We tested the efficacy of a commercial product (Glucan-MOS) derived from yeast Saccharomyces cerevisiae, containing two combined products, β-1,3-1,6 glucans and mannans on the growth, feed efficiency, stress and innate immune responses of juvenile pacu (Piaractus mesopotamicus) after a stressful handling and bacterial inoculation. For this, we evaluated the serum cortisol and plasma glucose levels, the respiratory activity of leukocytes, the serum lysozyme levels, as well as the number of circulating erythrocytes and leukocytes of fish fed during 30 days with diets containing increased levels of Glucan-MOS (0.0, 0.1, 0.2, 0.4 and 0.8%). The supplementation of 0.1% improved weight gain, feed conversion and the protein efficiency ratio compared to a control diet. The 0.2 and 0.4% Glucan-MOS diets were sufficient to increase the respiratory burst of leukocytes and lysozyme activity, the number of thrombocytes, neutrophils and monocytes in the blood after a stressful handling and bacterial challenge, and minimized stress response as shown by decreased cortisol and glucose levels when compared to the control. The results of this work reinforce the benefits of the adoption of feeding strategies including combination of both β-1,3-1,6 glucans and mannans as a dietary supplement in periods prior to intensive management. The 30-day period was sufficient to stimulate growth performance, improve nutrient utilization, minimize stress response and modulate innate immunity responses.

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This study evaluated the dietary supplementation of ginger Zingiber officinale essential oil for the Neotropical catfish Pseudoplatystoma reticulatum, its effects on fish hematology, immunology, the response of these variables to induction of stress (exposition to air for 3 min), and a bacterial challenge with Aeromonas hydrophila, and the effects on liver histomorphometry. Three levels of the ginger essential oil were evaluated (0.5, 1.0 and 1.5%) in addition to a control group (0%) in a feeding trial for 65 days in triplicate. Fish hematology and immunology were assessed at five different moments: after the feeding trial (0), after the stress induction (stress), and three points after the bacterial challenge (3, 6 and 24 h post-challenge). Fish fed the ginger essential oil supplemented diets did not exhibit significant differences between the hematocrit at the 0-sample point and the 24 h post-challenge point (P ≥ 0.05), while fish fed the control diet presented significantly lower values for the hematocrit when comparing those same two moments (P < 0.05). The thrombocytes count for fish fed the 0.5% essential oil supplemented diet was significantly higher than all other groups after the feeding trial (P < 0.05), and their total leukocytes count after the stress induction was also significantly higher than the other treatments (P < 0.05). Although the results mentioned above indicate that the ginger essential oil had positive health effects on the fish, no significant differences in survival after the challenge with A. hydrophila were observed (P ≥ 0.05). Lastly, histomorphometry suggests that the essential oil did not negatively impact fish hepatocytes.

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A utilização de imunoestimulantes em peixes é um método preventivo para combater infecções que frequentemente acometem os animais no ambiente produtivo, sendo uma alternativa biológica com grande potencial para minimizar o uso excessivo de antibióticos. Na aquicultura, os imunomoduladores são divididos em dois grupos, os imunonutrientes (vitaminas, minerais e aminoácidos) e os imunoestimulantes não nutricionais (óleos essenciais, extratos de plantas, fitoterápicos, prebióticos, probióticos e simbióticos), sendo estes últimos, muito estudados atualmente. Ambas alternativas objetivam maximizar o desempenho, reduzir o estresse, melhorar a saúde do trato gastrointestinal e, consequentemente, a imunidade e resistência às doenças dos peixes. Assim, com a presente revisão de literatura os objetivos são abordar os diferentes imunomoduladores utilizados na piscicultura, dando ênfase ao mecanismo de ação no organismo e níveis de inclusão, bem como ressaltar resultados de estudos realizados com diferentes espécies produzidas em sistema intensivo em larga escala.