The energy metabolism of young Friesian calves fed on a diet consisting of milk and meal : a thesis presented in partial fulfilment of the requirements for the degree of Master of Agricultural Science at Massey University, New Zealand
Two Friesian bull calves were selected from those born each week for six weeks during March and April 1975. The twelve calves were used in an experiment to study the energy metabolism of young calves when fed a milk and meal diet. 1. All calves were reared on fresh whole milk with pelleted concentrate available ad lib. Between 21 and 42 days of age intake was adjusted so that each animal received half of its daily allowance of ME from milk and half from meal. From each pair, one calf was assigned randomly to a high level, and its pair mate consequently to a low level of feeding. 2. Energy and nitrogen balances (seven days duration) were measured once for all pairs of calves and twice for the last three pairs. 3. Heat production (MJ/day) was related to liveweight (kg) by HP = .200 LW.980, and metabolizable energy to liveweight by ME = .340 LW.922. 4. The data for heat production, metabolizable energy intake and energy retention were interpreted to provide estimates of 'true' net energy required for maintenance of 0.26 MJ/kg0.75 daily. 5. The pooled values for ME required for maintenance were 0.37 and 0.41 MJ ME/kg0.75 daily determined by simple and multiple regression techniques respectively. The net efficiency of utilization of ME above maintenance was 0.63 determined by simple regression. 6. Pooled values for the partial net efficiencies of utilization of ME for the synthesis of protein and fat were 0.38 and 1.00 respectively. 7. ME required above maintenance per kg of liveweight gain was 16.53 and 12.85 for the high and low feeding levels respectively. The difference between these values was not significant and the pooled value was 14.89 MJ ME/kg liveweight gain. 8. Methane losses accounted for less than 2% of GE. The metabolizability (ME/GE) of the combined diet was 78% and DE/ME 0.94. 9. Obligatory losses of N were 0.19 gN/d/kg0.75, N maintenance (Nm) was 0.35 gN/kg0.75 daily, the digestibility was 81% and the biological value 0.53.