The establishment of fatty acid requirements in marine fish nutrition based on specific studies

• Grant number: 13/19597-7
• Support type: Scholarships abroad - Research Internship - Doctorate
• Effective date (Start): February 01, 2014
• Effective date (End): January 31, 2015
• Field of knowledge: Agronomical Sciences - Fishery Resources and Fishery Engineering - Aquaculture
• Principal researcher: Renata Guimarães Moreira Whitton
• Grantee: Bruno Cavalheiro Araújo
• Supervisor abroad: Brett David Glencross
• Home Institution: Instituto de Biociências (IB). Universidade de São Paulo (USP). São Paulo , SP, Brazil
• Research place: CSIRO Marine and Atmospheric Research, Australia

Abstract

The evaluation of feed ingredients is crucial to nutritional research and feed development for aquaculture species. Diet design, feeding strategy and faecal collection method are important to determine the digestible value of nutrients from any ingredient. Lipids are the most energetic substrate of all dietary nutrients. They normally provide nearly twice the energy supplied by proteins and even more than twice the energy supplied by carbohydrates. For the normal development of fish, including the ontogenetic and reproduction life cycle phases, long chains of highly unsaturated fatty acids (HUFA) of the n3 and n6 series, especially docosahexaenoic acid (C22:6n3; DHA) are necessary. Inadequate levels of DHA in nutrition of marine fish may affect cell membrane compositions, causing a greater incidence of deformities and mortality of larvae and juveniles. To produce a proper diet for fish, it is important to understand the physiology of target species, not by simply incorporating oils into the diet (the methodology applied in the PhD project to which this proposal is linked), but primarily employing procedures related to the digestibility of fatty acids, nutritional requirements, replacement of compounds of animal origin by plant compounds and formulations of commercial diets.Therefore, the main objective of this proposal is to acquire the knowledge about the processes of formulating specific diets for marine aquaculture, especially regarding the nutrition of fatty acids, considering nutritional needs and life stage of the target species. The development of this project will be important to gain some expertise and transfer this knowledge to our reality, since this is still an incipient area in Brazil. To acquire this knowledge, a full experiment has been planned using the marine fish species barramundi (Lates calcarifer), a model used in laboratory. The main purpose of this experiment is to investigate the influence of diets containing different levels of DHA on weight gain, survival, fatty acid composition of body tissues and digestibility. Additionally, we will evaluate the influence of DHA concentration on other essential fatty acids such as ARA and EPA.The results of this proposal will be important as a model to be used as a nutritional base for other fish species, especially those with high aquaculture potential, either in economic and/or conservation fields. The production of commercial diets also allows the balance of nutrients used, and can provide a more specific feed for animals according to the stage of their life cycle. Nowadays, the same diet used for animals in growth process is also used for breeding, although nutritional needs for both processes are completely different. Because of this a greater investment in specific diet formulations is needed, considering mainly the species to be produced, and the stage of the life cycle of the animal. This area of research is essential for the development of aquaculture, an economic activity of the great potential in Brazil.This proposal seeks to incorporate these new techniques into our laboratory, as well as collaborate in solving the most common problems in the industry of fish production in Brazil. It is also important emphasizing the extensive experience of Dr. Glencross in the nutrition of aquatic organisms and that he agreed to contribute to the discussion of the data that we are generating here, in Brazil, since this line of research is incipient in Brazil. This collaboration will surely provide the chance of producing a greater number of scientific productions. Other important factor is that this centre is the ideal place to gain expertise in the area of nutrition of aquatic organisms, mainly due to the recognized experience of their members in years of research, having the ideal facilities and prioritizing the application of the research results in the private sector, aiming to solve the real problems of the aquaculture industry. (AU)