ABSTRACT
This study aimed to determine the effects of dietary digestible protein (DP) on growth and physiological indicators in piapara. Three hundred piapara juveniles (24.0 ± 1.3 g) were distributed in 20 tanks of 130 L (15 fish/tank) with continuous aeration and water. Five isoenergetic diets (14.0 MJ·kg-1) were formulated to contain increasing levels of DP (21, 24, 27, 30 and 33%). After 77 days of feeding, increasing levels of digestible protein influenced final weight, specific growth rate and weight gain linearly (p < 0.05). Water ammonia concentration and liver alanine aminotransferase activity also showed a linear effect with an increasing DP level (p < 0.05), but no relationship was found between DP level and serum ammonia (p > 0.05). There was no linear and quadratic effect for hepatosomatic index, liver glycogen and liver lipid content (p > 0.05). On the other hand, the muscle lipid content decreased linearly with the increase in the DP level (p < 0.05), while the mesenteric fat index showed a linear and quadratic effect (p < 0.05) with an increasing curve until the peak of 25.77% DP. The activity of the hepatic malic enzyme also followed a quadratic pattern (p < 0.05) with a maximum point of 27.08% of DP. This contrasts with the hepatic enzyme glucose-6-phosphate dehydrogenase, which increased linearly with the increase in the DP level (p < 0.05). The results showed better productive performance for fish fed with the highest levels of DP, though greater excretion of ammonia in the water was also shown. Diets below 27% DP resulted in greater energy reserve, amino acid catabolism and lipogenesis. Therefore, the inclusion of 28 to 30% DP in the diet will be ideal for growth and physiological responses in piapara.(AU)
Este estudo teve como objetivo determinar os efeitos da proteína digestível (PD) da dieta sobre o crescimento e indicadores fisiológicos em piapara. Trezentos juvenis de piapara (24 ± 1,3 g) foram distribuídos em 20 tanques de 130 L (15 peixes/tanque) com aeração contínua e água. Cinco dietas isoenergéticas (14,0 MJ·kg-1) foram formuladas para conter níveis crescentes de PD (21, 24, 27, 30 e 33%). Após 77 dias de alimentação, níveis crescentes de proteína digestível influenciaram o peso final, taxa de crescimento específico e ganho de peso de forma linear (p<0,05). A concentração de amônia na água e a atividade hepática da alanina aminotransferase também apresentaram efeito linear com o aumento do nível de PD (p < 0,05), mas não foi encontrada relação entre o nível de PD e amônia sérica (p > 0,05). Não houve efeito linear nem quadrático no índice hepatossomático, no glicogênio hepático e na concentração de lipídios hepáticos (p > 0,05). Por outro lado, o conteúdo de lipídio muscular diminuiu de forma linear com o aumento do nível de PD (p < 0,05), enquanto o índice de gordura mesentérica apresentou efeito linear e quadrático (p < 0,05) com curva crescente até o ponto máximo em 25,77% de PD. A atividade hepática da enzima málica também seguiu um padrão quadrático (p < 0,05) com ponto máximo em 27,08% de PD, diferentemente da enzima glicose-6-fosfato desidrogenase hepática, que aumentou linearmente com o aumento do nível de PD (p < 0,05). Os resultados mostraram melhor desempenho produtivo para os peixes alimentados com os maiores níveis de PD. Por outro lado, também proporcionaram maior excreção de amônia na água. Dietas abaixo de 27% PD resultaram em maior reserva energética, catabolismo de aminoácidos e lipogênese. Portanto, a inclusão de 28 a 30% PD na dieta será ideal para o crescimento e respostas fisiológicas em piaparas.(AU)
Subject(s)
Animals , Proteins/physiology , Digestive System Physiological Phenomena , Characiformes/metabolism , Weight Gain/physiology , Alanine Transaminase/adverse effects , Eating/physiologyABSTRACT
In the present study, two approaches were followed to evaluate the metabolic responses of tambaqui (Colossoma macropomum), a frugivorous species, to intraperitoneal (IP) administration of glucose (GLU) and fructose (FRU) in fed (FED) and 10-day fasted (FAST) fish. Glucose and fructose tolerance tests were performed to assess the carbohydrate utilization and complementary NMR-metabolomics analyses were done to elucidate the impacts of sugar mobilization on the metabolic profile of plasma, liver and muscle. Blood was sampled from FED groups at 0, 3, 6 and 24 h; and at 0 and 24 h from FAST groups. Significant differences were observed in the hyperglycaemic peak between sugars at 3 h (GLU - 13.7 ± 2.0 mM vs. FRU - 8.7 ± 1.1 mM; saline 6.3 ± 0.6 mM) and on the return to normoglycaemia (GLU - 8.5 ± 2.2 mM vs. FRU - 5.2 ± 0.9 mM; saline 4.9 ± 0.6 mM) 6 h after IP on the FRU fish. The NMR-metabolomics approach allowed to conclude that tambaqui seems to be more responsive to the feeding regime (FED vs. FAST) than to the injected sugar (FRU vs. GLU). From the studied tissues, plasma showed no significant variations between feeding regimes at 24 h after IP, while muscle and liver revealed some variations on the final metabolome profile between FED and FAST groups. The metabolome variations between feeding regimes are indicative of changes on the amino acid utilization. Fish from FAST group seem to utilize amino acids as energy source rather than for protein synthesis and muscle growth. Variations on glucose concentration in muscle can also indicate different utilization of the sugars depending on the feeding regime.