Effects of Shrimp Shell-Derived Chitosan on Growth, Immunity, Intestinal Morphology, and Gene Expression of Nile Tilapia (Oreochromis niloticus) Reared in a Biofloc System.

Chitosan (CH) shows great potential as an immunostimulatory feed additive in aquaculture. This study evaluates the effects of varying dietary CH levels on the growth, immunity, intestinal morphology, and antioxidant status of Nile tilapia (Oreochromis niloticus) reared in a biofloc system. Tilapia fingerlings (mean weight 13.54 ± 0.05 g) were fed diets supplemented with 0 (CH0), 5 (CH5), 10 (CH10), 20 (CH20), and 40 (CH40) mL·kg-1 of CH for 8 weeks. Parameters were assessed after 4 and 8 weeks. Their final weight was not affected by CH supplementation, but CH at 10 mL·kg-1 significantly improved weight gain (WG) and specific growth rate (SGR) compared to the control (p < 0.05) at 8 weeks. Skin mucus lysozyme and peroxidase activities were lower in the chitosan-treated groups at weeks 4 and 8. Intestinal villi length and width were enhanced by 10 and 20 mL·kg-1 CH compared to the control. However, 40 mL·kg-1 CH caused detrimental impacts on the villi and muscular layer. CH supplementation, especially 5-10 mL·kg-1, increased liver and intestinal expressions of interleukin 1 (IL-1), interleukin 8 (IL-8), LPS-binding protein (LBP), glutathione reductase (GSR), glutathione peroxidase (GPX), and glutathione S-transferase (GST-α) compared to the control group. Overall, dietary CH at 10 mL·kg-1 can effectively promote growth, intestinal morphology, innate immunity, and antioxidant capacity in Nile tilapia fingerlings reared in biofloc systems.

Modulation of growth, immune response, and immune-antioxidant related gene expression of Nile tilapia (Oreochromis niloticus) reared under biofloc system using mango peel powder.

This study aimed to investigate the effects of mango peel powder (MGPP) on growth, innate immunity, and immune-antioxidant related gene expression of Nile tilapia reared under biofloc system. Three hundred Nile tilapia (average weight 14.78 ± 0.05 g) were distributed into 15 fiber tanks (300 L per tank) assigned to five treatments in triplication. Fish were fed basal diet containing different levels MGPP as follows: 0 (MGPP0: control), 6.25 (MGPP 6.25), 12.5 (MGPP 12.25), 25 (MGPP 25), and 50 (MGPP 50) g kg-1 diet for 8 weeks. Specific growth rate (SGR), weight gain (WG), final weight (FW), feed conversion ratio (FCR), skin mucus of lysozyme (SMLA), and peroxidase activities (SMPA), serum of lysozyme (SL) and peroxidase (SP) were measured every for weeks; while immune-antioxidant-related gene expressions were determined after 8 weeks post-feeding. The results indicated that MGPP 25 diet resulted in higher SGR, WG, FW, and FCR but no significant differences among treatments were noticed. In terms of immune responses, lysozyme and peroxidase activities in mucus and serum were significantly higher in MGPP 12.5 and MGPP 25 diets against the control. Similarly, significant up-regulation of IL-1 and IL-8 gene expressions was observed in fish fed MGPP 25 against the control. However, no significant differences in LBP, GSTa, GPX, and GSR among treatments were observed. Overall, dietary inclusion of MGPP 25 significantly enhanced immune response and immune related gene expressions but not growth performance and antioxidant gene expressions. The results implied that MGPP can be potentially used as an immunostimulants in Nile tilapia culture.

Influence of black rice (Oryza sativa L.) bran derived anthocyanin-extract on growth rate, immunological response, and immune-antioxidant gene expression in Nile tilapia (Oreochromis niloticus) cultivated in a biofloc system.

This study investigated the effects of dietary supplementation with anthocyanin extracted from black rice bran (AR) on the growth rate, immunological response, and expression of immune and antioxidant genes in Nile tilapia raised in an indoor biofloc system. A total of 300 Nile tilapia fingerlings (15.14 ± 0.032 g) were maintained in 150 L tanks and acclimatized for two weeks. Five experimental AR diets (0, 1, 2, 4, and 8 g kg-1) with various anthocyanin doses were used to feed the fish. We observed that the growth and feed utilization of fish fed with different dietary AR levels increased significantly after eight weeks (p < 0.05). In addition, the serum immunity of fish fed AR diets was much greater than that of those fed non-AR diets (p < 0.05). However, there were little or no difference in between fish fed AR enriched diets and the control AR-free diet (p > 0.05). After eight weeks, fish fed AR-supplemented diets had significantly higher mRNA transcript levels in immune (interleukin [IL]-1, IL-8, and liposaccharide-binding protein [LBP]) and antioxidant (glutathione transferase-alpha [GST-α] and glutathione reductase [GSR]) genes compared to control fish fed the AR-free diet, with the greatest enhancement of mRNA transcript levels (in the case of IL-8 by up to about 5.8-fold) in the 4 g kg-1 AR diet. These findings suggest that dietary inclusion of AR extract from black rice bran at 4-8 g kg-1 could function as a herbal immunostimulant to enhance growth performance, feed consumption, and immunity in Nile tilapia.