The Addition of Marigold Extract to the Diet Improved the Performance of Laying Hens in the Late Laying Period by Increasing Their Antioxidant Capacity, Lipid Metabolism, and Microbial Composition

The decrease in the production performance of laying hens during the later laying stage can be attributed to multiple factors, chief among them being oxidative stress and disrupted lipid metabolism. Quercetagetin, the active component of marigold extract, is a flavonoid whose polyhydroxy structure has greater antioxidant capacity than other flavonoids. In this study, we determined whether adding marigold extract to the diet can improve the antioxidant capacity and lipid metabolism of late-laying hens to increase their performance. In total, 800 Lohmann laying hens (45 weeks old) were randomly assigned to five treatment groups, each consisting of eight replicates (20 hens per replicate). Throughout the experiment, which lasted 24 weeks, the hens were fed diets containing 0, 200, 400, 600, or 800 mg/kg marigold extract. The results of the study showed that the addition of marigold extract to the feed significantly increased the egg production rate and qualified egg rate and reduced the feed-to-egg ratio; it also reduced the levels of oxidized products in eggs, serum, and liver, and improved the antioxidant capacity of the organism. Mechanistic studies showed that marigold extract could activate the Keap1-Nrf2 signaling pathway and up-regulate the gene expression of CAT, SOD, GPX, and Nrf2. In addition, marigold extract increased HDL and VLDL content in the liver, decreased TC and LDL content, and alteration of the cecal microbial composition. In conclusion, marigold extract showed good application value and potential as a safe and effective antioxidant additive in the late laying stage of laying hens.