The objective of this work was to estimate the nutritional requirements of net and metabolizable energy of Nellore, Nellore-Angus and Nellore Simmental cattle, as well as the efficiency of utilization of metabolizable energy for gain and maintenance and efficiency of energy deposition in the form of protein and fat. It was used 69 animals (23 Nellore, 23 Nellore-Angus and 23 Nellore-Simmental): four animals from each genetic group (12 in total) were slaughtered before the beginning of the experiment as the baseline group, and nine were used in a digestibility trial. The remaining animals were grouped in three dietary treatments (concentrate fed at 1 or 2% of body weight obtained with ad libitum intake or corresponding to 1% of the maintenance requirement). At the end of the experiment, all animals were slaughtered and body composition and empty body weight (EBW) were determined. The net energy requirements were estimated by using the equation of retained energt as a function of EBW0.75 and empty body weight gain (EBG). It was estimated the requirements of net and metabolizable energy for maintenance by using heat production equation in function of metabolizable energy intake. There was an effect of concentrate contents of the diet on the body weight:EBW ratio, as well as for body weight gain:EBG ratio. The net energy daily requirement for maintenance of Nellore, Nellore-Angus and Nellore-Simmental is 75.8 kcal/EBW0.75 and the metabolizable energy requirements for maintenance are 112.82 kcal/EBW0.75. The efficiency of metabolizable energy utilization for gain and maintenance are 41.22 and 67.17%, respectively, and the energy retention efficiency as protein and fat are 26.71 and 75.43%, respectively.
efficiency of energy utilization; finishing; metabolizable energy; net energy; requirements
