Protein utilization in correlation to energy intake.

The effect of 14 days' intake of mounting quantities of fats and energy on a constant optimum utilizable amount of dietary protein was studied in weaned rats weighing 60 g. Growth (PER, NPR) and utilization (NPU--body, LPU--liver) parameters of biological protein value were determined, supplemented by a study of the course of the antithetical processes of gluconeogenesis and glycolysis, of the pentose cycle, the citric acid cycle and of transamination processes in the animals' liver. According to the maximum PER, NPR, NPU and LPU values, a 14 days' intake of 59.2 g fats and 4.518 MJ, corresponding to a diet containing 10% protein, 30% fat and 2.274 MJ, had the best effect on the optimum utilizable amount of casein (21 g/14 days). A diet containing 35% and 40% fat stimulated gluconeogenesis, followed by a transamination process and inhibition of glycolysis, the citric acid cycle and lipogenesis (depression of pentose cycle activity and a decrease in the amount of body fat), and simultaneously reduced the values of all four parameters of protein biological value. The results demonstrate that very best diet for newly weaned rats is one containing 10% high quality protein, 30% fat and 2.274 MJ.