RESUMO
This study evaluated the supplementation of iron and copper nanoparticles in channel catfish diets and their influences on growth and health. A comparative feeding trial was carried out for 9 weeks to evaluate combinations of iron and copper nanoparticles: only iron nanoparticles (IronNP), only copper nanoparticles (CopperNP), CopperNP + IronNP, and a control diet supplemented with inorganic iron and copper (FeSO4 and CuSO4). After a 9-week feeding trial, growth performance, hematological parameters, whole-body proximate composition, and intestinal microbiota were evaluated, and fish were subjected to a bacterial challenge against Edwardsiella ictaluri to evaluate the contribution of the experimental treatments to fish health status. No statistical differences were detected for catfish fed the various diets in terms of production performance or survival after bacterial challenge. The hematocrit and RBC counts from fish fed the diet containing copper nanoparticles were significantly lower than the control group. A higher relative abundance of gram-positive bacteria was found in the digesta of catfish fed diets containing copper nanoparticles. Furthermore, in the context of hematology, iron nanoparticles did not impact the blood parameters of channel catfish; however, reduced hematocrits were observed in fish fed the copper nanoparticle diet, which lacked supplemental dietary iron, thus reinforcing the importance of dietary iron to catfish hematopoiesis. Nonetheless, additional studies are needed to investigate the effects of dietary copper nanoparticle supplementation in catfish diets to better illuminate its effects on the intestinal microbiota.
