Dietary Supplementation of Microalgal Astaxanthin Produced Dose-Dependent Enrichments of the Phytochemical and Elevations of Radical Absorbance Capacity in Tissues and Eggs of Layer Hens

Astaxanthin is a well-known antioxidant phytochemical that has limited bioavailability to humans. The present study was conducted to determine if astaxanthin present in full and defatted microalgae was bioavailable to layer hens and if dietary astaxanthin affected antioxidant status of the hens' tissues and eggs. A total of 50 White Leghorn Shavers (21-wk old) were divided into 5 groups (n = 10/group), caged individually in an environmentally-controlled room, and fed a corn-soybean meal basal diet supplemented with microalgal (Haematococcus pluvialis) astaxanthin (Heliae, Gibert, AZ) at 0, 20, 40, 60, and 80 mg/kg for 6 wk. Body weight, feed intake, and egg production and quality were recorded weekly. At the end of study, blood and eggs were collected from all hens and liver samples were collected from 6 hens/group for biochemical analysis. Data were analyzed by one-way ANOVA. Supplemental astaxanthin showed no effect on feed intake, body weight gain, egg production, and egg quality (component weights or shell thickness). Supplemental microalgal astaxanthin resulted in dose-dependent enrichments (P < 0.05) of astaxanthin and total carotenoids in the plasma, liver, and egg yolk of hens. The maximal concentrations of astaxanthin reached 4.1 µg/mL, 5.8 mg/kg, and 36 mg/kg, whereas those of total carotenoids reached 7.0 µg/mL, 75 mg/kg, and 114 mg/kg (on fresh tissue basis), respectively, in the plasma, liver, and egg yolk of hens. The oxygen radical absorbance capacity was also enhanced (P < 0.05) in a dose-dependent fashion in the liver and egg yolk of hens. Meanwhile, total glutathione concentration and activities of glutathione peroxidase and glutathione reductase in the liver of hens were decreased (P < 0.05) by the high dose of astaxanthin (80 mg/kg) supplementation, compared with the control. While the color of egg yolk was changed (P < 0.05, more orange) by the astaxanthin supplementation, there were no major changes in the fatty acid profiles of egg yolk caused by the diet treatments. In conclusion, supplemental dietary microalgal astaxanthin seemed to be highly bioavailable to be digested and deposited in the plasma, liver, and eggs of hens and to improve their antioxidant status, except at the highest dose of 80 mg/kg.