Modelos de crescimento e desempenho de Tilápias do Nilo (Oreochromis nioticus; linhagem supreme) alimentadas com dietas sem ou com suplementação de lisina e treonina, em gaiolas

Abstract

Two works were undertaken out to compare growth models (Experiment 1) and to evaluate the performance and nutrient deposition (Experiment 2) Nile tilapia (Oreochromis niloticus), Supreme strain, in cages. Nine-thousand juveniles (33.3 ± 4.91 g) each were distributed in six cages (12 m3 each) in Rosana?s Reservoir, in the Basin of the Paranapanema´s river, municipality of Euclides da Cunha Paulista-SP. Samples of fish were collected each 20 days to determined the body weight, the performance and the body composition, during 100 days. Fish were fed with commercial diet with 33.21% of crude protein and 3389 kcal of digestible energy/kg of diet for 80 days. After that, fish from three cages were used to make up the Treatment 1, fed with diet containing 35.25% of crude protein and 3516 kcal of digestible energy/kg of diet and the others fish were fed with diet containing 33.16% of crude protein and 3457 kcal of digestible energy/kg of diet, supplemented with L-lysine (0.28%) and L-threonine (0.24%) (Treatment 2). Linear and non-linear (Von Bertalanffy, Logistic, Gompertz e Brody) models were evaluated. Good fitting with models non-linear logistic and linear quadratic obtained at experiment 1. Therefore, the best fitting was obtained with the linear quadratic model. A linear increase on daily weight gain, feed intake and feed conversion ratio was observed. A quadratic effect on specific growth rate, protein efficiency ratio and nitrogen retention in time function was observed at treatment 2. According to the path analysis relating the fillet weight to the body weight, head weight, visceral weight and the measures of height, standard length and width, only the body the was decisive variable. Body fat is the nutrient that more influences the body and fillet compositions. The sintetics amino acids, lysine and threonine, contribuided to Nile tilapia growth, 30 to 600 g, reared in cages, allowing the reduction of crude protein from 35.25% to 33.16% without prejudice on the performance and body composition of Nile tilapia during the termination.