This study was conducted to evaluate the effect of dietary zinc sources in inorganic or organic form on productive performance and egg quality of laying hens from 28 to 36 weeks of age. A total of 150 Hy-Line W-36 laying hens were distributed in a completely randomized design as a factorial management 2 × 2 + 1 with 5 treatments, 5 replicates and 6 hens in each. The dietary treatments consisted of a control diet (corn-soybean meal) without zinc supplementation, or the control diet supplemented with 80 or 120 mg/kg Zn as Zn-Methionine or Zn sulfate. Egg production (EP), egg weight (EW) and feed intake (FI) were recorded daily and weekly, respectively. This information was used to calculate egg mass (EM) and feed conversion ratio (FCR). Egg shape index, haugh unit, egg shell thickness, shell weight and yolk color were evaluated at 36 weeks of age. Statistical analysis was conducted using an analysis of variance (ANOVA) followed by the Duncan multiple test (P<0.05). No interactions were found between level and Zn source in any of traits studied. In the entire experimental period, FI, EW, EP, EM and FCR were not affected by level or Zn source (P>0.05). Egg shape index (76.7 vs. 75.3%; P<0.05) and egg shell thickness (0.561 vs. 0.526 mm; P<0.0001) were significantly increased by Zn-Methionine than Zn sulfate. However, egg characteristics were not affected by Zn level in the diet. Egg shell index was higher in control than other treatments (P<0.05). Results of this study have demonstrated that laying hens performance was not affected by source or level of Zn supplementation in the diet. Therefore, it is not necessary to increasing zinc in 120 mg/kg of diet. The dietary inclusion of Zn-Methionine could be utilized more effectively on egg shape index and egg shell thickness compared to Zn sulfate.
