The suitability of selected protein sources for inclusion in formulated diets for the South African abalone, Haliotis midae

Five protein-rich ingredients, casein, fishmeal, soya oil cake, Spirulina spp. and torula yeast, were fed to Haliotis midae in semi-purified diets to evaluate their suitability as practical feed ingredients in abalone diets. All diets contained 30% protein and 5% fat, except for the Spirulina spp.-based diet which contained 19% protein. Two algal diets, fresh Plocamium corallorhiza and dried Ecklonia maxima were fed as controls: Abalone fed on fishmeal and Spirulina spp.-based diets displayed significantly higher growth rates than those fed on diets containing soya oil cake, torula yeast, casein and E. maxima. Growth rates of abalone fed P. corallorhiza were significantly lower than those on any other diets. The feed conversion ratios of the formulated diets ranged from 0.7 for the casein-based diet to 1.0 for the torula yeast-based diet. These values were lower than those obtained for the abalone fed the seaweed control diets. Protein efficiency ratios of abalone fed the formulated diets ranged from 3.3 for the torula yeast-based diet to 6.5 for the Spirulina spp.-based diet. These values were higher than those obtained from abalone fed the seaweed control diets. It was concluded that fishmeal and Spirulina spp. algae are the most suitable proteins for inclusion in practical diets for H. midae.