Supreya Wannavijit. Effects of longan by-products as feed supplementation on growth performance, immune response, gene expression and digestive enzymes of nile tilapia (oreochromis niloticus) rear under biofloc system. Doctoral Degree(Animal Science). Chiang Mai University. Library. : Chiang Mai University, 2568.
Effects of longan by-products as feed supplementation on growth performance, immune response, gene expression and digestive enzymes of nile tilapia (oreochromis niloticus) rear under biofloc system
Abstract:
The utilization of agricultural by-products as sustainable feed additives has gained considerable attention in aquaculture, especially under biofloc systems that support efficient nutrient recycling and water quality management. Longan (Dimocarpus longan Lour.) processing generates large amounts of peel and seed by-products that are rich in bioactive compounds with potential benefits for fish growth, immune modulation, and antioxidant activity. To explore these possibilities, this study investigated the effects of fermented longan peel, fermented longan seed, and longan peel powder supplementation on Nile tilapia (Oreochromis niloticus) reared under biofloc conditions. The evaluation focused on growth performance, immune responses, gene expression, and digestive enzyme activities, providing insights into the feasibility of incorporating longan by-products as functional feed ingredients. Fermented longan peel experimentThe present study investigated the effects of fermented longan peel (FLP) supplementation on growth performance, nutrient digestibility, digestive enzyme activity, innate immune responses, and intestinal gene expression of Nile tilapia (Oreochromis niloticus). A total of 300 fish (average initial weight: 15.0 ± 0.03 g) were randomly assigned to five dietary treatments (0, 5, 10, 20, and 40 g/kg FLP) in triplicate for 8 weeks. Dietary FLP significantly improved final weight, weight gain, and specific growth rate in the FLP20 group compared to control (P 0.05), with polynomial regression analysis indicating optimal inclusion at ~2122 g/kg (R² = 0.820.86). Carbohydrate and protein digestibility were significantly higher in FLP20 (P 0.05), accompanied by enhanced intestinal amylase, protease, and trypsin activities, while lipase activity remained unaffected. Mucosal and serum immune, including lysozyme, peroxidase, and alternative complement activity (ACH50), were significantly elevated in FLP20 and FLP40 (P 0.05). Furthermore, intestinal expression of growth-related (IGF-1, GH, Ghrelin, NPY-α, Galanin), immune-related (TLR-7, TNF-α, NFκB), and antioxidant-related (hsp70, Keap-1, nrf-2, GST-α, Ef-α) genes was significantly upregulated (1.32.5 fold, P 0.05) in FLP2040 groups compared to control. In conclusion, dietary inclusion of FLP at 20 g/kg effectively enhances growth, digestive function, immunity, and gene expression, highlighting its potential as a sustainable functional feed additive for tilapia aquaculture.Fermented longan seed experimentThis study investigated the effects of dietary supplementation with fermented longan seed (FLS) on growth performance, In vitro digestibility, digestive enzyme activity, innate immune responses, and gene expression in Nile tilapia (Oreochromis niloticus). A total of 300 fish (initial weight: 22.55 ± 0.03 g) were randomly assigned to five diets containing 0, 5, 10, 20, and 40 g/kg FLS in triplicate for 8 weeks. Growth performance significantly improved in the FLS 5 group, which achieved the highest final weight (99.46 ± 0.43 g), weight gain (76.89 ± 0.48 g), and SGR (2.47 ± 0.01%/day) compared with the control (P 0.05). Feed efficiency was enhanced, with FCR reduced to 0.83 ± 0.01 in FLS 5 and 0.80 ± 0.01 in FLS 40 at week 8 (P 0.05). In vitro digestibility of carbohydrate (2.80 μmol maltose/g feed/amylase activity) and protein (26.97 μmol DL-alanine/g feed/trypsin activity) was significantly higher in FLS 20-40 groups than in the control (P 0.05). Intestinal protease and trypsin activities were significantly elevated across all FLS treatments (P 0.05), while amylase peaked at FLS10 (51.76 ± 0.33 μmol maltose/hr/mg protein), and lipase activity remained unaffected (P > ; 0.05). Mucosal immunity was enhanced after 8 weeks, with skin lysozyme peaking at FLS20 (1.06 ± 0.03 μg/mL) and peroxidase at FLS5 (0.15 ± 0.01 μg/mL) (P 0.05). Serum immune responses were similarly improved, with significantly higher lysozyme (7.29 ± 0.17 μg/mL), peroxidase (0.18 ± 0.01 μg/mL), and ACH50 (342.10 ± 37.53) in FLS5 compared to the control (P 0.05). Gene expression analysis revealed significant upregulation of growth-related (IGF-1, GH, EF-α), orexigenic (ghrelin, NPY-α, galanin), antioxidant (nrf-2, GST-α), and immune-related (TNF-α, NFκB) genes in FLS1020 groups (P 0.05), while Keap-1 was suppressed and hsp70 was reduced at moderate FLS levels. These findings indicate that moderate dietary inclusion of FLS (520 g/kg) optimally enhances growth, digestive efficiency, innate immunity, and antioxidant capacity in Nile tilapia, supporting its use as a functional and sustainable feed additive in aquaculture.Longan peel powder experimentThis study investigated the effects of dietary inclusion of longan peel (LP) powder on growth performance, immune responses, digestibility, and immune-antioxidant related gene expressions in Nile tilapia (Oreochromis niloticus) reared under biofloc conditions. A total of 300 healthy fish (average initial weight: 13.70 ± 0.06 g) were randomly assigned into five dietary treatment groups: 0 g kg⁻¹ (LP0), 10 g kg⁻¹ (LP10), 20 g kg⁻¹ (LP20), 40 g kg⁻¹ (LP40), and 80 g kg⁻¹ (LP80), with three replicates each, for 60 days. Results demonstrated that LP supplementation significantly improved weight gain (WG), specific growth rate (SGR), feed conversion ratio (FCR), and enhanced nutrient digestibility, with carbohydrate digestibility increasing by 88108% and protein digestibility showing a significant dose-dependent improvement, peaking at 40 g/kg inclusion (P 0.05), compared to the control group. Skin mucus and serum immune parameters (lysozyme and peroxidase activities) were markedly enhanced in LP-fed groups at both 4 and 8 weeks (P 0.05). Similarly, mRNA transcript analysis revealed significant upregulation of immune-related genes (IL-1, IL-8, and LBP) and antioxidant-related genes (GST-α, GPX, and GSR) (P 0.05). Polynomial regression analysis indicated that the optimal inclusion level of LP powder ranged between 4548 g kg⁻¹ for maximizing growth, immunity, digestibility, and immune-antioxidant gene expressions. Collectively, the findings confirm that longan peel powder is a promising functional feed additive for Nile tilapia aquaculture.