Investigating the effect of different sources and levels of zinc on the immune performance and antioxidant capacity of laying hens

This experiment was conducted for 10 weeks (40 to 52 weeks old) to investigate the effect of different sources and levels of zinc on the immune and antioxidant performance of laying hens. For this purpose, 240 high-line laying hens (36-W) were used in a completely randomized design, with 8 treatments and 5 replications (6 birds per replication). The experimental treatments include 1- control (without zinc supplement), treatment 2, 3, and 4, respectively, including the control diet + 80, 120, and 160 mg/kg of zinc sulfate with a purity of 34%, and treatment 5, 6 and 7, respectively The control diet included 50, 75 and 100 mg/kg zinc hydroxy chloride with 55% purity, and treatment 8 included the control diet + 124 mg/kg zinc-methionine complex. The findings showed that, in general, different levels of zinc supplementation in organic and hydroxy form caused significant improvement in feed conversion ratio, shell weight, Haugh unit, and blood glucose reduction compared to other treatments. During the test, organic and hydroxy sources increased antibodies against the influenza vaccine (P<0.05). Also, treatments containing zinc supplements increased superoxide dismutase and total antioxidant capacity (P<0.05). This increase was associated with a decrease in serum malondialdehyde (P<0.05). Different levels and sources of zinc had no significant effect on shape index, yolk color, and glutathione peroxidase level (P<0.05). The results show that adding hydroxy chloride at 100 mg/kg can improve the antioxidant and safety indicators of eggs.