Dietary organic selenium improves growth, serum biochemical indices, immune responses, antioxidative capacity, and modulates transcription of stress-related genes in Nile tilapia reared under sub-optimal temperature.

A 56-day feeding experiment was carried out to investigate the influences of dietary organic selenium (OS) on the growth, body composition, serum biochemistry, stress responses, and immune indices of Nile tilapia reared under sub-optimal temperature. Fish (5.61 ± 0.5 g) were allotted in seven experimental groups (5 replicates per each) and fed on a basal diet supplemented with 0.0 (CTR), 0.1, 0.2, 0.3, 0.4, 0.5, and 0.6 mg OS/kg diet and reared under temperature ranged 21.50 ± 0.50 °C. Final body weight, weight gain, and specific growth rate were significantly increased in OS groups compared to the CTR group. Moreover, the feed conversion ratio was significantly decreased in OS groups, especially at fish groups fed 0.3-0.6 mg OS/kg diet compared to the other groups. The lowest survival rate (%) was found in OS groups between 0.0 and 0.2 mg/kg diet. A significant increase in the crude protein (%) and dry matter (%) in OS groups alongside a significant decrease in the ash (%) compared to the CTR group. Blood proteins (total protein, albumin, and globulin), reduced glutathione, immunoglobulin M, and complement C3 values alongside the serum lysozyme and catalase activities were significantly increased compared to the CTR group. Contrarywise, serum transaminases (alanine transaminase and aspartate transaminase), cortisol, urea, and creatinine values were significantly decreased in OS groups than the CTR group. No significant differences were noticed in the mRNA transcripts of the hepatic heat shock protein 70 among all experimental groups. Meanwhile, significant differences were observed in the mRNA transcripts of hepatic heat shock protein 27, superoxide dismutase, and glutathione peroxidase genes among all experimental groups. The second order polynomial regressions illustrated that the optimal inclusion OS level in diets for Nile tilapia reared under sub-optimal temperature is 0.36-0.39 mg/kg diet based on weight gain and cortisol levels, respectively. Conclusively, the present study exemplified that dietary inclusion with 0.36-0.39 mg OS/kg diet improved the growth, immunity and modulate the stress responses in Nile tilapia reared under sub-optimal temperature.

Dietary spirulina (Arthrospira platenesis) mitigated the adverse effects of imidacloprid insecticide on the growth performance, haemato-biochemical, antioxidant, and immune responses of Nile tilapia.

The present study was performed to evaluate the toxic effects of imidacloprid (IMI) insecticide on the growth performance, oxidative status, and immune response of Nile tilapia, Oreochromis niloticus (L.), and the protective role of dietary supplementation of spirulina, Arthrospira platensis, (SP). Fish (20.2 ± 0.5 g) were assigned to bifactorial design (2 IMI levels x 3 SP levels) to represent 6 treatments in triplicates. Spirulina was incorporated in diets at levels of 0.0 (control), 20, and 40 g/kg diet. Under each SP level, fish were exposed to 0.0 or 0.05 µg IMI/L. Fish in each treatment were fed on the corresponding diets up to apparent satiation thrice a day for 8 weeks. Two-way ANOVA revealed a significant decline in growth indices, hepatic superoxide dismutase, catalase, and glutathione peroxidase activities in the IMI-exposed fish. Contrariwise, serum alanine and aspartate aminotransferases, alkaline phosphatase, urea, creatinine, and malondialdehyde levels were markedly higher along with significant reductions of the reduced glutathione, nitric oxide as well as lysozyme values in the IMI-exposed fish group. The dietary supplementation of SP showed stimulating effects on the growth performance, haemato-biochemical, oxidants/antioxidants, and immune biomarkers of Nile tilapia with optimum level of 20 g SP/kg diet. Interestingly, the dietary supplementation of SP to Nile tilapia attenuated the above-mentioned variables with improving the growth performance, haemato-biochemical, oxidative stress, and immunity biomarkers. Therefore, the dietary supplementation of 20 g SP /kg diet could be a valuable candidate as a natural antioxidant for ameliorating the IMI toxicity in Nile tilapia.

The effects of dietary clinoptilolite and chitosan nanoparticles on growth, body composition, haemato-biochemical parameters, immune responses, and antioxidative status of Nile tilapia exposed to imidacloprid.

This study aimed at the evaluation of the mitigating effects of dietary zeolites (ZEO) and/or chitosan nanoparticle (ChNP) on imidacloprid (IMID)-induced toxicity in Nile tilapia (Oreochromis niloticus). Fish (18.03 ± 0.01 g) were allocated into six groups; one fed on a basal diet (control) (CTR), and the other groups were fed diets supplemented with ChNPs (5 g kg-1) and/or ZEO (20 and 40 g kg-1) (ZEO20 and ZEO40) for 60 days. In the last 14 days of the experiment, all groups were exposed to a sub-lethal dose of IMID (½ of 96 h LC50 = 0.0545 µg L-1). Dietary ZEO20 significantly improved all growth parameters (P ˂ 0.05), while ChNPs had no significant effects. The crude protein of the fish body was significantly increased in all groups compared to the CTR (P ˂ 0.05). No significant impacts of ChNPs, ZEO, and their interaction (P > 0.05) were noticed on the moisture, dry matter, and ash percentages. Compared to the CTR, hematocrit values were significantly decreased (P ˂ 0.05) in ChNP and ZEO20 groups; meanwhile, their levels were significantly increased (P ˂ 0.05) in the ZEO40 group and all combined treatments. Fish fed diets with ChNPs and/or ZEO had significant increments in the MCV values (P ˂ 0.05). Moreover, fish fed diets supplemented with ChNPs or their combination with ZEO had the lowest glucose and alkaline phosphatase levels compared with the CTR. Serum aspartate transferase levels were significantly decreased in all treated groups (P ˂ 0.05) compared to the CTR. ChNPs alone or combined with ZEO significantly exhibited the highest lysozyme and nitro blue tetrazolium values (P ˂ 0.05). On the other hand, fish in the CTR group had the highest malondialdehyde and lowest nitric oxide levels compared to the other groups. Interestingly, the lowest IMID residues in fish flesh were found in fish groups fed diet with a combination of ZEO and ChNPs. Partial or complete protection of the hepatic and splenic tissues were observed in fish group with combined treatment with ChNPs and ZEO. In conclusion, the application of ZEO and/or ChNPs in Nile tilapia diets looks to be a leading approach to mitigate the toxic impacts of IMID.

Effects of dietary Nannochloropsis oculata on growth performance, serum biochemical parameters, immune responses, and resistance against Aeromonas veronii challenge in Nile tilapia (Oreochromis niloticus).

The current work was planned to assess the effects of dietary microalga, Nannochloropsis oculata (NP) on the growth indices, serum biochemistry, non-specific immunity, and resistance of Nile tilapia (Oreochromis niloticus) juveniles against challenge with pathogenic Aeromonas veronii. Fish (10.21 ± 0.28 g) were randomly divided into four treatments in triplicates and were fed on diets supplemented with different levels of NP (0, 5, 10, and 15%) for eight weeks. The results showed that the dietary 5% NP significantly improved the growth parameters (final body weight, weight gain, specific growth rate, and total feed intake) (P < 0.05). Meanwhile, the feed conversion ratio was significantly decreased in NP-supplemented groups with respect to the control group. The serum protein profile (total protein, albumin, globulin, and albumin/globulin ratio) was significantly decreased by 15% NP supplemented group. Meanwhile, liver enzymes (alanine transaminase, and aspartate transaminase) activities were not significantly affected by NP dietary supplementation (P < 0.05). Serum lysozyme activity, nitric oxide (NO), and nitroblue tetrazolium (NBT) levels were significantly enhanced only in 5% NP supplemented group (P < 0.05). Interestingly, the hepatopancreatic and intestinal tissues had apparently normal histomorphology of Nile tilapia fed at 5% NP-supplemented diets. Significant upregulation of cytokines [interleukin 1beta (IL-1ß), interleukin 8 (IL-8), interferon-gamma (IFN-γ), transforming growth factor-beta (TGF- ß), and tumor necrosis factor-alpha (TNF-α)], with significant downregulation of the antioxidant gene [superoxide dismutase (SOD)] in 10% and 15% NP supplemented groups. Attractively, the relative level of protection (RLP) against challenge with pathogenic A. veronii was significantly elevated in 10% and 15% NP supplemented groups. Conclusively, the obtained results reflect the beneficial roles of dietary NP to improve growth and boost the immune responses of Nile tilapia.