Egg Yolk Colour Depending upon the Composition of the Feeding Mixture for Laying Hens

The aim of this study was to verify the possibility of replacement of fish meal by specially treated meal made of yellow lupin seed in relation to the yolk colour. The experiment was performed with 72 laying hens divided into two groups. The experimental group including 36 laying hens received a feeding mixture containing meal made of yellow lupin seed (the JUNO variety) which replaced fish meal used as an animal protein component in feeding mixtures in the control group. Samples of eggs were collected monthly in the course of seven months to determine the colour of egg yolk. Yolk colour was determined by the spectrophotometric method using the CIELAB system. Measurement with the exclusion of gloss was carried out using a portable spectrophotometer. The average values of parameter L* decreased significantly (α = 0.05), which confirmed the darkening of eggs. Parameters a* showed a significant increase (ANOVA α = 0.01), whereas the differences in the individual months ranged from 1.1 to 3.9. Yolk had distinct red-orange colour. Parameters b* did not show significant differences, however, the yolk tended to have an intensive yellow colour. The presence of yellow lupin seed meal in the feeding mixture resulted in a more distinct yellow-red colour of egg yolk