Effects of dietary lutein sources on lutein-enriched egg production and hepatic antioxidant system in laying hens

The present study was conducted to investigate the effects of two dietary lutein sources such as the commercial lutein and the emulsified crude extract of spinach containing lutein on the transfer of lutein into egg yolks as well as the antioxidant defense system in the liver of laying hens. A total of thirty-six, 24-week-old White leghorn hens were randomly assigned to a basal diet (CON) and that supplemented with a commercial lutein (LUT, 40 mg lutein /kg of diet) and the crude extract of spinach dissolved into oils with lecithin (ECE, 40 mg lutein/kg of diet) for 5 weeks. There was no difference in body weight and the relative live weight among dietary groups. The concentration of egg yolk lutein and yolk color significantly increased (P<0.05) in the LUT and ECE groups compared with the CON group. The LUT group showed a higher yolk lutein and much a lower variability of average yolk lutein content, although there was no significant difference in egg yolk lutein content between the LUT and ECE groups. In antioxidant activity, the specific activity of hepatic superoxide dismutase (SOD) in the LUT group was significantly (P<0.05) greater than that in the CON and ECE groups, whereas glutathione peroxidase (GPX) and glutathione S-transferase (GST) activities and lipid peroxidation were not affected by dietary sources of lutein. In conclusion, the dietary supplementation of lutein and the emulsified crude extract of spinach to laying hens resulted in a significant increases in the content of egg yolk lutein and yolk color, indicating that both supplements may potentially be applicable for the production of egg-enriched lutein in laying hens. This study also suggest that a commercial lutein more consistently produces the quality of lutein-enriched eggs and improves hepatic SOD activity compared with the emulsified crude extract of spinach.