COMPARATIVE-STUDIES ON THE NUTRITION OF 2 SPECIES OF ABALONE, HALIOTIS-TUBERCULATA L AND HALIOTIS-DISCUS HANNAI INO .4. OPTIMUM DIETARY-PROTEIN LEVEL FOR GROWTH

A 100 day growth experiment was conducted to identify the optimum diet ary protein level for the juveniles of two species of abalone, Halioti s tuberculata and Haliotis discus hannai. A mixture of vitamin-free ca sein and gelatin (4.34:1) supplemented with crystalline amino acids wa s used as the protein source to simulate the amino acid profile of aba lone body. Eight purified diets were formulated to provide graded prot ein levels ranging approximately from 0 to 50%. The weight gain, prote in gain, soft body to shell ratio, and carcass levels of protein and l ipid of both abalone species were significantly (ANOVA, P < 0.05) affe cted by the dietary protein level. The protein requirements of these a balone were evaluated from weight gain and protein gain respectively, by using the second-order polynomial regression analysis. On the basis of weight gain, the optimum protein levels were estimated to be 22.3- 32.3%, and 23.3-35.6% for H. tuberculata and H. discus hannai, respect ively. According to the protein gain, the statistical analysis indicat ed that the optimum ranges of protein requirements were 24.0-34.5% and 25.2-36.6% for H. tuberculata and H. discus hannai, respectively. Bas ed on these results, about 35% dietary protein from good quality sourc es is recommended for the maximum growth of both abalone species; and, if dietary protein is reduced from 35 to 25%, the growth of these aba lone may be depressed with 5% likelihood.