MEASUREMENTS OF FEED-INTAKE AND EXCRETION IN FISH USING RADIOGRAPHY OR CHEMICAL INDICATORS

Experiments were conducted to determine the effectiveness of measuring feed consumption and excretion in salmonid fish by radiographic and c hemical indicator methods. To do this it was also necessary to measure concurrently the digestibility. Digestibility was determined in 16 di ets of different origin comparing n-alkanes (C-28 and C-32) as indiges tible indicators with chromium sesquioxide and celite. Research was al so conducted comparing the radiographic method for measuring feed inta ke with that of using C-32 alkane as an external indicator to measure faecal output The results show that n-alkanes can be used as internal and external indicators in measuring faecal output, digestibility and intake in fish. The radiographic method and the n-alkane indicator met hod are compatible for the measurement of feed consumption, but both m ethods give high variability, making small differences in feed consump tion difficult to detect.