Colossoma macropomum or black pacu is the most produced native species in South America and disease are the main obstacles to development its production. Among the most important bacteria for the species we highlight the group of mobile Aeromonas , Flavobacterium columnare and Pseudomonas sp., in which treatments with various groups of antimicrobials are used indiscriminately and without criteria, causing waste problems in the final product, environmental impact and immunosuppression in animals. Thus, emerging alternatives to antimicrobials have been tested and include the use of probiotics, whose main mechanism of action is inhibition of pathogens, production of digestive enzymes and improvement of the immune system. In the present work we investigated the probiotic potential bacteria isolated from the black pacu intestine, which after catalase tests, bile tolerance, pathogen antagonism and sensitivity to commercial antimicrobials indicated four lactic acid bacteria Pediococcus pentosaceus , Lactococcus lactis , Staphylococcus hominis and Enterococcus hirae. The four strains were lyophilized and added to the black pacu diet at a concentration of 106 CFU / kg with soybean oil added (2%) and the control group received only the lyophilized skimmed milk with the oil. Fish were fed three times a day for 60 days to determine productive performance and blood samples were taken on days 0, 7, 15, 30, 45 and 60 to determine hematological (hematocrit, hemoglobin concentration, total erythrocyte count, mean corpuscular volume (MC V), mean corpuscular hemoglobin (HCM) and mean corpuscular hemoglobin concentration (CHCM) and immunological variables (lysozyme concentration, complement system activity and leukocyte respiratory activity) . The results found so far demonstrated that the four probiotic strains did not significantly change the hematological variables of black pacu , however, the leukocyte respiratory activity (oxidative burst) was higher in fish fed with the diet containing the bacterium Pediococcus pentosaceus and Lactococcus lactis. The results found shown that at least two native bacteria isolated from black pacu could in future be used commercially to prevent bacterial disease and provide consumers with a waste free and environmentally sustainable fish.
Acknowledgment: This work was supported by Fundação de Amparo à Pesquisa do Estado de São Paulo - Brazil (FAPESP - São Paulo Research Foundation), Grants 2018/07553-9 and CNPq 305007/2016-5.