Impact of silver nanoparticles (Ag-NPs) as a dietary supplement on growth performance, carcass traits, blood metabolites, digestive enzymes, and cecal microbiota of growing rabbits

The present study investigated the impact of silver nanoparticles (Ag-NPs) on growth performance, carcass traits, liver and kidney functions, immunity and antioxidant indicators, digestive enzymes, and cecum bacteriology of growing rabbits. 100 5-week-old New Zealand White (NZW) male rabbits were randomly divided into 5 equal groups and fed for 8 weeks on the basal diet only or on the basal diet supplemented with different levels of Ag-NPs (0.25, 0.50, 0.75, or 1.00 mg/kg diet). Animals in each group were randomly distributed in 10 cages (replicates), with two rabbits each. Different dietary concentrations of Ag-NPs significantly increased live body weight (LBW) and feed conversion ratio (FCR). Also, body weight gain (BWG) increased dramatically during all experimental periods except 11-13 weeks of age. Levels of 0.25 and 1 mg of Ag-NPs/kg diet showed the highest increase in LBW, BWG, and FCR. All studied carcass traits, except liver %, were not affected by Ag-NPs levels. Rabbits fed diet supplemented with 1 mg Ag-NPs had the highest liver %. Serum total protein, albumin, and globulin levels were increased (P<0.05) in groups treated with 0.25 and 0.75 mg Ag-NPs. In contrast, serum values of aspartate transaminase (AST) and alanine transaminase (ALT), urea and creatinine were significantly reduced with the supplementation of Ag-NPs up to 0.75 mg/kg diet. The immunoglobulins M, G, and A (IgM, IgG, and IgA), complement 3 (C3) and lysozyme activity were improved with the inclusion of nano-silver in the rabbit feeds, particularly at the level of 0.25 mg Ag-NPs/kg feed. The inclusion of Ag-NPs in rabbit diets at different concentrations increased the total antioxidant capacity and the activities of superoxide dismutase, catalase, and glutathione peroxidase. Growing rabbits fed on diets supplemented with Ag-NPs had higher levels of digestive enzymes than the control group. The addition of Ag-NPs reduced the load of E. coli, Salmonella spp. and Colioform in the rabbit cecum. Overall, the inclusion of 0.25–1 mg Ag-NPs/kg to NZW rabbit diets has shown beneficial effects on health and performance.