Energy and protein requirements for maintenance and gain of nellore cattle in tropical conditions

Research on the purebred Zebu cattle requirements are scarce in tropical areas. Therefore, we evaluated body composition as well as protein and energy requirements for cattle maintenance and growth. Using comparative slaughter, 30 purebred Nellore bulls non-castrated presenting initial average body weight (BW) of 380.2 ± 28.7 kg. Five animals were assigned as reference group and the remaining 25 were fed ad libitum; randomly distributed in 5 five treatments in completely randomized design: maintenance diet (containing 60% Tifton 85 hay and 40% concentrate, daily offer of 1.2% of BW) and increased concentrate levels: 17; 34; 51 and 68% for 112 days of confinement. The net energy demand for were obtained by the equation: RE= 0.0430*EBWeq0.75*GEBW1.3595. The requirements for maintenance found out for net and metabolizable energy were 78.99 and 116.13 kcal/ kg EBW0.75/day, respectively. The efficiency of metabolizable energy for maintenance was 68.01% and 46.50%, respectively. The demand for metabolizable protein was 4.81 g/kg BWJ0.75/day and the efficiency of its use for weight gain was 51.5%. We found the equation: NPg = 131.8*GEBW+22.7*RE to estimate net protein daily demand for weight gain on male non-castrated Nellore bovines in tropical weather.