The work was carried out to evaluate changes in body composition and study the net requirements of mineral matter (MM), calcium (Ca), phosphorus (P), magnesium (Mg) and potassium (K) for empty body weight gain (EBWG) and live weight gain (LWG) of calves from birth to 110 days of age. Eighteen Holstein bull calves with initial average live weight of 40.84 kg and final of 87.03 kg were used. Six animals were slaughtered at birth and six at 50 and six at 110 days of age. Regression analysis of the logarithm of the amount of MM, Ca, P, Mg and K body retained in function of the logarithm of empty body weight (EBW) were fitted. The net requirements of macroelements for weight gain were obtained by derivation of the prediction equations of corporal composition. The EBW and EBWG all elements content increased at newly born to 110 days of age, however the LWG elements requirements decreased in same period. The net requirements for 1 kg EBWG, when EBW ranged from 27.57 to 74.27 kg was ranged from 69.76 to 74.33 g for MM; 24.24 to 24.67 g for Ca; 14.64 to 16.06 g for P; 0.48 to 0.53 g for Mg and 3.18 to 3.61 g for K. The net requirements for 1 kg LWG when LW changes from 30 to 100 kg was changed from 63.37 to 55.20 g for MM; 22.02 to 18.32 g for Ca; 13.30 to 11.93 g for P; 0.44 to 0.39 g for Mg and 2.89 to 2.68 g for K.
empty body weight; live weight; macrominerals; nutritional requirements
