Krajcovicová-Kudlácková M, Dibák O
Physiol Bohemoslov. 1986;35(3):243-50.
Male Wistar rats aged 30, 75 and 150 days were fed for 14 days ad libitum on diets with an optimum protein content (15% for 30-day-old, 12.5% for 75-day-old and 10% for 150-day-old animals) and a mounting fat content (from 5 to 40%), supplemented by saccharides (from 76 to 41%). Net protein utilization was determined for each of the diets from the body nitrogen and protein intake values. Protein retention values were determined from protein intake on the basis of net protein utilization (NPU). Energy intake was computed from fat and saccharide intake, using energy coefficients. The optimum fat content of the diet, evaluated from the maximum protein retention value per day and the minimum amount of energy needed for the retention of 1 g protein, is 30% at 30 days, 15% at 75 days and 10% at 150 days. Protein retention per kg body weight falls with advancing age--mildly at 75 days compared with 30 days, but markedly at 150 days. From their smaller weight increments and NPU values and also from their lower protein retention, 150-day-old animals are characterized by slower growth and higher protein requirements for maintenance of their organism likewise demonstrated by the growth parameter net protein ratio (NPR). Energy requirements for total protein retention/day per kg body weight diminish with age. In old age a small amount of energy is needed only for the maintenance of body functions. This study contributes to the expression of the interrelationship of energy requirements and protein retention.
分别选取30日龄、75日龄和150日龄的雄性Wistar大鼠，随意喂食14天，饲料中蛋白质含量适宜（30日龄动物为15%，75日龄动物为12.5%，150日龄动物为10%），脂肪含量递增（从5%增至40%），糖类含量递减（从76%减至41%）。根据机体氮和蛋白质摄入量计算每种饲料的净蛋白质利用率。根据净蛋白质利用率（NPU），从蛋白质摄入量确定蛋白质潴留值。利用能量系数，根据脂肪和糖类摄入量计算能量摄入量。根据每日最大蛋白质潴留值和潴留1克蛋白质所需的最低能量计算得出，30日龄时饲料的最佳脂肪含量为30%，75日龄时为15%，150日龄时为10%。每千克体重的蛋白质潴留量随年龄增长而下降——与30日龄相比，75日龄时下降幅度较小，但150日龄时明显下降。150日龄的动物体重增加较小、NPU值较低，蛋白质潴留量也较低，其生长较慢，维持机体所需的蛋白质需求量较高，生长参数净蛋白质比（NPR）也表明了这一点。每千克体重每日用于蛋白质潴留的总能量需求随年龄增长而减少。在老年时，仅需少量能量来维持身体机能。本研究有助于阐述能量需求与蛋白质潴留之间的相互关系。
