O5 Predicting the efficiency of utilisation of energy for maintenance (km) or gain (kg) for sheep and cattle from feed quality components

Abstract

<p>In the current Australian feeding standards for ruminants (CSIRO, 2007) the metabolisablecff energy intake (MEI) required for maintenance (MEm), where retained energy (RE) is zero, is estimated from fasting heat production (FHP) and the efficiency of utilisation of energy for maintenance (km). The efficiency of utilisation of energy for gain (kg) is estimated from the regression of RE:MEI at all levels of feeding (LoF). As FHP is affected by prior LoF, the accuracy of prediction of km and kg relies on feeding at maintenance prior to measurement. The UK feeding system (ARC, 1980) uses fixed values of km and kg for different feedstuffs. The Australian system predicts efficiencies from the energy density (M/D, MJ/kg DM) of the diet (km = 0.02 × M/D + 0.5, kg = 0.043 × M/D), however, it is unclear where the data used to derive these relationships was obtained. Therefore, the aim of the current study was to determine the relationship between km or kg and M/D or other proximate analysis components using data obtained from in vivo calorimetry studies</p>