Eight weeks feeding trial was carried out to assess the growth promoting and the immune-stimulatory effects of the supplementation of Amphora coffeaeformis (A. coffeaeformis) in the Nile tilapia diets and its resistance to bacterial infections. Fish were fed on diet containing 0, 10, 20 and 30 g of A. coffeaeformis per kg . Growth performance parameters and body composition of experimental fish were evaluated. Serum protein profile (albumin, globulin, total protein and A/G ratio), serum liver function enzymes, and serum lysozyme were assessed. Therefore, fish in all the experimental groups were challenged with pathogenic Aeromonas hydrophila following the feeding experiment. The results showed that the growth-promoting influence of A. coffeaeformis was observed on Nile tilapia performance, the optimum growth and feed utilization were obtained at fish maintained on 10g A. coffeaeformis kg -1 diet. A. coffeaeformis supplementation improved the protein and lipid contents in fish bodies without significant differences among them, especially when fed 20 or 30 g per kg, while no significant differences in the moisture and ash contents were observed among different treatments. As well, the physiological parameters (serum protein profile and serum lysozyme) were improved when fish were fed on A. coffeaeformis enriched diet. Besides, lysozyme activity was giving good results in 10, 20 and 30 g per kg. Fish mortality after challenged against A. hydrophila decreased with increasing A. coffeaeformis level in fish diets. These results indicated that A. coffeaeformis supplement is promising as an alternative method to antibiotics for disease prevention in Nile tilapia culture, and the optimum level of A. coffeaeformis in the fish diet should be ranged between 10 to 20 g kg -1 diet.
Several studies investigated the usage of spirulina (Arthrospira platensis) in aquaculture as a functional dietary additive or plant proteins replacers; however, more efforts still needed to test its nano form inclusion in aquafeed. In this study, Nile tilapia (Oreochromis niloticus) fed dietary spirulina (A. platensis) nanoparticles (SNP) at 0 (control), 0.1, 1 and 10 g/kg diet while the fifth diet was mixed with 10 g/kg of the normal form of A. platensis as a positive control. The final weight (FW), weight gain (WG) and feed conversion ratio of fish fed SNP at 10 g/kg displayed improved values comparing with the other groups (p < 0.05). Further, fish fed 1 g SNP had higher FW and WG than the control and 0.1 g SNP and 10 g normal A. platensis. The incorporation of SNP at 1 and 10 g/kg in Nile tilapia diets significantly (p < 0.05) enhanced total protein, albumin, globulin, lowered the values of serum glucose and activities of ALT and AST compared with control and spirulina groups. The SOD, CAT, GPx, lysozyme and respiratory burst activities were meaningfully promoted (p < 0.05) in fish received 1 and 10 g/kg diet concerning the control and spirulina groups. Nile tilapia challenged with Aeromonas hydrophila showed congestion of the kidney, liver and spleen tissues while SNP alleviated the inflammation induced by A. hydrophila. Different levels of SNPincorporated group showed lower cumulative mortality than the other groups. In conclusion, the obtained results illustrated that spirulina in nano form is recommended to enhance Nile tilapia well-being.
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