The aim of this study was to assess the impact of a commercial probiotic, Sanolife PRO‐F, on water quality, growth performance, blood profiles and intestinal morphometry of monosex Nile tilapia. A field trial was conducted for 10 weeks in which tilapia fingerlings (20 ± 1.26 g) were randomly distributed into three replicate ponds which were subdivided into three treatment groups, receiving Sanolife PRO‐F at 0 (B0), 0.1 (B1) and 0.2 (B2) g/kg diet, respectively. The results showed a significant improvement in growth performance, feed conversion ratio and blood profiles in tilapia fed on treated diets. The whole intestinal lengths, anterior and terminal intestinal villi heights and anterior goblet cells count were greater in tilapia fed on treated diets. There were no noticeable differences in growth and intestinal morphology between tilapia fed on B1 and B2 diets. The ammonia concentration in water was lower with B1 diet while electric conductivity, salinity and total dissolved solids were higher with the B2 diet. The pH level of pond water was enhanced by both diets, B1 and B2. In conclusion, application of Sanolife PRO‐F at 0.1–0.2 g/kg diet might have beneficial effects on growth, immunity, stress responses and gut health and function as well as the water quality of farmed Nile tilapia.

Dietary supplementation of selenium nanoparticles (Se-NPs) at different levels (0, 0.5, 1, and 2 mg kg diet) was evaluated to find out the effects on serum and skin immune responses as well as stress resistance in the red sea bream (Pagrus major). After 45 days of experimental trial, serum and mucosal immune responses were significantly high in fish fed 1 mg Se-NPs kg diet (P < 0.05). In this group, alternative complement pathway, total serum protein, antioxidant activity of catalase enzyme, serum bactericidal activity, serum lysozyme activity, and amounts of skin mucus secretions as well as stress resistance against low salinity stress increased significantly, when compared to fish fed Se-NP-free diet (P < 0.05). Furthermore, fish fed Se-NPs at 2 mg kg diet exhibited higher alternative complement pathway, total serum protein, mucus lysozyme activity, serum and mucus peroxidases, amount of mucus secreted, and tolerance against low salinity stress than the fish fed Se-NP-free diet (P < 0.05). Interestingly, the nitro blue tetrazolium activity in all groups fed with diets supplemented with Se-NPs are significantly higher than Se-NP-free diet (P < 0.05). The present results demonstrate that the dietary supplementation with Se-NPs (mainly from 1 to 2 mg kg level) could be useful for maintaining the overall health status of red sea bream.

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