The objective of this work was to evaluate the performance prediction by the CNCPS 5.0, NRC 2000 and BR-CORTE systems, as well as the average daily weight gain (ADG) and the carcass traits of young Zebu bulls. Fourty-four young bulls were used: 19 Nelore PO, 7 Nelore OB, 10 Tabapuã PO and 8 Guzerat PO, with initial body weight of 266, 236, 222 and 219 kg and initial average age of 9, 10, 8 and 8 months respectively. The experimental period was of 112 days. The individual intake was measured using markers (LIPE, chromic oxide and indigestible acid detergent fiber). The data on rib-eye area (REA), subcutaneous fat thickness (SFT) and rump fat thickness (P8) were obtained using ultrasonography. For the comparison of the estimated and observed ADG values, linear regression analysis was used. ADG, REA, SFT and P8 did not differ amongst the genetic groups. For the CNCPS 5.0 and NRC 2000 systems, the lowest ADG values predicted were estimated based on the available energy; for BR-CORTE, the lowest values were estimated based on available protein. The NRC 2000, CNCPS 5.0 and BR-CORTE systems overestimated the ADG, and were inadequate for predicting the performance of young Zebu bulls.
Bos taurus indicus; Guzerat; markers; Nelore; Tabapuã; ultrasonography
