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The present study was conducted to investigate the effects of dietary water hyacinth (Eichhornia crassipes) leaves powder (WLP) on growth performance, skin mucus and serum immune response, as well as antioxidant capacity of pikeperch (Sander lucioperca). During 7 weeks culture period, 120 fish (21.2 ± 0.55 g) were fed by experimental diets containing 0% (control), 0.5%, 1% and 1.5% WLP (four treatments in triplicate). At the end of the feeding trial, results revealed a significant increase in final weight (FW), weight gain (WG), daily weight gain (DWG) and specific growth rate (SGR) in fish fed with the highest value 1.5% WLP. Furthermore, increased skin mucus total immunoglobulin (Ig) level and lysozyme (LYZ) activity was noticed in 1 and 1.5% WLP groups, protease in 1.5% WLP group, and alkaline phosphatase (ALP) in 0.5 and 1% WLP groups. Haematological evaluation showed a significant rise in red blood cell (RBC) and haematocrit (HCT) at all WLP inclusion levels, while haemoglobin (Hb) value only increased in group fed by 0.5% dietary WLP. Also, remarkable increase in LYZ, protease and alternative complement (ACH50) activity were observed in WLP‐treated groups. Moreover, higher catalase (CAT) activity was detected in WLP supplemented groups, while higher superoxide dismutase (SOD) activity was detected in 0.5 and 1.5% WLP groups. However, glutathione peroxidase (GPx) activity was higher only in 0.5% WLP group. In conclusion, the present findings showed beneficial effects of water hyacinth leaves powder as a plant‐derived growth promotor and immunostimulant in the pikeperch.

The current study is designed to assay the efficacy of chlorogenic acid (ChA) in the diet on growth performance, digestive enzyme activity, serum immunological, biochemical, and antioxidant variables, and mucosal immune response as well as disease resistance of rainbow trout (Oncorhynchus mykiss) juveniles. Rainbow trout juveniles received diets supplemented with different inclusion levels of ChA (0 (ctrl), 200 (CA1), 400 (CA2), 600 (CA3), and 800 (CA4) mg kg−1 diet) for 60 days. According to the findings, fish from CA3 and CA4 groups demonstrated the best results considering the final weight (FW) and weight gain (WG) ( P < 0.05 ). Also, the group that received 600 mg kg−1 ChA-supplemented diet showed the lowest feed conversion ratio (FCR) and the highest specific growth rate (SGR) compared to other groups ( P < 0.05 ). Moreover, the minimum survival rate (SR) was only detected in the CA4 treatment ( P < 0.05 ). Regression analysis exhibited that rainbow trout growth indices were polynomially linked to dietary chlorogenic acid concentrations. In this regard, the optimal levels of chlorogenic acid according to growth parameters (FCR and SGR) were 0.71 and 0.62 gr kg−1 diet, respectively. The results exhibited superior performance of protease and amylase activities in CA2, CA3, and CA4 groups with the maximum amount in the group receiving 600 mg kg−1 ChA-enriched diet ( P < 0.05 ). Serum lysozyme (LYZ), immunoglobulin (Ig), and components 3 and 4 (C3 and C4) values of CA2, CA3, and CA4 groups were significantly higher than others with the highest amount in the CA3 group (P <0.05). Additionally, serum nitroblue tetrazolium (NBT) value in the CA3 and CA4 groups and myeloperoxidase (MPO) in the CA3 group were notably more than others ( P < 0.05 ). Moreover, the lowest aspartate aminotransferase (AST), alkaline phosphatase (ALP), alanine aminotransferase (ALT), and lactate dehydrogenase (LDH) and the highest total protein (TP) and globulin (GLO) values were observed in CA3 treatment ( P < 0.05 ). CA2 and CA3 groups demonstrated increased serum catalase (CAT) and decreased malondialdehyde (MDA) values compared to the control while the highest CAT and lowest MDA values were observed in CA3 treatment ( P < 0.05 ). Considering mucus immunity, the significantly maximum LYZ and protease values were demonstrated in CA2 and CA3 groups, and the highest ALP, Ig, and esterase values were demonstrated in the CA3 group. In comparison with the control, the mortality rates of the groups that received the ChA diets were remarkably ( P < 0.05 ) lower postchallenge with Y. ruckeri, and the highest survival and relative percentage of survival (RPS) ( P < 0.05 ) belonged to the CA3 group. Results obtained from the current study suggested ChA as a functional dietary additive to raise growth parameters, immune indices, antioxidant capacity, and resistance to disease in rainbow trout.