INFLUENCE OF BODY CONDITION ON MAINTENANCE ENERGY-REQUIREMENTS OF CHAROLAIS COWS

The objective of the experiment was to test whether maintenance energy requirements of non-lactating, non-pregnant beef cows increased with body fatness. Twelve Charolais cows were initially fed to attain eithe r lean or fat body condition. Subsequently, over a period of 66 days f ood allowances were regularly adjusted for zero live-weight change. Fo r the following 76 days, lean and fat cows received either 400 or 553 kJ metabolizable energy (ME) per kg initial live weight0.75 per day, r espectively. Fat cows maintained their body weight and composition whe reas lean cows lost 296 g body weight, 221 g lipid and 65 g protein da ily. Calculated maintenance energy requirements averaged 516 and 536 k J ME per kg live weight0.75 per day for lean and fat cows respectively but were not significantly affected by body fatness. Diet dry matter, organic matter, crude protein and energy apparent digestibilities but not acid-detergent fibre digestibility were significantly higher in f at animals.