Effects of Sunlight Illumination of Marigold Flower Meals on Egg Yolk Pigmentation.

The effect of sunlight illumination of marigold flower meal on the pigmentation of feed for laying hens and of their resulting egg yolks was evaluated by high-performance liquid chromatography and by subjective and light reflectance colorimetry techniques. Illumination did not have an effect on the identity of carotenoids in the flower meal. Interestingly, illuminated marigold flower meals yielded an oleoresin with a higher all-trans-zeaxanthin level, with respect to meals kept in darkness. A higher level of all-trans-zeaxanthin was also present in feed pigmented with that oleoresin. Additionally, this pigmented feed showed the best color values and resulted in egg yolks with good color; remarkably, these egg yolks had a low pigment content with respect to control treatments. Thus, sunlight illumination of marigold flower meal showed a positive effect on egg yolk color; the main factors contributing to this effect were not the identity or quantity of carotenoids in laying hen feed or egg yolks, but rather other as yet unidentified marigold component(s) which was (were) somehow influenced by sunlight illumination.