Use of Lactic Acid Bacteria from Nile tilapia Oreochromis niloticus as Probiotics for Sustainable Production and Improvement in Fish Welfare

Abstract

Two studies were conducted to investigate the effectiveness of lactic acid bacteria (LAB) from the intestine, gills, and skin of Nile tilapia Oreochromis niloticus as probiotics to promote growth, bolster the immune system, and improve general fish welfare. Results of the first study including LAB characterization indicated four major strains in the three organs as Lactobacillus fermentum (60.0%), L. brevis (16.7%), L. acidophilus (13.3%) and L. xylosus (10.0%). Safety tests of these LAB isolates conducted on some samples of the fish confirmed that they were non-pathogenic. In the second study L. fermentum, which showed the greatest promise as a probiotic, was used at different dilution levels to prepare diets for feeding O. niloticus juveniles weighing 18.1±0.1g. Diets 1-5 contained 0 colony forming unit (cfu)/g, 103cfu/g, 105cfu/g, 107cfu/g and 109cfu/g of L. fermentum, respectively. The feeding trials in fish fed diets 1-5, resulted in growth from the initial weight of 18.1g to 32.0e, 46.0a, 44.3b, 43.9c and 40.8d g, respectively. Inclusion of L. fermentum in the diets increased carcass protein, pack cell volume, hemoglobin, RBC, and reduced glutamate (P<0.05). Challenge tests conducted on the fish using pathogenic Pseudomonas aeruginosa indicated that the diets supplemented with L. fermentum improved fish immune responses. In conclusion, the studies revealed that LAB from O. niloticus can act as probiotics to improve growth, immune responses, and fish welfare.