Made available in DSpace on 2016-04-28T14:59:44Z (GMT). No. of bitstreams: 1 2007- Priscila de Andrade Massi.pdf: 1544991 bytes, checksum: 0aa0d9a3ed5ea1374208ba33e49177d9 (MD5) Previous issue date: 2007-06-22 / They were used three hundred slow-growing broilers from 35 to 70 and 35 to 84 days of age, and three hundred fast-growing broilers from 28 to 49 days of age to evaluate the effects of the energy levels on performance, carcass characteristics and economic indicators of broilers raised in a free-range system.The experimental design was the completely randomised with five levels of metabolizable energy and four replications of fifteen each. The slow-growing broilers, from 35 to 75 days age, had linear reduction on feed consumption with the increase of the metabolizable energy levels. The metabolizable energy levels influenced in a quadract form the feed:gain ratio, being estimated in 3046 kcal/kg of the diet the level that would result in the best feed:gain ratio (2,648). From 35 to 84 days of age, the metabolizable energy level affected in a linear form the feed consumption and the feed:gain ratio that reduced with the increase of the metabolizable energy level in the broilers diets. About the carcass characteristics, from 35 to 70 days age were observed quadract effects on the absolute weight of the hot carcass, the abdominal fat, the gizzard, the small intestine, and the live weight after fasting and on the relative weight of the gizzard and the feet. They were observed linear effects on absolute weights of the abdominal fat, the small intestine and on the small intestine length. From 35 to 84 days of age were observed linear increases in absolute and relative weight of the abdominal fat. The metabolizable energy levels did not affect the other studied parameters. From 35 to 70 days of age, the metabolizable energy levels influenced in a quadract form the cost for gain unit, being the gross margin average reduced in a linear way with the increase of the metabolizable energy level of the diet. From 35 to 84 days of age the cost for gain unit increased in a linear form with the increase of the metabolizable energy levels and the smaller level the metabolizable energy resulted in greater gross margin average. In relation of the fast-growing broilers was observed that the metabolizable energy levels affected the feed:gain ratio that improved in a linear form and the feed consumption that showed a quadract effect. They were observed linear increases in the live weight after fasting, the absolute weights of the hot carcass, the abdominal fat, the proventricle and the small intestine and in the relative weights of the abdominal fat and the gizzard. Quadract effects were observed in the carcass yeld, the absolute weights of the liver and the head with neck and in the relative weight of the liver. The metabolizable energy levels influence in a quadract form the cost for gain unit and the greater rate of the gross margin average was obtained with the level of 2900 kcal of ME/kg. / Foram utilizados 300 frangos de corte de crescimento lento nos per?odos de 35 a 70 e de 35 a 84 dias de idade, e 300 frangos de corte de crescimento r?pido no per?odo de 28 a 49 dias de idade para avaliar os efeitos dos n?veis de energia metaboliz?vel (EM) sobre o desempenho, caracter?sticas de carca?a e indicadores econ?micos de frangos semiconfinados. O delineamento experimental foi o inteiramente casualizado com cinco tratamentos e quatro repeti??es de quinze aves cada. Os frangos de crescimento lento apresentaram no per?odo de 35 a 70 dias de idade, redu??o linear no consumo de ra??o (CR) com o aumento dos n?veis de EM. Os n?veis de EM influenciaram de forma quadr?tica a convers?o alimentar (CA), o que permitiu estimar em 3046 kcal/kg de ra??o o n?vel que proporcionaria a melhor CA (2,648). No per?odo de 35 a 84 dias de idade, o n?vel de EM afetou de forma linear o CR e a CA que reduziram com o aumento de EM na ra??o dos frangos de corte. Quanto ?s caracter?sticas de carca?a, no per?odo de 35 a 70 dias de idade, foram observados efeitos quadr?ticos sobre os pesos absolutos da carca?a quente, da gordura abdominal, da moela, do intestino delgado e do peso vivo ap?s o jejum e sobre os pesos relativos da moela e dos p?s. Foram observados efeitos lineares sobre os pesos relativos da gordura abdominal e do intestino delgado e sobre o comprimento do intestino delgado. No per?odo de 35 a 84 dias de idade, foram observados aumentos lineares nos pesos absolutos e relativos da gordura abdominal. Os n?veis de EM n?o influenciaram os demais par?metros estudados. No per?odo de 35 a 70 dias, os n?veis de energia metaboliz?vel influenciaram de forma quadr?tica o custo por unidade de ganho (CPUG), tendo a margem bruta m?dia (MBM) reduzido linearmente com o aumento do n?vel de energia metaboliz?vel da ra??o. No per?odo de 35 a 84 dias de idade o CPUG aumentaram de forma linear com o aumento dos n?veis de energia metaboliz?vel e o menor n?vel de EM resultou em maior ?ndice de MBM. Quanto aos frangos de crescimento r?pido, observou-se que os n?veis de EM afetaram a CA que melhorou de forma linear e o CR que apresentou efeito quadr?tico. Foram observados aumentos lineares no peso vivo ap?s jejum, nos pesos absolutos da carca?a quente, da gordura abdominal, do proventr?culo e do intestino delgado, e nos pesos relativos da gordura abdominal e da moela. Efeitos quadr?ticos foram observados no rendimento de carca?a e nos pesos absolutos do f?gado e da cabe?a com pesco?o e no peso relativo do f?gado. Os n?veis de energia metaboliz?vel influenciaram de forma quadr?tica o CPUG e o maior ?ndice de MBM foi obtido com o n?vel de 2900 kcal/kg.