1985 Volume 56 Issue 12 Pages 920-924
Ten castrated male Holstein calves were used to determine the requirements of metabolizable energy for maintenance at 4 and 6 months of age. Calves were fed rations with either soybean meal or cottonseed meal as a main source of dietary protein. Results obtained were: 1) No differences were found in mean live weights of calves fed different rations, Means of live weight at 4 and 6 months of age were 79.6±5.7kg and 108.4±4.4kg, respectively. Changes in live weight during a 7-day-comparison period following a 2-week-preliminary period were -0.59kg and 0.62kg for 4-and 6-month-old calves, respectively. 2) Digestibility and metabolizability of dietary energy did not differ with rations, but were significantly higher at 6 months of age than 4 (P<0.01). The proportion of metabolizable energy to digestible energy was 0.85 irrespective of age or rations. Coefficients of digestibility for fiber fractions contributed to the difference with age in energy digestibility, which reflected on metabolizability. 3) Calves ingested metabolizable energy of 508 KJ/kg0.75 at 4 and 554 KJ/kg0.75 at 6 months of age, irrespective of rations. Heat production averaged 520 kJ/kg0.75 uninfluenced by age or rations. Negative energy retention was observed at 4 months of age, but positive at 6 months old. Regression analyses of energy retention (ER, kJ/kg0.75) on metabolizable energy intake (MEI, kJ/kg0.75), including fasting metabolism reported elsewhere, resulted in a statistically significant equation as follows: ER=0.747(±0.018) MEI-390, se=4.9, r=0.994. 4) Metabolizable energy required for maintenance was 522 kJ/kg0.75 irrespective of age or rations. The coefficient of regression, 0.747, showed the net efficiency of utilization of metabolizable energy for maintenance of 4- and 6-month-old calves. Jpn. J. Zootech. Sci., 56 (12): 920-924, 1985
