Various zinc sources and levels supplementation on performance, egg quality and blood parameters in laying hens

The objective of this study was to investigate the effects of dietary zinc (Zn) sources and levels supplementation on performance, egg quality, blood parameters, and egg yolk Zn content in laying hens from 28 to 36 weeks of age. Two hundred laying hens (Hy-Line W-36) were weighed individually and placed randomly in cages with five treatments, five replicates of 8 birds in each by 2×2+1 factorial arrangement. Treatments consisted of a control diet (corn-soybean meal as a basal diet without Zn supplementation) and the diet supplemented with 80 and 120 mg of Zn/kg, added as either Zinc-sulfate (ZnSulf) or Zn-methionine (ZnMet), respectively. No significant differences were observed for treatments on laying hen performance from 28 to 36 weeks of age. Eggshell thickness significantly improved (P<0.001) by ZnMet in comparison to ZnSulf. Eggshell thickness significantly improved by increasing Zn from 80 to 120 mg/kg of the diet (P<0.05). Plasma HDL (P<0.001), alkaline phosphatase activity (P<0.05), total protein, and albumin concentrations (P<0.001) were significantly increased by ZnMet in comparison to ZnSulf supplementation. Plasma Fe, Cu, Zn, P and Zn content of the egg yolk were not affected by Zn sources or levels. Plasma Ca was higher in hens receiving 120 mg/kg ZnMet/kg than other treatments (P<0.01). In conclusion, more positive effects on eggshell quality and some blood parameters were found by dietary ZnMet supplementation at 80 or 120 mg/kg diet than ZnSulf in laying hens under the conditions of this study.