactis and IAld-treated groups compared with the CG. IAld treatment significantly affected p38, and NF-κB, and Nrf2 cytokine expression in hepatocytes. The findings provide a reference for the use of L. lactis in improving production and intestinal nutrition in aged laying hens.