Supplemental microalgal astaxanthin produced coordinated changes in intrinsic antioxidant systems of layer hens exposed to heat stress

Astaxanthin is a well-known antioxidant phytochemical that has limited bioavailability to humans. The present study was conducted to determine if microalgal astaxanthin was bioavailable to layer hens and affected antioxidant status of their 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, 10, 20, 40, and 80 mg/kg for 6 wk. Heat stress was induced during weeks 4-6 when the ambient temperature was raised 3 degrees C above the optimal temperature. Supplemental microalgal astaxanthin resulted in dose-dependent enrichments (P < 0.05) of astaxanthin and total carotenoids in the plasma and egg yolk of hens. The maximal concentrations of astaxanthin reached 4.1 mu g/mL, 5.8 mg/kg, and 36 mg/kg, whereas those of total carotenoids reached 7.0 mu g/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-S transferase in the liver of hens were decreased (P < 0.05) by the supplemental astaxanthin, compared with the control. Egg yolk color was changed (P < 0.05, more red) by the supplementation, and total PUFA concentration increased (P < 0.05) in the highest astaxanthin treatment group. In conclusion, supplemental dietary microalgal astaxanthin seemed to be highly bioavailable to be deposited in the plasma, liver, and eggs of hens, independent of heat stress, and resulted in coordinated changes in the intrinsic antioxidant systems.