Estimation of maintenance energy requirements of beef cattle and sheep

Metabolizable energy intake and heat production were measured in a series o f calorimetry experiments carried out at the Agricultural Research Institut e of Northern Ireland, Hillsborough, between 1993 and 1996 with beef cattle and sheep. A total of 75 estimates were made with cattle: 23 with Charolai s cross steers; 16 with Simmental cross steers and 36 with Angus cross stee rs (450-628 kg liveweight). Fifty-six estimates were made with lambs: 24 wi th Blackface cross, eight with Suffolk cross and 24 with Texel cross (23-53 kg liveweight). The diets offered to both cattle and sheep contained propo rtionately 0.0-0.8 cereal-based concentrates, the remainder being grass sil age. Linear regressions of energy retention (measured by calorimetry) again st metabolizable energy intake were produced for the cattle and sheep studi es. From these linear regressions an estimate of metabolizable energy requi red for maintenance (MEm) was obtained. For cattle, the derived MEm was 0.6 14 MJ/kg LW0.75 per day, and for sheep the derived MEm was 0.460 MJ/kg LW0. 75 per day. The estimates were proportionately 0.34 higher in cattle and 0. 32 higher in sheep than the 1990 values of the UK Agricultural and Food Res earch Council.