Bacterial-resistance, growth and immune competence of Oreochromis niloticus fed Lactobacillus fermentum

Abstract

Aquaculture production can be boosted with enhanced feed efficiency, growth and disease resistance using probiotics. In this study, the effects of Lactobacillus fermentum (LF) probiotic on growth, intestine, immune competence of Oreochromis niloticus, and the resistance to virulent Aeromonas hydrophila were investigated. A basal  (LF1) diet (35% crude protein) was formulated and five treatments with L. fermentum included at 1 x 10³ cfu/g (LF2), 1 x 10⁵ cfu/g (LF3), 1 x 10⁷ cfu/g (LF4), 1 x 10⁹ cfu/g (LF5) and 1 x 10¹¹ cfu/g (LF6). The six diets were each allotted to three groups of Oreochromis niloticus (1.85±0.01g mean weight) for 90 days. After which fish were injected with A. hydrophilia, fed and observed for 15 days. At the end of the 90 days, LF diets fed fish had higher (p<0.05) mean weight gain. Feed conversion ratio and specific growth rate were superior in fish fed LF3 and LF4. Villi height was significantly high in LF3, while microbial loads were more in the guts of fish fed probiotics. Blood packed cell volume and haemoglobin increased significantly in the groups fed LF. Hydrogen peroxide and malondialdehyde reduced significantly (p<0.05) in the liver and kidney of fish fed L. fermentum, while glutathione transferase and glutathione peroxidase activities were increased.  The challenge test with virulent Aeromonas hydrophila showed improved resistance in fish fed probiotic. Thus, the study disclosed improved growth performance, enhanced health status and better survival with the supplementation of Lactobacillus fermentum in the diets of Oreochromis niloticus.