The production of tambaqui Colossoma macropomum has been undergoing financial losses due to parasitic infection by the acanthocephalan Neoechinorhynchus buttnerae, raising an alert for aquaculture in South America. The lack of adequate treatment and use of unlicensed chemicals encourages research for alternative solutions with minimal side effects. The objectives of this study were to evaluate the in vitro antiparasitic potential of commercial nutraceutical products (Natumix® and BioFish®) against N. buttnerae and to assess the respective in vivo toxic effects on the host tambaqui. For in vitro assays, parasitized fish were necropsied for acanthocephalans sampling. The parasites were exposed to three concentrations (0.078, 0.313 and 1.25 mg/ml) of each product, as well as controls (one without product and another with a solubilizer). For the in vivo acute toxicity test, juvenile fish (<0.1 g) were exposed to five increasing concentrations of each product. Mortality of tambaqui was recorded at 24, 48, 72 and 96 h. The estimated lethal concentration (LC) for 10, 50, 90 and 99% of fish was determined to classify the toxicity of the products on the target species. After in vitro efficacy tests, the highest concentrations (1.25 mg/ml) caused 100% mortality of the parasites in both products, but only Natumix® caused 100% mortality using the intermediate concentration (0.313 mg/ml) after 24 h. According to the acute toxicity result, the LC50 classified the nutraceutical products as slightly toxic for tambaqui. The tested products had a parasiticidal effect on N. buttnerae, and the toxicity test showed that both products have therapeutic potential when added to the diet.

The present study evaluated the effects of commercial guarana (Paullinia cupana) powder as a growth-promoter and natural antioxidant supplement in aquafeeds. In Experiment 1, fish were fed with graded levels of guarana powder (0, 1.25, 2.5, 5 and 10 g/kg) during 60 days. Growth, hemato-immunological and biochemical performance were evaluated in healthy fish and in fish after infection by Aeromonas jandaei. In Experiment 2, the supplemented feed was stored for 90 days, in which tests were carried out regarding the quantity of phenolic compounds and the inhibition of lipid peroxidation. As a result of Experiment 1, fish fed guarana-supplemented diets and infected by A. jandaei presented better parameters of leukocyte respiratory activity, total proteins, globulin, albumin, alanine aminotransferase (ALT), leukocytes, lymphocytes, neutrophils, monocytes and thrombocytes. As a result of Experiment 2, levels of phenolic compounds were not altered (p > 0.05) by the guarana-supplemented diets. An increase in the concentration of malondialdehyde (MDA) and a lower oxygen radical absorbance capacity (ORAC) was observed in the fish fed diets with the highest level of guarana supplementation. As conclusion, guarana did not impair productivity and revealed a possible cytoprotective and hepatoprotective effect in fish infected by A. jandaei. Therefore, guarana seems to be an interesting additive to be included at levels of up to 1% in special feeds to be used prior to stressful situations in aquaculture. Additionally, guarana had no protective effect against lipid peroxidation and showed a pro-oxidant effect in diets with higher supplementation levels.