The objective ofthis work was to estimate the nutritional requirements of net and metabolizableenergy of Nellore, Nellore-Angus and Nellore Simmental cattle, as well as theefficiency of utilization of metabolizable energy for gain and maintenance andefficiency of energy deposition in the form of protein and fat. It was used69 animals (23 Nellore, 23 Nellore-Angus and 23 Nellore-Simmental): four animalsfrom each genetic group (12 in total) were slaughtered before the beginningof the experiment as the baseline group, and nine were used in a digestibilitytrial. The remaining animals were grouped in three dietary treatments (concentratefed at 1 or 2% of body weight obtained with ad libitum intake or correspondingto 1% of the maintenance requirement). At the end of the experiment, all animalswere slaughtered and body composition and empty body weight (EBW) were determined.The net energy requirements were estimated by using the equation of retainedenergt as a function of EBW0.75 and empty body weight gain (EBG).It was estimated the requirements of net and metabolizable energy for maintenanceby using heat production equation in function of metabolizable energy intake.There was an effect of concentrate contents of the diet on the body weight:EBWratio, as well as for body weight gain:EBG ratio. The net energy daily requirementfor maintenance of Nellore, Nellore-Angus and Nellore-Simmental is 75.8 kcal/EBW0.75and the metabolizable energy requirements for maintenance are 112.82 kcal/EBW0.75.The efficiency of metabolizable energy utilization for gain and maintenanceare 41.22 and 67.17%, respectively, and the energy retention efficiency as proteinand fat are 26.71 and 75.43%, respectively.
