Exigência de lisina e estimativa da relação ideal aminoácido/lisina por modelagem da deposição de nitrogênio pelo método de Goettingen

Abstract

The object of project was to determine the maximum genetic potential of nitrogen retention, modeling the digestible lysine requirements and estimate the amino acid relationships: lysine to methionine and cystine, threonine, tryptophan, arginine, valine, isoleucine and leucine with broiler slow growth, male, of Redbro plume strain. For this, the research was divided into two stage. The first stage consisted of three nitrogen balance tests in the following periods of age of the birds: 14-28 days (early phase); 42 to 56 days (growth phase); 70 the 84 days (last phase). The birds were housed individually and the collection period were divided into five days of adaptation and two periods of excreta collection, each with five days. The experimental design was completely randomized. The treatments were the same in different ages and consisted of seven isocaloric diets with different levels of nitrogen, being formulated by the technique of dilution, obtained from successive dilutions from the highest level and a diet free of nitrogen. The nitrogen levels were 8, 16, 24, 32, 40 and 48 g / kg. To prove that the responses of birds were due to the limiting amino acid has been added the seventh treatment consisting of diet with lower levels of nitrogen, but with the same lysine content of the second level. In the second stage they used 72 birds Redbro plume, males for each phase of the nitrogen balance. The treatments consisted of nine diets with eight repetitions formulated according to the nutritional recommendations suggested for chickens lineage Redbro plume, but the ideal relations of amino acids used was suggested by Brazilian tables. The diets with different amino acids were obtained by limiting dilution of the control diet with corn starch (70%) and supplemented with crystalline amino acids, amino acid except for the study. The relationship between amino acid utilization efficiency (b / c) estimated for each treatment relative to the amino acid was used to determine the ideal ratio of amino acids. The results of the first stage estimated the maximum potential for nitrogen retention was 3276, 2585 and 2603 mg/BWkg0.67.day, nitrogen maintenance requirement was 225, 135 and 122 mg/BWkg0.67.day and efficiency of nitrogen utilization were 313×10-6, 406×10-6 and 415×10-6 in the phases of 14-28, 42-56 and 70-84 days old birds. The digestible lysine intake for the periods I, II and III, based on 60% of the maximum potential for nitrogen retention, were 711, 989 and 1272 mg/day (1.225, 1.137 and 1.09 % of lysine in the diet for a daily feed intake of 58, 87 and 117 g/day), respectively. From the results of the experiments of stage II, the following aminoacidic relations were estimated: 67, 73 and 71metionina + cystine; 63, 69 and 69 threonine; 17, 18 and 17 tryptophan; 105, 102 and 103 arginine; 85, 80 and 78 valine; 67, 67 and 68 isoleucine; 104, leucine 109 and 108, respectively, for initial phase, growing and finishing the birds.