The experiment was conducted to determine the protein requirements for maintenance (PM) and weight gain (NPg) in Brazilian Somali lambs (n = 48). A database of information on non-castrated rams (n = 48) with an initial body weight (BW) of 13.47 ± 1.76 kg was obtained, and the comparative slaughter technique was used to assess protein requirements. Eight lambs were initially slaughtered and used as a reference for estimation of the empty body weight (EBW) and initial body composition of the remaining animals. The lambs (n = 40) were distributed in a completely randomized block design involving five experimental diets, containing 4.93, 8.65, 9.41, 10.12, and 11.24 MJ/kg dry matter (DM). Daily nitrogen retention (DNR) was calculated as the difference between the final N content in the body minus the initial content estimated from the reference animals, divided by the number of experimental days. PM was estimated from the retained N regression equation as a function of ingested N (g per kg(0.75) EBW/day), extrapolating the equation to the zero level of N intake, followed by multiplication by a factor of 6.25. The protein content of the EBW was reduced from 119.72 to 102.07 g/kg of empty body weight gain (EBG) when BW increased from 13 to 28.70 kg, respectively. The requirement of protein for maintenance was 0.80 g per kg(0.75) EBW/day. Based on information described in the present study, we recommend the value of PM 0.80 g per kg(0.75) EBW/day, for hair sheep Brazilian Somalis raised in tropical regions. We also suggest that hair sheep have different requirements for protein maintenance and gain.
Keywords: Comparative slaughter; Growth; Maintenance; Protein; Sheep.