평균 체중이 각각 167kg(실험 1), 355kg(실험 2) 그리고 449kg(실험 3)인 한우 거세우 12두씩을 공시하여 성장단계별로 건물섭취량이 동일한 조건에서 CP 섭취량 증가가 단백질 균형 및 N 배설량에 미치는 효과를 조사하였다. 각 시험의 공시축은 CP 수준이 평균 9%. 14%, 18% DM가 되도록 ground corn grain을 corn gluten meal 일정 비율 대체 혼합한 배합사료를 섭취하였다. 사료 CP 섭취량 증가로 CP 소화율은 유의성있게 증가하였으나, 건물소화율은 유의하게 증가하지 않았다. 사료 CP 섭취량 증가는 분 N 배설량 증가보다는 주로 뇨 N 배설량을 증가(P<0.05)시켰다. 유지수준 이상에서 섭취된 CP의 체축적 효율은 육성기에 약 70%, 비육기에는 46~39%로 공시축의 성장과 체중증가에 따라서 크게 낮아졌다. 따라서 분뇨를 통한 N 배설량은 육성기에는 섭취 CP의 60%, 비육기에는 70%로 가축의 성장에 따라 증가하는 것으로 나타났다.
Three experiments with different stage of Hanwoo steers (average BW of 167kg, 355kg and 449kg, respectively) were conducted to examine the effect of different quantities of CP intake with similar DM intake on protein balance and N excretion. Twelve Hanwoo steers in each experiment were offered three diets containing three levels of protein (9, 14 and 18% on DM basis) in the concentrate formulated with using different amount of ground corn grain or corn gluten meal. There were significant effects of increasing CP intake on CP digestibility but not on DM digestibility. Despite different CP intake, apparent fecal N outputs were not significantly affected. However, amounts of N excreted into urine increased (p<0.05) with increasing CP intake. There was an obvious effect of live body weight on efficiency of body protein conversion of CP consumed in excess of animal requirement for maintenance, with slopes of 70% and 46~39% for growing and fattening stage, respectively. Nitrogen excretion into feces and urine in this experiment was 70% of the daily N consumption for fattening stage, compared with 60% for growing stage.
