Effects of dietary supplementation of organic and inorganic zinc on the performance characteristics, tissue mineralization, apparent mineral retention, and antioxidant status of broiler chicks

A 10-day study was carried out to evaluated the effects of organic (zinc proteinate, ZnPro) and inorganic (zinc sulfate, ZnSO₄•H₂O) zinc supplementation on growth, tissue mineralization, mineral excretion, and antioxidant responses in broiler chickens. Male Cobb 500 chicks were allotted into 10 treatments, and ten replicates per treatment with five birds per replicate in a 2 × 5 factorial design. Dietary Zn was supplied at 0, 19, 38, 57, and 76 mg/kg. ZnPro feeds included proteinates for copper, iron, and manganese, while Zn-sulfate diets used inorganic salts. Results Body weight (BW) and average daily gain (ADG) improved at 19 mg Zn/kg for both sources. Feed conversion ratio (FCR) was optimized at 19 mg Zn/kg for ZnPro and 30 mg Zn/kg for Zn-sulfate. Interactive effect was observed for Zn intake, excretion and retention. At higher inclusion of ZnPro levels (≥ 38 mg Zn/kg), chicks showed increased Zn intake and excretion. ZnPro levels higher than ≥ 56 mg Zn/kg promoted higher Zn retention. Zn retention in liver and tibia were maximized at 38 mg Zn/kg for both sources, and were similar until 76 mg Zn/kg. ZnPro resulted in higher liver Zn concentration and greater tibia manganese (Mn) deposition, while Zn-sulfate increased liver iron (Fe) concentration. Additionally, Zn-sulfate enhanced glutathione peroxidase (GSH-Px) activity in liver and breast muscle, while both sources modulated liver superoxide dismutase (SOD) activity. Conclusions Both Zn sources supported growth and antioxidant responses, with optimal DWG levels at 30 mg Zn/kg for Zn-sulfate and 19 mg Zn/kg for ZnPro, highlighting greater efficiency of the organic source. Inorganic Zn further boosted GSH-Px activity, enhancing tissue antioxidant capacity, while ZnPro demonstrated advantages in tissue mineral retention. Further research on environmental impacts of Zn excretion from high ZnPro diets is recommended.