Do zinc nanoparticles exert dose-dependent effects in broiler chickens? a meta-analysis of performance, immunity, and antioxidant response

This study aimed to investigate the effects of zinc nanoparticles (Zn NPs) on broiler chickens through a meta-analytical approach. A total of 125 scientific articles were initially screened via databases such as Scopus, Web of Science, PubMed Central, and Google Scholar, with “Zinc NPs” and “broiler chickens” as the main keywords. Following rigorous selection criteria, 25 articles were deemed eligible for inclusion. The data were processed via the PROC MIXED procedure in SAS 9.3.2 to evaluate various parameters, including growth performance, carcass characteristics, nutrient digestibility, hematological profiles, immune markers, and antioxidant activity. Zn NP supplementation significantly increased the concentrations of IgG and the serum antioxidant enzymes AST and ALT, with optimal doses of 40.89 mg/kg and 71.41 mg/kg, respectively. However, supplementation also led to reduced ether extract digestibility, diminished zinc levels in liver and bone tissue, and lowered red blood cell counts while increasing white blood cell counts. No significant changes were observed in the other parameters. Although Zn NPs offer benefits in terms of immune and antioxidant enhancement, they also pose drawbacks, particularly in terms of nutrient absorption and zinc retention. The recommended dosage ranges to balance these outcomes is 40.89–71.41 mg/kg.