~ 506 ~ International Journal of Fisheries and Aquatic Studies 2017; 5(1): 506-514 E-ISSN: 2347-5129 P-ISSN: 2394-0506 (ICV-Poland) Impact Value: 5.62 (GIF) Impact Factor: 0.549 IJFAS 2017; 5(1): 506-514 © 2017 IJFAS www.fisheriesjournal.com Received: 09-11-2016 Accepted: 10-12-2016 V Narmatha Department of Zoology Bharathiar University Coimbatore, Tamil Nadu, India Dr. P Saravana Bhavan Department of Zoology Bharathiar University Coimbatore, Tamil Nadu, India M Karthik Department of Zoology Bharathiar University Coimbatore, Tamil Nadu, India V Srinivasan Department of Zoology Bharathiar University Coimbatore, Tamil Nadu, India R Mahendran Department of Microbial Biotechnology Bharathiar University Coimbatore Tamil Nadu, India T Satgurunathan Department of Zoology Bharathiar University Coimbatore, Tamil Nadu, India Correspondence Dr. P Saravana Bhavan Professor Department of Zoology Bharathiar University Coimbatore, Tamil Nadu, India E-mail: bhavan@buc.edu.in Lactobacillus fermentum on ammonia reduction and growth promotion of Macrobrachium rosenbergii post- larvae, and in vitro competitive exclusions of pathogenic bacteria V Narmatha, Dr. P Saravana Bhavan, M Karthik, V Srinivasan, R Mahendran and T Satgurunathan Abstract The effect of a probiotic bacterium, Lactobacillus fermentum on ammonia reduction and growth promotion of Macrobrachium rosenbergii post-larvae, and in vitro competitive exclusion of certain pathogenic bacteria, Shigella sonnei, Salmonella bongori, Klebsiella pneumoniae, Escherichia coli and Pseudomonas aeruginosa were studied. It was also aimed to recommend the ideal quantum of water for maintenance of M. rosenbergii PL. L. fermentum was viable in the feed even on day 15 after the feed was formulated, and hence, the feed was freshly prepared once in 15 days and fed to experimental PL. Three groups of prawns (0.09±0.02 g) consisted of 15, 30 and 45 PL respectively were maintained with 25 L of ground water irrespective of number of PL. Each group was fed with 0.5, 1.0 and 1.5% of L. fermentum incorporated diet for a period of 60 days without renewing the water medium. Control was received the feed without incorporation of L. fermentum. Up to 30 days, there was no mortality of PL observed in any of the three experimental as well as control groups. The results revealed that up to 1.8 PL staged prawns can be maintained per liter of water without mortality for 30 days (1.8 PL l -1 ). The mortality was related with density of PL, ammonia content and concentration of L. fermentum in the aquarium. The ammonia concentration was found to be significantly reduced in each experimental group when compared with control. After 30 days, the survival rate was found to be the best in the experimental group maintained with 30 PL (1.2 PL l -1 ) and fed with 1% of L. fermentum incorporated feed, followed by 0.5% and 1.5% when compared with control. In this group, the nutritional indices, such as weight gain, specific growth rate, food conversion ratio and protein efficiency ratio were also found to be the best. The concentrations of total protein, amino acid, carbohydrate and lipid were also found to be significantly (P<0.05) increased in this group. L. fermentum colony was established in the gut of M. rosenbergii PL. The in vitro competitive exclusions of pathogenic bacteria revealed that P. aeruginosa was sensitive to Amoxycillin, which was produced 17 mm zone of inhibition. While, the test sample, L. fermentum was produced 25 mm zone of inhibition against P. aeruginosa. It indicates the fact that P. aeruginosa was effectively/competitively excluded by L. fermentum. As L. fermentum incorporated feed fed M. rosenbergii PL produced significantly less ammonia, it can be utilized on aquaculture industry as feed additive. Keywords: Prawn, mortality, survival, growth, protein, Pseudomonas aeruginosa 1. Introduction Aquaculture has become an important economic activity in many countries, including China, Thailand, Bangladesh, Vietnam, Taiwan, India, Myanmar, Indonesia, Malaysia and USA. It is the world’s fastest growing animal protein production sector for human consumption. Among various aquaculture sectors, crustacean aquaculture has become one of the fastest growing animal production sectors in the world. Among several species of freshwater prawns, Macrobrachium rosenbergii was the first species, studied extensively and farmed commercially [1] . This species is indigenous to South and Southeast Asia, and the northern oceanic and western Pacific Islands [2] . It has become the main species for small-scale as well as large-scale farming because of its fast growth, large size, good meat quality, omnivorous feeding habit and established domestic and export markets worldwide. Ammonia is the main excretory product of aquatic organisms including crustaceans [3] . The susceptibility of cultured aquatic species to high concentration of nitrogenous compounds,