Effects of Hesperidin and Naringin Dietary Supplementation on Egg Yolk Colour and Lipid Composition in Laying Hens

This research examines the effect of a 9-week feeding intervention on laying hens with flavonoid-enriched rations to modulate the colour and lipid quality of egg yolks. Triglycerides and phosphatidylcholine were the principal neutral and polar classes, respectively, as determined by TLC-FID. Oleic, palmitic, and linoleic were the major fatty acids (FAs) as determined by GC-FID/MS, while essential DHA predominated omega-3 FAs. Flavonoid supplementation did not markedly modify the total fat, lipid classes, or FA profile of yolks, whilst FAs were mostly affected by basal diet ingredients. However, higher-dose hesperidin and naringin improved the MUFA/PUFA ratio of yolk fatty acids. Egg yolks were not differentiated by colour or total carotenoid content irrespective of the feeding intervention. Study time, on the other hand, contributed to observed differences. Remarkably, a 1-week adaptation to a standardised regime proved adequate for the production of yolks with a homogenous colour profile, while incremental changes in the total carotenoids boosted red/yellow colouration. By completing the intervention, significant nutritional improvements emerged for all groups: (i) phosphatidylcholine levels increased; (ii) n-6/n-3 shifted to lower values; and (iii) peroxidisability indices diminished. The aforementioned findings, along with low atherogenic/thrombogenic indices and combined with the oxidative stability of yolk lipophilic constituents, feature eggs with consistent yolk colour and enhance lipid-rich yolks’ contribution towards a healthy diet.