Improving effect of N-acetylcysteine on growth and intestinal health in juvenile Cyprinus carpio involve the Nrf2/MAPK/NF-κB pathways

N-acetylcysteine (NAC) plays a beneficial role in improving animal growth and health. The current study evaluated the impact of dietary supplementation with NAC on the growth performance, physiological status and intestinal health of juvenile Cyprinus carpio. The experiment involved 5 groups, with 3 replicates in each group, and each replicate group containing 30 juvenile Cyprinus carpio (average weight 2.06 ± 0.01 g). Five experimental diets (36% crude protein and 9% crude lipid) were prepared by supplementing graded levels (0, 0.15%, 0.30%, 0.45% and 0.60%) of NAC in the basal diet. Subsequently, these 5 diets were utilized for an 56 d feeding trial with Cyprinus carpio. During the feeding trial, the water temperature was maintained between 24 and 28 °C, and the feeding rate was 3%–5% of body weight. After the feeding trial, fish were fasted for 24 h, anesthetized, and dissected on ice trays to collect samples for subsequent analysis. Results showed that NAC (0.30%, 0.45% and 0.60% diets) significantly improved the growth performance and intestinal mucosa development in Cyprinus carpio, and inhibited apoptosis. Similarly, NAC (0.30%, 0.45% and 0.60% diets) could enhance the homeostasis of the redox defense system in intestine of Cyprinus carpio, which is linked to enhanced glutathione metabolism, scavenging of reactive oxygen species and activation of Nrf2 pathway. Furthermore, dietary NAC improved anti-inflammatory and immunomodulatory functions, and involved in the regulation of MAPK/NF-κB signaling pathway. Summary, NAC (0.30%, 0.45% and 0.60% diets) could significantly promote the growth and intestinal health in Cyprinus carpio. These findings provide partial available information for promoting the utilization of NAC in aquafeed and improving the ecological and healthy cultivation of Cyprinus carpio.