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Third Edition

Fish
Nutrition


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Third Edition

Fish
Nutrition
Edited by

John E. Halver
School of Aquatic and Fishery Sciences
University of Washington
Seattle, Washington


and

Ronald W. Hardy
Hagerman Fish Culture Experiment Station
University of Idaho
Hagerman, Idaho

Amsterdam Boston London New York Oxford Paris
San Diego San Francisco Singapore Sydney Tokyo


This book is printed on acid-free paper. ∞
Copyright C 2002, 1989, 1972, Elsevier Science (USA)
all rights reserved.
no part of this publication may be reproduced or
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permission in writing from the publisher.
Requests for permission to make copies of any part of the work
should be mailed to: Permissions Department, Harcourt, Inc., 6277 Sea Harbor
Drive, Orlando, Florida 32887-6777
COVER IMAGES: Sea Bram and Catfish courtesy of New York SAREP.
Rainbow trout from Behnke, R. J. 1992. Native Trout of Western North
America, American Fisheries Society Monograph 6, Bethesda, Maryland, USA.

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Contents
List of Contributors

xi

Preface

1

Bioenergetics
Dominique P. Bureau, Sadasivam J. Kaushik,
and C. Young Cho
1.1
1.2
1.3
1.4
1.5
1.6
1.7
1.8
1.9
1.10
1.11
1.12
1.13
1.14
1.15
1.16

2

xiii

Introduction
History of Nutritional Energetics
Energy Exchange in Biological Systems
Energy Utilization and Requirements
Digestible Energy of Feedstuffs
Effect of Biological and Environmental Factors
Urinary and Branchial Energy and Metabolizable Energy
Factors Affecting Metabolic Waste Output
Heat Production
Minimal Metabolism
Heat Increment of Feeding
Digestion and Absorption Processes (HdE)
Recovered Energy and Growth
Reproduction
Integrating and Using Information from Bioenergetics
Limitations and Perspectives of Bioenergetics
References

2
3
5
7
14
16
18
21
24
29
35
37
43
47
48
53
54

The Vitamins
John E. Halver
2.1
2.2
2.3
2.4
2.5

Historical Introduction
The Water-Soluble Vitamins
The Fat-Soluble Vitamins
Other Factors
Anemias and Hemapoiesis
References

62
66
113
128
130
132

v


vi

Contents

3

Amino Acids and Proteins
Robert P. Wilson
3.1
3.2
3.3
3.4
3.5

4

4.6
4.7
4.8
4.9

Introduction
Structures and Biosynthesis
Functions
Fatty Acids and Dietary Energy
Optimal Levels and Ratios of Dietary n-3 and n-6
Polyunsaturated Fatty Acids
Dietary Phosphoglycerides: Inositol and Choline
Fatty Acid Peroxidation
Sources of Lipids for Farmed Fish Feeds
Prospects
References

182
184
194
201
206
227
232
239
244
246

The Minerals
Santosh P. Lall
5.1 Introduction
5.2 Essential Minerals for Finfish
5.3 Concluding Remarks
References

6

144
145
151
152
170
175

The Lipids
John R. Sargent, Douglas R. Tocher,
and J. Gordon Bell
4.1
4.2
4.3
4.4
4.5

5

Introduction
Protein Requirements
Qualitative Amino Acid Requirements
Quantitative Amino Acid Requirements
Other Methods of Estimating Amino Acid Needs
References

260
271
300
301

Intermediary Metabolism
Konrad Dabrowski and Helga Guderley
6.1
6.2
6.3
6.4

Introduction: Metabolic Circuitry and Control Mechanisms
Carbohydrate Metabolism
Protein and Amino Acid Metabolism
Conclusions
References

310
313
333
358
360


Contents

7

Nutritional Physiology
Michael B. Rust
7.1
7.2
7.3
7.4
7.5
7.6
7.7
7.8
7.9
7.10
7.11

8

Introduction
Gross Juvenile and Adult Anatomy
Sensory Organs
Food Capture Structures and Organs
Digestive Organs
Liver
Anatomy and Diet
Digestive Processes
Postabsorptive Transport and Processing
Control and Regulation of Digestion
Nutritional Physiology in Larval Fish
References

368
369
378
389
393
413
415
417
427
428
432
446

Nutritional Pathology
Ronald J. Roberts
8.1
8.2
8.3
8.4
8.5
8.6
8.7
8.8
8.9
8.10
8.11
8.12
8.13
8.14
8.15
8.16
8.17
8.18

9

vii

Introduction
Principles of Nutritional Pathology
The Deficiency and Imbalance Diseases
Micronutrients
Mineral Deficiencies and Imbalances
Dietary Mineral Toxicity
Mycotoxins
Toxic Algae
Cottonseeds
Senecio Alkaloids
Leucaena Toxins
Anthropogenic Chemicals
Binders
Photosensitizers
Sekoke Disease
Spleen- and Liver-Induced Cataracts
Single-Cell Protein Lesions
Antibiotic and Chemotherapeutic Toxicity
References

454
455
459
464
480
484
489
492
492
492
494
494
494
495
497
498
500
500
500

Diet Formulation and Manufacture
Ronald W. Hardy and Frederick T. Barrows
9.1 Introduction
9.2 Aims and Strategy of Fish Feed Production

506
514


viii

Contents

9.3
9.4
9.5
9.6
9.7

10

Feed Ingredients
Diet Formulation
Diet Manufacture and Storage
Ingredient and Diet Evaluation
Glossary
References

Adventitious Toxins
Jerry D. Hendricks
10.1 Introduction
10.2 Naturally Occurring Toxins in Formulated Fish Rations
10.3 Nonnatural Components and Additives in
Formulated Rations
10.4 Summary
References

11

630
641
641

Introduction
Formulation of Special Feeds
Feed Manufacturing
Summary
References

652
652
661
667
668

Nutrition and Fish Health
Delbert M. Gatlin III
12.1
12.2
12.3
12.4
12.5

13

602
603

Special Feeds
George M. Pigott and Barbee W. Tucker
11.1
11.2
11.3
11.4

12

515
538
558
578
594
596

Introduction
Factors Affecting Fish Health
Dietary Components Influencing Fish Health
Feeding Practices Affecting Fish Health
Concluding Remarks and Research Needs
References

672
673
675
694
698
699

Diet and Fish Husbandry
Richard T. Lovell
13.1
13.2
13.3
13.4
13.5

Introduction
Channel Catfish
Salmonids
Tilapias
Penaeid Shrimp
References

704
708
720
732
741
753


Contents

14

ix

Nutrient Flow and Retention
John E. Halver and Ronald W. Hardy
14.1
14.2
14.3
14.4
14.5
14.6
14.7
14.8
14.9
14.10
14.11
14.12
14.13
14.14
14.15
14.16

Introduction
Carbohydrate Metabolism
Glycolysis
Carbohydrate Synthesis
Pentose Phosphate Pathway
Glycogenolysis
Diet and Carbohydrate Metabolism
Lipid Metabolism
Odd-Chain-Length Fatty Acid Oxidation
Electron Transfer Cascade
Amino Acid Metabolism
Effect of Diet on Intermediary Metabolism
Measuring Protein Accretion and Degradation
Intake and Metabolism
Sexual Maturity and Metabolism
Prospects for Improvement of Protein Retention Efficiency
References

756
757
757
759
759
759
760
760
762
763
763
765
766
767
767
768
769

Appendix

771

Index

807


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List of Contributors
Numbers in parentheses indicate the pages on which the authors’ contributions begin.

Frederick T. Barrows (505), Bozeman Fish Technology Center, U.S. Fish
and Wildlife Service, Bozeman, Montana 59715
J. Gordon Bell (181), Institute of Aquaculture, University of Stirling,
Stirling FK9 4LA, Scotland, United Kingdom
Dominique P. Bureau (1), Fish Nutrition Research Laboratory, Department
of Animal and Poultry Science, University of Guelph, Guelph, Ontario
N1G 2W1, Canada
C. Young Cho (1), Fish Nutrition Research Laboratory, Department of
Animal and Poultry Science, University of Guelph, Guelph, Ontario N1G
2W1, Canada
Konrad Dabrowski (309), School of Natural Resources, Ohio State University, Columbus, Ohio 43210
Delbert M. Gatlin III (671), Department of Wildlife and Fisheries Sciences, Texas A&M University System, College Station, Texas 77843
Helga Guderley (309), Department of Biology, Universit´e Laval, Quebec,
Quebec G1K 7P4, Canada
John E. Halver (61, 755), School of Aquatic and Fishery Sciences, University of Washington, Seattle, Washington 98195
Ronald W. Hardy (505, 755), Hagerman Fish Culture Experiment Station,
University of Idaho, Hagerman, Idaho 83332
Jerry D. Hendricks (601), Department of Environmental and Molecular
Toxicology, Oregon State University, Corvallis, Oregon 97331
Sadasivam J. Kaushik (1), Unit´e Mixte INRA-IFREMER de Nutrition des
Poissons, Station d’hydrobiologie INRA, B.P. 3, 64310, Saint-P´ee-surNivelle, France

xi


xii

List of Contributors

Santosh P. Lall (259), Institute for Marine Biosciences, National Research
Council of Canada, Halifax, Nova Scotia B3H 3Z1, Canada
Richard T. Lovell (703), Department of Fisheries and Allied Aquaculture,
Auburn University, Auburn, Alabama 36849
George M. Pigott (651), College of Ocean and Fishery Sciences, University
of Washington, Seattle, Washington 98195
Ronald J. Roberts (453), Center for Sustainable Aquaculture, Hagerman
Fish Culture Experiment Station, University of Idaho, Hagerman, Idaho
83332
Michael B. Rust (367), Northwest Fisheries Science Center, Resource
Enhancement and Utilization Technologies Division, Seattle, Washington 98112
John R. Sargent (181), Institute of Aquaculture, University of Stirling,
Stirling FK9 4LA, Scotland, United Kingdom
Douglas R. Tocher (181), Institute of Aquaculture, University of Stirling,
Stirling FK9 4LA, Scotland, United Kingdom
Barbee W. Tucker (651), Sea Resources Engineering, Inc., Kirkland,
Washington 98033
Robert P. Wilson (143), Department of Biochemistry, Mississippi State
University, Mississippi State, Mississippi 39762


Preface
This third edition of Fish Nutrition was reviewed and updated with selections
from the myriad of publications which have appeared in the literature on
fish nutrition since the previous 1989 edition. During this decade aquaculture continued to advance more rapidly than any other field of animal
production in the world, and it is expected to continue to expand to provide
fish for a growing world population. As aquaculture production increases,
it must contend with rapidly approaching limits on key feed ingredients
and on increasing sensitivity to the effects of aquaculture on the aquatic
environment. Many of these effects are associated with diet, so fish nutrition research must focus on increasing the efficiency of production and
on lowering environmental effects through increased nutrient retention.
This will provide safe and nutritious fishery products in a sustainable and
environmentally compatible fashion.
Over 200 fish species have been examined as potential targets for fish production to utilize the special advantages of an animal capable of growing
efficiently in a wide variety of temperatures and ionic-strength waters. Universities, research centers, and various government agencies have adopted
fish as an important agricultural animal, with a resultant plethora of publications from scientists in many countries focused on an increasing number of
fishes and their nutritional requirements. Since it would have been impossible to include all these reports in this book, the authors have focused on
selected demonstrations of nutrient requirements and metabolism which
summarize the basic and applied principles of fish nutrition.
The chapter “Bioenergetics” has been entirely rewritten to include the
rapid advancements made since the last edition. “The Vitamins” chapter has
been updated and reflects the conclusion that many of the principles discussed previously still apply, even as new species of fish are examined. The
previous focus on teleost fish has been extended to include other types
with unique or different metabolic capabilities. The “Amino Acids and
Proteins” chapter has been expanded to include the many new species
studied. “The Lipids” chapter has been extensively revised as national and
international focus is aimed at understanding these compounds and their
effects on animal metabolism and health. More information is included in
“The Minerals” chapter to reflect the importance of minerals as activators
xiii


xiv

Preface

for many anabolic and catabolic reactions and to provide basic information concerning the importance of proper mineral balance, especially of
phosphorus, for lowering the environmental impacts of fish culture. The
chapter “Intermediary Metabolism” has been condensed to the principles
involved, with more extensive discussions to be found in other nutrient
chapters. “Nutritional Physiology” has been rewritten, extending the discussions to the larval stages of the life history of many species of fish, as well
as to juvenile and grow-out stages. The chapters “Nutritional Pathology”
and “Nutrition and Fish Health” have been rewritten. “Adventitious Toxins” are reviewed, and the roles of new toxins encountered discussed. “Diet
Formulation and Manufacture” has been expanded to include some of the
latest techniques in fish husbandry production and in feed manufacturing
processes, and the “Special Feeds” chapter outlines new possibilities in fish
feeds for new species and environments. Finally, the practical applications
of fish nutrition to “Diet and Husbandry” have been extended to include
new areas of fish production.
The Appendix reflects the many changes encountered in fish species and
diet database assembly during the past decade.
We hope this treatise continues to review “what we know and what we know
we do not know” to stimulate research and better understanding of nutrient requirements and their role in growth, reproduction, and fish health
as more and more effort is concentrated on using fish as the best animal
for protein and food production. Dividends from understanding nutrient
metabolism in fish at the cellular level can be extended to similar functions
in terrestrial animals, including humans.
This book would not have been possible without the dedicated and demanding efforts of the chapter authors to condense fragmented and often
contradictory information in the literature and from their own laboratories
into succinct discussions and presentations of the principles of fish nutrient
requirements and metabolism. Their efforts are sincerely appreciated. The
reader is invited to compare the developments in fish nutrition which have
occurred since the first edition appeared in 1972.
John E. Halver
Ronald W. Hardy


1
Bioenergetics
Dominique P. Bureau
Fish Nutrition Research Laboratory, Department of Animal and Poultry Science,
University of Guelph, Guelph, Ontario N1G 2W1, Canada

Sadasivam J. Kaushik
Unit´e Mixte INRA-IFREMER de Nutrition des Poissons, Station d’hydrobiologie INRA, B.P. 3,
64310, Saint-P´ee-sur-Nivelle, France

C. Young Cho
Fish Nutrition Research Laboratory, Department of Animal and Poultry Science,
University of Guelph, Guelph, Ontario N1G 2W1, Canada

1.1.
1.2.
1.3.
1.4.

1.5.
1.6.

1.7.
1.8.

Introduction
History of Nutritional Energetics
Energy Exchange in Biological Systems
Energy Utilization and Requirements
1.4.1. Gross Energy: Dietary Fuels
1.4.2. Fecal Energy and Digestible Energy
1.4.3. Measurement
1.4.4. Apparent versus True Digestibility
1.4.5. Digestibility of Whole Diets versus Digestibility of Ingredients
Digestible Energy of Feedstuffs
Effect of Biological and Environmental Factors
1.6.1. Feeding Level and Frequency
1.6.2. Water Temperature
Urinary and Branchial Energy and Metabolizable Energy
1.7.1. Measurement
Factors Affecting Metabolic Waste Output
1.8.1. Dietary Factors
1.8.2. Other Factors

Fish Nutrition, Third Edition
Copyright 2002, Elsevier Science (USA).
All rights reserved.

1


2

Bureau, Kaushik, and Cho

1.9. Heat Production
1.9.1. Methodological Approaches
1.9.2. Direct Calorimetry
1.9.3. Indirect Calorimetry
1.9.4. Comparative Carcass Analysis
1.9.5. Other Approaches
1.10. Minimal Metabolism
1.10.1. Effect of Body Weight
1.10.2. Effect of Temperature
1.10.3. Maintenance Requirement
1.10.4. Heat Losses Associated with Activity
1.11. Heat Increment of Feeding
1.12. Digestion and Absorption Processes (HdE)
1.12.1. Formation and Excretion of Metabolic Waste
1.12.2. Transformation of Substrates and Retention in Tissues
1.13. Recovered Energy and Growth
1.14. Reproduction
1.15. Integrating and Using Information from Bioenergetics
1.16. Limitations and Perspectives of Bioenergetics
References

1.1
Introduction
The catabolism of food is organized within the animal to harness chemical (free) energy and substrates for use in anabolic and other life-sustaining
processes. The physiological mechanisms which achieve this are very complex, allowing the catabolism of a large variety of food molecules using the
finite number of enzyme systems which are found in animal tissues (Krebbs
and Kornberg, 1957). To look quantitatively at the utilization of all dietary
components is extremely complex. However, since feeding, growth, and
production can be described in terms of partition of dietary energy yielding components between catabolism as fuels and anabolism as storage in
tissues, the study of the balance among dietary energy intake, expenditure,
and gain offers a relatively simple way of looking at dietary component
utilization by animals. This approach is called bioenergetics or nutritional
energetics.
This chapter is a nonexhaustive review of current knowledge, methods,
applications, and limitations of fish bioenergetics or nutritional energetics.
It focuses mostly on fish bioenergetics in an aquaculture setting. Energy
flow in the animal is presented based on the energy partition scheme and
nomenclature proposed by the U.S. National Research Council (NRC, 1981)
(Fig. 1.1).


1. Bioenergetics

3

Intake of Energy (IE)

Fecal Energy (FE)

Digestible Energy (DE)
Urine Energy (UE)
Branchial Energy (ZE)

Metabolizable Energy (ME)
Heat increment (HiE)
Net Energy (NE)
Voluntary Activity (HjE)
Basal Metabolism (HeE)
Recovered Energy (RE)

FIG. 1.1
NRC (1981) energy partitioning scheme and nomenclature.

1.2
History of Nutritional Energetics
Nutritional energetics has been studied for more than 200 years. In 1779,
Adair Crawford observed that the amount of air a man “phlogisticated” in
a minute was the same as that altered by a burning candle. Despite the fact
that Crawford formulated ideas about the origin of animal heat in terms of
the phlogiston theory that was popular at the time, his observations were some
of the first showing a relationship among gas exchanges, heat production,
and chemical reactions in animals. In 1783, Antoine Lavoisier and Pierre
Laplace performed a series of exceptional experiments, considered as the
foundation of bioenergetics and modern nutrition. They observed that heat
produced by a guinea pig could be measured by the amount of ice melted
and that the heat produced could be related to the respiratory exchange in
a quantitative way. Based on this series of studies Lavoisier formulated his
classical conclusion that life is a process of combustion. Lavoisier was, thus,
the first to recognize the true role of oxygen in the generation of heat by
animals. Lavoisier’s contribution to the study of animal energetics was not
limited to his elucidation of the relationship between respiration and the


4

Bureau, Kaushik, and Cho

production of heat but also included several aspects of energy metabolism of
animals. His studies with S´eguin on the metabolism of man, which involved
the measurement of oxygen consumption and carbon dioxide production,
showed that oxygen consumption is increased by the ingestion of food, by
the performance of muscular work, and by exposure to cold. Lavoisier also
measured the minimal metabolism in the resting, postabsorptive state and
showed proportionality between pulse frequency and metabolism. He also
showed that within a species, oxygen consumption is proportional to body
size (Blaxter, 1989).
Lavoisier believed that the site of heat production was located in the
lungs and that heat was carried throughout the body by the blood. It was
only in 1847 when Magnus showed that arterial blood carried more oxygen
and less carbon dioxide than did venous blood, and in 1848, when von
Helmholtz demonstrated that isolated muscle produced heat, that the belief
of Lavoisier was shown to be erroneous (Blaxter, 1989).
Nutritionists working at the Weende Agricultural Experimental Station
in Germany, in the nineteenth century, recognized that the components
of foods which make a significant contribution to the energy supply of the
animal could be characterized as three classes of compounds: proteins, fats,
and carbohydrates. The stoichiometry of the oxidation of these classes of
compounds allowed the calculation of the energy released as heat from
measurements of respiratory exchange, oxygen consumption, and carbon
dioxide production, along with measurements of urinary nitrogen excretion. This method of measuring heat production is referred to as indirect
calorimetry (or respirometry). In 1894, Rubner validated this approach to
calorimetry by showing that the heat produced by a dog is equal to the heat of
combustion of the fat and protein catabolized minus the heat of combustion
of the urine. Rubner, thus, was the first to demonstrate the fundamental laws
of thermodynamics applied to intact living animal systems (Blaxter, 1989).
Rubner is also credited with making the first systematic experimental
analysis of the effect of size on metabolism. He showed in 1883 that the
fasting metabolism of dogs of different body weights was approximately constant when expressed per unit area of body surface. In 1901, Voit, Rubner’s
student, showed that the fasting metabolisms of a number of species were
also proportional to their surface areas. Kleiber, and Brody and Proctor,
almost simultaneously in 1932, showed that metabolism was related directly
to body weight and metabolism was proportional to a power of weight higher
than 2/3, that is, about 0.75. Kleiber came to the conclusion that the 3/4
power of body weight was the most reliable basis for predicting the basal
metabolic rate of animals and for comparing nutrient requirements among
animals of different sizes. He also provided the basis for the conclusion that
the total efficiency of energy utilization is independent of body size. In 1945,
Brody published Bioenergetics and Growth, and in 1961, Kleiber published


1. Bioenergetics

5

The Fire of Life, two books, discussing several aspects of energy metabolism
of animals, that remain very influential to this day.
Ege and Krogh (1914) were the first to apply the principles of bioenergetics to fish. Ivlev (1939) worked with carp. Since then, there have been
several hundred reports on studies of energy utilization and expenditure for
several species of fish. Many reviews have also been made on fish bioenergetics, including those by Phillips (1972), Brett and Groves (1979), Cho et al.
(1982), Elliott (1982), Cho and Kaushik (1985), Tytler and Calow (1985),
Smith (1989), Cho and Kaushik (1990), Kaushik and M´edale (1994), Cho
and Bureau (1995), and M´edale and Guillaume (1999), which are most
relevant to aquaculture.

1.3
Energy Exchange in Biological Systems
The first law of thermodynamics, also known as the law of conservation
of energy, states that the total energy (E ) of a system, including its surroundings, remains constant unless there is input of energy (heat or work).
It implies that within the total system, energy is neither lost nor gained
during any changes. However, within that total system, energy may be transferred from one part to another or may be transformed into another form
of energy (heat, electrical energy, radiant energy, or mechanical energy).
Thermodynamic principles as they apply to biological systems are reviewed
in several textbooks (e.g., Patton, 1965; Blaxter, 1989; Mayes, 2000). Readers
are invited to refer to these for a more comprehensive presentation of these
principles.
All biological organisms must obtain supplies of free energy from their
environment to sustain living processes. Nonbiological systems may utilize
heat energy to perform work, but biological systems are essentially isothermic and use chemical energy to sustain life processes. Autotrophic organisms
couple their metabolism to some simple processes in their surroundings,
such as sunlight and inorganic chemical reactions, such as the transformation of Fe2+ to Fe3+ . Heterotrophic organisms obtain free energy from the
breakdown of organic molecules in their environment. Bioenergetics, or
biochemical thermodynamics, is the study of the energy changes accompanying such biochemical reactions (Mayes, 2000).
Life processes (e.g., anabolic reactions, muscular contraction, active transport) obtain energy by chemical linkage. This chemical coupling results
in some energy being transferred to synthetic reaction and some energy
lost as heat. As some of the energy liberated in the degradative reaction
is transferred to the synthetic reaction in a form other than heat, the normal chemical terms “exothermic” and “endothermic” cannot be applied.


6

Bureau, Kaushik, and Cho

The terms exergonic and endergonic are used to indicate that a process
is accompanied by the loss or gain, respectively, of free energy (Mayes,
2000). In practice, an endergonic process cannot exist independently but
must be a component of a coupled exergonic–endergonic system where
the overall net change is exergonic. The exergonic reactions are termed
catabolism, whereas the synthetic reactions are termed anabolism. The combined catabolic and anabolic processes constitute metabolism. A method of
coupling an exergonic to endergonic process is to synthesize a compound of
high-energy potential in the exergonic reaction and to incorporate this new
compound into the endergonic reaction, thus transferring free energy from
the exergonic to the endergonic pathway. Adenosine triphosphate (ATP) is
one of the compounds serving as a transducer of energy from a wide range
of exergonic reactions to an equally wide range of endergonic reactions or
processes (Mayes, 2000).
ATP is a phosphorylated nucleotide containing adenine, ribose, and
three phosphate groups. ATP has an intermediate standard free energy of
hydrolysis among high-energy phosphate molecules, whose characteristics
allow it to play an important role in energy transfer. As a result of its position
midway down the list of standard free energies of hydrolysis, ATP is able to
act as a donor of high-energy phosphate to form compounds with lower
free energies of hydrolysis (Mayes, 2000). Likewise, provided the necessary
enzymatic machinery is available, ADP can accept high-energy phosphate
to form ATP from compounds with high energies of hydrolysis. In effect, an
ATP/ADP cycle connects those processes that liberate free energy to those
processes that utilize it. Thus, ATP is continuously consumed and regenerated. However, it is worth recalling that the total ATP/ADP pool is sufficient
to maintain an active tissue for only a few seconds (Mayes, 2000).
The system that couples respiration to the generation of the high-energy
intermediate, ATP, is termed oxidative phosphorylation. Oxidative phosphorylation enables aerobic organisms to capture a far greater proportion
of the available free energy of respiratory substrates compared with anaerobic organisms. The mitochondrion is the organelle in which most of the
capture of energy derived from respiratory oxidation takes place. The mitochondria contain the series of catalysts known as the respiratory chain that
collect and transport reducing equivalents and direct them to their final reaction with oxygen to form water. Also present is the machinery for trapping
the liberated free energy as high-energy phosphate. Mitochondria also contain the enzyme systems responsible for generating the reducing equivalents
(such as NADPH) in the first place, i.e., the enzymes of β-oxidation and of
the citric acid cycle. The latter is the final common pathway for the oxidation
of all the major foodstuffs.
As mentioned earlier, the coupling of exergonic and endergonic reactions does not harness all the energy, and a significant portion of the energy


1. Bioenergetics

7

is dissipated as heat. One mole of glucose, for example, contains about
2803 kJ of free energy. When it is combusted in a calorimeter to CO2 and
water, 2803 kJ is liberated as heat.∗ When oxidation occurs in the tissues,
some of the energy is not lost immediately as heat but is captured in highenergy phosphate bonds. Under aerobic conditions, glucose is completely
oxidized to CO2 and water, and the equivalent of 36 high-energy phosphate
bonds is generated per molecule. The total energy captured in ATP per
mole of glucose oxidized is 1398 kJ, or the equivalent of roughly 50% of the
enthalpy of combustion. The rest is dissipated as heat. In turn, when ATP
generated by the catabolism of glucose is hydrolyzed during coupling with
an endergonic reaction, only a fraction of the free energy may be retained
in the synthesized compounds and the rest is liberated as heat. Therefore,
ultimately the free energy liberated by exergonic reactions that is not captured in the products of anabolism (protein, lipids, carbohydrates, nucleic
acids, etc.) is liberated as heat by biological organisms.
A very important aspect from a bioenergetics point of view is that heat
produced by a chemical reaction is always the same, regardless of whether
the process went directly or proceeded through a number of intermediate
steps (Blaxter, 1989). This means that the amount of heat produced by an
animal depends on the chemical nature (energy content) of the compounds
catabolized or the overall reaction and not the chemical reaction pathways
over which this catabolism occurred.

1.4
Energy Utilization and Requirements
The study of the balance among dietary energy supply, expenditure, and
gain offers a relatively simple way of looking at dietary component utilization
by animals. Study of the energy transactions in animals requires that components be expressed in compatible terms. Classically, all measurements of
energy transactions made by animal nutritionists were expressed in terms
of calories. The calorie used in nutrition is the 15◦ C calorie (the energy required to raise the temperature of 1 g water from 14.5 to 15.5◦ C). However,
the joule (J) was adopted in the Syst`eme International des Unit´es (International System of Units) as the preferred unit for expression of electrical,
mechanical, and chemical energy and by most nutrition journals as the basic
unit for expressing dietary energy. One joule is defined as 1 kg-m2 /sec2 or
107 erg. One 15◦ C calorie is equivalent to 4.184 J.


Editors note. The authors prefer to use the joule to measure energy content and reactions,
whereas many other authors use the calorie for energy measurements. These are convertible:
1 Cal = 4.184 J, or 1 kcal = 4.184 kJ. See below.


8

Bureau, Kaushik, and Cho

Many terms have been invented and applied to describe energy transactions occurring in animals. Historical terms, such as “specific dynamic
action of food,” are still used, even though they imply nothing about the underlying relationships; others such as “work of digestion” have specific but
incorrect implications regarding underlying relationships (Baldwin and Bywater, 1984). Different groups have tended to adopt and defend alternative
systems of nomenclature to describe the partition of energy in animals. This
is especially apparent in fish biology, where nomenclatures and mode of
expression of energy transaction are extremely diverse. In 1981, a subcommittee of the Committee on Animal Nutrition of the U.S. National Research
Council was appointed to develop a systematic terminology for description
of energy utilization by animals, including fish (NRC, 1981). This system
is presented schematically in Fig. 1.1 and has been widely adopted by animal nutritionists. This rational nomenclature has also been adopted by a
number of fish nutrition researchers and is used in this chapter. Its various
components are discussed below.
1.4.1. Gross Energy: Dietary Fuels
Gross energy (GE) is the commonly used term for the enthalpy ( H ) of
combustion in nutrition. However, as opposed to enthalpy, GE is generally
represented by a plus (+) sign. The GE content of a substance is usually
measured by its combustion in a heavily walled metal container (bomb)
under an atmosphere of compressed oxygen. This method is referred to as
bomb calorimetry. Under these conditions, the carbon and hydrogen are
fully oxidized to carbon dioxide and water, as they are in vivo. However, the
nitrogen is converted to oxides, which is not the case in vivo. The oxides of
nitrogen interact with water to produce strong acids, an endergonic reaction. These acids can be estimated by titration, allowing a correction to be
applied for the difference between combustion in an atmosphere of oxygen
and catabolism in vivo (Blaxter, 1989).
The GE content of an ingredient or a compounded diet depends on its
chemical composition. The mean GE values of carbohydrates, proteins, and
lipids are 17.2, 23.6, and 39.5 kJ/g, respectively (Blaxter, 1989). Minerals
(ash) have no GE because these components are not combustible. IE is the
notation adopted by the NRC (1981) for an animal’s intake GE of (Fig. 1.1).
IE is simply the product of feed consumption and GE.
1.4.2. Fecal Energy and Digestible Energy
Before the feed components can serve as fuels for animals, they must be
digested and absorbed (sometimes called “assimilated,” a term whose use


1. Bioenergetics

9

should be discouraged) from the digestive tract. Some feed components
resist digestion, and these pass through the digestive tract to be voided as
fecal material. Egestion (excretion through feces) of components containing GE is referred to as fecal energy (FE) losses. The difference between the
GE and the FE of a unit quantity of this diet is termed the digestible energy
(DE). DEI was adopted by the NRC (1981) to represent the intake of DE,
the product of feed intake and DE of the feed, or IE minus FE (Fig. 1.1).
Variation in the digestibility of foods is generally a major factor affecting
the variation in their usefulness as energy sources to the animal, since FE
is a major loss of ingested GE. Therefore, values for DE and values for
the digestibility of individual nutrients should be used to estimate levels of
available energy and nutrients (as opposed to GE or crude nutrients) in feed
ingredients for diet formulation (Cho and Kaushik, 1990). Formulation on
a GE or crude nutrients (e.g., crude protein) basis, rather than formulation
on a DE or digestible nutrients basis, is still very common in fish nutrition,
but sufficient information on DE values of common fish feed ingredients is
now available to allow feeds to be formulated on a DE or a digestible nutrient
basis. It is, however, important to emphasize that DE is only an indication of
the potential contribution of the energy from nutrients in the ingredient.
These values do not serve as measures of the utilizable energy or of the
productivity of the diet.
1.4.3. Measurement
The first task in the measurement of digestibility of feeds and feedstuffs is
the collection of fecal samples. In aquatic animals, separating fecal material
from water and avoiding contamination of the feces by uneaten feed necessitate the use of approaches that differ significantly from those commonly
used to measure digestibility interrestial animals and birds.
Quantitative collection of fish feces is very difficult, and therefore, digestibility measurements using direct methods, involving total collection of
fecal material, are rarely used with fish. Digestibility measurements in fish
must, therefore, rely on the collection of a representative fecal sample (free
of uneaten feed particles) and the use of a digestion indicator to obviate
the need to quantify dietary intake and fecal output (indirect method). The
inclusion of a digestion indicator in the diet allows the digestibility coefficients of the nutrients in a diet to be calculated from measurements of the
nutrient-to-indicator ratios in the diet and feces (Edin, 1918).
Several techniques have been used to collect fecal material from fish. The
suitability of these various techniques has been a subject of discussion and
disagreement among fish nutritionists for many years (Smith et al., 1980;
Cho et al., 1982; Cho and Kaushik, 1990; Hajen et al., 1993a; Smith et al.,


10

Bureau, Kaushik, and Cho

1995; Guillaume and Choubert, 1999). Some early, yet still widely used,
techniques are the collection of feces from the lower part of the intestine
by stripping (Nose, 1960), by suctioning fecal material, or by dissecting
the fish (Windell et al., 1978). It is generally agreed that forced evacuation
of fecal material from the rectum results in the contamination of the samples with physiological fluids and intestinal epithelium that would otherwise
have been reabsorbed by the fish before natural defecation. This affects the
reliability of this type of approach and, in general, leads to underestimation
of digestibility (Cho et al., 1982; Hajen et al., 1993; Guillaume and Choubert,
1999).
Techniques involving the collection of feces voided naturally by the fish
are, therefore, preferable. Smith (1971) developed a metabolic chamber
to collect feces samples voided naturally into the water by fish. With this
method, the fish need to be force-fed, and they frequently regurgitate and
may not be in a positive nitrogen balance status. This technique clearly imposes an unacceptable level of stress on the fish and produces estimates of
digestibility of questionable reliability (Cho et al., 1982). Other techniques,
such as the periodical collection of feces by siphoning from the bottom of
a tank, are also likely to yield inaccurate estimates of digestibility since the
breakup of feces by fish movement may lead to leaching of nutrients and,
therefore, overestimation of digestibility of nutrients.
To prevent these problems, specific devices were developed by Ogino et al.
(1973), Cho et al. (1975), and Choubert et al. (1979) to collect fecal material
passively. Ogino et al. (1973) collected feces by passing the effluent water
from fish tanks through a filtration column (TUF column). Cho and Slinger
(1979) developed a settling column to separate the feces from the effluent
water (Guelph system) and Choubert et al. (1979) developed a mechanically
rotating screen to filter out fecal material (St. P´ee system). These systems
are convenient and have been adopted in many laboratories around the
world. They are widely recognized as producing meaningful estimates of
digestibility of nutrients if used correctly, despite the fact that differences of
opinion about the accuracy of these systems remain. In a study comparing
the TUF column and the Guelph system, very similar apparent digestibility
coefficients (ADC) of dry matter, protein, lipid, and energy were obtained
with both methods for two reference diets (Satoh et al., 1992).
It is clear that differences exist in the estimates of digestibility with the
various techniques currently used (Cho et al., 1982). It is difficult to reach
objective conclusions about the accuracy and reliability of the various techniques, as there are relatively few solid experimental studies allowing serious comparisons. Direct measurements of energy and nutrient deposition
and various losses (nonfecal losses, heat production, etc.) are virtually the


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