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

ABSTRACT 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 wks. The 6 treatments fed the basal diet supplemented with 0 (control), 20, 40, 80, or 160 mg Zn/kg (ZnSO4•H2O). Dietary supplemental level at 80 mg/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