RESUMO A digestibilidade do trigo e seus co-produtos foi avaliada em dietas extrusadas para juvenis de tilápia do Nilo. Foram avaliados os coeficientes de digestibilidade aparente (CDAs) de matéria seca (CDAMS), energia bruta (CDAEB), proteína bruta (CDAPB), aminoácidos essenciais (AAEs) e aminoácidos não essenciais (AANEs) do triguilho, trigo, farelo de trigo, fibra grossa de trigo e gérmen de trigo. Utilizou-se uma dieta de referência e dietas de teste, com 5,0g/kg de óxido crômico (Cr2O3) como indicador externo. O CDAMS, CDAPB e CDAEB foram maiores (P< 0,05) no triguilho, trigo e germen de trigo do que para farelo de trigo e fibra grossa de trigo. Os CDAs de todos os aminoácidos (AAs) foram maiores que 80%, exceto para treonina no farelo de trigo e fibra grossa de trigo, superior a 90% para triguilho e germen de trigo. Os valores de todos os ingredientes investigados foram elevados para CDAPB, e os CDAs de AAEs e AANEs. Uma forte correlação negativa foi detectada para fibra bruta e cinzas com os ADCs de matéria seca, energia bruta e proteína bruta. De maneira geral, os ingredientes provenientes do trigo possuem boa digestibilidade da proteína e aminoácidos, porém o alto conteúdo fibroso reduz os CDAMS e CDAEB, em dietas extrusadas para a tilápia do Nilo.

SUMMARY In the present study, we investigated the digestibility of wheat and its coproducts in extruded diets for juvenile Nile tilapia. Specifically, we evaluated the apparent digestibility coefficients (ADCs) of dry matter (ADCDM), gross energy (ADCGE), crude protein (ADCCP), essential amino acids (EAAs), and non-essential amino acids (NEAAs) in winter wheat, spring wheat, wheat middling, wheat bran, and wheat germ in a diet fed Nile tilapia. A reference diet and test diets were used, with 5.0g/kg chromic oxide (Cr2O3) as the external indicator. The ADCDM, ADCCP, and ADCGE were higher (P< 0.05) in winter wheat, spring wheat, and wheat germ than for wheat middling and wheat bran. The ADCs of all amino acids (AAs) were >80%, except for threonine in wheat middling and wheat bran, exceeding 90% for winter wheat and wheat germ. The values of all investigated ingredients were high for ADCCP, and the ADCs of EAAs and NEAAs. A strong negative correlation was detected for crude fiber and ash with the ADCs of dry matter, gross energy, and crude protein. In general, wheat ingredients have good digestibility of protein and amino acids, but high fiber content reduces CDAMS and CDAEB in extruded diets for Nile tilapia.

This trial was conducted to determine the dietary digestible methionine + cystine requirement of Nile tilapia (550 to 700 g) based on the ideal protein concept. Six hundred fish were distributed in a completely randomized design with five treatments and four replicates, with 30 fish per experimental unit. The fish were fed diets containing approximately 262 g of digestible protein/kg, 3,040 kcal of digestible energy/kg and 7.90, 9.40, 10.90, 12.40 or 13.90 g of methionine + cystine/kg. The fish were hand-fed three times a day until apparent satiation for 30 days. No effects of dietary methionine + cystine on feed conversion ratio, daily protein deposition, whole body moisture, fillet moisture, crude protein, ether extract and ash, plasmatic HDL and LDL cholesterol were observed. Dietary methionine resulted in a linear increase in whole body protein and linear reduction in lipid deposition rate, hepatosomatic index, whole body ether extract and ash, plasmatic total cholesterol, plasmatic total lipids and plasmatic triglycerides. According to the Linear Response Plateau, the daily weight gain and fillet yield increased up to a level of 9.00 and 9.90 g methionine + cystine/kg of diet, respectively. The digestible methionine + cystine requirement of Nile tilapia is 9.00 g/kg for weight gain and 9.90 g/kg for fillet yield, corresponding to methionine + cystine:lysine ratios of 0.60 and 0.66, respectively.

O objetivo deste estudo foi a formulação de equações para estimar a energia digestível em alimentos para a tilápia. Foram utilizados valores obtidos na literatura da composição centesimal em proteína bruta, extrato etéreo, matéria mineral e energia bruta (variáveis independentes), bem como a energia digestível (variável dependente) obtidos em ensaios biológicos. Os dados foram submetidos à regressão linear múltipla "stepwise backward". Foi realizada análise de trilha para medir os efeitos diretos e indiretos de cada variável independente sobre a dependente. Para validar o modelo foram utilizados dados de estudos independentes, e os valores obtidos em um ensaio de digestibilidade com juvenis de tilápia do Nilo, testando-se cinco farinhas de carne e ossos (FCO), utilizando o sistema de coleta de fezes de Guelph e óxido de cromo (III) como indicador. A equação obtida não pode estimar os valores de energia digestível (ED) de origem animal e está descrito a seguir: ED (kcalkg-1) = -2364,970+1,287 x EB;R² = 0,775. Os coeficientes de trilha obtidos tem valores de médios a baixo, sendo o maior efeito direto o da energia bruta (0,529), enquanto a proteina bruta apresentou o maior efeito indireto, via energia bruta (0,439).

The objective of this study was to formulate a mathematical model to estimate digestible energy in animal feeds for tilapia. Literature results were used of the proximate composition of crude protein, ether extract, mineral matter and gross energy, as well as digestible energy obtained in biological assays. The data were subjected to stepwise backward multiple linear regression. Path analysis was performed to measure the direct and indirect effects of each independent variable on the dependent one. To validate the model, data from independent studies and values obtained from a digestibility trial with juvenile Nile tilapia testing five meat and bone meals (MBM) were used, using the Guelph feces collecting system and chromium oxide (III) as an indicator. The obtained model is described below and cannot estimate digestible energy (DE) of animal origin: DE (kcal kg-1) = -2364.970+1.287xGE;R² = 0.775. The path coefficients were medium or low, the highest direct effect was from gross energy (0.529), while the highest indirect effect was from crude protein, through gross energy (0.439).

The objective of this study was to formulate mathematical models to estimate digestible protein in some animal feeds for tilapia. Literature results of the proximate composition of crude protein, ether extract, and mineral matter, as well as digestible protein obtained in biological assays, were used. The data were subjected to multiple linear stepwise backward regression. Path analysis was performed to measure the direct and indirect effects of each independent variable on the dependent one. To validate the model, the experience used data from independent studies and values obtained from a digestibility trial with juvenile Nile tilapia testing five meat and bone meals, using the Guelph feces collecting system and chromium oxide (III) as an indicator. The obtained model used to estimate digestible protein values (DP) of animal origin is: DP(g kg-1) = -204.15+1.203xCP;R² = 0.953. The path coefficients showed a high direct positive effect (0.900) of crude protein on the digestible protein content. The mineral matter content has an indirect negative effect on protein digestibility (-0.710), reducing the crude protein content and quality.

This study was conducted to determine the digestible lysine requirements of Nile tilapia fingerlings. Fish (n = 300; average initial weight = 1.44 g) were distributed 15 300-L aquariums, in a completely randomized design with five treatments and three replicates, and fed extruded diets containing 11.3, 13.7, 16.1, 18.4 or 20.8 g/kg of digestible lysine. The arginine:lysine ratio was maintained at 1.3:1. All fish were fed diets containing 281 g/kg of digestible protein and 3,372 kcal digestible energy/kg, hand-fed until apparent satiation. There was no effect of the dietary lysine levels on survival rate, or protein and ash body rates. With increasing levels of lysine in the diet, a quadratic effect on weight gain, feed conversion, protein efficiency ratio, protein deposition rate, deposition rate of fat, body moisture and body lipids was observed, where the best values of the variables were estimated at 15.96, 16.4, 14.35, 15.21, 15.87, 15.21 and 16.29 g/kg of lysine, respectively. The digestible lysine requirement of Nile tilapia fingerlings is 15.21 g/kg (5.41 g/100 g of digestible protein), in diets balanced for the arginine:lysine ratio.

Este trabalho foi realizado para avaliar os efeitos da redução da proteína da dieta, por meio da suplementação com aminoácidos sintéticos, sobre o desempenho produtivo, a digestibilidade e o diâmetro da fibra muscular de tilápias-do-nilo. Os aminoácidos (lisina, metionina, treonina e arginina) foram suplementados de forma a manter o perfil de aminoácidos da dieta-referência. Foram utilizados 160 peixes com peso vivo médio inicial de 105,7 ± 2,5 g, distribuídos em 16 tanques (1 m³ cada) e alimentados com dietas contendo 26,74; 25,82; 23,09 ou 22,16% de proteína digestível durante 110 dias. Não foi observado efeito dos níveis de proteína nas dietas sobre o ganho de peso diário, o índice hepatossomático, a gordura visceral, o rendimento de filé, os teores corporais de umidade, proteína bruta e cinzas, o teor de cinzas no filé, a taxa de sobrevivência e o diâmetro das fibras do músculo dorsal. Com a redução dos níveis de proteína na dieta, foi observada redução linear dos coeficientes de digestibilidade aparente da energia bruta, proteína bruta, extrato etéreo e fósforo das dietas. Houve efeito quadrático dos níveis de proteína sobre a conversão alimentar, a taxa de eficiência proteica, a retenção de nitrogênio, o nitrogênio excretado, a umidade no filé, a gordura corporal e no filé e proteína no filé, de modo que os melhores valores foram estimados com 24,53; 24,25; 24,04; 25,15; 24,67; 24,14; 24,34; 25,11% de proteína digestível, respectivamente. É possível reduzir, de 26,74 para 24,53%, a proteína digestível em dietas para tilápias-do-nilo na fase de 100 a 500 g.

The objective of this work was to evaluate the effects of reduction of protein in diets for Nile tilapia by supplementation of synthetic amino acids on performance, digestibility and diameter of muscle fiber of Nile tilapias. The amino acids (lysine, methionine, threonine and arginine) were supplemented to keep the profile of amino acids in the reference diet. It was used 160 fish with initial live weight of 105.7 ± 2.5 g, distributed in 16 tanks (1 m³ each tank) fed diets containing 26.74; 25.82; 23.09 or 22.16% of digestible protein for 110 days. It was not observed any effects of protein levels in the diets on daily weight gain, hepatosomatic index, visceral fat, fillet yield, carcass humidity, crude protein and ash, fillet ash, survival rate and on the white muscle fiber diameter. A linear decrease on apparent digestibility coefficients, gross energy, crude protein, ether extract and phosphorus was observed when protein levels in the diet were reduced. There was a quadratic effect on feed conversion ratio, protein efficiency rate, nitrogen retention, nitrogen excretion, fillet humidity, carcass and fillet fat and fillet protein, in which the best-fit responses were estimated with 24.53, 24.25, 24.04, 25.15, 24.67, 24.14, 24.34 and 25.11% of digestible protein, respectively. It is possible to reduce the dietary protein level from 26.74 to 24.53% for Nile tilapia 100 to 500-g phase.

O objetivo deste trabalho foi avaliar os efeitos da metionina e colina sobre o desempenho produtivo e a morfologia do fígado de tilápia-do-nilo. Durante 87 dias, 160 peixes da linhagem Supreme, com peso vivo médio inicial de 77±0,8 g, distribuídos igualmente em 16 tanques de 1.000 L cada, foram cultivados em sistema com recirculação de água. Os peixes foram alimentados com rações, peletizadas, três vezes ao dia, até saciedade aparente. Foram utilizadas quatro rações com 33% de proteína bruta e 3.000 kcal kg-1 de energia digestível: controle, sem suplementação; suplementação com 3.000 mg kg-1 de metionina; com 2.000 mg kg-1 de colina; com 3.000 mg kg-1 de metionina e 2.000 mg kg-1 de colina. Não foi observado efeito do fornecimento de metionina ou colina sobre o ganho de peso diário, conversão alimentar, rendimento de filé, índice hepatossomático e gordura visceral. Os peixes alimentados com dietas suplementadas com colina e metionina tiveram menor teor de gordura nos filés e redução de inclusões lipídicas no tecido hepático. A suplementação com colina e metionina não afeta o desempenho produtivo de juvenis de tilápia-do-Nilo, mas a colina tem ação na utilização do lipídio hepático, evidenciada pela redução de inclusões lipídicas.

The objective of this work was to evaluate the effects of methionine and choline on the productive performance and on the liver morphology of Nile tilapias. During 87 days, 160 Supreme strain fish, with average weight of 77±0.8 g, equally distributed in 16 tanks with 1,000 L each, were cultivated in a recirculating water system. The fish fed on pelleted diets three times a day until apparent satiation. Four diets with 33% crude protein and 3,000 kcal kg-1 digestible energy were used: control, without supplementation; supplemented with 3,000 mg kg-1 methionine; with 2,000 mg kg-1 choline; with 3,000 mg kg-1methionine and 2,000 mg kg-1 choline. No effects of methionine or choline supplements were observed on daily weight gain, feed conversion, fillet yield, hepatosomatic index and visceral fat. Fish fed on diets supplemented with choline and methionine had lower fat content in the fillets and reduction of lipidic inclusion in the hepatic tissue. Choline and methionine supplementation does not affect productive performance of Nile tilapia juvenile; however, choline has an important action for hepatic lipid utilization, as evidenced by the reduction of lipidic inclusions.

O objetivo deste trabalho foi avaliar o eugenol como anestésico para a tilápia-do-nilo. Para a concentração ideal, foram avaliados seis tratamentos (50, 75, 100, 150, 200 e 250 mg L-1), com dez peixes por tratamento, anestesiados individualmente, acompanhados durante a indução e recuperação. A toxicidade foi estimada pela submissão de 210 peixes a 7 concentrações de eugenol (50, 75, 100, 150, 200, 250, 300 mg L-1), durante 600 s e, para a margem de segurança, 120 peixes foram submetidos a 75 mg L-1 durante cinco intervalos de tempo (600, 1.200, 1.800 e 2.400 s). As concentrações eficientes foram 50 e 75 mg L-1. Os valores de toxicidade letal (CL), aos 600 s, foram: CL01, 81,97 mg L-1; CL50, 184,26 mg L-1; e CL99, 286,55 mg L-1; e os tempos de concentrações letais (TCL) foram: TCL01, 566,97 s; TCL50, 1.611,66 s; e TCL99, 2.656,34 s. Concluiu-se que 75 mg L-1 são suficientes para a anestesia profunda de curta duração, com margem de segurança de 484,27 s, e 50 mg L-1 para longos períodos (600 s). A maior concentração terapêutica do eugenol custa R$ 0,065 por litro de água. A eutanásia pode ser realizada com 286,55 mg L-1 durante 600 s.

The objective of this work was to evaluate eugenol as anesthetic for Nile tilápia. For the best concentration of the anaesthetic, six treatments (50, 75, 100, 150, 200, and 250 mg L-1) were evaluated, with ten fishes per treatment, anesthetised individually and monitored during the induction and recovery. Toxicity was estimated in 210 fish submitted to seven eugenol concentrations (50, 75, 100, 150, 200, 250, and 300 mg L-1) for 600 s; and for safety margin, 120 fish were submitted to 75 mg L-1 for five time intervals (600, 1,200, 1,800, and 2,400 s). The effective concentrations were 50 and 75 mg L-1. Lethal concentration (LC) values for 600 s were: LC01 81.97 mg L-1, LC50 184.26 mg L-1, and LC99 286.55 mg L-1. Times of lethal concentration (TLC) were TLC01 566.97 s, TLC50 1,611.66 s, and TLC99 2,656.34 s. For fast deep anesthesia, 75 mg L-1 of eugenol is recommended, with a safety margin of 484,27 s; for long period anesthesia (600 s) 50 mg L-1 were recommended. The higher therapeutic concentration costs R$ 0.065 per liter. Eugenol was effective for euthanasia at 286.55 mg L-1 for 600 s.