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

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.

A detailed look at the impacts of biofloc on immunological and hematological parameters and improving resistance to diseases

The innate immunity of invertebrates serves as a critical trait that provides a valuable foundation for studying the common biological responses to environmental changes. With the exponential growth of the human population, the demand for protein has soared, leading to the intensification of aquaculture. Regrettably, this intensification has resulted in the overuse of antibiotics and chemotherapeutics, which have led to the emergence of resistant microbes or superbugs. In this regard, biofloc technology (BFT) emerges as a promising strategy for disease management in aquaculture. By harnessing the power of antibiotics, probiotics, and prebiotics, BFT offers a sustainable and eco-friendly approach that can help mitigate the negative impacts of harmful chemicals. By adopting this innovative technology, we can enhance the immunity and promote the health of aquatic organisms, thereby ensuring the long-term viability of the aquaculture industry. Using a proper carbon to nitrogen ratio, normally adding an external carbon source, BFT recycles waste in culture system with no water exchange. Heterotrophic bacteria grow along with other key microbes in the culture water. Heterotrophs play a major role in assimilating ammonia from feed and fecal waste, crucial pathway to form suspended microbial aggregates (known as 'biofloc'); while chemoautotrophs (e.g. nitrifying bacteria) oxidize ammonia into nitrite, and nitrite into nitrate promoting a healthy farming conditions. By using a highly aerated media and an organic substrates that contain carbon and nitrogen, protein-rich microbes are able to flocculate in culture water. Several types of microorganisms and their cell components have been studied and applied to aquatic animals as probiotics or immunostimulants (lipopolysaccharide, peptidoglycan, and 1-glucans) to enhance their innate immunity and antioxidant status, thereby enhancing their resistance to disease. In recent years, many studies have been conducted on the application of BFT for different farmed aquatic species and it has been observed as a promising method for the development of sustainable aquaculture, especially due to less use of water, increased productivity and biosecurity, but also an enhancement of the health status of several aquaculture species. This review analyses the immune status, antioxidant activity, blood and biochemical parameters, and level of resistance against pathogenic agents of aquatic animals farmed in BFT systems. This manuscript aims to gather and showcase the scientific evidences related to biofloc as a 'health promoter' in a unique document for the industry and academia.