Effects of dietary Zn-methionine supplementation on the laying performance, egg quality, antioxidant capacity, and serum parameters of laying hens

ABSTRACT This study was to determine the effects of dietary Zn-methionine (Zn-Met) supplementation on the laying performance, egg quality, antioxidant capacity, and serum parameters of laying hens. Jingh ong-1 strain laying hens (n = 720, 49 wk of age) were randomly assigned to 6 treatments with 6 replications of 20 birds. The control was fed a basal diet supplemented with 80 mg of Zn/kg as Zn sulphate of diet and the 5 groups were fed a basal diet supplemented with 20, 40, 60, 80, and 100 mg of Zn/kg as Zn-Met of diet for 10 wk, respectively. At the terminal experiment, there were significant differences between control and 80 mg/kg Zn-Met group in feed intake (P < 0.05) and feed conversion ratio (FCR) (P < 0.01). Egg weight (P < 0.05) and albumen height (P < 0.01) reduced and were not significantly influenced by supplemental 80 mg/kg Zn-Met group until being stored 15 d as compared to the control. Zn-Met group in 100 mg/kg significantly increased haugh unit (P < 0.05) as compared to the control. The activity of MDA in serum had a linear decrease in 20 to 100 mg/kg Zn-Met. The activity of CAT in liver and GSH-Px in serum had quadratic effects in response to the Zn-Met treatments. Compared to the control, 60 mg/kg Zn-Met group increased the T-AOC, GSH-Px activity in serum (P < 0.01), and the T-AOC (P < 0.05), CuZnSOD (P < 0.01), GSH-Px (P < 0.01) activity in liver. Compared with the control, the concentration of serum ionic Ca in 80, 100 mg/kg Zn-Met treatments reduced (P < 0.01) significantly while the activity of serum alkaline phosphatase (AKP) increased in the Zn-Met groups of 40, 60, and 80 mg/kg (P < 0.01), and 100 mg/kg (P < 0.05). In conclusion, dietary Zn-Met supplementation at 60 to 80 mg/kg had more positive effects on performance, egg quality, and antioxidant capacity in laying hens as compared to 80 mg/kg ZnSO4.