Dietary zinc supplementation affects eggshell quality and ultrastructure in commercial laying ducks by influencing calcium metabolism.

This study evaluated dietary Zn supplementation on productive performance, eggshell quality and ultrastructure, and calcium metabolism during eggshell formation in laying ducks. A total of 360 Longyan laying ducks (45-wk) were randomly divided into 5 treatment groups with 6 replicates of 12 birds each and fed for 20 wk. The 6 treatments fed the basal diet supplemented with 0 (control), 20, 40, 80, or 160mg Zn/kg (ZnSO₄.H₂O). Dietary supplemental level at 80mg/kg increased egg production (4.3%) and mass (5.7%), and decreased FCR (2.9%) compared to the basal diet, and these indices increased quadratically with increasing Zn supplemental levels (P < 0.05). The shell breaking strength (15.8%) and fracture toughness (10.6%) were higher with the supplementation of Zn at 80mg/kg than the basal diet, and increased quadratically with Zn supplementation (P < 0.05). Dietary supplementation of Zn at 80mg/kg improved shell ultrastructure by increasing total...