Digestible valine requirements for broilers from 22 and 42 days old/Exigencias em valina digestivel para frangos de corte de 22 a 42 dias de idade

Current experiment established different criteria to evaluate the requirements of digestible valine for broilers from 22 and 42 days of age, by different regression models (quadratic, exponential and Linear Response Plateau) and, in the case of statistical significance, the comparison of means by Duncan test at 5% probability. A total of 1,920 Cobb 500 male broilers were used and distributed in an entirely randomized experimental design, with 6 treatments (6 digestible valine levels: 0.7192, 0.7729, 0.8265, 0.8802, 0.9339 and 0.9876%) and 8 replications, with 40 broilers each. Data on performance and carcass characteristics were evaluated. The level of 0.8265% digestible valine was considered standard. The inclusion of 0.816, 0.848 and 0.903% of digestible valine levels, corresponding to digestible valine:lysine ratios of approximately 76.00%, 79.00% and 84.12%, provided best feed intake, weight gain and feed conversion ratio, respectively for broiler from 22 to 42 days of age. Keywords: digestible amino acids, ideal protein, performance, regression analyses. Um experimento foi realizado com o objetivo de estabelecer criterios de avaliacao das exigencias de valina digestivel para frangos de corte de 22 a 42 dias de idade utilizando-se diferentes modelos de regressao (quadratico, exponencial e de retas segmentadas ou Linear Response Plateau). Foram utilizados 1.920 frangos de corte machos com 22 dias de idade, distribuidos em delineamento inteiramente ao acaso, com seis tratamentos (6 niveis de valina digestivel: 0,7192; 0,7729; 0,8265; 0,8802; 0,9339 e 0,9876) e oito repeticoes de 40 aves. Utilizou-se como padrao o nivel de 0,8265% de valina digestivel. A inclusao dos niveis 0,8160; 0,8484 e 0,9031% de valina digestivel proporcionou os melhores resultados de consumo de racao, ganho de peso e conversao alimentar respectivamente. Palavras-chave: aminoacidos digestiveis, proteina ideal, desempenho, analises de regressao.