Abstract
During the course of an investigation on the digestibility of the protein in diets, our attention was attracted to the NH3-N, and urea-N excreted by carp and goldfish.
This work was undertaken to determine quantitatively these substances excreted under several different conditions: A-Fish were fed in an approximately air-saturated water; B-Similar to A, but in a water deficient in O2; C-Starved in O2 suffcient water; D-Starved in water deficient in O2
The results obtained were as follows:
(1) Under the normal condition (A), the form of the nitrogen excreted seems to be essentially NH3-N (Table 3).
(2) When the fishes were kept starved or in a water of low O2- content for a long time (B, C, D), urea-N excreted increases in amount (Table 1, 2, 4).
