Sources, dynamics in vivo, and application of astaxanthin and lutein in laying hens: A review.

Astaxanthin (Ax) and lutein are important fat-soluble pigments and essential nutrients for human and animal health. Haematococcus pluvialis microalga and Phaffia rhodozyma yeast are ideal species for commercial Ax production. Marigold flowers are a main source of commercial lutein. Dynamics of dietary Ax and lutein in the gastrointestinal tract are similar to lipids, but their activities are tremendously challenged by many physiological and dietary factors; few data are available about these in poultry. Dietary Ax and lutein have insignificant effects on egg production and egg physical properties, but have pronounced effects on yolk color, nutrition, and functionality. The two pigments can also enhance antioxidative capacity and immune function of laying hens. A few studies have shown that Ax and lutein can improve fertilization and hatchability of laying hens. Considering the pigmentation and health benefits of Ax and lutein from hen feed to human food, the commercial availability, chicken yolk improvement, and immune function of Ax and lutein are the focuses of this review. The potential roles of carotenoids in the cytokine storm and gut microbiota are also briefly presented. The bioavailability, metabolism, and deposition of Ax and lutein in laying hens are suggested for future research.