Humoral and skin mucosal immune parameters, intestinal immune related genes expression and antioxidant defense in rainbow trout (Oncorhynchus mykiss) fed olive (Olea europea L.) waste.

A six-week feeding trial was carried out to evaluate the effects of inclusion of dietary olive waste cake (OWC, 0, 0.5, 2.5 and 5 g kg-1 diet) on performance, antioxidant condition and immune responses of rainbow trout (Oncorhynchus mykiss) (2.5 ± 0.1 g). Supplementing diet with 2.5 and 5 g OWC kg-1 diet significantly enhanced serum and mucosal lysozyme activity in fish. Regarding mucosal immunity, fish fed 2.5 and 5 g OWC kg-1 diets had higher skin mucus total Ig concentrations than other groups. In relation to antioxidant status, those in 2.5 g OWC kg-1 and the control groups exhibited the highest and the least liver superoxide dismutase and glutathione peroxidase activities, respectively. Furthermore, the activity of liver glutathione S transferase in fish fed 2.5 and 5 g OWC kg-1 diets was higher than the other treatments. In respect to gut cytokines gene expression, our findings demonstrated dietary OWC did not influence interlukines-1ß and 10 genes expression, but relative expression of IL8 gene gradually up-regulated with increasing dietary OWC level. Moreover, fish fed 0.5 g OWC kg-1 and the control diets had the highest and the lowest gut tumor necrosis factor-α gene expression values, respectively. The relative expression of transforming growth factor-ß significantly down-regulated in gut of fish fed 2.5 and 5 g OWC kg-1 diets compared to other groups. Supplementing diet with OWC pronouncedly improved growth and feed conversion ratio in fish compared to the control. Overall, the findings of this study suggested that inclusion of 2.5 g OWC kg-1 diet can improve growth rate, oxidative stress status, humoral and skin mucosal immune responses in O. mykiss fingerlings and it can be considered as a functional feed additive for this species.

Dietary supplementation of lemon verbena (Aloysia citrodora) improved immunity, immune-related genes expression and antioxidant enzymes in rainbow trout (Oncorrhyncus mykiss).

The use of veterinary drugs for the treatments of fish diseases has often health and environmental side effects and thus alternative more sustainable strategies are needed. In this study we have explored the effect of dietary administration of lemon verbena (Aloysia citrodora) leaves powder on growth, immune parameters and antioxidant enzyme activity of rainbow trout (Oncorrhyncus myskiss). The results show that adding lemon verbena (LV) leaves powder (0.5, 1 and 2%), as feed supplement does not affect significantly rainbow trout growth, but increases the levels of some immune parameters. All enriched-diets induced an increase in the levels of lysozyme activity and total immunoglobulin in rainbow trout serum (P < 0.05), whilst 1 and 2% enriched-diets increased lysozyme and immunoglobulin in skin mucus. Expression of interleukin-1ß (IL-1ß) was enhanced in all fish supplemented with LV leaves powder (0.5, 1 and 2%) whilst only the diet with the highest dose (2%) induced a significantly higher expression of IL-8 and tumour necrosis factor (TNF-α). Fish fed with LV leaves powder at 1 and 2% had significantly lower expression of transforming growth factor (TGF-ß, P < 0.05). Furthermore, all enriched-diets significantly increased the activity of super oxide dismutase (SOD, P < 0.05) and diets containing 1 and 2% of LV leaves powder also increased activity of glutathione-S-transferase (GST) and glutathione peroxidase (GPx). In conclusion, LV leaves powder administered as feed supplement at 2% enhances the expression of some immune-related genes (IL-1ß, IL-8 and TNF- α), rises the levels of lysozyme and total immunoglobulin in serum and skin mucus and increases the activity of antioxidant enzymes (SOD, GST and GPx) in rainbow trout.