Exigência em lisina digestível para tilápias-do-Nilo de 500 a 600 g de peso vivo

Abstract

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