Use of Longan By-products as Feed Additives for Nile Tilapia (Oreochromis niloticus) Culture Under Biofloc System

Abstract

Tilapia is one of the most important aquaculture species in Thailand and around the world. The intensification and expansion of farmed fish has caused degradation of water and outbreak of diseases. To deal with diseases, the most common way is the use of antibiotics. However, an abuse of antibiotics can lead to the development of antibiotic-resistant bacterial strains, environmental hazards, food safety problems and decline in human resistance to pathogens. The objective of this work is to evaluate the effects of longan seed and longan peel on growth performance, innate immune response, relative immune and gene expression. Longan seed experiment Longan seed experiment This study evaluates the effects of longan seed powder (LS) on the growth performance, immunological response, and immune-antioxidant related gene expression of Nile tilapia (Oreochromis niloticus). Three hundred fish (13.82 ± 0.06 g) were divided into five experiments and fed 5 diets, including the basal diet (control without LS) and basal diet containing 10 (LS10), 20 (LS20), 40 (LS40), and 80 (LS80) g kg-1 LS for eight weeks. A completely randomized design (CRD) with three replications was utilised. The growth performance and immune response were measured at weeks 4 and 8 post feeding, while the gene expressions were determined at the end of the feeding trial. The results revealed that administration of LS could significantly (P < 0.05) improve specific growth rate (SGR), weight gain (WG), and feed conversion ratio (FCR) in Nile tilapia as compared to the control group. However, no significant differences (P > 0.05) were observed in survival rates among treatments. LS-supplemented diets showed enhanced serum peroxidase activity (SPA), serum lysozyme activity (SLA), skin mucus lysozyme activity (MLA), and skin mucus peroxidase activity (MPA) at weeks 4 and 8 post-feeding, with the highest values observed in the LS20 diet (P < 0.05). Additionally, LS-supplemented diets significantly up-regulated (P < 0.05) immune and antioxidant related gene expressions (IL1, IL8, LBP, GSTa, GPX, and GSR) in the liver and intestine, with highest values observed in the LS20 treatment. The present results confirmed the beneficial effects of LS as a functional feed additive and immunostimulant for Nile Tilapia culture in a biofloc system. Longan peel experiment The effects of longan peel powder (LP) in Nile tilapia (Oreochromis niloticus) on the growth performance, immunological response, and immune-antioxidant related gene expression. Three hundred fingerlings (13.82 ± 0.06 g) were fed five diets containing 0, 10, 20, 40, and 80 g kg-1 of LP. The growth performance and immune response were measured after weeks 4 and 8 of LP feeding. while the gene expressions were determined at the end of the feeding trial. As a result, revealed that administration of fish fed the longan peel diet gained weight and significantly improved specific growth rate (SGR), and feed conversion ratio (FCR) compared with the control (P < 0.05). The skin mucus lysozyme (MLA), skin mucus peroxidase (MPA), serum lysozyme (SLA), and serum peroxidase (SPA) activities were significantly higher (P < 0.05) in fish fed the LP diet after four and eight weeks. The highest MLA, MPA, SLA, andSPA levels were observed in fed LP40. The results of LP diets supplements on gene expressions of Nile tilapia IL1, IL8, LBP, GSTa, GPX, and GSR in the liver and intestine significantly improved compared to the control group (P < 0.05). with highest values observed in the LP40 treatment. Accordingly, LP can be potential used as a feed supplement in Nile tilapia farming under the biofloc system.