Effect of excess dietary fluoride on laying performance and antioxidant capacity of laying hens
The objective of this study was to investigate the effects of excess dietary fluoride (F) on laying performance and antioxidant capacity of laying hens. A total of 576 laying hens, 51 wk old, was randomly divided into 6 groups, each of which included 6 replicates of 16 hens. Graded amounts of sodium fluoride (NaF) were added to the basal diet to achieve concentrations of 16 (control), 200, 400, 600, 800, and 1,000 mg/kg F, respectively. Dietary F at 1,000 mg/kg significantly decreased ADFI, laying rate, and average egg weight, and increased feed conversion ratio (FCR) (P < 0.05). No significant differences were observed in serum total antioxidant capacity (T-AOC) level or catalase (CAT) concentration among all the treatments, while hens fed F at 800 and 1,000 mg/kg had higher activity of serum glutathione peroxidase (GSH-PX) and concentration of malondialdehyde (MDA) (P < 0.05) as compared to the control group. Compared with the control group, dietary F at 400 mg/kg increased liver MDA concentration (P < 0.001), and decreased CAT concentration of liver (P < 0.001); 600 mg/kg F decreased liver T-AOC levels (P < 0.001); and 800 mg/kg of F decreased liver total superoxide dismutases (T-SOD) activity (P < 0.001). Compared with the control group, feeding F at 600 mg/kg decreased kidney T-AOC levels and T-SOD activity (P < 0.001), and increased MDA concentration of kidney (P < 0.001), while dietary 1,000 mg/kg of F decreased kidney GSH-PX activity (P < 0.05) and CAT concentration (P < 0.001). In conclusion, these results indicated that excessive F ingestion had an adverse effect on laying performance by inducing oxidative stress and impairing the antioxidant system of laying hens.