A COMPARISON OF TWO DIFFERENT METHODS IN DETERMINING THE PROTEIN REQUIREMENT OF THE TROPICAL BAGRID CATFISH, MYSTUS NEMURUS

摘要

Two separate experiments were simultaneously conducted to determine the dietary protein requirement of the tropical bagrid catfish, Mystus nemurus. In Experiment, 1, which is a standard dose-response study, seven isoenergetic semipurified diets containing dietary protein levels from 20 to 50% in 5% increments were fed to triplicate groups of M. nemurus [mean initial body weight (BW) 7.610.2 g] for 10 weeks. Using the two-slope broken-line analysis, the dietary protein requirement for M. nemurus basedon percentage weight gain was estimated to be 44%. Considering a reasonable feeding rate of 2-2.5 g/(100 g BW.d), the protein intake rate was calculated to be 8.8-11.0 g protein (kg BW.d). In Experiment 2, the daily protein requirement of M. nemurus (mean initial BW 12.1 ± 0.1 g) was determined by feeding a practical diet containing 36.2% protein at various rates [1, 2, 2.5, 3, 3.5, 4 and 5 g/(100 g BW.d)] for 10 weeks. Based on fish weight gain, protein retention and feed efficiency ratios, the optimal protein requirement was estimated to be 9.1 g protein/(kg BW.d). Considering a reasonable feeding rate of 2-2.5 g/(100 g BW.d), the protein requirement of M. nemurus was calculated to be met by a diet containing 36.3 to 45.4% protein. It was concludedthat with some refinement, the protein requirement of M. nemurus determined in Experiment 2, when expressed as a dietary concentration, was similar to protein requirement values determined in experiment 1 and in previous studies with M. nemurus despitedifferences in methodology. The advantages and disadvantages of these two different methods in determining protein requirement of fish were discussed.