Integrated metagenomics and metabolomic to reveal the effects of dietary comfrey polysaccharides on the oxidative stability and fatty acid composition of egg yolks in laying hens.

This study investigated the influences of comfrey (Symphytum officinale L.) polysaccharides (CPs) in the diet of laying hens on the oxidation stability and fatty acid composition of the egg yolks based on metagenomic and metabolomics techniques. Dietary CPs improved the total phenolic content in fresh and stored eggs. The activity of superoxide dismutase was increased, and the content of malondialdehyde was reduced in the stored eggs of the 1.0 % group of CPs. Dietary supplementation with 1.0 % CPs increased some polyunsaturated fatty acid (PUFA) contents in stored egg yolk, including dihomo-γ-linolenic acid (C20:3n6), arachidonic acid (C20:4n6), and docosahexaenoic acid (C22:6n3). The abundances of Methanobrevibacter, Parabacteroides, and Merdibacter in the caecum were increased in the 1.0 % group of CPs. The content of melatonin was increased, and the contents of palmitic acid and myristic acid in the caecum were decreased by CPs. These results suggested that CPs could improve the antioxidant status and fatty acid composition of egg yolks.