Rômullo Guilherme dos Santos Almeida

This study evaluated the use of the essential oil of Lippia origanoides (EOLO) as an anesthetic for juvenile pacu, Piaractus mesopotamicus. Two experiments were performed. In Experiment I, anesthetic induction and recovery times and ventilatory frequency (VF) were determined for fish (n= 48; 29.94 ± 6.69 g) exposed to different EOLO concentrations [0 (control - 4000 µL alcohol L^-1), 25, 50, 100, 200 and 400 µL L^-1]. From the responses obtained in Experiment I, the EOLO concentrations of Experiment II (n= 36; 29.25 ± 5.90 g) were determined, which evaluated the effects of 0 (control - 2000 µL alcohol L^-1), 50 (outside recommended induction and recovery times) and 200 µL L^-1 (within recommended induction and recovery times) by analyzing immunohematological and biochemical parameters at different collection times (1 h and 24 h post-induction). Fish survival was 100% in both experiments. The EOLO concentration of 25 µL L^-1 was not able to induce deep anesthesia in the animals, while the concentration of 200 µL L^-1 showed induction and recovery times within the range indicated for fish and was efficient at reducing VF during induction. No differences were observed in immunohematological and biochemical parameters among concentrations, but differences were observed in comparisons between collection times. Nonetheless, blood variables returned to levels considered normal for the species in approximately 24 hours. Therefore, an EOLO concentration of 200 µL L^-1 can be considered safe for use prior to biometric management of P. mesopotamicus.

The use of immunostimulants in fish is a preventive method to combat infections that frequently affect animals in the productive environment, being a biological alternative with great potential to replace antibiotics. They can be divided into two groups, immunonutrients (vitamins, minerals and amino acids) and non-nutritional immunostimulants (essential oils, plant extracts, herbal medicines, prebiotics, probiotics and symbiotics), which are currently the most used. Both alternatives aim to maximize performance, reduce stress, improve the health of the gastrointestinal tract and consequently immunity and resistance to disease in fish. Thus, this literature review aims to address the different immunomodulators used in fish farming, emphasizing the types of immunomodulators, mechanism of action in the body, levels of inclusion, as well as reporting studies carried out with different species produced in an intensive system of large scale.

PDF Abstract 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.