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Type: Thesis
Title: Understanding lipid utilisation in large (> 2 kg) Yellowtail Kingfish (Seriola lalandi)
Author: Chown, Samantha Naomi
Issue Date: 2019
School/Discipline: School of Agriculture, Food and Wine
Abstract: Yellowtail Kingfish (Seriola lalandi) (YTK) are carnivorous marine finfishes that are commercially farmed in Australia. YTK present the greatest opportunity for expansion of the Australian aquaculture industry, but improved diet formulations and feed conversion ratios are essential for production gains and economic upscaling. Lipids constitute a major cost component of aquafeeds but lipid composition has not been optimised for YTK. The purpose of this research was to increase understanding of how YTK utilise dietary lipids, and to improve feed conversion efficiency and product quality for human consumers. Fish oil (FO) as a dietary lipid source is central to this research as YTK require dietary omega 3 (n-3) long chain polyunsaturated fatty acids (LC PUFA) from FO for healthy development and growth, but FO is limited and less economically sustainable than other types of oil/lipid. The first study presented in this thesis sought to benchmark the fatty acid composition of wild YTK compared to aquacultured YTK. Tissue total lipid content was on average 4-times higher in aquacultured than wild YTK, with significantly higher concentrations of total saturated, omega 9, omega 7 and omega 6 fatty acids in tissues, but n-3 LC PUFA concentrations were not significantly different in the white muscle of wild and aquacultured YTK. The second and third studies were carried out with YTK grown in tanks using aquafeeds with varying lipid formulations. Generally, the fatty acid composition of aquacultured fish is reflective of the composition of aquafeeds, however this was not always the case for YTK in the following experiments. The key findings were that YTK have the capacity to spare in full Docosahaexonoic Acid (DHA) in white muscle at the expense of oleic acid (18:1n-9) when dietary levels of n-3 LC PUFA were <1.6 g 100 g-1 feed and that the digestibility of saturated fatty acids decreased with increasing chain length. Both of these findings could be used to manipulate dietary formulations and improve utilisation of n-3 LC PUFA. The fourth study investigated the potential for finishing diets to be utilised to modify the tissue fatty acid composition of YTK prior to harvest. Results showed significant changes in white muscle n-3 LC PUFA over 33 days at warm water temperatures, however further research was recommended to optimise the duration of finishing periods under a range of conditions. It was also recommended that the n-3 LC PUFA content of YTK feeds be closely monitored with strict lower limits set to ensure optimal product quality. The fifth and final study validated a method for the quantification of bioactive free fatty acid and oxylipin levels in YTK blood plasma. The approach was then used to determine the effects of dietary levels of n-3 LC PUFA on plasma free fatty acids and oxylipin bioactives. This method provides a new tool for aquaculture nutritionists to assess the impact of changes to YTK aquafeed formulations. In summary, this thesis has provided insight into the factors that affect fatty acid utilisation in YTK which have the potential to positively influence future aquafeed formulations, while also providing new methods to investigate lipid metabolism in the future.
Advisor: Gibson, Robert
McWhorter, Todd
Stone, David
Dissertation Note: Thesis (Ph.D.) -- University of Adelaide, School of Agriculture, Food and Wine, 2019
Keywords: Yellowtail Kingfish
omega 3 (n-3) long chain (LC) polyunsaturated fatty acids (PUFA)
product quality
Provenance: This thesis is currently under Embargo and not available.
Appears in Collections:Research Theses

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