Dietary inclusions of dried macroalgae meal in formulated diets improve the growth of greenlip abalone (Haliotis laevigata)

Wild greenlip abalone predominantly consumes macroalgae, but under culture conditions in Australia, they are fed formulated diets. Dried macroalgae meals are promising ingredients for abalone diets. In this 92-day study, the growth, feed utilisation and digestive enzyme activities of greenlip abalone (Haliotis laevigata; 2.89 g) fed dried macroalgae meals (Ulva sp. meal or Gracilaria cliftonii meal) in formulated diets were investigated. Seven experimental formulated diets, a basal diet (0 % diet) and three inclusion levels of Ulva sp. meal (5, 10 and 20 % inclusions) and Gracilaria sp. meal (5, 10 and 20 % inclusions) were used. Diets were formulated to contain 35 % crude protein, 5 % crude lipid and 17.5 MJ kg⁻¹ gross energy. A commercial diet was also fed to abalone and compared with the 0 % diet. Growth and feed conversion ratio (FCR) of abalone fed the 0 % diet and commercial diet were similar. Abalone fed 5 % Gracilaria sp. meal or Ulva sp. meal exhibited superior growth to abalone fed 0 %. However, increasing dietary Gracilaria sp. meal inclusions (>10 %) led to further growth improvements but impaired protein and energy retentions. In contrast, abalone fed >10 % Ulva sp. meal inclusions exhibited similar growth to those fed 0 and 5 % Ulva sp. Although Ulva sp. and Gracilaria sp. meals are currently not commercially viable, this study clearly demonstrates the potential to develop abalone feeds with inclusions of dried macroalgae meal. We recommend a dietary inclusion of 10 % Gracilaria sp. meal or 5 % Ulva sp. meal to improve abalone growth.