Requirements of protein for maintenance and growth in ram hair lambs

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.