Insect meal has shown promise as a potentially sustainable source of nutrients for aquafeeds, offering an alternative to expensive and ecologically undesirable ingredients, in the context of population explosion and climate change. Despite this promising outlook, its effects on fish growth and immune responses remain to be thoroughly investigated. Our scientific goal was to experimentally test responses to replacements of the fish meal with a protein source derived from black soldier fly larvae meal (BSFLM). Possible impacts on growth, immunological response, and the expression of selected immune-system related genes were evaluated in Koi carp (Cyprinus carpio var. koi) using a biofloc culture system. Three hundred fish (20.0 ± 0.2 g) were allocated into five groups: a control group receiving a basal diet containing 0 g kg⁻¹ BSFLM and four experimental groups in which fish meal was replaced with 50, 100, 150, and 200 g kg⁻¹ BSFLM for eight weeks. After 4 weeks of feeding, there were no statistically significant differences in specific growth rate (SGR), feed conversion ratio (FCR), and survival rate between fish fed BSFLM-enriched diets at 50, 100, 150 g kg⁻¹ and a control (0 g kg⁻¹ BSFLM) diet. However, fish fed 200 g kg⁻¹ BSFLM showed significantly improved weight gain (WG) and SGR compared to the control after 4 weeks; this difference persisted through 8 weeks (p < 0.05). After eight weeks, there was a moderate to weak negative linear regression shown in FCR (r = 0.470) and SR (r = 0.384), respectively, with the BSFLM levels, but significant and highly correlated linear relationships were observed in WG (r = 0.917) and SGR (r = 0.912). Immunological response analysis showed slight changes in lysozyme and peroxidase levels by replacing fish meal with BSFLM, but these apparent differences were not significantly related to experimental diets. Interestingly, mRNA transcripts of immune-related genes (TNF-α, TGF-β, IL1, IL10, and hsp70) were upregulated in the groups receiving higher amounts of BSFLM, with statistically significant differences observed in certain comparisons. Our findings reveal that fish meal can be effectively replaced by BSFLM, and that this not only has a positive effect on immune-related gene expression in Koi carp, but also on growth rate, pointing to the future potential role of BSFLM as an alternative fish meal protein in aquafeed formulation.

We investigated, herein, the effects of dietary inclusion of sugarcane bagasse powder (SB) on Nile tilapia development, mucosal and serum immunities, and relative immune and antioxidant genes. Fish (15.12 ± 0.04 g) were provided a basal diet (SB0) or basal diet incorporated with SB at 10 (SB10), 20 (SB20), 40 (SB40), or 80 (SB80) g kg⁻¹ for 8 weeks. Our results demonstrated that the dietary incorporation of sugarcane bagasse powder (SB) at 20 and 40 g kg⁻¹ significantly ameliorated FW, WG, and SGR as opposed to fish fed basal, SB10, and SB80 diets. However, no significant changes in FCR and survivability were observed between the SB supplemented diets and the control (basal diet). The mucosal immunity exhibited significantly higher SMLA and SMPA activities (p < 0.005) in fish treated with SB diets after eight weeks. The highest SMLA and SMPA levels were recorded in fish fed SB80 followed by SB20, SB40, and SB10, respectively. For serum immunity, fish fed SB incorporated diets significantly ameliorated SL and RB levels (p < 0.05) compared with the control. However, SP was not affected by the inclusion of SB in any diet throughout the experiment. The expression of IL1, IL8, LBP, GSTa, GPX, and GSR genes in the fish liver was significantly increased in fish fed the SB20 and SB10 diets relative to the basal diet fed fish (p < 0.05); whereas only the IL8, LBP, and GPX genes in the intestines were substantially augmented via the SB20 and SB80 diets (p < 0.05). IL1 and GSR were not influenced by the SB incorporated diets (p > 0.05). In summary, sugarcane bagasse powder (SB) may be applied as a feed additive to improve growth performance, immune response, and immune and antioxidant-related gene expression in Nile tilapia.

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.

This study aimed to assess the impacts of dietary supplementation with passionfruit (Passiflora edulis) peel powder (PSPP) on the growth, immune response, and expression of immune and antioxidant-related genes in Nile tilapia (Oreochromis niloticus) maintained in a biofloc system. Fish were fed basal diets supplemented with different doses of PSPP at 10 g kg⁻¹ (PSPP10), 20 g kg⁻¹ (PSPP20), 40 g kg⁻¹ (PSPP40), and 80 g kg⁻¹ (PSPP80). The basal diet, without PSPP-supplementation, was used as a control at 0 g kg⁻¹ (PSPP0). We observed that the dietary supplementation groups fed different levels of PSPP exhibited no substantial difference or only slight increases in growth performance and immunological response in Nile tilapia (p > 0.05), whereas fish fed diets supplemented with PSPP at concentrations of 10 g kg⁻¹, 20 g kg⁻¹, and 40 g kg⁻¹ had significantly higher mRNA transcripts (approximately 1.5–4.5 fold) of immune (il-1, il-8, and lbp) and antioxidant (gst-α, gpx, and gsr) gene expressions than fish in the control treatment group (0 g kg⁻¹). These findings suggest that dietary supplementation with PSPP may effectively stimulate the immune and antioxidant defense system and may function as feed additives in Nile tilapia cultured in a biofloc system.

This study explored the effects of mango seed (MS) powder supplementation on the growth, immune response, gene expression, and intestinal morphology of Nile tilapia (Oreochromis niloticus) over an 8-week period. A total of 300 Nile tilapia fingerlings (average weight of 15.29 ± 0.05 g) were divided into five treatment groups and fed either a basal diet or one of four experimental diets containing MS powder at concentrations of 10 (MS10), 20 (MS20), 40 (MS40), and 80 (MS80) g kg⁻¹. The results demonstrated that Nile tilapia fed MS-supplemented diets experienced significant improvements (p < 0.05) in weight gain (WG), specific growth rate (SGR), and survival rate (SR) compared to the control group (0 g kg⁻¹ MS). The MS-treated groups also showed a significant increase (p < 0.05) in the height and branching of intestinal villi along the entire length of the intestine, as well as a significantly higher villus-to-crypt depth ratio (V/C), indicating enhanced intestinal health and functionality. Moreover, although MS supplementation did not increase peroxidase activity, it did lead to a significant increase (p < 0.05) in the activity of skin mucus and serum lysozyme, along with upregulated gene expression of immune-related (IL-1, IL-8, and LBP) and antioxidant genes (GST-α, GPX, and GSR). Polynomial regression analysis identified an optimal MS dosage of 36.43–45 g kg⁻¹ for effectively improving growth, immunity, and immuno-oxidant gene expression in Nile tilapia. These results emphasize mango seed (MS) as a promising natural supplement for improving the diet of Nile tilapia and, potentially, other freshwater fish widely used in aquaculture.