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. One hundred 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 coliform 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.