DIETARY SUBSTITUTION EFFECT OF FISH MEAL (FM) AND MACROALGAE (MA) WITH SOYBEAN MEAL (SM) AND TUNIC OF SEA SQUIRT (TSS) ON GROWTH AND BODY COMPOSTION OF JUVENILE ABALONE (Haliotis discus REEVE) FARM  

Dietary substitution effect of fish meal (FM) and macroalgae (MA) with soybean meal (SM) and tunic of sea squirt (TSS) Halocynthia roretzi, which is fishery byproduct, respectively, on growth and body composition of juvenile abalone (H. discus Reeve) farm. Juvenile abalone (27,600) averaging 3.3 g were randomly distributed into one of five experimental diet treatments (2,300 per treatment, replicated twice). Five experimental diets [Commercial diet (Com), FM50, FM100, MA50 and MA100 diets] were prepared in duplicate. The 50% FM, 100% FM, 50% MA, and 100% MA were substituted with the 50% SM, 100% SM, 50% TSS and 100% TSS in the FM50, FM100, MA50, and MA 100 diets, respectively. The five experimental diets were pelletized by an extruded pelleter in Ewha Oil and Fat Industry Co. (Busan, Korea). Finally, the dry Undaria was prepared to compare with the effects of extruded diets on the performance of abalone. The feeding trial lasted for 16 weeks.

Survival of abalone fed the MA50, MA100 and Undaria was significantly higher than of abalone fed other diets (Table 1). Weight gain and specific growth rate (SGR) of abalone fed the MA50, MA100 and FM50 diets were significantly higher than of abalone fed the Com, FM100 and Undaria diets. The essential amino acids, such as leucine, lysine and methionine tended to decrease with an increased FM substitution with SM in the experimental diets. However, all essential and nonessential amino acids tended to increase with an increased MA substitution with TSS in the experimental diets. The 18:2n-6 content tended to increase with an increased FM and MA substitution with TSS in the experimental diets, which was well reflected form high 18:2n-6 content in TSS. The chemical composition of the soft body of abalone was significantly different among the experimental diets. In conclusion, FM could be substituted with TSS up to 50% and MA could be completely (100%) substituted with TSS when 14% FM and 25% MA were included without a reduction in weight gain and SGR of abalone farm.