Impacts of fishmeal replacement with peanut meal on growth, antioxidant capacity, digestive enzyme activity and protein metabolism-related gene expression in swimming crab Portunus trituberculatus

To assess the effects of fishmeal (FM) replacement with peanut meal (PM) on growth performance, antioxidative capacity and the expression of genes associated with protein metabolism and inflammation in Portunus trituberculatus, a 56-day feeding trial was conducted. The basal diet (PM0) comprised 30 % FM, while the experimental diets were formulated by replacing fishmeal with peanut meal at 10 % (PM10), 20 % (PM20), 30 % (PM30), and 40 % (PM40) substitution levels, respectively. The results revealed that 30 % and 40 % FM replacement with PM markedly reduced PWG. Crabs fed PM30 and PM40 diets exhibited significantly lower activities of pepsin and trypsin in hepatopancreas compared to other treatments, while the highest Na⁺, K⁺-ATPase activity was recorded in crabs fed diet PM20. Crabs fed PM20 diet showed higher T-SOD, T-AOC and nitric oxide activities in the hemolymph than those fed others. The expression of 4e-bp1, a gene associated with the TOR signaling pathway, was markedly up-regulated in the hepatopancreas of crabs fed PM30 and PM40 diets, whereas tor expression in muscle was down-regulated with increasing FM replacement. Furthermore, gpx and cat expression in the hepatopancreas was markedly down-regulated, while myd88 and tlr4 expression in the intestine was up-regulated in crabs fed 30 % and 40 % replacement diets. In summary, the optimal replacement level of fishmeal (FM) with peanut meal (PM) was 20.05 %, while replacements exceeding 30 % suppressed growth and impaired protein metabolism.