Lipid to carbohydrate ratio in donkey's ear abalone (Haliotis asinina, Linne) diets
Five isonitrogenous diets were prepared to vary in the percentage inclusion of lipid/carbohydrate as follows: diet 1, 1.3:47.8%; diet 2, 5.8:43.4%; diet 3, 10.2:39.5%; diet 4, 14.8:36.1%; and diet 5, 19.0:31.4%. The calculated values of gross energy in diets 1 to 5 were 17.6, 18.8, 19.6, 20.6 and 21.6 MJ kg-1 feed, respectively. Abalones, Haliotis asinina, Linne, with a shell length of 11-12 mm and 0.9 g average weight, were stocked in 15 net cages at 50 piece per cage. Three net cages were each fed to satiation once a day in the evening for 28 weeks with growth recorded every 4 weeks. The abalone fed diet 1, containing 1.3% fat and 47.8% carbohydrate obtained the final average body weight that was significantly (P<0.05) higher than those fed diets 2 to 5. In terms of feed conversion ratio (FCR), diets 1 to 4 were not significantly different from one another but these diets were significantly better than diet 5. The survival ranged from 74.7% to 92.7% although it was not significantly different among treatments. These data indicate that high levels of dietary lipid negatively affect abalone growth whereas high levels of carbohydrate support this growth. A high lipid diet resulted in low total feed intake probably because of its high caloric value, leading to poor growth. More experiments need to be conducted to determine the energy requirement of abalone.