ABSTRACT Recent studies have evidenced exogenous enzymes as nutritional tool to elaborate low-polluting aquafeeds. This study aimed to evaluate effects of enzyme complex (EC) on apparent digestibility coefficients (ADC) of energy and nutrients, including amino acids, as well nitrogen (N) and phosphorus (P) loss in pre-growout Nile tilapia (Oreochromis niloticus). Diets without EC (Control) or with EC supplemented at 225 (EC225) or 450 mg/kg diet (EC450) and fed to Nile tilapia (n = 135, 150 ± 20 g) distributed in an entirely randomized design of three treatments and three replicates of 15 fish each. Fish fed diet EC450 showed higher digestibility of energy, protein, amino acids and mineral, and increased digestible energy (DE; +221.25 kcal/kg diet), digestible protein (DP; +10.54 g/kg diet) contents of diets, whereas reduced N (−23.82%) and P (−18.46%) loss relative to fish fed diet control. This study evidenced that EC at 450 mg/kg diet optimizes the ADC of multiple nutrients, including amino acids, and identified its potential to enhance the nutritive value of feeds and elaborate sustainable feeds for Nile tilapia.

RESUMO Estudos recentes têm evidenciado enzimas exógenas como ferramenta nutricional para elaboração de dietas aquáticas pouco poluentes. Este estudo teve como objetivo avaliar os efeitos de um complexo enzimático (CE) nos coeficientes de digestibilidade aparente (CDA) de energia e nutrientes, incluindo aminoácidos, bem como perda de nitrogênio (N) e fósforo (P) em tilápia-do-nilo, Oreochromis niloticus em crescimento. Dietas sem CE (Controle) ou com EC suplementado em 225 (CE225) ou 450 mg/kg dieta (CE450) foram fornecidas para tilápias do Nilo (n = 135, 150 ± 20 g) distribuídas em um desenho inteiramente aleatório de três tratamentos e três repetições de 15 peixes cada. Peixes alimentados com a dieta EC450 apresentaram maior digestibilidade da energia, proteína, aminoácidos e minerais, e aumento nos conteúdos de energia digestível (ED; +221,25 kcal/kg dieta) e proteína digestível (PD; +10,54 g/kg dieta) das dietas, enquanto houve redução na perda de N (−23,82%) e P (−18,46%) em relação aos peixes alimentados com a dieta de controle. Este estudo evidenciou que o CE a 450 mg/kg de dieta otimiza o CDA de múltiplos nutrientes, incluindo aminoácidos e identificou seu potencial para melhorar o valor nutritivo dos alimentos, assim como elaborar dietas sustentáveis para tilápias do Nilo.

ABSTRACT This research was conducted to determine optimal dietary histidine requirement of grow-out Nile tilapia, Oreochromis niloticus, based on muscle development, expression of muscle-growth-related genes, and blood parameters. Fish (n = 288, initial body weight of 64.17±0.53 g) were fed extruded diets with graded levels of histidine (4.23, 5.44, 7.17, 8.91, and 11.57 g kg−1), containing approximately 289 g kg−1 crude protein and 3565 kcal kg−1 digestible energy. The study followed a completely randomized design with five treatments and four replicates each, for 65 days. There was a quadratic effect of dietary histidine on final body weight, feed conversion, and net protein utilization, and the best values were optimized at 8.09, 7.88, and 7.33 g kg−1, respectively. Feed intake, hepatosomatic index, survival, body composition, and blood parameters of total protein, glucose, triglycerides, cholesterol, hematocrit, and hemoglobin were not affected by dietary treatments. Predominance of hypertrophic growth and higher mRNA levels of myogenin and MyoD were observed in fish fed histidine from 5.44 to 11.57 g kg−1 compared with fish fed histidine at 4.23 g kg−1. The mRNA expression of myostatin was not affected by dietary treatments. The dietary requirement of histidine for grow-out Nile tilapia was determined at 8.09 g kg−1, considering growth performance, muscle development, and gene expression responses.

ABSTRACT This study aimed to determine the length-weight relationship and mathematical models to predict dressed and fillet weight and yield and fillet composition of wild traíra, Hoplias malabaricus (Bloch, 1794). A total of 80 marketable-sized fish from 292.28 to 2879.57 g and 32.06 to 61.19 cm were used. The length:weight ratio was estimated using the equation: W = a × L b, in which W is body weight (g) and L is length (cm). The models of dressed and fillet weight and yield and body were elaborated using first-order ( y ^ i = β 0 + β 1 x i ) or second-order ( y ^ i = β 0 + β 1 x i + β 1 x i 2 ) linear regression analyses. The value of slope b in the length:weight ratio was 3.3732 and intercept was 0.0029. The prediction equations obtained for dressed weight, fillet weight, dressed yield, fillet yield, fillet gross energy, moisture, crude protein, crude lipid, and ash were, respectively: y ^ = 0.3244 + 0.9373 W, y ^ = 0.7651 + 0.4181 W, y ^ = 939.8015 + 0.0019 W, y ^ = 420.55170 + 0.0064 W, y ^ = 997.9600 + 0.0630 W, y ^ = 810.6500 − 0.0085 W, y ^ = 184.080 − 0.0111 W, y ^ = 3.1131 + 0.0049 W, and y ^ = 10.6110 + 0.0009 W, in which W is the body weight of fish (g). We demonstrated the possibility of elaborating realistic expressions to describe degutted weight, fillet weight, and fillet composition. However, lower mathematical adjustment was observed to estimate realistic prediction of dressed and fillet yield.

The objective of the present study was to develop models for predicting live weight from the length-weight relationship and body composition of Nile tilapia. A total of 3,000 juvenile fish (initial weight = 28.6±4.16 g and standard length = 13.8±0.16 cm) were distributed into three circular cages (12 m3 each). The fish were hand-fed extruded diets containing 332 g kg-1 of crude protein and 3,230 kcal kg-1 of digestible energy, until apparent satiety, twice daily, for 100 days. Twelve fish were collected from each cage every 20 days for measurements of body weight and length, and proximate composition analysis; statistical analysis was conducted using linear regression. The value of the slope b and the intercept for the length-weight relationship were 3.0604 and 0.0203, respectively. The prediction equations obtained for body moisture (MO), crude protein (CP), crude lipid (CL), and ash against body weight (BW) in g/100 g of fish were as follows: MO = 70.0090 - 0.0071BW; CP = 13.7550 + 0.0037BW; CL = 9.2636 + 0.0057BW; and ash = 4.2392 - 0.0024BW. It is possible to develop equations to predict body weight and composition, which can be used to control the production of Nile tilapia and improve its commercial value.

O trabalho foi realizado com o objetivo de avaliar a composição proximal e perfil de ácidos graxos de lambaris-do-rabo-vermelho de acordo com a classe de peso corporal: Classe I (3,24 - 4,46g); Classe II (9,08 - 11,62g); Classe III (15,8 - 18,89g) e Classe IV (32,25 - 54,64g). Não foi observado efeito do peso corporal sobre o conteúdo de cinzas corporal dos peixes. Os peixes de Classe I apresentaram maiores teores de umidade e menores teores de lipídios corporal em relação aos peixes das classes II, III e IV. O maior nível de lipídios foi observado em peixes da Classe IV e não sendo observadas diferenças entre peixes das Classes II, III e IV. O ácido palmitico (16:0) e oléico (18:1 n-9) foram os ácidos graxos saturados e monoinsaturados mais abundantes, respectivamente, independentemente da classe de peso dos peixes. A quantidade total de ácidos graxos saturados foi maior nos peixes da Classe I, que também apresentaram níveis mais elevados dos ácidos palmítico, linoléico e docohexaenóico. Os peixes de Classe II, III e IV apresentaram maior relação de ácidos graxos n-3/n-6 em comparação com os peixes da Classe I, porém os peixes de todas as classes de peso demonstraram valor nutricional satisfatório para consumo humano em termos de proteína bruta, lipídios e relações de ácidos graxos n-3/n-6 e AGP/AGS.

This work was carried out to evaluate the proximate composition and fatty acids acid profile of "lambari-do-rabo-vermelho" according to body weight class: I (3.24 - 4.46g); Class II (9.08 - 11.62g); Class III (15.8 - 18.89g) and Class IV (32.25 - 54.64g) with 25 fish each class of to determine the proximate and fatty acids compositions. No significant effects on the fish ash content into fish weight class were observed. Fish from Class I showed highest humidity and lowest whole body lipid levels compared to fish from classes II, III and IV. The highest level of lipid was observed in fish from Class IV and no differences were observed between fish from Classes II, III and IV. Palmitic (16:0) and oleic (18:1 n9) acids were the major saturated and monounsaturated fatty acids, respectively, in the whole body, independently of fish weight class. The total amount of saturated fatty acids was higher (P <0.05) in the fish of Class I, which also showed higher levels of palmitic, linoleic and docohexaenoic acids. Fish from Class II, III and IV showed the highest level of n-3/n-6 ratio compared to fish from Class I, but all class of fish weigh analyzed were shown nutritional value satisfactory for human consumption in terms crude protein, lipids and n-3/n-6 and AGP/AGS ratios.

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.

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.

O suprimento adequado de aminoácidos dietéticos para tilápias tem sido estudado por muitos anos. No entanto, ainda não foi estabelecida uma concordância geral sobre a exigência de aminoácidos para tilápias. A fim de otimizar a eficiência e reduzir o excesso de nitrogênio, as dietas devem ser elaboradas considerando-se os valores de digestibilidade de cada aminoácido dos alimentos. Devido às variações nas exigências de aminoácidos pela introdução novas linhagens de tilápias, a investigação contínua sobre exigências de aminoácidos é necessária para a elaboração de dietas ambiental e economicamente sustentáveis que melhorem também o crescimento dos peixes, a eficiência alimentar e o rendimento de filé. O conceito de proteína ideal em dietas de tilápias foi introduzido há mais de dez anos, e novas pesquisas têm mostrado a importância da proteína e aminoácidos no desempenho e na saúde dos peixes submetidos a desafios frente a fatores internos e externos.

The optimal dietary supply of amino acids to tilapia has been studied for many years. Nevertheless, a general agreement on the amino acid requirement for tilapias has not been established. In order to optimize efficiency and reduce surplus nitrogen, values of digestibility of each amino acid of feed must be considered. Due to variations in the amino acid requirement due to new tilapia strains introduction, continuous research on amino acid requirements is necessary to elaborate economical and environmental sustainability diets, also improving fish growth, efficiency and fillet yield. The concept of ideal protein in tilapia diets was introduced more than ten years ago, and new researches have shown the importance of protein and amino acids on fish performance and health, when tilapias are submitted to constant challenging from internal and external factors.

Este estudo foi realizado com o objetivo de determinar a exigência de lisina digestível para juvenis de tilápia-do-nilo. Noventa e seis peixes revertidos sexualmente e com peso vivo inicial de 5,72 ± 0,10 g foram alimentados por 42 dias com quatro rações (29.51% de PB e 3.235 kcal de energia digestível/kg) contendo diferentes níveis de L-lisina HCl (0,1; 0,3; 0,5 e 0,7%, correspondendo a rações com 1,04; 1,27; 1,51 e 1,741% de lisina digestível, respectivamente). Os peixes foram distribuídos em 16 tanques com capacidade de 1.000 L cada um, em um delineamento inteiramente casualizado, com quatro tratamentos, três repetições e seis peixes por unidade experimental. Não foi observado efeito dos níveis de lisina sobre o índice hepato-somático, a gordura visceral, a sobrevivência e os teores de água e extrato etéreo na carcaça. A análise de Linear Response Plateau do ganho de peso e da conversão alimentar versus níveis de lisina digestível demonstrou estimativa de exigência de 1,56 e 1,44% de lisina digestível, respectivamente. Foi observado efeito quadrático sobre o rendimento de carcaça, que aumentou até o nível de 1,61% de lisina digestível. Considerando o desempenho, recomenda-se que dietas para juvenis de tilápia-do-nilo devem conter 1,44% de lisina digestível (5,23% da proteína da dieta).

This trial was carried out to determine the digestible lysine requirements of Nile tilapia juveniles. Ninety- six reverted fishes averaging initial weight of 5.72 ± 0.10 g were fed four diets (29.51% of crude protein and 3,235 kcal/kg of digestible energy) containing increasing levels of L-lysine HCl (0.1, 0.3, 0.5, and 0.7%), during 42 days. The following treatments were evaluated: dietary lysine levels of 1.04; 1.27; 1.51 and 1.741%. Fishes were allotted to 1000-L 16 tanks, as a completely randomized design with four treatments, three replicates and eight fishes per experimental unit. No treatment effects on hepatosomatic index, visceral fat, survival rate and water ether extract in the carcass were observed. The Linear Response Plateau analysis of weight gain and feed:gain ratio versus digestible lysine level yielded an estimated digestible lysine requirement of 1.56 and 1.44% for Nile tilapia juveniles, respectively. Quadratic effect of treatments on carcass yield that increased up to 1.61% of digestible lysine was observed. Considering the performance, it is recommended diets containing up to 1.44% of digestible lysine (5.23% of protein) for Nile tilapia juveniles.

Este estudo foi realizado para se avaliar a redução dos níveis de proteína em dietas para tilápia-do-nilo (5 a 125 g), adotando-se o conceito de proteína ideal. Cento e sessenta peixes (4,40 ± 0,9 g) foram distribuídos em um delineamento inteiramente casualizado, com quatro tratamentos [25,5; 27; 28,5 e 30% (controle) de proteína digestível], três repetições e dez animais por unidade experimental. Os aminoácidos sintéticos foram suplementados para se manter as proporções de aminoácidos de acordo com o conceito de proteína ideal. Os aminoácidos lisina, metionina e treonina foram suplementados para se obter os níveis de aminoácidos da dieta controle. As dietas foram fornecidas à vontade, durante 83 dias. Não foram observados efeitos dos níveis de proteína sobre o ganho de peso, a conversão alimentar, o índice hepatossomático, o peso da gordura visceral, a taxa de sobrevivência, os níveis de proteína na carcaça e o diâmetro da fibra intermediária. O aumento nos níveis de proteína resultou em redução linear na taxa de eficiência protéica e de retenção do nitrogênio e aumento linear na excreção de nitrogênio. Foi observado efeito quadrático sobre o rendimento de carcaça e o teor de extrato etéreo na carcaça; os melhores valores foram obtidos com 28,40 e 27,31% de proteína na dieta, respectivamente. Concluiu-se que é possível a redução do nível de proteína de 30 para 27,5% em dietas para juvenis de tilápia do Nilo, sem efeitos negativos sobre o crescimento, rendimento de carcaça e a composição química dos filés. No entanto, a redução do nível de proteína de 30 para 25,5% acarreta redução no diâmetro das fibras musculares vermelha e branca.

This trial was carried out to evaluate the effects of ideal protein concept on reduction of dietary protein content for Nile tilapia (5 to 125 g). A hundred and sixty juvenile fishes (4.40 ± 0.9 g) were assigned to a randomized experimental design with four treatments [25.5, 27, 28.5 and 30% (control) of digestible protein], three replicates and ten fish by experimental unit. Crystalline amino acids were added to maintain amino acid levels according to the ideal protein concept. The amino acids (lysine, methionine and threonine) were supplemented at levels to simulate amino acid levels of the reference diet. Diets were fed ad libitum during 83 days. No significant effects of protein levels on weight gain, feed:gain ratio, hepatossomatic, visceral fat, survival rate, carcass protein and intermediate fiber diameter were observed. The protein efficiency rate and nitrogen retention decreased linearly and excreted nitrogen increased linearly as the dietary digestible protein levels increased. Quadratic effect for carcass yield and carcass ether extract content was observed, with the best values at 28.40 and 27.31% dietary protein, respectively. It was concluded that is possible to reduce the dietary protein from 30 to 27.5% for juvenile Nile tilapia, with no change on growth, carcass yield and fillet chemical composition. However, the reduction of white and red fibers diameter was observed when dietary protein decreased from 30 to 27.5%.

Este estudo foi realizado para determinar a exigência de metionina + cistina para alevinos de tilápia do Nilo (2,61 ± 0,14g). Foi utilizado o modelo em blocos ao acaso, com seis tratamentos, três repetições e cinco peixes por unidade experimental. Foi utilizada ração basal contendo 28% de proteína bruta e 3173kcal ED kg-1 de ração, suplementada com DL-metionina, resultando em rações com 0,87; 0,95; 1,03; 1,11; 1,19 e 1,27% de metionina + cistina. As rações foram fornecidas à vontade durante 41 dias. Não foram observados efeitos (P>0,05) dos níveis de metionina + cistina sobre a taxa de sobrevivência e índice hepato-somático. Foi observado efeito quadrático (P<0,05) sobre o ganho de peso, que aumentou até o nível de 1,22% de metionina + cistina na ração. A conversão alimentar e a taxa de eficiência protéica aumentaram (P<0,05) até o nível de 1.00% de metionina + cistina. Foi observado efeito quadrático (P<0,05) sobre o rendimento de carcaça que aumentou até o nível de 1,13% de metionina + cistina. O nível de 1,00% de metionina + cistina, correspondente a 3,54% da proteína bruta, contendo 0,54% de metionina na ração, mostrou melhor resultado no desempenho.

This study was carried out to determine the methionine + cystine requirement for Nile tilápia, fingerlings (2.61 ± 0.14g). A randomized block designs, with six treatments, three replicates and five fish by experimental unit was used. Basal diet was utilized with 28% crude protein and 3173DE kcal kg-1 of digestible energy, supplemented with DL-methionine, resulting in diets with 0.87; 0.95; 1.03; 1.11; 1.19 and 1.27% of methionine + cystine. Diets were fed to satiation during 41 days. No effects (P>0.05) of methionine + cystine levels on survival rate and hepatosomatic index were observed. A quadratic effect (P<0.05) for weight gain was observed, which increased up to 1.22% methionine + cystine in the diet. Feed conversion ratio and protein efficiency ratio increased (P<0.05) up to 1.00% of methionine + cystine. A quadratic effect (P<0.05) of methionine + cystine level on carcass yield was observed, which increased up to 1.13% of methionine + cystine. The concentration of 1.00% methionine + cystine corresponding to 3.54% crude protein, in the presence of 0.54% methionine in the diet, showed the best njperformance.

Objetivou-se, nesta pesquisa, avaliar o efeito da densidade de estocagem sobre o desenvolvimento de girinos de rã-touro em tanques-rede. Foram utilizados 360 girinos com peso médio inicial 0,01g e comprimento inicial médio de 0,92±0,06 cm, distribuídos em um delineamento em blocos ao acaso com cinco tratamentos (0,50; 1,00; 1,50; 2,00 e 2,50 indivíduos/L) e quatro repetições, em 20 tanques-rede experimentais (12 L). Foi fornecida dieta com 40,00% de proteína bruta, na proporção de 8,00% do peso vivo, duas vezes ao dia. Observou-se aumento linear da biomassa por tanque, em função da densidade de estocagem. O peso final médio e a taxa de sobrevivência apresentaram redução linear, com o aumento da densidade. Observaram-se lotes mais uniformes dos girinos cultivados em menores densidades. A conversão alimentar não foi influenciada pelas diferentes densidades de estocagem. As variáveis físico-químicas da água estiveram em níveis adequados. Concluiu-se que, com menores densidades, obtêm-se girinos maiores e lotes mais uniformes com melhor taxa de sobrevivência.

This research was conducted to evaluate the effect of different stocking density on the bull-frogs tadpoles development in net-pond. Three hundred and sixty animals, averaging initial weight of 0.01g and initial length of .92±.06 cm were allotted to 20 net-pond (12L) in a block randomized design with five treatments (.5, 1.0, 1.5, 2.0 and 2.5 tadpoles/L) and four replicates. The diet with 40.00% crude protein was fed twice a day at 8.00% live weight. Linear increase in biomass, as the stocking rates increased, was observed. Average final weight and the survival rate showed linear decrease, as the stocking rates increased. It was observed more uniformity groups in the lower density. Feed/gain was not affected by the different stocking rates. Physical and chemical traits had adequate levels. It was concluded that, under low stocking rates, better results of weight, uniformity of group and survival rate of the tadpoles were obtained.

Este experimento foi realizado para avaliar os efeitos da adição de diferentes níveis de fitase (0, 500, 1500 e 3000 unidades de fitase ativa [UFA]/kg de ração) em dietas para a tilápia do Nilo (8,88 ± 0,02 g). Todas as rações foram fornecidas até saciedade durante 45 dias. O nível de fitase baseou-se nos parâmetros de desempenho e digestibilidade e foi estimado pelos modelos quadrático e/ou LRP ("broken line"). De acordo com os resultados obtidos com os níveis de fitase, o modelo LRP apresentou o melhor ajustamento de dados. A suplementação de fitase aumentou o desempenho, a retenção de minerais nos ossos, a digestibilidade da proteína e a disponibilidade de cálcio e fósforo. Os melhores resultados de desempenho, retenção de minerais nos ossos e digestibilidade foram obtidos com 700 UFA/kg de ração.

This experiment was carried out to evaluate the effects of addition of different levels of phytase (0, 500, 1500 and 3000 units of active phytase [UFA]/kg diet) in the diets for Nile tilapia (8.88 ± 0.02 g). All diets were fed to satiation daily for 45 days. The phytase level determination was based on the performance and digestibility parameters and was estimated by the quadratic and/or the broken line models. The broken line model showed a better adjustment for phytase levels according to the observed results. Phytase supplementation increased performence, bone minerals, protein digestibility and calcium and phosphorus availability. The best results of performance, bone mineral retentions and digestibility were obtained with 700 UFA/kg of diet.

Este estudo foi realizado para determinar a energia digestível e a digestibilidade aparente de nutrientes do farelo de canola pela tilápia do Nilo (Oreochromis niloticus). O óxido de crômio (0,1%) foi utilizado como indicador inerte em dieta semi-purificada, com coleta de fezes pelo sistema Guelph. Os peixes foram alimentados até saciedade aparente. O farelo de canola apresentou valores de energia e nutrientes digestíveis de: 77,84; 71,99; 86,92; 88,19; 67,16 e 29,86% para a matéria seca, energia, proteína, lipídios, cálcio e fósforo, respectivamente, correspondendo a 2969,98 (kcal/kg); 69,97; 32,6; 1,2; 0,41 e 0,28%, de energia digestível, matéria seca, proteína e lipídios digestíveis e cálcio e fósforo disponíveis, respectivamente. Os resultados obtidos neste trabalho evidenciam que a tilápia do Nilo pode utilizar eficientemente o farelo de canola.

This study was carried out to determine the digestible energy and apparent nutrient digestibility of canola meal for Nile tilapia (Oreochromis niloticus). The chromic oxide (0.1%) was used as an inert indicador in the semi-purified diet and faeces were collected by Guelph system. Fish were fed to apparent satiation. The apparent nutrient and energy digestibility of canola meal were: 77.84, 71.99, 86.92, 88.19, 67.16, and 29.86% for dry matter, energy, protein, lipids, calcium and phosphorus, respectively, corresponding to 2969,98 (kcal/kg); 69.97, 32.6, 1.2, 0.41, and 0.28% of, digestible energy, dry matter, protein and lipids and available calcium and phosphorus, respectively. The results obtained in this experiment evidence that Nile tilapia may be able to utilize canola meal eficiently.

Foram utilizados 1200 alevinos revertidos de tilápia do Nilo com peso inicial médio 0,13 ± 0,01g, distribuídos em 20 aquários de 1000L para avaliar os efeitos da inclusão de levedura desidratada na dieta. Os animais foram distribuídos em um delineamento inteiramente casualizado com cinco tratamentos (0,00; 7,80; 15,60; 23,40 e 31,20% de levedura na dieta) e quatro repetições. Não foi observado efeito dos tratamentos sobre a conversão alimentar e sobrevivência. Foi observado efeito quadrático sobre o ganho de peso (Y=l,7133 + 0,0477X-0,0017X²) e custo em ração/kg ganho (Y=0,6170-0,0112X+0,0004X²). Concluiu-se que o melhor nível de inclusão de levedura seca na dieta para alevinos revertidos de tilápias do Nilo é de 14%.

One hundred and two thousand reversed of Nile tilápia fingerlings (Oreochromis niloticus) with initial weight mean 0.13 ± 0.01 g, distributed in twenty 1000-liter fish aquarium, were used to evaluate the inclusion of dried yeast in the diet. Samples were distributed in a entirely randomized design with five treatments (0.00; 7.80; 15.60; 23.40 and 31.20% yeast in the diet) andfour replicates. There was no effect of treatments on food conversion and survival. A quadratic effect over weight gam (Y=1.7133+0.0477X- 0.0017X²) and cost of diet/kg gain (Y=0.6170-0.0112X+0.0004X²) was observed. It was concluded the best level of dried yeast in diet for reversed Nile tilapia fingerlings is 14%.