Energy and protein requirements of woolless sheep under tropical conditions

Abstract

The objective of this study was to determine the energy and protein requirements for maintenance and weight gain of growing woolless sheep and, in addition, to estimate the shrunk body weight (SBW) and empty body weight (EBW) of the animals according to their body weight (BW) in the fed state. Data from 150 animals from three comparative slaughter experiments with confined castrated sheep averaging 5 ± 0.96 months of age and similar BW (20.74 ± 2.99 kg) were used. Three models were evaluated to estimate EBW from SBW: linear, linear with intercept and non-linear. The following requirements were estimated: net energy for maintenance (NEm), metabolizable for maintenance (MEm), net energy for gain (NEg), efficiency of use of metabolizable energy for gain, metabolizable protein requirement for maintenance (MPm), net protein requirement for gain (NPg), and efficiency of use of metabolizable protein for gain (k). Fasting losses corresponded to 6.18% of BW and the better model to establish the relationship between SBW and EBW was nonlinear. The NEm and MEm were 70.44 and 109.34 kcal/kg EBW0.75/day, respectively. For NEg, the adjusted model was based on the ratio of the energy retained as a function of the EBW and the desired empty body weight gain (EBG). Considering two lambs weighing 15 kg and 30 kg with a daily gain of 100 g, the estimated NEg is 181 and 360 kcal/kg EBW0.75/day, respectively. The estimated kg was 0.407. For MPm, the value of 3.19 g/kg EBW0.75/day was estimated. The estimated NPg for animals of 15 and 30 kg, with the same gain rate was 13.13 and 13.61 g/day, respectively, which corresponds to the protein concentration in gain of 170 and 161 g/kg EBG, and efficiency of use of the metabolizable protein for gain ranging from 0.66 to 0.41. The nutritional requirements of woolless sheep did not follow the standards assumed by the international feeding systems, except for the energy requirements for maintenance and efficiency of use of the metabolizable energy for maintenance, which did not differ. The losses represented by the gastrointestinal tract (GIT) after fasting and slaughtering periods are higher in woolless sheep compared to those presented by the international feeding systems.