The objective of this work was to evaluate average daily gain (ADG) and carcass traits in Nellore and Red Norte steers, finished in feedlots and to evaluate performance predictions by using the systems BR-CORTE, CNCPS 5.0 and NRC (2000). It was used 41 steers: 19 Nelore animals with initial body weight of 361 ± 31 kg and 22 Red Norte animals with initial body weight of 367 ± 30 kg. Adaptation period lasted 28 days. Animal performance evaluation was composed of three 28 day period, totaling 84 days. At the end of each period, animals were weighed after a 16-hour feeding fast. Average gain weight of Red Norte steers was greater than Nellore breed animals (1.43 vs. 1.81 kg/day, respectively). Red Norte animals also presented greater loin eye area (75.41 cm² vs. 68.67 cm²). It was not observed any differences on subcutaneous fat thickness and on rump fat among the genetic groups. None of the nutritional requirement system evaluated were efficient in predicting animal performance. For Nellore breed, daily average gain observed was 1.53kg/day, with values of 1.53, 1.70 and 1.82 kg/day predicted by NRC, CNCPS and BR-CORTE systems. Although average values and predicted by NRC were similar, according to the regression equation, intercept and inclination were different from zero and one. For Red Norte breed, performance observed was 1.88 kg/day with values of 1.50, 1.66 and 1.72 predicted by the systems NRC, CNCPS and BR-CORTE, probably because database of those systems is based mainly on results obtained from Angus bovines.
composite breeds; markers; nutritional requirements; prediction equations; zebu cattle
