Project number: 2004-237
Project Status:
Completed
Budget expenditure: $466,788.00
Principal Investigator: Chris G. Carter
Organisation: University of Tasmania (UTAS)
Project start/end date: 30 Jan 2005 - 30 Jul 2008
Contact:
FRDC

Need

The research proposed here has received consistantly strong support from the TSGA, The TasFRAB, the Atlantic Salmon Aquaculture Subprogram and the Aquaculture Nutrition Subprogram. The research addresses two Challenges in the FRDC R&D Plan 2000-2005:
Challenge 2 Increasing production through aquaculture (FRDC R&D Plan 2000-2005) is addrssed by this research. The research proposed contributes by increasing understanding of how to increase production under Australian environmental conditions and how to increase efficiency.
Challenge 5 Reducing the quality of fish protein fed to aquatic livestock (FRDC R&D Plan 2000-2005). The proposed research contributes by increasing understanding of processes that drive growth efficiency.

It must be stressed that the research proposed here has been developed in collaboration with Skretting and this means that results will impact on aquafeeds rapidly and in a meaningful way. However, the data generated will be disseminated for use by other feed manufacturers, the aquaculture industry and other researchers.

Tactical Needs
The proposed research aims to demonstrate which feeds are most appropriate for use at the different temperatures experienced by both the salmon and barramunid aquaculture industry during the normal production cycles and over the geographical range they are farmed. The research has to be conducted in Australia because the performance of Atlantic salmon at high temperatures is not important in Northern Europe and the performance of barramundi at low temperatures important is not relevant in South East Asia. Consequently, it is unlikely that commercially driven research of relevance to Australian conditions will be conducted outside of Australia. The vital importance of understanding the relationship between dietary protein and energy in relation to temperature and low growth has been very clearly identified by individual Salmonid growers and by the TSGA for several years. However, farm data cannot be used to solve the issues retrospectively and a clear need for controlled experiments exists. Barramundi aquaculture is expanding rapidley across Australia and they are being farmed under many different environmental (temperature) regimes, there is a clear need to understand the relationship between dietary protein and energy in relation to temperature. In addition to providing direct information about the performance of both species of fish in relation to diet composition the experiments are designed so that data can be incorporated into "factorial models" of growth. These are used by feed companies as well as under development by key researchers. The proposed research will make an important contribution to the data base for these and for both species.

Strategic Needs
The research seeks to address the lack of information about mechanisms that determine efficient growth in fish by consideration key physiological and nutritional variables in relation to temperature. The PI has an extensive record of uses physiological tools to investigate amino acid (protein) and energy utilisation by fishes. Developing this approach in realtion to temperature is of strategic importance for equiping Australian aquaculture with tools to investigate other species. Protein synthesis is a major driver of growth but it is energetically expensive (20-40% of costs of growth)and understanding the interaction between diet composition and efficient growth is a major driver behind the proposed research. The research will develop physiological tools using barramundi as a model, these will then be tested and deveoped further using salmon.

Objectives

1. Generate critically identified data for incorporation into factorial growth models that describe nutrient supply and nutrient retention in relation to temperature.
2. Determine the optimum dietary protein to energy ratio for Atlantic salmon at normal to high temperatures.
3. Determine the maintenance dietary protein and energy requirements for Atantic salmon at normal to high temperatures.
4. Develop biochemical tools to understand the effect of temperature on the growth performance of fish.
5. Use biochemical tools to understand the effect of temperature on protein turnover and growth performance in barramundi.
6. Use biochemcial tools to understand the effect of temperature on protein turnover and growth performance in Atlantic salmon.

Final report

ISBN: 978-1-86295-453-3
Author: Chris Carter
Final Report • 2009-04-03
2004-237-DLD.pdf

Summary

This research has advanced our understanding of how fish growth is influenced by nutrition, by environment and by the interaction between nutritional and environmental factors. When the research started the majority of nutrition research considered the performance of feeds under optimum environmental conditions. In stark contrast the Australian aquaculture industry is increasingly facing the proposition of growing fish under sub-optimum conditions. Atlantic salmon are grown at elevated summer temperatures whereas barramundi and several sub-tropical species are affected by low winter temperatures. In addition, aquafeed companies lacked critical information about the optimum balance of protein and energy required for feed formulations at elevated temperatures. The research addressed a significant need for fundamental and applied information about nutrition of fish under limiting environment conditions. Integration of molecular techniques into the research program enhanced the value of the research considerably.

We successfully modelled protein and energy requirements for seawater Atlantic salmon at an elevated temperature of 19°C. This temperature was selected because although it is at the upper end of temperatures at which feeding would continue on-farm, salmon still feed and grow. Importantly, Atlantic salmon exhibited the same type of response to differences in dietary composition and nutrient intake as at lower temperatures. The research provided critical and previously unknown information for aquafeed companies to use for their high temperature feed formulations. For example, the optimum dietary protein to energy for Atlantic salmon diets fed at 19°C was predicted to be 19.8 grams of digestible protein per MJ of energy.

A critical feature of elevated temperature is decreased oxygen content in water. A second experiment compared the performance of seawater Atlantic salmon at 19°C at moderately low dissolved oxygen typical of those experienced in summer on-farm. Overall, growth performance was significantly affected by oxygen but only marginally by diet composition. Low oxygen decreased appetite and caused lower growth, growth efficiency was not affected. 

Keywords: Aquafeeds, Atlantic salmon, barramundi, elevated temperature, extreme environmental conditions, growth, nutrition.

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