抄録
Feeding experiments lasting 30 days have been carried out with diets containing varying levels of casein to see the utilization of dietary protein by young carp. The composition of the diets used is shown in Table 1. Within a range of 0.4 to 55.0% of crude protein in the diet, the increase in body weight was in proportion to the content of protein, whereas the accumulation of protein in the body was found to reach the definite value when the crude protein level in the diet was close to 38% (Figs. 1, 2 and Table 2). From these results it is considered that the mode of weight gain and protein accumulation by carp is considerably different at higher levels of protein in the diet. The protein accumulation rate (protein accumulated/protein consumed) showed its highest value at near 21% of protein level, while the protein utilization value (protein accumulation rate × protein content of diet) attained its highest value at 38% of protein level (Table 3). These results show that the requirement by young carp for dietary protein is about 38% of protein in the diet when casein is used as the sole protein source. The relationships between the protein content of diet and the conversion factor, feed efficiency, protein efficiency ratio (PER) and net protein utilization (NPU) were determined and the results are shown in Figs. 2, 4 and 5.
