RESUMO -Quatrocentas aves com peso médio de 675,00 g foram distribuídas em delineamento de blocos casualizados, com base no peso das aves, com cinco tratamentos e quatro repetições. As dietas experimentais foram constituídas de cinco níveis de energia metabolizável (2.800, 2.900, 3.000, 3.100 e 3.200 kcal de EM/kg de ração) formuladas para atender às exigências nutricionais, exceto de energia metabolizável. O aumento do nível de energia das rações foi obtido pela adição de óleo de soja. Realizaram-se análises de variância e de regressão, associando-se os níveis de energia aos valores das variáveis estudadas. As aves foram avaliadas quanto ao desempenho (consumo de ração, ganho de peso e conversão alimentar) e às características de carcaça nos períodos de 22 a 35 dias, 36 a 42 dias, 43 aos 49 dias e de 22 a 49 dias de idade. O ganho de peso e a conversão alimentar de frangos de corte da linhagem Hubbard mantidos em ambiente de alta temperatura não são influenciados pelos níveis de energia metabolizável da ração. Os níveis de energia da dieta não afetam os rendimentos de carcaça, coxa, sobrecoxa, asa, tulipa, moela coração fígado, proventrículo e intestino. Entretanto, a gordura abdominal aumenta e o rendimento de peito decresce proporcionalmente à elevação da energia da dieta em ambiente de altas temperaturas.Palavras-chave: características de carcaça, consumo de ração, conversão alimentar, desempenho, ganho de peso Metabolizable energy levels in diets for broiler maintained in environment of high temperatureABSTRACT -Four hundred birds Hubbard linage with average weight of 675g were distributed to completely randomized block design, based in birds he weight, with five treatments and four replications. The experimental diets were constituted of five metabolizable energy levels (2,800, 2,900, 3,000, 3,100 and 3,200 kcal of ME/kg ration) formulated to attend the nutritional requirements, except for metabolizable energy. The increase of energy was obtained by the addition of soybean oil. The variance and regression analysis was made, associating the energy levels with the values of the studied characteristics. The birds were evaluated by performance (feed intake, weight gain and feed: gain ratio) and carcass characteristics in the periods from 22 to 35 days, 36 to 42 days, 43 to 49 days and 22 to 49 days of age, respectively. Weight gain and feed:gain ratio of broilers maintained in high temperature environment were not influenced by metabolizable energy levels of diets. Metabolizable energylevels of the diet did not affect: carcass, thigh, over thigh, wing, tulip, gizzard, heart, liver and proventricle and intestine. However, the abdominal fat increases and breast yield proportionally decrease with the increase of the metabolizable energy levels of the diet in high temperature environment conditions.

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Non-ruminantsFull-length research article Non-linear mixed models in the study of growth of naturalized chickens ABSTRACT -This study was conducted to examine the inclusion of random effects in non-linear models, identify the most suitable models, and describe the growth of naturalized chickens. Live-weight records of 166 birds of the Graúna Dourada, Nordestina, and Teresina ecotypes were estimated. The asymptotic weight (A), integration constant, related to animal initial weight (B), and the maturing rate (k) parameters of the non-linear Gompertz, Logistic, and von Bertalanffy models were estimated and adjusted using the Gauss-Newton method. Residual variance decreased by more than 50% when random effects were added to the model. The best fits in the estimate of the growth curve of females were obtained by associating the random effects with the three parameters of the Gompertz and Logistic models. The association of random effects with two parameters (asymptotic weight and maturing rate) and with the three parameters of the Logistic model provided the best fits for the males. The Teresina ecotype has the highest adult weight in both sexes, despite its slower growth. The opposite is true for the Graúna Dourada ecotype, formed by lighter and earliergrowing animals. The inclusion of random effects in models provides greater accuracy in the estimate of the growth curve.

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