Physiology of animal suffering

280 Pages·2004·1.361 MB·English

by  Neville G Gregory

Physiology and Behaviour
of Animal Suffering
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Physiology and Behaviour
of Animal Suffering
Neville G. Gregory
Royal Veterinary College
and
Biotechnology and Biological Sciences Research Council

Blackwell
Science
© 2004 Universities Federation for Animal First published 2004
Welfare (UFAW)
ISBN 0-632-06468-4
Series editors:
James K. Kirkwood, Robert C. Hubrecht A catalogue record for this title is available
and Elizabeth A. Roberts from the British Library
Blackwell Science, a Blackwell Publishing Gregory, Neville G.
company Physiology and behaviour of animal
Editorial offices: suffering / Neville G. Gregory.
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Tel:[phone] Includes bibliographical references and
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Contents
Foreword ix
Preface xi
1 Introduction 1
1.1 What Is Suffering? 1
1.2 Why Worry about Animal Suffering? 1
1.3 When Can We Stop Worrying about Animal Suffering? 1
1.4 Recognising Suffering in Animals 7
1.5 Can Animals Go Mad? 8
1.6 What Constitutes Animal Suffering? 9
1.7 Conclusions 10
2 Stress 12

2.1 Stress Physiology 12
2.2 Stress-related Disorders 17
2.3 Restraint Stress 19
2.4 Stress-induced Analgesia 21
2.5 Stress-induced Seizures and Fits 21
3 Anxiety and Fear 22
3.1 Introduction 22
3.2 Anxiety 23
3.3 Experimental Models 25
3.4 Fear 26
3.5 Fright 28
3.6 Phobias 28
3.7 Panic 29
3.8 The Role of the Amygdala 30
3.9 Losing One’s Mother 31
v
vi Contents
4 Emotional Numbness and Deprivation 32
4.1 Anhedonia 32
4.2 Depression 33
4.3 Social isolation in the Newborn 34
4.4 Sensory Deprivation in Early Life 35
4.5 Sensory Deprivation in Later Life 36
4.6 Social Isolation and Barren Environments 36
4.7 Stereotypies and Neurotic Behaviours 37
4.8 Learned Helplessness 40
4.9 Post-traumatic Stress Disorder 40
4.10 Sleep Disorders 42
4.11 Weaning 44
4.12 Physiology of Emotions 45
5 Aggression, Overcrowding and Discomfort 46
5.1 Aggression 46
5.2 Overcrowding and Confinement 51
5.3 Discomfort 54
6 Exercise 56
6.1 Overexertion 56
6.2 Endurance Riding 57
6.3 Horse-racing Injuries 58
6.4 Greyhound Racing Injuries 61
6.5 Migration 63

7 Cold 64
7.1 Cold Discomfort and Pain 64
7.2 Skin Freezing and Chilblains 65
7.3 Hypothermia 66
7.4 Sensitivity to Cold 67
7.5 Hypothermia and Cold Survival 67
7.6 Cold in Combination with Starvation 69
7.7 Cold-induced Analgesia 70
8 Heat and Burns 72
8.1 Heat Stress 72
8.2 Heat Intolerance 73
8.3 Some Species Differences 74
8.4 Pain 75
8.5 Burns and Scalds 76
Contents vii
9 Thirst and Hunger 83
9.1 Thirst and Dehydration 83
9.2 Overhydration 86
9.3 Osmotic Stress 86
9.4 Hunger 87
9.5 Underfeeding 88
9.6 Emaciation 89
9.7 Inappropriate Diets 91
9.8 Forced Moulting 92
9.9 Force-feeding and Overeating 92
10 Pain 94
10.1 The Value of Pain 94
10.2 Pain Associated with Trauma 95
10.3 Ways in Which Animals Express Pain 99
10.4 Pain Pathways and Consciousness 102
10.5 Cortical Regions 106
10.6 Applied Neurology of Pain 107
10.7 Pain in a Given Context 119
11 Trauma 131
11.1 Injuries in Selected Body Regions and Tissues 131
11.2 Some Common Causes of Injury 133
11.3 Intended or Avoidable Causes of Trauma 142
11.4 Types of Injury 172
12 Sickness and Disease 183
12.1 Is Suffering an I nevitable Consequence of Being Ill? 183
12.2 Do the Behaviours Expressed During Sickness Serve a
Purpose? 185
12.3 Cytokines and Sickness Behaviours 186
12.4 Cancer 187
12.5 Stress and Immune Function 188
12.6 Corticosteroid Therapy 191
12.7 Anaemia 191
12.8 Hazards of Improving Disease Control 191
12.9 Diseases Used for Controlling Pests 192
13 Digestive System 193
13.1 Nausea 193
13.2 Vomiting and Retching 193
13.3 Gut Pain 195
13.4 Diarrhoea 197
13.5 Gut Injuries 198
viii Contents
13.6 Stress and the Gut 198
13.7 Gastrointestinal Ulcers 199
14 Poisoning 201
14.1 Wartime Poisons 201
14.2 Environmental Toxicants 202
14.3 Vertebrate Pesticides 203
15 Respiratory System 207
15.1 Asphyxia 208
15.2 Breathlessness 209
15.3 Carbon Dioxide Inhalation 211
15.4 Drowning 212
15.5 Pulmonary Oedema 214
15.6 Hypoxia 215
15.7 Altitude Sickness 217
15.8 Decompression 218
15.9 Collapse of the Lung and Pneumothorax 219
15.10 Asthma and Allergies 219
15.11 Ammonia 220
15.12 Signs of Respiratory Distress 220
15.13 Agonal Gasping 222
16 Dying 223
16.1 Euthanasia 224
16.2 Decapitation 226
16.3 Religious Slaughter 227

16.4 Death from Brain Injury 227
16.5 Recognising Insensibility and Brain Death 229
References 232
Abbreviations 258
Index 260
Colour plate sections falls after page 148
Foreword
The human population of the world exceeds six billion and is still growing rapidly.
We live in a closed system with finite resources. Whether we like it or not, our
interests are frequently in conflict with those of other species. We use animals for
food, for companionship, and in research, and we compete with many free-living
animals for habitat and food. Side-effects of many of our activities present threats
not just to individual animals but to species viability. We cannot avoid having to
manage this situation and, frequently and unavoidably, this involves having to
weigh the interests of individuals of one species against the interests of individu-
als of another.
During the last century (and coincident with the period over which much of the
human population growth has occurred), remarkable advances in comparative
neuroanatomy, physiology and behavioural sciences have provided strong evidence
that the capacity for subjective experience of unpleasant (and pleasant) feelings is
not limited to humans only. In contrast to the view, commonly-held among influ-
ential thinkers prior to this scientific enlightenment, it is now generally accepted

that subjective experience, and thus the capacity to suffer, are widespread in the
animal kingdom (at least in the vertebrate branch). This knowledge has brought
with it a particular responsibility, when pursuing human interests or environmental
management for the preservation of biodiversity, to avoid or minimise the risks of
causing harm to individuals of other species.
Growing awareness of this responsibility has led, around the world, to a strik-
ing proliferation of codes and legislation aimed at protecting and improving animal
welfare. In practice, pursuit of these aims depends frequently upon making valid
assessments of welfare status. Concern for an animal’s welfare is concern about
its subjective quality of life – on how it feels. This cannot be measured but can
only be inferred from observations of its physical state and behaviour in the light
of our own experiences of what it is like to have feelings and of what these are
like under various circumstances. Subjectivity cannot be avoided in this process –
in the step from what is observed to what is inferred. But, the greater our knowl-
edge of the neurological and other machinery that generates feeling, and of how
and when it operates, the safer and surer our inferences are likely to be.
ix
x Foreword
This is a very valuable and timely book in this context. It provides a wide-
ranging and informative overview of the physiological and behavioural responses
to many diseases, injuries and other stresses, and of the mechanisms that underlie
the associated subjective experiences. Improvements in animal welfare do not come
about merely by wishing them (to quote Sir Peter Medawar), but depend upon a
proper understanding of the causes of suffering and of the ways in which these
can be prevented or alleviated. In this book, Neville Gregory makes a major
contribution to promoting understanding of animal suffering and thus, both to
tackling many forms of it and also to properly taking suffering into account in
cost/benefit judgments when pursuit of human or environmental interests put other
animals at risk.
James K Kirkwood
June 2004