Egg white composition, antioxidant capacity, serum and yolk lipids and oxidative damage of the oviduct magnum in laying hens fed diets contaminated with different concentrations of cadmium

Abstract

Total of 384 healthy 38-week-old hens were randomly divided into four treatments. Layers in four groups were fed a basal diet and a basal diet with Cd at the level of 15, 30 and 60 mg/kg for nine weeks. Results showed that Cd could dose-dependently deposited in magnum and a positive correlation occurred between the accumulation of Cd in magnum and Cd content in egg whites. When compared with control group, 60 mg/kg Cd decreased magnum ovomucin, ovalbumin, lysozyme and ovomucoid gene expressions, but increased avidin gene expression obviously. Hens receiving 60 mg/kg Cd exhibited a significant decrease in egg white ovalbumin content and its proportion in total protein and increase in total cholesterol and LDLC levels in serum and yolk. The level of GSH and activities of T-SOD and CAT in magnum and GSH-Px activity in egg white were decreased significantly, while MDA level in both magnum and egg white was increased obviously in 60 mg/kg Cd group. Besides, Cd induced oxidative stress, inflammation, endoplasmic reticulum stress (ERS) and mitophagy accompanied by a significant up-regulation of the expressions of Keap1, IL1β, TNFα, NF-κB, p65, p-p65, Grp78, CHOP, ATF4, ATF6, IRE1α, Grp94, PINK1, Parkin, Fundc1, GRP75, VDAC1, MCU, MFF, Bnip3 and LC3I/II and a significant down-regulation of the expressions of Nrf2, HO-1, SOD1, SOD2, SOD3, MFN1, MFN2 and PGC1α. These results indicated that Cd can increase serum and yolk cholesterol level and induce magnum oxidative stress, inflammation, ERS and mitophagy through Nrf2/NF-κB and IRE1α/IP3R/GRP75/VDAC1/MCU pathways, thus disrupting egg white composition. Highlights Cd exposure disrupted the synthesis of egg white protein in oviduct magnum and destroyed antioxidant status and protein composition in egg white. Cd exposure significant enhanced serum and yolk total cholesterol and LDL cholesterol levels. Cd exposure induced magnum oxidative stress, inflammation, ERS and mitophagy through Nrf2/NF-κB and IRE1α/IP3R/GRP75/VDAC1/MCU pathways.