International Journal of Aquaculture, 2025, Vol.15, No.1, 11-20 http://www.aquapublisher.com/index.php/ija 12 In light of this situation, some tools are commonly employed in an attempt to mitigate these effects, such as the use of chemotherapeutics in the prophylaxis and treatment of bacterial infections (Cardoso et al., 2021). However, when applied inappropriately, this practice has consequences for the environment and for animals, because, as well as leaving chemical residues in the environment, it can promote the selection of resistant bacterial strains (Hossain and Heo, 2021). Considering this scenario, other tools are being developed with the intention of reducing the use of chemotherapeutics, among which are phytochemicals. These have been investigated as nutritional strategies for use as modulators of immune, physiological, and antioxidant responses, acting as health promoters in animal production (Xu et al., 2020). An example of phytotherapeutics with great potential for use in aquaculture is açaí (Euterpe oleracea), an Amazonian fruit. Açaí (E. oleracea) is a species from the Arecaceae family, native to several countries in the Amazon region, such as Brazil, Venezuela, and Ecuador (Oliveira et al., 2020). This fruit stands out for its antioxidant, anti-inflammatory, and immunomodulatory properties, in addition to being rich in bioactive compounds such as polyphenols, essential fatty acids, and vitamins (Moura et al., 2022). Its main chemical constituents are anthocyanins, polyphenols, and flavonoids (Inácio et al., 2013). Furthermore, studies have shown that this fruit provides a wide range of therapeutic benefits and promotes health due to its nutritional value and phytochemical composition (Pacheco-Palencia et al., 2008). In consideration of the above, this research aimed to evaluate the impact of different levels of inclusion of freeze-dried açaí in the diet of koi carp on liver health through histological methods. 2 Materials and Methods 2.1 Biological materials The juvenile koi carp (C. carpio) were acquired from the Girassol fish farm in Joinville, Brazil, with an average weight of (6.2 ± 1.2) g and an average length of (7.8 ± 1.4) cm. The açaí (E. oleracea) used was of commercial origin. The feeding trial was conducted at the Aquatic Organism Health Laboratory (AQUOS) at the Federal University of Santa Catarina (UFSC), and all procedures were approved by the Animal Ethics Committee (CEUA) of UFSC (CEUA/UFSC 5552130324). 2.2 Dietas experimentais The procedure for preparing the feed was adapted from Heluy et al. (2023), using a commercial freeze-dried açaí product (Liomeal®), incorporated into a commercial feed that meets the nutritional requirements of the target species (Figure 1). For the formulation of the diets, 20 kg of feed was ground in a Willey knife mill. The feed was then divided into four treatments (5, 10, 15, and 20 g/kg) and a control group without açaí addition (0.0%), resulting in a total of five experimental diets. Figure 1 Hexagons indicate loss of the cord-like appearance of koi carp hepatocytes in the DC0.0% group (A); and maintenance of the cord-like appearance of koi carp hepatocytes in DA1.0% (B); Tukey (p<0.05)
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