THE EFFECTS OF SUBSTITUTION OF FISH MEAL AND MACROALGA WITH SOYBEAN MEAL AND RICE BRAN IN A COMMERCIAL JUVENILE ABALONE (Haliotis discus hannai Ino) DIET ON GROWTH PERFORMANCE

The effects of fish meal (FM) and macroalga (MA) substitution with fermented soybean meal (SM) and rice bran (RB) were tested on a commercial diet in juvenile abalone on an abalone farm. Juvenile abalone (21,600) averaging 3.6 g were randomly distributed into one of four experimental diet treatments (1,800 per treatment, replicated twice). Four experimental diets [Standard (Std), FM50, FM50+MA50 and FM50+MA100 diets] were prepared in duplicate. The 50% FM, combined 50% FM and 50% MA, and combined 50% FM and 100% MA were substituted with the 50% SM, combined 50% SM and 50% RB, and combined 50% SM and 100% RB in the FM50, FM50+MA50 and FM50+MA 100 diets, respectively. The four experimental diets were pelletized by an extruded pelleter in Ewha Oil and Fat Industry Co. (Busan, Korea). Finally, the dry Undaria and Laminaria japonica were prepared to compare with the effects of extruded diets on the performance of abalone.

Survival of abalone fed the formulated diets for 16 weeks was significantly higher than that of abalone fed the dry MA (Undaria and L. japonica) (Table 1). Weight gain and specific growth rate (SGR) of abalone fed the all formulated diets were significantly higher than those of abalone fed the dry MA. The essential amino acids, such as arginine, isoleucine, lysine, methionine, threonine and valine were relatively low in the FM50 diet, but arginine, histidine, isoleucine, leucine, phenylalanine and valine were relatively high in the FM50 + MA50 and FM50 + MA 100 diets compared to the Std diet. A sum of n-3 highly unsaturated fatty acid (HUFA) content were relatively high in the Std diet compared to that of the FM50, FM50 + MA50 and FM50 + MA100 diets, especially 18:3n-3, 20:5n-3 and 22:6n-3 contents decreased in proportion to an amount of substitution of FM and MA with SM and RB, respectively, but 18:2n-6 content increased. No 20:5n-3 and 22:6n-3 was observed in MA (Undaria and L. japonica) diets. The greatest shell growth (length, width and height) and soft body weight was observed in abalone fed the Std diet. In conclusion, the substitutability of the SM for FM seemed to be rather limited in the commercial diet for abalone farms. However, dietary substitution of MA with RB could be made up to 50 % in the commercial diet.