Imunoestimulação em tambaqui (Colossoma macropomum): desempenho produtivo, respostas hemato-imunológicas e desafio com Aeromonas jandaei

Abstract

Tambaqui (Colossoma macropomum) is the main native species produced in Brazil and in its breeding epizootic outbreaks occur, caused by bacteria of the genus Aeromonas, culminating in respiratory losses. In this sense, there is a growing search for alternatives that increase the response of fish against pathogens by stimulating the immune system. Thus, the objective of the study was to evaluate the influence of dietary supplementation of the immunostimulant Aquate Fish®, with Saccharomyces cerevisiae yeast, on productive performance, hemato-immunological parameters and challenge with Aeromonas jandaei in tambaqui juveniles. For this, four treatments were evaluated, with three repetitions: T1= control (without addition); T2= 6.0; T3=9.0; T4= 12.0 g kg-1 of Aquate Fish® additive. Treatments were administered via diet for 30 days. Zootechnical performance parameters such as weight gain, feed conversion, condition factor, hepatosomatic index and survival were evaluated; hematological parameters such as hematocrit, haemoglobin, erythrocytes, and Wintrobe hematimetric indices; in biochemical variables, levels of total proteins, aspartate aminotransferase and alanine aminotransferase, as well as albumin, globulin and albumin:globulin ratio were determined; for immunological analysis, the respiratory activity of leukocytes and lysozyme concentration were determined. After 30 days, fish from different treatments were inoculated with A. jandaei (108 CFU mL-1), while fish from the control group were inoculated with PBS and observed daily for 10 days. Supplementation with S. cerevisiae had no influence on zootechnical performance variables, and in 30 days there was no fish mortality. Changes were noted in hemato-immunological parameters: significant reduction in hematocrit values in the 12 g kg-1 treatment compared to 6 and 9 g kg-1, increase in aspartate aminotransferase in the 6 g kg-1 treatment, which significantly differed from the 0 and 9 g kg-1 treatments, and significantly increased leukocyte respiratory activity in the 9 g kg-1 treatment compared to the 12 g kg-1 Aquate Fish® treatment. After the challenge, lower survival was recorded for fish in the control group inoculated with A. jandaei and also in the treatments with 6 and 9 g kg-1 of the additive, significantly different from the control group with PBS, which reached 100% survival. Among treatments with Aquate Fish®, the highest survival rate (75%) was recorded with 12 g kg-1. The results indicate that dietary supplementation of tambaqui with Aquate Fish® does not promote negative effects on zootechnical performance and hemato-immunological parameters, and a concentration of 12 g kg-1 increases resistance to infection by A. jandaei.