Effects of dietary administration of water hyacinth (Eichhornia crassipes) leaves extracts on innate immune parameters, antioxidant defence and disease resistance in rainbow trout (Oncorhynchus mykiss)

Abstract

The present trial investigated the effects of dietary administration of (WLEA) and (WLEM) as an immunostimulant on non-specific immune parameters, antioxidant defence and resistance against Streptococcus iniae in rainbow trout (Oncorhynchus mykiss) fingerlings (4.8 ± 0.2 g). One group fed un-supplemented diet compared with six groups fed WLEA and WLEM supplemented diets at different levels (2.5, 5, 10 g/kg). At the middle (28th) and end of feeding trial (56th) as well as 24-h post challenge, several serum innate immune parameters; lysozyme (LYZ), total immunoglobulin (Ig), alternative complement activity (ACH50) and respiratory burst activity (RBA) as well as antioxidant defence parameters; superoxide dismutase (SOD), catalase (CAT) and glutathione peroxidase (GPX) were evaluated. The results indicated that administration of WLE supplemented diets could significantly increase the immune and antioxidant parameters in 28th, 56th and 24 h post challenge (P < 0.05). On the 56th, serum immune parameters increased significantly in many groups compared with 28th (P < 0.05). Also, 24-h post challenge, a significant increase in Ig, ACH50 and RBA activity was observed in most of WLE supplemented groups compared normal condition. No significant increase of antioxidant parameters observed in many groups on 56th compared 28th as well as 24-h post challenge compared normal condition (P > 0.05). Fish fed 1% WLEM and 1% WLEA supplemented diets exhibited increased immune response and antioxidant capacity compared other groups (P < 0.05). The results of challenge test showed that administration of WLE supplemented diets significantly increased trout resistance (P < 0.05); the highest survival rate, was observed in the 1 % WLEM group. The present results confirmed the beneficial effects of WLE as an immunostimulant on rainbow trout and the best result was obtained in fish fed 1% WLEM supplemented diet.