Egg yolk colour in organic production as affected by feeding – Consequences for farmers and consumers.

• Spinach and marigold flower meals, colouring alternatives in organic egg production. • Dose-dependent variable lutein/zeaxanthin ratios in egg yolk indicate interactions. • Higher carotenoid transfer for spinach/marigold mixture vs. conventional source. In organic table egg production, saponified extracts of carotenoids are not allowed to intensify egg yolk colour. Therefore, we investigated the suitability of organically produced marigold flower meal (Tagetes erectus , TE) and spinach (Spinacia oleracea , SO) as carotenoid sources (mixture of 25% TE and 75% SO) to reach values of 9–10 'Roche Yolk Colour Fan' units (RYCF units). Feeding a completely unsupplemented control diet resulted in a yolk colour of 4.7 RYCF units, a total supply of 11.1 g/kg, 14.6 g/kg and 17.5 g/kg of TE and SO as stand-alone carotenoid sources induced a significant increase to 8.0, 8.2 and 8.9 RYCF units. Under 'winter-feeding conditions', i.e. minimal carotenoid supply in the diet, 17.5 g/kg TE and SO resulted in 9.3 ± 0.7 RYCF units. It can be concluded that supplementing TE and SO is suitable to improve the yolk colour in organically produced table eggs. [ABSTRACT FROM AUTHOR]