This work was conducted to study the net requirements of energy for maintenance and weight gain, the net requirements of protein for weight-gain and the dietetic requirements of protein and energy, as well as, the changes in corporal composition of dairy steers as live weight increased, with the purpose of meat production. Sixteen Holstein dairy steers with initial average age and weight of 20 months and 202.0 kg were used. The animals were divided into five groups: one group of animals was slaughtered at the beginning of the trial (AI), the other was submitted to restricted feeding (AR) and three groups were ad libitum fed (AL-1, AL-2 and AL-3) and they were slaughtered when the individual weights of 250.0, 300.0, and 350.0 kg were reached, respectively. The AR group received 15.0% above maintenance requirements levels of protein and energy. The diet contained 1:1 forage to concentrate ratio on dry matter basis with 12.48% of crude protein. The net requirement of energy for maintenance (NEm) was determined by regression of log heat production in function of metabolizable energy intake, as the heat production at zero level of energy intake. Regression equations of log body contens of protein, fat and energy in fucntion of the log of the empty body weight (EBW) were fitted, based on the data from AI, AL-1, AL-2 and AL-3 steers, allowing to estimate body composition for any EBW, in the studied range. Equations to estimate composition of EBW gain were obtained by differentiation of regression equations. The estimated net energy requirement for maintenance of the steers were 68.44 kcal/kg.75. The estimated net protein requirements for weight gain was similar to those values recomended by AFRC (1993). The estimated total metabolizable energy requirement was, nearly 10.0% lower than recomended twose by AFRC (1993).
dairy steers; body compositon; requirements; protein; energy