Effects of dietary cadmium supplementation on production performance, cadmium residue in eggs, and hepatic damage in laying hens

This study was conducted to investigate the adverse effects of cadmium (Cd) on the production performance, serum biochemistry, liver antioxidant status, histopathology, and egg residue in laying hens. A total of 72 healthy Hy-Line brown laying hens at 40-week-old were randomly assigned to four diets containing 0 (control diet), 15, 30, or 60 mg/kg Cd for 6 weeks. Laying hens exposed to 60 mg/kg Cd had lower egg production rate and worse feed to egg ratio (P< 0.05). Dietary Cd exposure (>= 15 mg/kg) significantly decreased hepatic glutathione peroxide (GPX) activities, while increasing malondialdehyde (MDA) (P< 0.05). Hepatic histopathology and ultrastructure also showed damage and the symptoms were exacerbated in a dose-dependent manner. The residue of Cd in the yolk was increased with increasing dietary Cd concentration. The mRNA expression levels ofmt4L, mt3, sod1, sod2, gpx1, gpx3, andgpx4in the liver of laying hens exposed to 60 mg Cd/kg feed were significantly decreased (P< 0.05). In conclusion, dietary Cd exposure at >= 15 mg/kg induced hepatic damage in laying hens, indicating that the content of Cd in feed must be critically controlled.