Fifty F1 Limousin x Nellore bulls were allotted to ten treatments, with five concentrate levels (25; 37.5; 50; 62.5 e 75%) and two diet protein balance methods (one isoprotein and the other changing protein as diet energy changed). The roughage used was Coastcross grass hay (Cynodon dactylon). After the slaughter, all animal body parts were weighted and sampled. The samples were dried, most of the fat was extracted with ether, grinded, and the concentrations of macrominerals were determined. Ca, P, Na, K and Mg contents in the body were determined as function of their concentrations in the several parts of the body. Macrominerals contents retained in the body were determined by regression equations of the logarithm of macrominerals contents in the body as function of the logarithm of empty body weight (EBW). By deriving the prediction equations of macrominerals body content as function of the logarithm of EBW, it was obtained the net macrominerals requirements, for gains of 1 kg EBW, through the equation Y' = b. 10ª. Xb-1, being "a" and "b" intercept and the regression coefficient, respectively, of the prediction equations of macrominerals contents in the body. There was a decrease in the empty body and in the gain of empty body concentrations for all macrominerals studied, with live weight increase. The relationship g Ca/100 g of retained protein and g P/100 g of retained protein were 8.70 and 3.46, respectively.
concentrate levels; crossbred; macrominerals; needs
