A trial involving 27 zebu bulls at pasture with initial live weight (LW) of 311.0 kg were conducted with the objective of determining their energy requirements. Three animals were slaughtered at the beginning of the trial, performing the reference group; four had restricted grazing time to limit the energy intake to a level close to the maintenance level. The remaining were uniformly allotted to a complete randomized design, into four treatments: mineral mix, self-feeding protein and protein suplementation three times per week (Monday, Tuesday and Friday) and daily. The net energy requirement for maintenance (Nem) was estimated as the antilog of the intercept of the equation obtained by the linear regression between the heat production logarithm (HP) and the metabolizable energy intake (MEI). The "a" coefficient of the exponential equation obtained between HP and MEI was also determined from non-supplemented animals (mineral) and supplemented animals (protein supplementation) plus animals from the maintenance group. The amount of energy and fat in the gain increased as the body weight of the animals increased. The net energy requirements for gain (Neg) of zebu steers can be obtained through the equation: Neg = ER = 0.0617*BW0.75*EBG1.0564. The daily energy requirement for maintenance was 64.00 kcal/LW0.75. The estimated utilization efficiency of ME for maintenance value was 0.64 and the calculated utilization efficiency of ME for gain value was 0.26.
net energy; pasture; total digestible nutrients; zebu cattle
