Effects of Host-Associated Lactic Acid Bacteria on the Growth Performance, Antioxidant, Immune Responses and Gut Microbiota of Red Tilapia (Oreochromis sp.)

Hew, Shu Ying (2023) Effects of Host-Associated Lactic Acid Bacteria on the Growth Performance, Antioxidant, Immune Responses and Gut Microbiota of Red Tilapia (Oreochromis sp.). Masters thesis, Tunku Abdul Rahman University of Management and Technology.

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Abstract

Economic sustainability and emergence of infectious diseases are challenges in tilapia aquaculture. Lactic acid bacteria (LAB) are well-known feed additives with probiotic effects in improving overall performance of livestock. The current study evaluated the effects of host-associated LAB (HaLAB) on growth performance, antioxidant, immune responses and gut microbiota of red tilapia (Oreochromis sp.) by conducting a 86 days feeding trial with 180 fingerlings. The HaLAB used was Leuconostoc lactis TARicum AI2 (NCBI accession number: MW362783), whereby its probiotic characteristics were evaluated in previous study, coated on commercial feed at 109 CFU g-1. The fingerlings were divided into 3 tanks per treatment (control and HaLAB diets) and were fed twice a day. After trial, the growth performance were evaluated and compared, fillet, serum and organs such as liver and intestine were collected for antioxidant, immune responses and microbiota diversities analysis. Results showed tilapia fed with HaLAB diet had significant improvement in feed conversion ratio (FCR) and protein efficiency ratio (PER) as compared to those fed with control diet (p > 0.05), although antioxidants (catalase, superoxide dismutase, glutathione peroxidase and myeloperoxidase), serum lysozyme and antibacterial activities showed no significant differences between two diets (p < 0.05). In general, cytokine expressions were upregulated in HaLAB group as compared to control group. The gut microbiota for both groups were majorly composed of Fusobacteria, Bacteroidetes, Actinobacteria and Proteobacteria, with Cetobacterium (Fusobacteria) as the predominant genus. HaLAB group revealed significantly higher proportion of Firmicutes as compared to control (p < 0.05). Alpha diversity indices showed no significance between two diets (p > 0.05). Beta diversity indices proved exclusive groups of bacteria present in specific diet only. The genera Leuconostoc and Clostridium were more abundant in HaLAB group. In conclusion, tilapia fed with HaLAB diet had FCR and PER significantly enhanced, upregulated cytokine expressions and modulated gut microbiota. Keywords: Host-associated probiotics, lactic acid bacteria (LAB), Oreochromis sp. (red tilapia), Feed Conversion Ratio (FCR), Intestinal microbiota