The present study was carried out to evaluate the dietary effects of host‐associated lactic acid bacteria on growth performance, metabolic enzyme activities, and immune response of Macrobrachium rosenbergii juveniles. To formulate the test diets, a control (Con) diet was supplemented with a commercial probiotic and three host‐derived bacteria Enterococcus faecalis (EC), Lactococcus lactis I (LC‐I), and L. lactis II (LC‐II), which were previously isolated from the gastrointestinal tract of adult individuals of M. rosenbergii. Juvenile M. rosenbergii (0.65 ± 0.008 g) were randomly stocked at 20 individuals/100 L of fiberglass tanks with three replications for each test diet. After 50 days, juveniles fed the diets LC‐I and LC‐II showed significantly higher (p < .05) weight gain, specific growth rate, and the lowest feed conversion ratio. The analyses of glutamic oxaloacetate transaminase and glutamic pyruvate transaminase in muscle and hepatopancreas revealed significantly (p < .05) reduced values in LC‐I fed juveniles. The total hemocyte count and phenoloxidase activity were significantly increased (p < .05) in LC‐I and LC‐II fed juveniles. The relative mRNA expression patterns of immune‐related α2‐M, LGBP, ProPO, Cu, Zn‐SOD, TG, PE, AKP, and ACP genes were significantly (p < .05) upregulated in juveniles fed with LC‐I followed by the diet LC‐II. Finally, the study suggests that the growth performance and immune response of M. rosenbergii can be improved through supplementation of host‐associated L. lactis bacteria for its higher production.

Aim: Methodology:Results: Interpretation:This study aimed to identify lactic acid bacteria (LAB) isolated from with an emphasis on their antimicrobial activities against pathogens.Six broodstocks were collected from local fishermen and brought to the laboratory where all of them were sacrificed and their digestive tracts were collected. Fourteen isolates grew in MRS agar medium and subjected to pH between 6.3 -6.6 at 37°C. The strains were tested for their ability to inhibit the growth of pathogens; , and . Molecular identification of the strains were performed by amplifying and sequencing the 16S rDNAby which the results were then compared to the database of known 16S rDNAsequences.The results showed that 57% of the strains inhibited growth against both and whereas only 21% of the strains inhibited growth against all the pathogens tested. The identification result showed that 6 strains had high similarity with , whereas 4 isolates had high similarity with and 4 isolates were affiliated with .All strains were identified as lactic acid bacteria, and strains with the best ability to inhibit pathogens will be selected for further studies on their potential as dietary additive. Macrobrachium