Efeito agudo e subcrônico da amônia sobre a tilápia do Nilo Oreochromis niloticus

• Ano de defesa: 2018
• Autor(a) principal: Franklin Fernando Batista da Costa
• Tipo de documento: Dissertação
• Tipo de acesso: Acesso aberto
• Idioma: por
• Instituição de defesa: Universidade Federal de Minas Gerais; UFMG
• Palavras-chave em Português: Produção Animal; Zootecnia; Produção animal; Amônia; Toxidade Testes; Compostos nitrogênicos; Tilápia (Peixe) Criação
• Link de acesso: http://hdl.handle.net/1843/BUOS-BC2HEM

The presence of nitrogen compounds in closed environments and commercial fish production is frequent. These compounds can be found in the form of NH3, NO2- and NO3-, which can reach high levels especially in water retention systems such as Recirculated Aquaculture Systems (RAS) and Biofloc Technology (BFT). The toxicity of each of these compounds to culture animals is dependent on the concentration in the environment. Among the nitrogenous forms cited, ammonia is the most toxic to aquatic organisms due to its ability to cause damage to the animal's body. Nile tilapia is one of the most cultivated species of fish in the world, yet its production in intensified environments encounters problems with ammonia accumulation. In view of the above, the objective of this study was to estimate the LC50 of this compound for tilapia juveniles, besides studying and evaluating the changes caused in the hemic and gill tissues due to the acute and subchronic exposure to ammonia and the effectiveness of the detoxification period. The acute toxicity tests lasted 96 h, while the subchronic test and the detoxification period lasted 8 and 4 days, respectively. Groups of 12 juveniles of tilapia (12.76±1.24 cm and 34.07±10.42 g) were allocated in 20 tanks of 100 L of water and constituted the treatments that received increasing concentrations of ammonia, with exception of the detoxification period. All treatments were performed with two replicates. In the acute stage, the animals were submitted to concentrations 0,42±0,03; 0,87±0,18; 1,52±0,25; 2,00±0,21; 3,77±0,46; 5,02±0,50; 5,52±0,63; 8,43± and 8,71±0,06 mg.L-1 - NH3-N and in the chronic stage at 0,42±0,03; 0,87±0,18; 1,52±0,25; 2,00±0,21 and 3,77±0,46 mg.L-1 NH3-N. The remaining animals from the acute and subchronic tests were used in subchronic experiment (06 and 12 mg. L-1 TA-N). The estimated LC50 for ammonia at 24, 48, 72 and 96 h in this study was 133.29; 124.58; 113.52 and 112.57 mg.L-1 TA-N; 6.08; 5.32; 4.42 and 4.35 mg.L-1 NH3-N, respectively. The mean lactate, ALT, AST, glucose and urea parameters increased in the higher ammonia concentrations compared to the control (P <0.05). Histopathological analysis revealed alterations in the gills of animals exposed to ammonia in the acute (96 h), subchronic (8 days) and detoxification (4 days) tests. Hyperplasia with lamellar fusion, loss of secondary lamellar structure, lamellae with severe loss of structure, necrosis, epithelial detachment, hyperplasia, aneurysm and edema were lesions found in the gills of the acute and subchronic test animals. There was recovery in the gills of animals that went to the detoxification period, however, they still presented alterations. Tilapia juveniles were tolerant to ammonia and the estimated safety levels were considered real. The detoxification period is efficient for the recovery of tilapia juveniles intoxicated by ammonia.