Pazdiora, Raul Dirceu [UNESP]Resende, Flávio Dutra de [UNESP]Faria, Marcelo Henrique deSiqueira, Gustavo Rezende [UNESP]Almeida, Geraldo Benedito de Souza [UNESP]Sampaio, Ricardo Linhares [UNESP]Pacheco, Paulo SantanaPrietto, Murilo Sergio Rodrigues2014-05-202014-05-202013-04-01Revista Brasileira de Zootecnia. Sociedade Brasileira de Zootecnia, v. 42, n. 4, p. 273-283, 2013.1516-3598http://hdl.handle.net/11449/4922The objective of this study was to evaluate animal performance and carcass characteristics of 64 Nellore young bulls at 22 months of age finished in a feedlot and slaughtered at five body weights (350; 455; 485; 555 and 580 kg) fed diets containing coated or uncoated urea. The experimental design adopted was completely randomized, set in a 4 × 2 factorial arrangement, and for the variables assessed in the control animals, it was 5 × 2. No effect of interaction between slaughter weights and diets were observed, so the variables were analyzed separately, compared by polynomial contrasts and by the F test, respectively. The time animals remained in the feedlot to reach slaughter weights was 66, 88, 145 and 194 days. Average daily gain (ADG) showed quadratic behavior, with a maximum of 1.44 kg/day with animals of 491.7 kg. Dry matter intake (DMI) (kg/day) was similar in all the treatments, but it decreased linearly as body weight increased. The bionutritional efficiency worsened linearly as body weight rose. The elevation in slaughter weight resulted in linear decrease in the percentage of beef round and increase in forequarter. Backfat thickness and rib eye area of the longissimus increased linearly and the percentages of muscle and protein in the carcass reduced and those of fat and ether extract increased linearly as body weight increased. Average daily gain, DMI, feed efficiency and carcass characteristics were not affected by diets containing coated or uncoated urea. However, animals fed coated urea presenter better crude fiber and neutral detergent fiber intake.273-283engBody compositionFat thicknessFeed efficiencyFeedlotgain yieldhigh grain rationsArtigo10.1590/S1516-35982013000400007S1516-35982013000400007WOS:000317523500007Acesso abertoS1516-35982013000400007.pdf