Improvement in energy allocation in Greenlip Abalone (Haliotis laevigata Donovan) fed diets substituted with different types and levels of macroalgal meal

Macroalgae meal may provide a useful source of dietary energy for cultured abalone. The inclusion of dried macroalgal meals in formulated diets may also provide other benefits such as improvement in growth, health and survival. In this 92 d study, energy allocation in Greenlip Abalone, Haliotis laevigata, fed either a commercial diet, the control diet (0% macroalgae meal inclusion), or diets containing three inclusion levels (5, 10 and 20%) of either of two enriched macroalgae meals, Gracilaria cliftonii and Ulva sp., was investigated. Energy budget models, which also accounted for shell growth energy and mucus production energy, were determined for each diet. Results varied in relation to energy budget components and diets. Overall, abalone fed the enriched G. cliftonii ingested significantly more dietary energy and exhibited higher somatic growth energy compared to those fed the commercial diet, the 0% control diet or the enriched Ulva sp. diets. Additionally, ingested feed energy decreased while somatic growth energy tended to increase with increasing enriched G. cliftonii meal inclusion level. In contrast, inclusion at any level with enriched Ulva sp. meal did not result in an improvement of somatic growth energy compared to the commercial or the 0% control diet. For ingested feed energy, 20% enriched Ulva sp. meal inclusion resulted in significantly higher values compared to either the commercial diet, control diet or the two other enriched Ulva sp. meal diets. However, abalone fed the 20% dried Ulva sp. meal diet lost significantly more energy through faecal egestion than those fed the commercial or the 0% control diets, suggesting reduced diet digestibility with increasing enriched Ulva sp. inclusion. The majority of ingested feed energy was allocated to somatic growth across treatments, while shell growth energy accounted for the smallest proportion of the energy budgets. Results suggest that the inclusion of enriched G. cliftonii meal (10% inclusion optimum) in formulated diets for Greenlip Abalone has energetic benefits for feed utilisation and growth which may lead to improved business productivity. Inclusion of selected macroalgae species in formulated diets for abalone is an approach where the benefits from feeding live macroalgae can be successfully transferred into these diets.