Pomegranate peel dietary supplementation in laying hens affects egg yolk color and eggshell quality, decreases yolk lipid oxidation and influences yolk lipidomic profile

Pomegranate peel is a byproduct of the pomegranate juice industry, rich in bioactive compounds. The objective of this study was to evaluate the quality and nutritional parameters of eggs from laying hens fed a diet supplemented with a pomegranate peel byproduct ( PPB ). A total of 48 Isa Brown laying hens were allotted to four groups (12 replicates per group) and offered the following diets for 8 weeks: Control (0% PPB); PPB1 (1% PPB); PPB2.5 (2.5% PPB); PPB5 (5% PPB). Eggs were collected and analyzed for egg quality parameters, yolk Malondialdehyde ( MDA ) levels, fatty acid profile, total phenol content, α-tocopherol, cholesterol and lipidomic profile. Sampling was performed weekly, whereas a complete egg quality analysis was performed every two weeks. The results showed that eggshell weight was greater in PPB5 group compared to Control and PPB1 ( P =0.008). Eggshell thickness was greater in PPB5 compared to PPB1 ( P =0.016). Egg shape index was increased in PPB2.5 treatment ( P =0.006). The higher PPB inclusion levels (2.5% and 5%) increased yolk coloration ( P =0.014) and reduced yolk MDA content ( P <0.001) compared to Control. However, cholesterol content was higher in PPB1 compared to Control ( P =0.028). Regarding lipidomic analysis, differentiations in yolk lipid profile were found in PPB2.5 and PPB5 yolks compared to Control ( P = 0.022 and P = 0.034 in ESI- and ESI+, respectively). Mainly ceramides were upregulated. Overall, PPB supplementation up to 5% in laying hens can improve several egg quality characteristics and reduce yolk lipid peroxidation.