Positive effects of dietary nanosized sodium butyrate on growth performance, immune, antioxidant indices, and resistance of Nile tilapia to waterborne copper toxicity

Abstract

Although, copper (Cu) is commonly used in aquaculture as a chemotherapeutic agent to prevent and control algal blooms and bacterial infections, it could negatively impact the health and performance of aquatic animals. Moreover, sodium butyrate used as a feed additive plays a potential role in improving the performance and well-being of many aquatic species. Therefore, in this study, Nile tilapia, Oreochromis niloticus (L.) with average weight of 8.5–9.5 g, were fed on diets containing nanosized sodium butyrate (NSB) at levels of 0.0 (control), 0.25, 0.5, 1.0, 2.5, 5.0, and 10 mg/kg feed for eight weeks. Following the feeding period, fish from each treatment were subsequently exposed to waterborne Cu (0.5 mg/L) for further ten days. Results obtained herein revealed that with optimum values of 1.0–2.5 mg/kg diet, dietary NSB linearly and quadratically boosted fish performance, with no effects on the whole body composition of Nile tilapia. We also observed that when dietary NSB levels in Nile tilapia diets were increased from 1.0 to 10.0 mg/kg feed, serum alpha-amylase, lipase, and total proteases activities were linearly and quadratically increased compared with the control group. In NSB-fed fish, no changes in glucose, aspartate (AST), or alanine aminotransferase (ALT) levels, but significant increases in total proteins and total lipids levels were seen (notably at 2.5–10.0 mg/kg feed). Higher values of superoxide dismutase (SOD), catalase (CAT), glutathione peroxidase (GPx), lysozyme (Lys), respiratory burst activity (RBA), and total immunoglobulin (total Ig) were also observed in NSB-fed fish particularly at 2.5–10.0 mg NSB/kg feed. Contrastively, the control fish exhibited highest glucose, AST, and ALT values coupled with lower total proteins and total lipids values after Cu exposure. The control fish exposed to Cu toxicity showed higher values of SOD, CAT, and GPx, as well as malondialdehyde and nitric oxide levels coupled with lowest values of Lys, RBA, and total Ig. Also, the Cu residue in the control fish’s body post-Cu exposure was significant higher than those of fish fed on NSB diets (5.0–10 mg/kg feed). Feeding Nile tilapia on NSB significantly reduced the Cu uptake and, subsequently, the Cu residue in the fish body. Hence, significant recovery of the above-mentioned variables was observed in NSB-fed groups, especially at 2.5–10.0 mg/kg feed treatments. Therefore, this study demonstrated that dietary NSB (1.0–2.5 mg/kg feed) has significant role in boosting fish performance, enhancing antioxidant-immune biomarkers, and reducing the Cu uptake and bioaccumulation in fish bodies.