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Previous issue date: 2015-12-02 === Coordena??o de Aperfei?oamento de Pessoal de N?vel Superior - CAPES === The determination of digestible lysine requirements for Nile tilapia is essential to adjust the correct balance of amino acids in it?s food. Lysine is the amino acid reference for studies in ideal protein, which is currently an important concept in animal nutrition once it allows a reduction in the protein amount of the diet without compromising performance, and furthermore reducing the nitrogen excretion and eutrophication risks of the water. This study aimed to determine the digestible lysine requirement for Nile tilapia in the final phase of growth (500 to 600 g of body weight). Isocaloric and isoproteic experimental diets were utilized with different levels of digestible lysine in each formulation. The amounts of L-lysine HCl 78% used were 0.000; 0.388; 0.776; 1.164, and 1.552% replacing the ingredient glutamic acid 99%; which adjust the treatments to 0.932; 1.23; 1.53; 1.83, and 2.14% of digestible lysine. Nile tilapia weighing 519 g making a sum of 300 animals were utilized in this experiment. They were distributed in 25 water tanks each one measuring a 1000 liters using a renewable system of water. The pH, dissolved oxygen, temperature, salinity and conductivity were monitored daily and ammonia was measured weekly. Slaughters happened when fishes reached 28 and 50 days counting from the beginning of the experiment. The following animal science aspects were evaluated at the end: weight gain (WG), daily weight gain ratio (DWGR), specific growth rate (SGR), food intake (FI), consumption of digestible lysine (CDL), food conversion (FC) protein efficiency gain (PEG), lysine efficiency gain (LEG), nitrogen retention efficiency (NRE), protein deposition rate (PDR), Daily fat deposition rate (DFDR), protein retention efficiency (PRE), and survival rate (SR). The data was interpreted by analysis of variance with 5% probability. There was quadratic effect for GP, CA, TCE, ELG, EPG. The estimated value of lysine for both the largest GP and the best CA is 1.31% digestible lysine. There was no significant differency regarding the food intake, carcass or filet characteristics. This result is in part due to the fact of the gain being proportional throughout the body of the fish. In the second slaughter were obtained quadratic effect in the ether extract and carcass moisture. The Nile tilapia in the weight range of 500 to 600 grams of body weight presents the requirement for 1.31% of digestible lysine, corresponding to 5.31% of digestible dietary protein and 0.431% per Mcal of digestible energy for greater weight gain and better food conversion in it?s experiment conditions === A determina??o da exig?ncia de lisina para a til?pia-do-Nilo ? importante para a elabora??o de ra??es com adequado balanceamento de amino?cidos. A lisina ? o amino?cido refer?ncia nos estudos de prote?na ideal, um conceito relevante atualmente uma vez que permite a redu??o na quantidade de prote?na da ra??o sem comprometimento do desempenho, diminuindo ainda a excre??o de nitrog?nio para a ?gua e o risco de eutrofiza??o. O presente trabalho objetivou determinar a exig?ncia em lisina digest?vel para a til?pia-do-Nilo na fase de 500 a 600 g de peso vivo. Foram utilizadas dietas experimentais que consistiram em ra??es isocal?ricas, isoproteicas e com valores crescentes de lisina digest?vel. A L-lisina HCl 78% foi utilizada com valores crescentes (0,000; 0,388; 0,776; 1,164 e 1,552%), em substitui??o ao ingrediente ?cido glut?mico (99%), perfazendo os tratamentos com 0,932; 1,23; 1,53; 1,83 e 2,13% de lisina digest?vel. Foram utilizadas 300 til?pias-do-Nilo com peso m?dio de 519 g e distribu?dos em 25 caixas d??gua de 1000 L em sistema aberto de circula??o de ?gua. O pH, oxig?nio dissolvido, temperatura, salinidade e condutividade da ?gua foram monitorados diariamente e a am?nia foi medida semanalmente. Foram realizados 2 abates, aos 28 dias e aos 50 dias de experimento. Foram avaliados os seguintes ?ndices zoot?cnicos: ganho de peso (GP), ganho de peso di?rio (GPD), taxa de crescimento espec?fico (TCE), ingest?o alimentar (IA), consumo de lisina digest?vel (CLD), convers?o alimentar (CA), efici?ncia proteica para ganho (EPG), efici?ncia de lisina para ganho (ELG), efici?ncia de reten??o de nitrog?nio (ERN), taxa de deposi??o de prote?na (TDP), taxa de deposi??o di?ria de gordura (TDG), efici?ncia de reten??o de prote?na (ERP) e taxa de sobreviv?ncia (TS). Os dados foram interpretados por meio de an?lise de vari?ncia a 5% de probabilidade. Houve efeito quadr?tico para GP, CA, TCE, ELG, EPG, sendo o valor estimado de lisina tanto para o maior GP quanto para a melhor CA de 1,31% de lisina digest?vel. N?o houve diferen?a significativa para o consumo de ra??o, rendimento de carca?a, rendimento de fil?, caracter?sticas da carca?a e do fil?. Esses resultados se devem em parte ao fato do ganho ter sido proporcional em todo o corpo do peixe. No segundo abate houve efeito quadr?tico no extrato et?reo e na umidade da carca?a. A Til?pia-do-Nilo na faixa de peso de 500 a 600 gramas de peso vivo apresenta a exig?ncia de 1,31% de lisina digest?vel, que corresponde a 5,31% da prote?na digest?vel da dieta e a 0,431%/Mcal de energia digest?vel para o maior ganho de peso e melhor convers?o alimentar nas condi??es deste experimento.
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