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.

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.

Colliroja, Astyanax fasciatus, is a new aquaculture species, and information on its dietary essential amino acid requirements is lacking. The whole body composition of 120 farmed fish (16.2 ± 8.8 g) was determined to estimate the dietary essential amino acid requirement based on the ideal protein concept ((each essential amino acid/lysine) x100), and the findings were correlated to the whole body essential amino acid content of Nile tilapia Oreochromis niloticus. The dietary essential amino acids, including cysteine and tyrosine, accounted for 5.46, 4.62, 1.16, 3.28, 5.63, 2.01, 2.59, 2.84, 4.66, 3.39, 0.65, and 3.51% of the total protein for lysine, arginine, histidine, isoleucine, leucine, methionine, methionine+tyrosine, phenylalanine, phenylalanine+tyrosine, threonine, tryptophan, and valine, respectively. There were positive linear and high correlations (r = 0.971) between the whole body amino acid profiles of colliroja and Nile tilapia. Thus, the whole body amino acid profile of colliroja might be used to estimate accurately the essential amino acid requirement.

Colirroja, Astyanax fasciatus, es una nueva especie de la acuicultura y no hay información sobre sus requerimentos de aminoácidos esenciales en la dieta. Se determinó la composición corporal de 120 peces de cultivo (16,2 ± 8,8 g) para estimar los requirimientos nutricionales de aminoácidos essenciales en la dieta, incluyendo cistina y tirosina, basada en el concepto de proteína ideal ((cada aminoácido essencial/lisina) x 100) y los resultados se correlacionaron con el perfil corporal de la tilapia del Nilo Oreochromis niloticus. El perfil dietético de aminoácidos essenciales explica el 5,46, 4,62, 1,16, 3,28, 5,63, 2,01, 2,59, 2,.84, 4,66, 3,39, 0.65 y 3,51% de la proteína, respectivamente para lisina, arginina, histidina, isoleucina, leucina, metionina, metionina+cistina, fenilalanina, fenilalanina+tirosina, treonina, triptófano y valina. Hubo una alta correlación lineal positiva (r = 0,971) entre el perfil corporal de aminoácidos de colirroja y el de tilapia del Nilo. Por lo tanto, el perfil corporal de los aminoácidos basado en el concepto de proteína ideal podría ser utilizado para estimar con precisión el requisito de aminoácidos essenciales de colirroja.

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.

This study ascertains the length-weight relationship and predicts body composition equations in cultivated Astyanax aff. fasciatus. A total of 300 fish were distributed in five groups according to body weight: 1.19 ± 0.18, 3.7 ± 0.70, 7.55 ± 0.97, 12.28 ± 2.32 and 22.16 ± 2.64 g. The length-weight relationship was elaborated using linear (y i = b0 + b1x i) or second-order (y i = b0 + b1x i + b1x i²) regression analysis. The value of the b slope in the length-weight relationship was 3.6971 and the intercept was 0.0031. The prediction equations obtained for body moisture, crude protein, crude lipid and ash were, y = 71.680 - 0.404BW, y = 17.140 - 0.095BW, y = 8.432 +0.364BW and y = 3.720 - 0.032BW, respectively, where BW is the body weight of fish (g). The use of prediction equations to describe body composition as a tool to support fish production and commercialization is suggested.

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.

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.

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.

Avaliou-se a influência da adição (1,2%) de ácido linoléico conjugado (CLA) na dieta sobre o desempenho, a deposição e o perfil de ácidos graxos na carne de pacus. Foram utilizados 112 pacus em crescimento (256,19 ± 24,09), distribuídos em delineamento inteiramente casualizado, com dois tratamentos e quatro repetições, em oito tanques (1 m³ cada), e alimentados até a saciedade aparente, três vezes ao dia, durante 60 dias. Utilizou-se dieta extrusada, com 28% PB e 3.000 kcal ED/kg de ração. A cada duas semanas, foram coletados oito peixes de cada tratamento (dois de cada repetição) para determinar a composição de ácidos graxos no tempo. Pela análise de Broken-line, a máxima deposição do cis-9, trans-11, trans-10, cis-12 e do CLA total foi estabelecida com 23, 20 e 21 dias, respectivamente. Não foram observadas diferenças no desempenho e na composição química do peixe inteiro, do filé e do fígado. A deposição de CLA ocorreu em altas concentrações em todos os tecidos do pacu. O fornecimento de CLA na dieta afetou a composição de ácidos graxos poliinsaturados e monoinsaturados no peixe inteiro, filé e fígado. A deposição de CLA em pacus corresponde a até 3,6% dos lipídios totais no peixe inteiro e no filé.

This work was carried out to evaluate the effect of dietary conjugated linoleic acid (CLA) inclusion (1.2%) on pacu performance and fillet fatty acids deposition and profile. A hundred and twelve growing pacus (256.19 ± 24.09 g of initial weight) were allotted to a completely randomized design with two treatments and four replicates, in eight tanks (1 m³ each) and hand fed to apparent satiation, three times a day, for 60 days. Extruded diet with 28% CP and 3,000 kcal DE/kg of ration was fed. Every each two week, eight fish per treatment (two per replicate) were collected to determine the fillet fatty acid composition. Broken-line analysis indicated that the cis-9, trans-11, trans-10, cis-12 and the total CLA maximum deposition in "pacu" tissue muscle were established at 23, 20 and 21 days, respectively. CLA was deposited in high concentrations in all pacu tissues studied. No differences on performance and whole fish, fillet and liver compositions were observed. CLA dietary inclusion affected the total percentages of polyunsaturated and monounsaturated fatty acids in whole fish, fillet and liver. It was concluded that pacu can incorporate CLA in whole body and fillet up to 3.6% of total lipids.

Objetivou-se determinar a exigência de fósforo disponível para tilápias-do-nilo. Utilizaram-se 144 peixes com peso vivo inicial de 35,33 ± 0,66 g, distribuídos em delineamento de blocos ao acaso, com quatro tratamentos e três repetições. Foram fornecidas dietas com 29,0% PB, 2.980 kcal/kg de energia digestível (ED) e quatro níveis de fósforo disponível (0,25; 0,35; 0,45 ou 0,55%), obtidos pela utilização de fosfato bicálcico como fonte de fósforo. As dietas foram fornecidas aos peixes três vezes por dia, até aparente saciedade, durante 46 dias. Não foi observado efeito dos níveis de fósforo disponível na dieta sobre o índice hepatossomático, a taxa de sobrevivência e os teores de água e proteína bruta na carcaça. O aumento dos níveis de fósforo disponível na dieta promoveu aumento linear do ganho de peso médio, da excreção de fósforo e dos teores de cinza na carcaça e de cinzas, cálcio e fósforo nos ossos. Houve efeito quadrático dos níveis de fósforo disponível sobre o consumo de ração, a conversão alimentar e a taxa de eficiência protéica, que foram melhores nos níveis 0,37; 0,48 e 0,48% de fósforo disponível, respectivamente. A exigência de fósforo disponível para tilápia-do-nilo de 35 a 100 g é de 0,48% (0,53% na matéria seca).

The objective of this work was to determine the available phosphorus requirement of Nile tilapia. A total of 144 fishes with initial weight 35.33 ± 0,66g LW were distributed to a completely randomized blocks design, with four treatments and three replicates. Diets with 29.0% CP and 2980 kcal/kg DE and four available phosphorus levels (0.25; 0.35; 0.45 e 0.55%) were used. The dicalcium phosphate was used as phosphorus source. The diets were fed to the fishes three times a day to apparent satiation, during 46 days. No significant effect of dietary available phosphorus on hepatosomatic index, survival rate and carcass water and protein contents were observed. The increase of available phosphorus levels in the diet promoted linear increase of average weight gain and phosphorus excretion, and content of ash in carcass and ashes, calcium. There was a quadratic effect of dietary available phosphorus on feed intake, feed conversion ratio and protein efficiency ratio and the best values were obtained with 0.37, 0.48 and 0.48%, respectively. Dietary requirement of available phosphorus for Nile tilapia from 35 to 100 g is 0.48% (0.53% DM).