Prebióticos na alimentação da tilápia-do-nilo sob baixa temperatura: desempenho produtivo, respostas fisiológicas e morfologia intestinal

Abstract

Intensive systems are increasingly used in species of increasing economic importance, such as the Nile tilapia (Oreochromis niloticus), considered a consolidate species in global aquaculture and one of the most important in Brazilian fish farming. In the Southern region of the country, mainly, physiological changes occur in fish when there is a decrease in water temperature in the winter months, which can facilitate the occurrence of diseases, and a potential solution to reduce physiological disorders in the animal is the use of prebiotic additives such as β-glucan and mannanoligosaccharides (MOS), which can boost the fish's immune system under low water temperature. In this study, 180 tilapia juveniles were randomly distributed in 12 experimental nurseries with an average temperature of 18,32 ± 1,83ºC, composing a completely randomized design with three replications, to evaluate the diets: control, without prebiotic supplementation (DC), 0.2% MOS inclusion (DM), 0.2% inclusion βglucans (DG) and 0.1% MOS + 0.1% inclusion β-glucans (DMG). The fish were fed twice a day (10h00m e 17h00m) for 90 days. Productive performance, hematological, immunological, and intestinal morphology parameters were evaluated. Weight gain, feed conversion index, specific growth rate and condition factor were not influenced by diets, feed intake was significantly lower with DG (P<0.05) when compared with DC. There were no changes in hematology or blood biochemistry (P>0.05) due to the inclusion of prebiotics in the diet. The level of lysozyme in serum was increased by DM (P<0.05), in the case of lysozyme in mucus, it was increased by treatments DM and DG (P<0.05), when compared to DC. The greatest response in the respiratory activity of leukocytes was observed in fish fed with DMG (P<0.05). The phagocytic function of the leukocytes and the length of the height of the intestinal villi were higher (P<0.05) in fish that received prebiotic supplements when compared to fish that received DC. Dietary supplementation with 0.2% MOS and 0.1% MOS + 0.1% β-glucans positively modulates the non-specific immune response and intestinal morphology, as well as the inclusion of 0.2% β- Dietary glucans improve the intestinal structure of Nile tilapia kept at low water temperature for 90 days.