Metabolizable energy for broilers of different growth potentials raised in a free-range system. / Energia metabolizável para frangos de corte de diferentes potenciais de crescimento criados em sistema de semiconfinamento.

AUTOR(ES)
DATA DE PUBLICAÇÃO

2007

RESUMO

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.

ASSUNTO(S)

exigência nutricional frangos de corte macho nutritional requirement male broilers producao animal acesso a piquete free-range

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