Hydroxychloride zinc and copper supplementation improves growth, feed efficiency, and gut health in broiler chickens

High-dose copper (Cu) supplementation is used as an alternative to antibiotic growth promoters for improving gut health in broiler chickens. The aim of this study was to evaluate the effects of hydroxychloride Zn (HyZ) and Cu (HyC) at different inclusion levels on productive traits and gut health biomarkers in broiler chickens. A total of 990 Ross 308 broilers were assigned to 55 floor pens (18 birds per pen) and received five dietary treatments as follows: (T1) an inorganic diet (INO) with 15 mg/kg Cu from CuSO₄ and 100 mg/kg of Zn from ZnSO₄; (T2) a hydroxychloride diet with 15 mg/kg of Cu from HyC and 100 mg/kg of Zn from HyZ; (T3 and T4) hydroxychloride diets with 80 mg/kg Zn from HyZ and either 100 (T3) or 150 (T4) mg/kg of Cu from HyC; and (T5) a hydroxychloride diet containing 80 mg/kg Zn from HyZ and Cu from HyC supplied at 200 mg/kg in the starter phase (1-10 days), 100 mg/kg in the grower phase (10-24 days), and 60 mg/kg in the finisher phase (24-35 days). Gut integrity and cecal bacterial populations were assessed on day 21, while carcass composition, liver, tibia and excreta mineral profiles, and tibia strength were evaluated on day 35 of the experiment. Hydroxychloride diets significantly improved body weight by ~ 4% at day 35 compared to INO (P < 0.05). Feed conversion ratio improved by 2.5% with T2 over INO, with further improvements in T3 (3.8%) and T4 (3.2%) (P < 0.05). Birds on T5 performed similarly to T3 throughout the trial (P > 0.05). INO birds had the lowest breast meat yield and the highest abdominal fat percentage (P < 0.05). Hydroxychloride diets reduced serum FITC-d levels and cecal Enterobacteria counts while increasing tibia breaking strength, Zn, and P levels (P < 0.01), and tended (P = 0.06) to increase cecal Bifidobacteria populations. In conclusion, these results suggest that replacing ZnSO₄ and CuSO₄ with HyZ and HyC has the potential to enhance gut health, body weight gain, and feed efficiency in broiler chickens.