Abstract
Digestible crude protein (DCP) of feeds could be calculated based on the DCP content of the feed components determined at different water temperatures with various sizes of fish. This was verified in Experiment I with rainbow trout, carp, tilapia and ayu, and the DCP values were almost similar for the different sizes of a particular fish. The effect of temperature on DCP values ofanimal protein sources differed among the species; the influence was not prominent for white fish meal and local fish meal, whereas a dependence was noted in the case of carp and tilapia for meat meal, and rainbow trout and ayu for silk worm pupa meal. Among the plant protein sources, the DCP values were dependent on fish species as well as temperature in the case of corn gluten meal and rice bran, but only on fish species in the case of soybean meal and wheat flour. The digestibility of the protein feedstuffs were highest at 15°C for rainbow trout, 25°C for carp and tilapia, and 20°C for ayu. In Experiment II, it was found that the DCP values calculated on the basis of DCP of each feedstuff were similar to those practically determined, suggesting that the DCP of diets could be calculated if the composition of the diet is known.
