Effects of dietary supplementation with manganese dioxide nanoparticles on growth, Mn metabolism and kidney health of yellow catfish Pelteobagrus fulvidraco

The present study was performed to investigate yellow catfish manganese (Mn) requirement with Mn dioxide nanoparticles (MnO2NPs) as Mn source, and to evaluate effects of dietary Mn on growth performance, Mn metabolism and kidney health. Using MnO2NPs as the Mn sources, six experimental diets were formulated with dietary Mn levels at 1.67, 4.35, 7.37, 13.63, 26.06 and 50.37 mg Mn/kg diet, respectively, and fed to yellow catfish for 8 weeks. Yellow catfish growth performance and feed intake were the highest in the group of 13.63 mg Mn/kg diet, and the lowest in the group of 1.67 mg Mn/kg diet; and the feed conversion rate showed opposite trend with growth performance. Dietary Mn addition increased Mn content in the whole body, kidney and serum. The mRNA abundances of dmt1, zip8 and znt10 increased with the increase of dietary Mn level. Yellow catfish fed high dietary MnO2NPs level had higher mRNA abundances of dynamin1, dynamin2, cav1, cltc and eps15. Dietary Mn excess damaged the kidney histology. Yellow catfish fed the 13.63 mg Mn/kg diet had higher T-AOC, T-SOD, Mn-SOD, CAT activities, and mRNA levels of sod1, sod2 and cat (antioxidant response), but lower mRNA abundances of grp78, ire1, peric and atf4 (endoplasmic reticulum stress), tnf alpha, il1 beta and il6 (inflammatory response). The broken-line analysis of WG and the linear regression of whole-body Mn retention against dietary Mn levels showed that optimal Mn requirement was 12.57 mg Mn/kg diet and 8.33 mg Mn/kg diet, respectively, with MnO2NPs as Mn source. For the first time, we explored the effects of dietary MnO2 nanoparticles on growth performance, Mn uptake and metabolism, antioxidant responses, endoplasmic reticulum stress and inflammatory responses of the kidney, and determined the optimal dietary Mn requirement of yellow catfish fed MnO2 nanoparticles-added diet.