Influences of dietary Cu levels on growth performance, muscle development, antioxidant capacity, and inflammatory response of juvenile yellow catfish (Pelteobagrus fulvidraco)

The experiment was conducted to investigate the influence of dietary CuO nanoparticles (CuO NPs) on growth performance, muscle development, antioxidant capacity, and inflammatory responses of juvenile yellow catfish Pelteobagrus fulvidraco. The three diets were formulated with CuO NPs addition at 0 (without CuO NPs addition, low-Cu group, control), 9 (middle-Cu group), and 15 (high-Cu group) mg kg−1 diet, respectively, and final dietary levels for three diets were 2.07 (low-Cu group: served as a control group), 9.19 (middle-Cu group), and 13.96 mg kg−1 (high-Cu group), respectively. Each diet was randomly assigned to three replicate groups of 60 fish. The feeding experiment continued for 12 weeks. Among three dietary groups, yellow catfish juveniles fed a middle Cu diet possessed the highest growth performance, and the lowest feed utilization (P<0.05); muscle lipid content was the highest for fish fed a low Cu diet (P<0.05) and presented no significant differences between the middle-Cu and high-Cu groups (P>0.05). The Cu content in muscle tissue increased with increasing dietary Cu levels. CuO NPs fortification in the diets influenced mRNA of genes involved in endocytosis and metal ion transpor (P<0.05). The muscle fiber density was lower but muscle fiber diameters were higher for fish fed middle Cu diet (P<0.05). The myod, mrf4, mef2a, and mef2d mRNA expression levels were higher in yellow catfish given a middle Cu diet (P<0.05). The high Cu group had the lowest myog and the greatest mstn mRNA expression levels. The yellow catfish fed a middle Cu diet had the lowest MDA content, the highest T-AOC, CAT and Cu, Zn SOD activities, and the highest nrf2, sod1, and cat mRNA expression (P<0.05). The middle Cu group had the lowest tnfβ, il6, and il8 mRNA expression (pro-inflammatory) and the highest il10, tgfb1a, and tgfb2 mRNA expression (anti-inflammatory) (P<0.05). In conclusion, 9.19 mg Cu kg−1 diet is optimal for improving growth, muscle development, and increasing the antioxidant capacity and anti-inflammatory responses in juvenile yellow catfish; 2.07 and 13.96 mg Cu kg−1 diet will adversely affect the growth performance, muscle development and health in the fish. Statement of relevance For the first time, we explored the effects of dietary CuO NPs on growth performance, muscle Cu transport, antioxidant and inflammatory responses, which provided good basis for dietary CuO NPs addition in the aquafeeds.