Increased dietary protein improves the commercial production of hybrid abalone (Haliotis laevigata × Haliotis rubra)

Over the past decade, Australian abalone were produced using a range of commercially formulated grow-out diets with crude protein (CP) levels ranging from 27% to 30% throughout their production cycle. Recent research identified higher optimal dietary CP levels of greater than or equal to 35%for younger than 1-y-old abalone at higher water temperatures (20-22°C). To validate the results of the laboratory-based research, the current trial was designed to investigate the effect of feeding two different commerciallymanufactured diets (standard-protein diet, 32%CP, versus a high-protein diet, 39%CP) to hybrid abalone (Haliotis laevigata ×Haliotis rubra; initial weight: 3.10 g) on growth performance, feed utilization, and sales revenue under on-farm conditions. During this 18-mo trial, abalone were cultured using normal commercial practices over two summer periods at Great Southern Waters abalone farm (Indented Head, VIC, Australia). A significant improvement in specific growth rate (SGR) led to a 9% improvement in biomass gain for abalone fed with the high-protein diet. This improvement was achieved with no differences in survival, and minimal difference in feed input between diets. In addition, the feed conversion ratio of abalone fed with the high-protein feed was 7.1% superior to that of animals fed with the standardprotein diet. On the basis of a farmgate value ofAUD35/kg abalone, for an additional feed input cost ofAUD2/m² slab tank/y, a 9.5%increase in basic annual sales revenue (AUD44/m2 slab tank/y) was achieved feeding the high-protein diet. In addition, due to an increased SGR by feeding the high-protein diet, the duration of a typical 3-y production cycle for hybrid abalone may be shortened by up to 3.4 mo. By adopting the high-protein diet, farmers may also harvest abalone sooner, and reduce exposure to one less summer. This may reduce heat-related mortalities and further improve productivity, and when combined with savings made with biomass and feed efficiency gains, a more than 10%improvement in productivity across the entire grow-out period for hybrid abalone may be achieved.