Author: Duong Duong Ngoc
Duong Ngoc, Duong, 2017 Bioenergetics of Australian greenlip abalone (Haliotis laevigata Donovan), Flinders University, School of Biological Sciences
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The greenlip abalone, Haliotis laevigata, is a commercially important Haliotis species for aquaculture, mainly cultured in land-based systems, in southern Australia. In order to improve production and reduce culturing time, it is necessary to understand many aspects such as the production improvement the genetics of animals, the impact of major physical aspects, nutritional requirements and the influence of environmental factors such as water temperature. Studying bioenergetics, based on an energy balance, is one way to understand the basic biology of an animal and how the ingested food energy is partitioned and used for oxygen consumption, somatic growth, reproduction, excretion, mucus production and shell growth under different dietary and feeding scenarios or water temperatures.
In order to study the bioenergetics of abalone, five experimental trials (presented as Chapter 2, 3, 4, 5 and 6) were conducted to investigate the effects of diet and water temperature. Trial 1 (Chapter 2) was carried out to study the bioenergetics of greenlip abalone fed live macroalgae (Gracilaria cliftonii and Ulva sp. with or without enrichment) or commercial formulated diets. Ingested food, absorbed and somatic growth energy of greenlip abalone, fed live non-enriched G. cliftonii or commercial diets, improved compared to those fed live Ulva sp. The largest component of the energy budgets in abalone fed both live macroalgae diets and the commercial diets was somatic growth energy, except for abalone fed live Ulva sp. where it was the respiration energy. Nutrient enrichment increased the level of crude protein in live macroalgae and the amount of ammonia excretion energy in abalone.
In trial 2 (Chapter 3) the bioenergetics of abalone fed dried enriched G. cliftonii or Ulva sp. at graded levels at 5, 10 and 20% were investigated. The components of the greenlip abalone energy budget changed in response to dried macroalgae meal types and inclusion levels. Improvements in ingested food energy, absorbed energy and somatic growth energy were observed in abalone fed inclusion of ≥ 10% dried G. cliftonii meal in the diet. A major portion of ingested food energy went to somatic growth energy and respiration energy.
In trial 3 (Chapter 4), the bioenergetics of abalone fed formulated diets of 27, 30, 33 and 36% crude protein levels at 14, 17 and 20 °C water temperatures were examined. Ingested food energy, somatic growth energy and respiration energy became significantly higher as water temperature rose from 14 to 20 °C, reflecting that up to 20 °C, greenlip abalone had not reached their upper tolerance limit. An increase in dietary crude protein (CP) levels had little influence on the components of energy budget. Thus, the dietary crude protein level of ~ 27 % is recommended for abalone at different seasonal water temperatures. Across treatments, the largest proportion of the abalone energy budget, fed graded levels of CP at different water temperatures, was respiration energy.
Trial 4 (Chapter 5) was conducted to evaluate the effects of inclusion of a commercial probiotic and prebiotic at 22 or 25 °C on each component of the energy budget and also to establish energy budgets of greenlip abalone in response to dietary manipulation at different water temperatures. The energy budget of greenlip abalone at 22 and 25 °C was not affected by dietary pro/prebiotic supplementation, but water temperature had a significant impact. Ingested food energy and absorbed energy were reduced, while ammonia excretion energy, egested faecal energy and pedal mucus production energy were increased when the abalone were under thermal stress (25 °C) compared to their optimal temperature for growth (22 °C). Abalone had available energy for somatic growth and reproduction at 22 °C, but they had negative somatic growth energy and showed no visible sign of gonad development at 25 °C. Egested faecal energy was the main component of energy budget at both 22 and 25 °C water temperature.
In trial 5 (Chapter 6), the bioenergetics of abalone fed a variety of antioxidant additives, at high water temperature, was studied. Supplementation of 5.0% grape seed extract (GSE) had positive effects on ingested food energy, absorbed energy and somatic growth energy at 25 °C, whereas, green tea extract (GTE), Peanut skin extract (PE) and Vitamin C (Vit C) had no effect on the energy budget. A major portion of the ingested food energy was egested faecal energy as well as respiration energy during thermal stress.
Overall, the findings presented in this thesis will improve knowledge about the bioenergetics of greenlip abalone which are currently not well understood. This may help to choose more effective diets, systems, and even genetic selection in order to sattain efficiency where growth is the main energy target. Additionally, it also may assist in predicting ingested food energy, respiration energy, ammonia excretion energy, nutrient effluent levels, somatic growth energy and abalone culture management.
Keywords: bioenergetics, abalone, energy budget, macroalgae, Ulva sp. Gracilaria cliftonii, antioxidants, probiotic, prebiotic, temperature, protein, grape seed extract
Subject: Biological Sciences thesis
Thesis type: Doctor of Philosophy
Completed: 2017
School: School of Biological Sciences
Supervisor: A/Prof. James Harris