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Summary The National Research Council (NRC) has published commercially, but other emerging species could be included. several previous reports on the nutrition and feeding of fish, Other elements of the task included: a review of strategies to the most recent of which is the Nutrient Requirements of increase nutrient retention and thus reduce fecal and meta- Fish (1993). Since 1993 a large amount of information on bolic excretions that contribute to environmental pollution; a fish and shrimp nutrition has been published. Consequently, discussion of the benefits and detriments of including marine many of the requirements and recommendations set forth in products in fish feeds; and consideration of the relationship the 1993 report are no longer relevant or appropriate. Since between diet formulation and the nutrient content of fish, publication of the previous report, aquaculture production especially omega-3 fatty acid levels. has expanded more than 10-fold and has become of much The project was sponsored by the Agricultural Research greater national and international significance, as a food Service of the United States Department of Agriculture, supplier and source of income. In fact, aquaculture now the National Oceanic and Atmospheric Administration, the supplies half of the seafood and fisheries products consumed United Soybean Board, and the NRC. To ensure international worldwide. Given the state of the world’s fisheries, future representation, the committee was composed of scientists demand for seafood and fisheries products can only be met from the United States, Canada, France, Norway, Taiwan, by expanded aquacultural production. Such production will and the United Kingdom. likely become more intensive and increasingly depend on A primary realization of the committee is that continued nutritious and efficient aquaculture feeds containing ingre- growth of aquaculture production depends on precision feed dients from sustainable sources. This challenge can only be formulation using information on nutritional requirements, met by applying the latest nutritional and feed production as well as nutrient levels and availability in feed ingredi- information. ents, to produce efficient feeds that maximize fish growth The need for an updated nutrient requirement publication and health while minimizing environmental effects. Thus, for aquatic species has been apparent for several years. With the report contains nutritional recommendations condensed the support of industry leaders and federal agencies, funding from the scientific literature as well as substantial other in- was obtained for a new report. In developing the NRC study, formation to provide a context for understanding how to use it was decided that one publication should address both the information in preparing feeds and applying appropriate coldwater and warmwater fish and shrimp. It was recognized feeding regimes to support efficient aquacultural production. that the audience for the new report would be varied, ranging The committee recognized the global shift in aquaculture from research scientists and those involved in regulation to feeds toward higher use levels of ingredients derived from people working with commercial aspects of fish and shrimp grains, oilseeds, and other alternative sources to replace in- feeding, and therefore the report should attempt to address gredients produced from marine resources and the nutritional topics of importance for each audience. Also, because aqua- challenges this will create. culture has grown rapidly throughout the world, international This publication is expanded considerably from the 1993 representation was considered crucial. report and contains several new chapters and sections. It The task given to the committee is presented in Appendix begins with an Introduction that documents the expansion of A. In brief, the committee was asked to prepare a report that aquaculture during the past two decades and the rapid growth evaluates the scientific literature on the nutrient require- in the number of research reports on the nutrient require- ments of fish and shrimp in all stages of life. The report was ments of fish and shrimp. The topic of finding alternatives to focus primarily on the species that are most important to fish meal and fish oil derived from marine resources in 1
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2 NUTRIENT REQUIREMENTS OF FISH AND SHRIMP aquatic feeds is also introduced, along with a brief overview 6 discusses dietary lipid levels and requirements for specific of the various topics covered in the report. fatty acids, phospholipids, and cholesterol by both fish and Chapter 2 discusses basic concepts and methodology used shrimp. The chapter ends with a discussion of other issues in experimental studies to determine the nutrient require- relevant to aquaculture. ments of aquatic animals. Conducting nutritional studies Although fish and shrimp do not have specific require- using aquatic animals presents challenges to nutritionists ments for dietary carbohydrates or fiber, these are major compared to conducting studies with livestock and poultry. components of most commercial fish feeds. Chapter 7 Several challenges are associated with the species’ aquatic reviews types of carbohydrates, the role of starch and non- existence, including differences in husbandry and feeding starch polysaccharides, the metabolic fate of glucose, and and the fact that aquatic animals are poikilothermic (their the nutritional role of digestible carbohydrates in fish and body temperatures vary with the temperature of their sur- shrimp. Also covered is the digestibility of various carbohy- roundings). Another challenge is the high degree of vari- drate classes by fish. ability among individuals, strains, and stocks compared to Mineral nutrition of aquatic species is more complicated livestock and poultry. These complications make it necessary than that of terrestrial species because the former can absorb to use appropriate experimental designs with adequate repli- some minerals from the aquatic medium in which they live. cation such that treatment effects can be detected. The need Chapter 8 discusses six macrominerals and seven trace min- for proper interpretation of results is also discussed, along erals. Other minerals such as cobalt and molybdenum are with the importance of choosing a valid response criterion. mentioned briefly. The chapter concludes with comments Chapter 3 examines the digestive physiology of fish and about the sources and forms of minerals and their interactions shrimp. This material, which was not included in previous with other dietary components. NRC publications on fish, begins with a description of the An update of the 1993 report’s review of vitamin require- anatomical features of the digestive organs of fish and the ments is provided in Chapter 9. The chapter is divided into composition and role of digestive secretions. The processes fat-soluble and water-soluble vitamins and also includes a of digestion and nutrient absorption are then discussed. The brief discussion of other vitamin-like compounds. Sources second part of the chapter covers shrimp. and stability of vitamins used in feeds are also covered. Dietary energy utilization and metabolic integration are Chapter 10, titled “Feed Additives,” is an update of the the topics of Chapter 4. It begins with the classical energy- chapter titled “Other Dietary Components” in the 1993 partitioning scheme, which describes various losses of publication. It includes a discussion of substances such as energy between the feed and the energy ultimately retained antimicrobial agents, enzymes, and other compounds that are or recovered. Factors that affect the partitioning of energy commonly found in, or added to, feeds for fish and shrimp. in practical feeding systems for fish and shrimp are then Chapter 11, titled “Antinutritional Factors and Adventitious addressed. The discussion of energy utilization has been Toxins in Feeds,” presents tables of antinutrients and other expanded considerably from the 1993 report. undesirable substances found in fish feeds, as well as an Chapters 5, 6, 7, 8, and 9 cover proteins and amino ac- extensive publication list. ids, lipids, carbohydrates and fiber, minerals, and vitamins, Chapter 12 addresses nutrient digestibility and availabil- respectively. Constituting more that 40% of the total report, ity. In addition to a discussion of topics such as methodology these chapters contain an extensive discussion of each of the and potential errors, the digestibility of proteins, carbo- nutrient classes and a review of experiments to determine hydrates and fiber, lipids, and minerals is reviewed. This nutrient requirements. Each chapter contains a comprehen- chapter also contains five tables with digestibility values for sive list of references. The material in these chapters forms various fish species and shrimp that can be used in formulat- the basis for the nutrient requirements listed later in the ing feeds for various aquatic species. publication. Chapter 13 reviews some of the more applied aspects of Chapter 5, on proteins and amino acids, begins with fish nutrition and feeding. Subjects addressed are feeding an overview of the biochemistry and roles of proteins and early life stages, production diets, and feed management. amino acids. The essential amino acids are then discussed in Coverage includes important topics such as feeding in in- more detail and the principles involved in quantifying amino tensive production systems and pollution loading and waste acid requirements are reviewed. This includes a discussion management. of the ideal protein concept (optimal amino acid propor- Feeding larval fish is a topic covered briefly in the 1993 tions) and factorial approaches to determining amino acid report, but now has a chapter of its own. Chapter 14 reviews requirements. the practical feeding aspects as well as the limited data on Knowledge about lipid functions and requirements has nutritional requirements of larval fish and shrimp. expanded considerably, and this is reflected in a much Chapter 15 addresses ingredients used in fish nutrition, longer section than in the 1993 report. After general com- formulation, and processing of feeds for aquatic animals. ments about the structures and functions of lipids, Chapter These topics were covered in the previous report, but this
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3 SUMMARY chapter provides updated information as well as more details the estimates presented. As such, values in these tables are on various considerations associated with feed production the best estimates of the committee rather than an average for aquatic animals. of literature values. Chapter 16 contains new material and covers two topics Chapter 19 consists of tables of feed ingredients for feed- that have attracted considerable public and consumer atten- stuffs commonly fed to fish and shrimp, including average tion during the past decade. The first issue is the limitations composition values. Readers should be aware that values to supply and use of marine resources, particularly fish meal among different products available in the marketplace may and fish oil. Many commercial aquaculture feeds contain differ from the average values presented in these tables. appreciable amounts of fish meal and fish oil, and there Aquaculture production is sure to increase, both in is concern that the increasing demand on these resources quantity and in the range of organisms being produced, and will outstrip supply unless levels in feeds are reduced. As increasing aquaculture production should be conducted in a consequence, a considerable amount of research is being a manner that lowers the environmental effects of various devoted to identifying, developing, and evaluating alternative production systems and that utilizes sustainably produced ingredients, and this research is discussed within the chapter. feed ingredients. These goals are both connected to nutri- The second issue is the nutritional value of fish and aquatic ent requirements; without solid information on nutrient products in human nutrition. Fish are unique and rich sources requirements of the range of farmed aquatic species, feeds of long-chain, polyunsaturated fatty acids that are important cannot be formulated using alternative feed ingredients. components of the human diet. These topics are also covered The committee designed this report to be a comprehensive in the chapter. summary of extant knowledge on nutrient requirements of In Chapter 17, the committee identifies critical research fish and shrimp and also to be forward-looking by including needs for defining nutrient requirements. It is hoped that this information to explain the nutritional science that underpins chapter will aid researchers, administrators, and others as nutrient requirements. This approach allows the reader to future research agendas are developed. understand better both the strengths and weaknesses of cur- Chapter 18 contains tables of nutrient requirements for rent information, and thus use it appropriately. The reader fish and shrimp. Requirements are expressed on a dry-matter will also understand the importance of nutrient requirements basis. These are minimum requirements that assume 100% to the production of efficient, economical, and sustainable bioavailability and do not contain “margins of safety” or feeds for use in aquaculture. The committee also hopes that other adjustments for specific practical feeding situations. the information assembled in this report inspires scientists For the most part, requirement values in the literature were to strive to develop better estimates of nutrient requirements obtained with young, rapidly growing fish or shrimp. The of farmed fish and shrimp using both conventional and new committee critically evaluated published studies to arrive at approaches.