The optimal dietary Zn requirement in meat ducks from 22 to 42 days of age: effects on growth performance, tibial characteristics, and feather follicle development

This study aimed to determine the optimal dietary zinc (Zn) requirement for meat ducks during days (d) 22-42. A total of 336 ducks were assigned to 1 of 6 dietary treatments supplemented with 0, 20, 40, 60, 80, or 100 mg/kg Zn in the form of ZnSO₄·7H₂O. Results showed that final body weight (FBW), average daily gain (ADG), and average daily feed intake (ADFI) increased linearly with increasing dietary Zn levels (P<0.05), while the Zn concentrations of the serum, tibia, liver, pancreas increased linearly and quadratically (P < 0.05). Dietary supplementation of 40-60 mg Zn/kg enhanced copper-zinc superoxide dismutase (CuZn-SOD) and glutathione peroxidase (GSH-PX) activities (P < 0.05) and reduced the malondialdehyde (MDA) content in serum (P<0.05). Supplementation with 80-100 mg Zn/kg improved tibial ash content and tibial density (P<0.05). Furthermore, supplementation of 100 mg Zn/kg improved feather quality and follicle development by upregulating TAK1, Smad2, and BMP2 mRNA expression and downregulating BMP4 mRNA expression (P < 0.05). Based on regression analysis, the optimal dietary Zn requirement was estimated to be 71.7-104.1 mg/kg when using a basal diet containing 25.5 mg Zn/kg. Furthermore, the dietary Zn requirement for improving bone and feather quality was higher than that for supporting growth.