Evaluation of dietary chitosan effects on growth performance,immunity, body composition and histopathology of Nile tilapia (Oreochromis niloticus) as well as the resistance to Streptococcus agalactiae infection

The present investigation aimed to evaluate the effect of dietary chitosan supplementation on growth performance, body composition, immune response and histopathology of Nile tilapia, and also the in vitro antibacterial activity of chitosan against Streptococcus agalactiae (S. agalactiae). About 180 fish (average body weight 39.3 ± 0.3 g) were randomly divided into three groups according to chitosan supplementation: control group (basal diet without chitosan), Ch3 group (3 g chitosan/kg diet) and Ch5 group (5 g chitosan/kg diet). Growth performance parameters and body proximate composition were measured before infection but biochemical parameters and lysozyme and antibacterial activities before and after experimental infection. Results of the present investigation showed dietary chitosan (5 g chitosan/kg diet) significantly (p < .05) improved growth performance parameters, body composition (dry matter, crude protein, ether extract, ash, and carbohydrate) and serum biochemistry (total protein, albumin, globulin, with no effect on AST, ALT, urea and creatinine) before infection in Ch5 group than the control. After infection, liver enzymes (serum AST and ALT) were maintained lower in fish fed Ch3 or Ch5 than the control. Serum lysozyme and bactericidal activities significantly increased (p < .05) in chitosan groups before and after the challenge. The mortality rate was markedly reduced in the Ch3 group and prohibited in the Ch5 group after the experimental infection. In conclusion, feeding 3 or 5 g chitosan/kg diet increased the growth rate and improved FCR of Nile tilapia. In addition, it reduced mortality by its antibacterial and immunostimulant effects.     

Amperometric determination of ascorbic acid in real samples using a disposable screen-printed electrode modified with electrografted o-aminophenol film

Ascorbic acid (AA) is an antioxidant considered to play a crucial role in human health. Therefore, diverse methods for the determination of AA in foods have been developed, most of them time-consuming and requiring costly instrumentation. A simple and sensitive method for the quantification of AA in fresh fruits and vegetables and commercial juices using an amperometric sensor is presented on the basis of disposable screen-printed carbon electrodes (SPEs) modified with an o-aminophenol (o-AP) film selective for the detection of AA. The sensor exhibited a linear response for AA from 2-20 microM, with a correlation coefficient r2 = 0.998 and a limit of detection of 0.86 microM. Common possible interferents of the sample matrices were tested, and results showed high selectivity of the o-AP SPEs toward AA. The sensor exhibited an excellent reproducibility (RSD% = 1.98, n = 8) and surface stability. The method was validated by a comparison to a reference method, and excellent correlation is obtained.     

The optimized inclusion level of Bacillus subtilis fermented Azolla pinnata in Nile tilapia (Oreochromis niloticus) diets: immunity,antioxidative status,intestinal digestive enzymes and histomorphometry,and disease resistance

Fish Physiology and Biochemistry - A 95-day feeding trial was conducted to evaluate the outcomes of feeding Bacillus subtilis fermented Azolla (BSFA) on nonspecific immunity, antioxidative status,...