Energy budgets for Greenlip Abalone (Haliotis laevigata Donovan) fed graded dietary crude protein levels at seasonal water temperatures

Abstract Understanding the energy budgets of cultured abalone fed graded dietary crude protein levels at different water temperatures gives us the ability to optimise diets for different seasons. In this 91-d study we investigated the effects of feeding four diets containing graded levels of crude protein (CP; 27, 30, 33 and 36%) at three seasonal water temperatures (14, 17 and 20 °C) on the energy budget components for 6-month-old Greenlip Abalone, Haliotis laevigata, (0.91 g; 19.46 mm shell length). The increase of water temperature significantly increased individual energy budget components, rates for somatic growth energy, respiration energy and shell growth energy of abalone. Ammonia excretion energy rate was positively related to increasing dietary CP levels. In contrast, there were significant interactions between water temperature and dietary CP levels for ingested feed energy rate, absorbed energy rate and egested faecal energy rate. For energy budgets, respiration energy accounted for the largest proportion and ranged between 34.1 and 43.9% of the ingested feed energy. Somatic growth energy (16.80–28.10%) also accounted for a large proportion of the energy budget. Although egested faecal energy was lower, it still accounted for 8.2–17.9% of the ingested feed energy. In contrast, pedal mucus production energy (4.12–6.20%), ammonia excretion energy (0.28–1.40%) and shell growth energy (0.22–0.46%) accounted for relatively smaller proportions of ingested feed energy. Water temperature significantly impacted energy budgets more than dietary CP level. To maximise energy transfer to somatic growth, a water temperature of 20 °C is recommended for culturing Greenlip Abalone. Additionally, to minimise energy loss through faecal egestion, a dietary CP level of 36% is recommended for the diet of 6-month-old Greenlip Abalone at optimum water temperatures. However, the increase in ammonia excretion energy at high dietary CP should also be considered when managing water quality and waste production in abalone farms, especially where tank water exchange is limited. These findings provide a better understanding of the energy budgets for Greenlip Abalone, in relation to temperature and dietary protein levels, and will aid in the development of sustainable diets applicable to the three-four years of culture.