Study on optimum dietary protein sources for abalone, Haliotis asinina (Linne)

Experiment was conducted to evaluate nutritional quality of several protein sources in diet for juvenile abalone Haliotis asinina (Linne). Five isonitrogenous and isocalorie diets were formulated containing fish meal, soybean meal, soybean meal and spirulina, fish meal shrimp head meal and squid meal, and fish meal shrimp head meal squid meal soybean meal and spirulina in diet 1, 2, 3, 4 and 5 respectively, Gracilaria sp. was used as control feed (diet 6). Each test diet was fed to three replicate group of juvenile abalone with average initial weight of 0.15 g, 1.0 cm in shell length and 0.49 cm in shell width for 36 weeks. The abalone were contained in plastic basket were hanged in flow-through cement tank with water flow rate of 1.8 l/min. Plastic sheet was provided as substratum and shelter. Experimental group of abalone fed on diet 3 with soybean meal and spirulina as protein sources had significantly higher rate of growth compared to abalone fed on other diets (P0.05). Growth rate on a decending order were abalone fed on diet 5, 2, 4 and 1 respectively. The significantly lowest growth was obtained from abalone fed diet 1 (P0.05). Abalone fed on diet 2 and diet 6 (control) recorded similar growth rate which significantly higher than diet 4 and significantly lower than diet 5. Survival rate of abalone fed on diet 3 was significantly higher than diet 6 but not significantly higher than other treatments. Feed conversion were 3.25, 2.77, 2.09, 2.65, 2.34 and 1.54 for diet 1, 2, 3, 4, 5 and 6 respectively. Feed conversion were significantly different among treatments except diet 2 and 4. No histological change in the gastro-intestinal tract was observed in abalone fed the test diets. The results indicated that plant protein source was better than animal protein source. Spirulina was the best among plant protein sources tested. Gracilaria sp. was inferior to soybean meal diet for smaller size abalone (less than 1.2 g) but superior for larger size (bigger than 12 g). The difference in protein quality is not well understood and needs further studies.