www.pdfgrip.com


Pain Management in
Veterinary Practice

www.pdfgrip.com


www.pdfgrip.com


Pain Management in
Veterinary Practice
Editors
Christine M. Egger
Lydia Love
Tom Doherty

www.pdfgrip.com


This edition first published 2014
Editorial offices:

C

2014 by John Wiley & Sons, Inc.

1606 Golden Aspen Drive, Suites 103 and 104, Ames, Iowa 50010, USA

The Atrium, Southern Gate, Chichester, West Sussex, PO19 8SQ, UK
9600 Garsington Road, Oxford, OX4 2DQ, UK

For details of our global editorial offices, for customer services and for information about how to apply for permission to reuse the copyright
material in this book please see our website at www.wiley.com/wiley-blackwell.
Authorization to photocopy items for internal or personal use, or the internal or personal use of specific clients, is granted by Blackwell
Publishing, provided that the base fee is paid directly to the Copyright Clearance Center, 222 Rosewood Drive, Danvers, MA 01923. For those
organizations that have been granted a photocopy license by CCC, a separate system of payments has been arranged. The fee codes for users
of the Transactional Reporting Service are ISBN-13: 978-0-8138-1224-3/2014.
Designations used by companies to distinguish their products are often claimed as trademarks. All brand names and product names used in
this book are trade names, service marks, trademarks or registered trademarks of their respective owners. The publisher is not associated with
any product or vendor mentioned in this book.
The contents of this work are intended to further general scientific research, understanding, and discussion only and are not intended and
should not be relied upon as recommending or promoting a specific method, diagnosis, or treatment by health science practitioners for any
particular patient. The publisher and the author make no representations or warranties with respect to the accuracy or completeness of the
contents of this work and specifically disclaim all warranties, including without limitation any implied warranties of fitness for a particular
purpose. In view of ongoing research, equipment modifications, changes in governmental regulations, and the constant flow of information
relating to the use of medicines, equipment, and devices, the reader is urged to review and evaluate the information provided in the package
insert or instructions for each medicine, equipment, or device for, among other things, any changes in the instructions or indication of usage
and for added warnings and precautions. Readers should consult with a specialist where appropriate. The fact that an organization or Website
is referred to in this work as a citation and/or a potential source of further information does not mean that the author or the publisher endorses
the information the organization or Website may provide or recommendations it may make. Further, readers should be aware that Internet
Websites listed in this work may have changed or disappeared between when this work was written and when it is read. No warranty may be
created or extended by any promotional statements for this work. Neither the publisher nor the author shall be liable for any damages arising
herefrom.
Library of Congress Cataloging-in-Publication Data
Pain management in veterinary practice / editors, Christine M. Egger, Lydia Love, Tom Doherty.
pages ; cm
Includes bibliographical references and index.
ISBN 978-0-8138-1224-3 (pbk. : alk. paper) – ISBN 978-1-118-76133-5 (emobi) – ISBN 978-1-118-76134-2 (epdf) –

ISBN 978-1-118-76160-1 (epub) 1. Pain in animals–Treatment. I. Egger, Christine M., editor of compilation.
II. Love, Lydia, editor of compilation. III. Doherty, T. J. (Tom J.), editor of compilation.
[DNLM: 1. Pain Management–veterinary. 2. Veterinary Medicine–methods. SF 925]
SF910.P34P35 2014
636.089 60472–dc23
2013024797
A catalogue record for this book is available from the British Library.
Wiley also publishes its books in a variety of electronic formats. Some content that appears in print may not be available in electronic books.
Cover images: Front cover, Top and Bottom Left: Gregory Hirshoren, University of Tennessee CVM; Back Cover, Left: Kristie Mozzachio
and Valarie V. Tynes; Middle and Right: Gregory Hirshoren
Cover design by Modern Alchemy LLC
Set in 9.5/11.5 pt Times by Aptara R Inc., New Delhi, India

1 2014

www.pdfgrip.com


Contents
Contributors
Preface

ix
xiii

Section 1: Introduction and Anatomy, Physiology, and Pathophysiology of Pain

1

1


Introduction: Pain: An Issue of Animal Welfare
Alice Crook

3

2

Anatomy, Physiology, and Pathophysiology of Pain
Yael Shilo and Peter J. Pascoe

9

3

Mechanisms of Cancer Pain
Cholawat Pacharinsak and Alvin J. Beitz

29

Section 2: Pharmacology of Analgesic Drugs

39

4

Opioids
Tanya Duke-Novakovski

41


5

Nonsteroidal Anti-Inflammatory Drugs and Corticosteroids
Stuart Clark-Price

69

6

Local Anesthetics
Kip A. Lemke

85

7

␣-2 Adrenoceptor Agonists
Reza Seddighi

93

8

Nontraditional Analgesic Agents
Lydia Love and Dave Thompson

105

9


Novel Methods of Analgesic Drug Delivery
Lesley J. Smith

115

10 Pharmacokinetic Principles for the Design of Intravenous Infusions
Bruno H. Pypendop

Section 3: Nonpharmacological Pain Therapy

125

131

11 Canine Rehabilitation
Lowri Davies

133

12 Equine Rehabilitation
Lowri Davies

147

13 Custom External Coaptation as a Pain Management Tool: Veterinary Orthotics and Prosthetics
Martin W. Kaufmann and Patrice M. Mich

155


14 Myofascial Pain Syndrome in Dogs
Rick Wall

161

15 Traditional Chinese Herbal Medicine and Homeopathy in Pain Management
Lynelle Graham, Mona Boudreaux, and Steve Marsden

171

16 Mechanisms of Acupuncture Analgesia
Shauna Cantwell

177

v

www.pdfgrip.com


vi

Contents

17 Equine Acupuncture
Arthur I. Ortenburger

183

18 Canine Chiropractic and Pain Management

Robin Downing

189

19 Equine Chiropractic
Henry S. Adair

195

Section: 4 Management of Pain in Veterinary Species

199

20 Recognition and Assessment of Acute Pain in the Dog
Kate L. White

201

21 Treatment of Acute Pain in the Dog
Kate L. White

209

22 Recognition and Assessment of Chronic Pain in Dogs
Anna Hielm-Bjăorkman

227

23 Treatment of Chronic Pain in Dogs
Anna Hielm-Bjăorkman


239

24 The Recognition and Assessment of Pain in Cats
Kersti Seksel

269

25 Treatment of Acute Pain in Cats
Jacob A. Johnson

275

26 Treatment and Assessment of Chronic Pain in Cats
Bonnie Wright and Jessica K. Rychel

289

27 Cancer-associated Pain and its Management
Lydia Love and Lisa DiBernardi

299

28 Recognition and Treatment of Pain in the Small Animal Critical Care Patient
Jane Quandt

311

29 Recognition and Assessment of Pain in Horses
Emma Love


317

30 Treatment of Acute and Chronic Pain in Horses
Bernd Driessen and Laura Zarucco

323

31 Recognition and Assessment of Pain in Ruminants
Kevin J. Stafford

349

32 Treatment of Acute and Chronic Pain in Ruminants
Alexander Valverde

359

33 Recognition and Treatment of Pain in Camelids
Tamara Grubb

373

34 Recognition and Treatment of Pain in Pet Pigs
Kristie Mozzachio and Valarie V. Tynes

383

35 Recognition and Assessment of Pain in Small Exotic Mammals
Lesa Thompson


391

36 Treatment of Pain in Small Exotic Mammals
Cheryl B. Greenacre

399

37 Recognition and Treatment of Pain in Birds
Karen L. Machin

407

38 Recognition and Treatment of Pain in Reptiles, Amphibians, and Fish
Lysa Pam Posner and Sathya K. Chinnadurai

417

www.pdfgrip.com


Contents

Section 5: Incorporating Pain Management into Your Practice and Hospice and Palliative Care

vii

425

39 Integrating Pain Management into Veterinary Practice

Robin Downing

427

40 Pain Management in Hospice and Palliative Care
Keri Jones

431

Index

437

www.pdfgrip.com


www.pdfgrip.com


Contributors
Henry S. Adair, DVM, MS, CERP, DACVS, DACVSMR
Associate Professor, Equine Surgery
Director of Equine Performance and Rehabilitation
Department of Large Animal Clinical Sciences
College of Veterinary Medicine
University of Tennessee
Knoxville, TN

Lowri Davies, BVSc, MRCVS, CVA, CCRP
The SMART Veterinary Clinic Ltd

Weigbridge Referral Center
Swansea, Wales, UK
Lisa DiBernardi, DVM, DACVIM (Oncology), DACVR
(Radiation Oncology)
Animal Specialty Hospital of Florida
Naples, FL
Palm Beach Veterinary Specialists
West Palm Beach, FL

Alvin J. Beitz, BS, PhD
Professor and Chair
Distinguished Teacher
Department of Veterinary and Biomedical Sciences
College of Veterinary Medicine, University of Minnesota
St. Paul, MN

Robin Downing, DVM, CVPP, CCRP, DAAPM
Hospital Director
The Downing Center for Animal Pain Management, LLC
Windsor, CO

Mona Boudreaux DVM, CVA, MMQ
Owner
A Time To Heal
Wonder Lake, IL

Bernd Driessen, DVM, PhD, DACVAA, DECVPT
Professor, Anesthesiology
School of Veterinary Medicine
University of Pennsylvania

New Bolton Center
Kennett Square, PA

Shauna Cantwell, DVM, MVSc, CVA, CVSMT, DACVAA
Courtesy Professor
University of Florida
Medicine Wheel Veterinary Services, Inc.
Ocala, FL

Tanya Duke-Novakovski, BVetMed, MSc, DVA, DACVAA,
DECVAA
Professor, Veterinary Anesthesiology and Analgesia
Department of Small Animal Clinical Sciences
Western College of Veterinary Medicine
University of Saskatchewan
Saskatoon, Canada

Sathya K. Chinnadurai, DVM, MS, DACZM, DACVAA
Associate Veterinarian
Chicago Zoological Society/Brookfield Zoo
Brookfield, IL
Stuart Clark-Price, DVM, MS, DACVIM-LA, DACVAA
Assistant Professor, Anesthesia and Analgesia
Head, Anesthesia Clinical Service
Department of Veterinary Clinical Medicine
College of Veterinary Medicine
University of Illinois
Urbana, IL

Lynelle Graham, DVM, MS, DACVAA

Clinical Professor of Anesthesia
Veterinary Clinical Sciences
University of Minnesota
St. Paul, MN
Cheryl B. Greenacre, DVM, DABVP (Avian), DABVP (Exotic
Companion Mammal)
Professor, Avian and Zoological Medicine
Department of Small Animal Clinical Sciences
College of Veterinary Medicine
University of Tennessee
Knoxville, TN

Alice Crook, BSc, DVM
Coordinator
Sir James Dunn Animal Welfare Centre
Adjunct Professor
Department of Companion Animals
Atlantic Veterinary College
University of Prince Edward Island
Charlottetown, Canada

ix

www.pdfgrip.com


x

Contributors


Tamara Grubb, DVM, PhD, DACVAA
Assistant Clinical Professor, Anesthesia and Analgesia
Veterinary Clinical Sciences
Washington State University
Pullman, WA

Patrice M. Mich, DVM, MS, DABVP, DACVAA, CCRT
Medical Director
OrthoPets
Center for Animal Pain Management and Mobility Solutions
Denver, CO

Anna Hielm-Bjăorkman, DVM, PhD, CVA (IVAS)
Assistant Professor
Department of Equine and Small Animal Medicine
Pain and Rehabilitation Clinic and Research Center
Faculty of Veterinary Medicine
Helsinki University
Helsinki, Finland

Kristie Mozzachio, DVM, DACVP
Mozzachio Mobile Veterinary Services
Hillsborough, NC
Adjunct faculty
North Carolina State University College of Veterinary Medicine
Raleigh, NC
Arthur I. Ortenburger, DVM, MS
Associate Professor of Surgery
Department of Health Management
University of Prince Edward Island

Charlottetown, Canada

Jacob A. Johnson, DVM, DACVAA
Assistant Professor, Anesthesia and Pain Management
Auburn University College of Veterinary Medicine
Auburn, AL
Keri Jones, DVM, CVPP
Medical Director
Homeward Bound Animal Hospital
Arvada, CO
Martin W. Kaufmann, ABC, c-PED
OrthoPets
Center for Animal Pain Management and Mobility Solutions
Denver, CO
Kip A. Lemke, BS, DVM, MS, DACVAA
Professor, Anesthesiology
Chief of Anesthesiology Service
Department of Companion Animals
College of Veterinary Medicine
University of Prince Edward Island
Charlottetown, Canada
Emma Love, BVMS, PhD, DVA, DECVAA, MRCVS, FHEA,
RCVS
Senior Teaching Fellow in Veterinary Anaesthesia
University of Bristol
Bristol, UK
Lydia Love, DVM, DACVAA
Director of Anesthesia and Pain Management
Animal Emergency and Referral Associates
Fairfield, NJ

Karen L. Machin, DVM, PhD
Associate Professor
Department of Veterinary Biomedical Sciences
Western College of Veterinary Medicine
University of Saskatchewan
Saskatoon, Canada
Steve Marsden, DVM, ND, MSOM, Lac, Dipl.CH, CVA
Director
College of Integrative Veterinary Therapies
Edmonton, Canada

Cholawat Pacharinsak, DVM, MS, PhD, DACVAA
Assistant Professor
Director of Anesthesia, Pain Management, and Surgery
School of Medicine
Stanford University
Stanford, CA
Peter J. Pascoe, BVSc, DVA, DACVAA, DECVAA
Professor, Veterinary Anesthesia and Critical Patient Care
Department of Surgical and Radiological Sciences,
School of Veterinary Medicine
University of California
Davis, CA
Lysa Pam Posner, DVM, DACVAA
Associate Professor Anesthesiology
Director of Anesthesia Services
College of Veterinary Medicine
North Carolina State University
Raleigh, NC
Bruno H. Pypendop, DrMedVet, DrVetSci, DACVAA

Professor, Veterinary Anesthesia and Critical Patient Care
Department of Surgical and Radiological Sciences
School of Veterinary Medicine
University of California
Davis, CA
Jane Quandt, DVM, MS, DACVAA, DACVECC
Associate Professor, Anesthesiology
College of Veterinary Medicine
University of Georgia
Athens, GA
Jessica K. Rychel, DVM, CVMA, CCRP
Veterinary Emergency and Rehabilitation Hospital
Fort Collins, CO

www.pdfgrip.com


Contributors
Reza Seddighi, DVM, MS, PhD, DACVAA
Assistant Professor, Anesthesia and Analgesia
Department of Large Animal Clinical Sciences
College of Veterinary Medicine
University of Tennessee
Knoxville, TN

Lesa Thompson, MA, BVM&S, DZooMed
(Mammalian), MSc, MRCVS, RCVS
Tokyo, Japan
Valarie V. Tynes, DVM, DACVB
Premier Veterinary Behavior Consulting

Sweetwater, TX

Kersti Seksel, BVSc (Hons), MRCVS, MA (Hons), FACVSc,
DACVB, CMAVA, DECVBM-CA
Registered Veterinary Specialist, Behavioral Medicine
Sydney Animal Behavior Service
Seaforth, Australia
Yael Shilo, DVM, DACVAA
Senior Anesthesiologist,
Anesthesia Department
Veterinary Teaching Hospital
Koret School of Veterinary Medicine
The Hebrew University of Jerusalem
Rehovot, Israel

Rick Wall, DVM, CCRP, DAAPM
Certified Myofascial Trigger Point Therapist
Center for Veterinary Pain Management and Rehabilitation
The Woodlands, TX

Lesley J. Smith, DVM, DACVAA
Clinical Professor of Anesthesiology and Pain Management
Department of Surgical Sciences
School of Veterinary Medicine
University of Wisconsin
Madison, WI
Kevin J. Stafford, MVB, MSc, PhD, FRCVS, FANZCVSc
Professor
Institute of Veterinary Animal and Biomedical Sciences
Massey University

Palmerston North, New Zealand
Dave Thompson, DVM
Clyde Park Veterinary Clinic
Wyoming, MI

Alexander Valverde, DVM, DVSc, DACVAA
Associate Professor, Anesthesiology
Department of Clinical Studies
Ontario Veterinary College
University of Guelph
Guelph, Canada

Kate L. White, MA, Vet MB, DVA, DECVAA, MRCVS
Clinical Associate Professor, Anesthesia
Head of Division of Medicine
College of Veterinary Medicine
University of Nottingham
Sutton Bonington Campus
Loughborough, UK
Bonnie Wright, DVM, DACVA, CVMA, CVPP, CCRP
Veterinary Emergency and Rehabilitation Hospital
Fort Collins, CO
Laura Zarucco, DMV, PhD
Associate Professor of Surgery
Dipartimento di Scienze Veterinarie
Scuola di Agraria e Medicina Veterinaria
Universit`a degli Studi di Torino
Grugliasco, Italy

www.pdfgrip.com


xi


www.pdfgrip.com


Preface
New analgesics and new formulations of old analgesics are constantly being introduced to the veterinary market, yet the ability to
recognize and quantify pain in veterinary species remains a challenge. Pain assessment and scoring systems are being validated in
many veterinary species, but clinically relevant, objective methods
of assessment of all types of pain in all species remain elusive.
Ultimately, it is left to the caregiver to decide if analgesic therapy
is indicated, and this requires empathy and logic. The purpose of
this book is to provide the reader with easily accessible, evidencebased information to aid in the recognition and treatment of pain in
veterinary species.

daily practice and to discuss scientific evidence, or lack thereof,
supporting these modalities.
The recognition and treatment of acute and chronic pain in
dogs, cats, small exotic mammals, birds, reptiles, amphibians,
fish, camelids, ruminants, pigs, and horses is discussed in Section IV. Chapters on the treatment of cancer pain and the recognition and treatment of pain in intensive care patients are also
included. The chapters in this section discuss pharmacological and
non-pharmacological strategies for use in each species to provide
a balanced pain management protocol. Much of the information
from these chapters is summarized in tables to allow easy access to
information.
The fifth and final section includes a chapter describing strategies
for incorporating pain management into veterinary practice, including some economic and legal considerations, and a final chapter
discussing veterinary hospice and palliative care.


ORGANIZATION AND FEATURES OF THE BOOK
Section I begins with an introductory chapter discussing welfare issues associated with pain and its management in veterinary
species. The chapters that follow provide a review of the current
understanding of the physiology and pathophysiology of acute pain,
chronic pain, and cancer pain.
Section II provides extensive information about the pharmacology of opioids, nonsteroidal anti-inflammatory drugs, alpha-2
adrenoreceptor agonists, local anesthetics, and non-traditional analgesics (e.g., anti-epileptic drugs, NMDA receptor antagonists, and
nutritional supplements). Novel methods of drug delivery and the
pharmacokinetics of continuous rate infusions are also discussed.
The non-pharmacological management of pain, including physical therapy, orthotics and prosthetics, myofascial trigger point therapy, acupuncture, chiropractic, herbal therapy, and homeopathy are
discussed in Section III. These chapters are not intended to provide
expert training in these areas. They are meant to provide a basic
explanation of some techniques that can be easily incorporated into

ACKNOWLEDGMENTS
The authors wish to thank the staff of Wiley for their support and
encouragement. This work would not have been possible without the contributions of the authors who come from academic,
research, and clinical practice backgrounds in the USA, Canada,
Great Britain, Europe, New Zealand, and Australia. A feature common to all is the desire to improve the recognition, prevention, and
treatment of pain in animals. We hope that this book contributes
significantly to that endeavor.
Christine M. Egger
Lydia Love
Tom Doherty

xiii

www.pdfgrip.com



www.pdfgrip.com


Section 1
Introduction and Anatomy, Physiology,
and Pathophysiology of Pain

Chapter 1. Introduction: Pain: An Issue
of Animal Welfare 3
Alice Crook

Chapter 3. Mechanisms of Cancer Pain 29
Cholawat Pacharinsak and Alvin J. Beitz

Chapter 2. Anatomy, Physiology, and
Pathophysiology of Pain 9
Yael Shilo and Peter J. Pascoe

Pain Management in Veterinary Practice, First Edition. Edited by Christine M. Egger, Lydia Love and Tom Doherty.
C 2014 John Wiley & Sons, Inc. Published 2014 by John Wiley & Sons, Inc.

1

www.pdfgrip.com


www.pdfgrip.com



1
Introduction: Pain: An Issue
of Animal Welfare
Alice Crook

eral body function or productivity (e.g., food and water intake,
weight gain) that are relatively easy to quantify; such measures
reflect what was happening to the animal over the period between
observations. The second approach includes physiological measures (such as changes in heart rate or cortisol concentrations) that
are widely used in studies assessing pain in animals (Stafford &
Mellor, 2005; Vickers et al., 2005; Whay et al., 2005) and are,
in principle, particularly useful in prey species that are considered stoic and therefore unlikely to show pronounced behavioral
responses until injuries are advanced (Phillips, 2002; Rutherford,
2002). However, the physical restraint required to obtain such
measurements may itself be stressful and confound the results
(Weary et al., 2006). Also, while cortisol measurements are useful for comparing treatments and controls, they are not useful in
assessing the degree of pain an individual animal is experiencing
(Rutherford, 2002).
Behavioral measures—the third approach—represent a way in
which animals can “self-report.” Weary (2006) provides a comprehensive review of the ways such measures are used to recognize
and quantify animal pain, and discusses the evidence necessary to
ensure that the measures are valid (i.e., that the measure provides
useful information about the pain the animal is experiencing) and
reliable (i.e., repeatable). The three main classes of behavior used
in pain assessment are pain-specific behaviors (e.g., gait impairment in lame dairy cows (Flower et al., 2008) or head shaking
and rubbing in dehorned dairy calves (Vickers et al., 2005)); a
decline in frequency or magnitude of certain behaviors (e.g., locomotory behaviors in rats postoperatively) (Roughan & Flecknell,
2003); and choice or preference testing (e.g., hens’ responses to
different concentrations of carbon dioxide used in stunning) (Webster & Fletcher, 2004). Rutherford (2002) discusses the usefulness
of behaviors associated with acute, subacute, and longer-lasting

pain in assessing the experience of pain in animals, including
specific parameters that may be useful for veterinarians in clinical assessment of pain and by scientists studying pain in animals.
These include simple and more complex behavioral responses, both
qualitative and quantitative, which may or may not be adaptive,
such as behaviors associated with escape or avoidance, guarding
or protection (e.g., postural changes), and depression or “learned
helplessness.”

There has been considerable progress since the early 1990s in pain
research in animals and in our understanding of related physiology and pharmacology, enabling great strides to be made in pain
management. But pain is still a huge welfare issue for animals:
farm animals are routinely subjected to painful husbandry procedures with no anesthesia or analgesia; perioperative pain management in small and exotic animals is inconsistent; and management
of cancer-related and chronic pain remains a challenge. Pain can
diminish animal well-being substantially due to its aversive nature,
the distress arising from the inability to avoid such sensations, and
the secondary effects that may adversely affect the animal’s quality
of life (QOL). Pain may affect an animal’s appetite, sleep habits
(e.g., fatigue), grooming (e.g., self-mutilation), ability to experience normal pleasures (e.g., reduced play and social interaction),
personality and temperament, and intestinal function (e.g., constipation), and may prolong the time needed for recovery from the
underlying condition (ACVA, 1998; McMillan, 2003). Untreated
pain may also result in systemic problems; for example, hepatic
lipidosis in cats as a result of inappetance and inadequate caloric
intake (Mathews, 2000).
Much is known about the recognition and assessment of pain in
animals; however, more work is needed to develop valid and reliable pain scoring systems for all species that are practical in reallife situations. Perception of animal pain directly affects analgesic
usage, and there is a wide range in attitudes among veterinarians,
farmers, and pet owners. This can best be addressed through education. There are also economic, regulatory, and other constraints
to effective pain management, particularly in large animals.

RECOGNITION AND ASSESSMENT OF PAIN

IN ANIMALS
Pain is an unpleasant sensory and emotional experience associated
with actual or potential tissue damage, or described in terms of such
damage (IASP, 1994). The experience of pain is always subjective.
Self-reporting is the gold standard in people, yet how can we know
the experience of animals?
Three approaches are used in the recognition and measurement
of pain in animals. The first approach includes measures of gen-

Pain Management in Veterinary Practice, First Edition. Edited by Christine M. Egger, Lydia Love and Tom Doherty.
C 2014 John Wiley & Sons, Inc. Published 2014 by John Wiley & Sons, Inc.

3

www.pdfgrip.com


4

Section 1 / Introduction and Anatomy, Physiology, and Pathophysiology of Pain

Pain Recognition Tools
Pain researchers and clinicians alike agree that there is a need
for sensitive and specific measures that are practical for real-time
assessments in a variety of animal settings including farms, veterinary clinics, and laboratories (Vi˜nuela-Fern´andez et al., 2007).
Multidimensional pain scales that integrate objective and subjective
behavioral observations with various other measures can be used
to characterize an individual animal’s experience of pain (Rutherford, 2002). Another approach is to develop questionnaires for use
by animal owners that can be used in the assessment of pain and
its impact on QOL (McMillan, 2003; Wiseman-Orr et al., 2004;

Yazbek & Fantoni, 2005). Wiseman-Orr (2006) provides a thorough discussion of the approaches and potential pitfalls of designing
and validating questionnaires where self-reporting is not possible
and the questionnaires are designed for use by a proxy, as in the
case of animals. Work continues in the development of scientifically validated pain recognition tools for veterinarians for clinical assessment of pain and for scientists studying pain in large,
small, exotic, and laboratory animals (Roughan & Flecknell, 2003;
Wiseman-Orr et al., 2004; Yazbek & Fantoni, 2005; Morton, 2005;
Wojciechowska et al., 2005; Făollmi et al., 2007; Flecknell et al,
2007; Weary & Fraser, 2008).

PAIN AND CONSCIOUSNESS
Pain is always subjective and psychological variables such as past
experience, attention, and other cognitive activities affect the individual’s experience of pain (Melzack, 1993). Self-reporting is the
gold standard in people and, because of the subtlety of communication possible with language, the understanding of pain has been
greatly advanced through human subjects’ descriptions of pain and
the effects of different modalities of analgesia (Johnson, 2008).
However, “The inability to communicate verbally does not negate
the possibility that an individual is experiencing pain and is in need
of appropriate pain-relieving treatment” (IASP, 1994).
If we cannot know the subjective emotional experiences of other
human beings, how can we possibly know the emotional experience of animals? For most people, the evidence that animals have
nociceptive receptors and pathways, physiological responses, and
behavioral reactions to pain similar to that of people, is sufficient to
accept that animals experience pain and suffer as a result. However,
some scientists, surprisingly, suggest that animals are not capable
of experiencing pain. Psychologist Bermond (2001), for example
argues that animals other than anthropoid apes have an “irreflexive consciousness” (a consciousness without past or future) due to
the lack of a well-developed prefrontal cortex, and that reflection
is a requirement to experience suffering and pain as unpleasant.
Therefore, he distinguishes between “the registration of pain as
a stimulus, which does not induce feelings of suffering and the

experience of pain as an emotion, which does induce suffering”
(Bermond, 2001).
What kind of observations can provide evidence for or against the
experience of pain and other affective states in animals? The neurophysiologist Gentle (2001) carried out an elegant series of studies
to provide information on cognitive perception of pain in chickens by looking at the effect of selective attention on pain-related
behavior. Noting that the human experience of pain can be modulated by shifts in attention through such modalities as relaxation

training, hypnosis, and other therapies, he reasoned that if a
chicken’s response to a painful event was simply an unconscious
automatic reaction the response would not be influenced by shifting the bird’s attention. On the other hand, if the bird actually
felt the pain as an unpleasant experience, redirecting its attention
might reduce the signs of pain, as in people (e.g., installation of
overhead television screens in dental offices). In his work, Gentle
induced gout in one leg of chickens by injecting sodium urate crystals. Chickens kept in barren cages avoided placing weight on the
affected leg and, if encouraged to walk, did so with a limp. These
pain-related behavioral signs were greatly reduced or eliminated in
chickens given a variety of motivational changes including nesting,
feeding, exploration, and social interaction. The shifts in attention
not only reduced pain but also reduced peripheral inflammation.
This work has far-reaching consequences. The evidence that
motivational changes, by altering the birds’ attention, significantly
altered pain-related behaviors, and hence probably the pain experience for the animal, indicates a cognitive component of pain in
the chicken and provides evidence of consciousness. On a practical
level, these results also reinforce the importance of environmental
enrichment, which will promote shifts in attention and, thereby,
potentially improve the welfare of birds suffering pain under commercial conditions. Strategies, such as distraction and refocusing
attention through positive interaction, are very familiar to veterinarians and animal health technicians as adjuncts to pain management
in small animals in clinical settings.

ATTITUDES TOWARD ANIMAL PAIN

“Freedom from pain, injury, or disease (by prevention or rapid diagnosis and treatment)” is one of the Five Freedoms widely accepted
as the major components of good animal welfare (Farm Animal
Welfare Council, 2009). The recognition and effective treatment
of pain is central to animal welfare (Rutherford, 2002). There is a
strong emphasis on pain among animal welfare researchers, with
the number of pain-related articles in scientific journals considerably outweighing articles on the other Freedoms (freedom to behave
normally, freedom from fear and distress, freedom from hunger and
thirst, and freedom from discomfort) (Phillips, 2008).
National animal welfare advisory bodies in Australia, New
Zealand, and the European Union have recommended steps to avoid
or minimize animal pain and associated suffering, and the World
Organization for Animal Health (OIE) produced a special edition
in its Technical Series on “Scientific assessment and management
of animal pain” (Mellor et al., 2008). Veterinary associations commonly have positions or policies advocating the effective management of pain in animals (CVMA, 2007; AVMA, 2011).
In theory, then, we agree that animals should not be in pain, yet
studies show that attitudes toward pain vary greatly among societal
groups responsible for animal care, including veterinarians. Veterinary attitudes toward pain and pain management in companion
and production animals have been studied in Canada (Dohoo &
Dohoo, 1996; Hewson et al., 2006b, 2007a, 2007b), the United
States (Hellyer et al., 1999), the United Kingdom (Lascelles et al.,
1999; Capner et al., 1999; Huxley, 2006), Finland (Raekallio et al.,
2003), Scandinavia (Thomsen et al., 2010), Europe (Hugonnard
et al., 2004; Guatteo et al., 2008), and New Zealand (Laven et al.,
2009). Other surveys have looked at the attitudes of veterinary and

www.pdfgrip.com


1 / Introduction: Pain: An Issue of Animal Welfare
animal science students (Levine et al., 2005; Heleski & Zanella,

2006; Kielland et al., 2009).
These studies reveal some common themes. Considerable variation in clinical recognition and treatment of pain exists in both
companion and production animal practice. A perception that an
animal is in pain is a decisive factor in the provision of analgesia, yet
there is great variation in pain ratings among veterinarians. Women
and more recent graduates generally tended to rate pain more highly
and treat it more frequently (Dohoo & Dohoo, 1996; Lascelles et al.,
1999; Raekallio et al., 2003; Williams et al., 2005; Huxley, 2006;
Laven et al., 2009) and increased usage of analgesics among newer
veterinarians may well be due to the changes in emphasis of the
treatment of pain that have taken place in veterinary medicine during the past 10–15 years (Thomsen et al., 2010). Although the vast
majority of respondents generally agree that provision of analgesia
is beneficial, and that animals recover more quickly postoperatively
if analgesia is provided, the myth still persists that postoperative
pain provides some benefit in preventing animals from being too
active (Raekallio et al., 2003; Guatteo et al., 2008), even among
veterinarians who graduated in the 2000s (Thomsen et al., 2010)—
despite the position, held since 1998, of the American College of
Veterinary Anesthesiologists that unrelieved pain provides no benefits to animals (ACVA, 1998). Even where a large majority of
respondents agree about the importance of treating pain, there is
much variation in the circumstances under which pain is treated
(Hellyer et al., 1999; Hugonnard et al., 2004; Whay & Huxley,
2005).
Data from repeat Canadian surveys were somewhat encouraging.
A 1994 survey showed that approximately 50% of Canadian veterinarians did not use analgesics postoperatively in dogs and cats
(Dohoo & Dohoo, 1996). Usage among the other 50% varied with
the procedure, and opioids were used almost exclusively, predominantly butorphanol. A similar survey in 2001 showed a marked
increase in analgesic usage, with only about 12% of Canadian
veterinarians not using analgesics (Hewson et al., 2006b). Given,
however, the low usage of perioperative analgesics for many surgeries, together with a continued overreliance on weak opioids (e.g.,

butorphanol, meperidine) and under usage of strong opioids and
NSAIDs, it was evident that postoperative pain was not being managed effectively much of the time.
In the 1994 survey, pain perception scores attributed to different surgical procedures were one of two primary factors affecting
analgesic usage (the second was concern about the use of potent opioid agonists in the postoperative period) (Dohoo & Dohoo, 1996).
Perception of pain was also a strong predictor of postoperative
analgesic usage in 2001 (Hewson et al., 2006a); ratings of pain
caused by different surgeries had increased markedly since 1994.
In both surveys, veterinarians identified lectures and seminars at
the regional level, as well as review articles, as the preferred way
to receive continuing education regarding pain and analgesia.
PAINFUL HUSBANDRY PRACTICES IN FARM
ANIMALS
The use of at least some degree of perioperative analgesia is
fairly widespread in small animal practice (Lascelles et al., 1999;
Hugonnard et al., 2004; Hewson et al., 2006b), even if consistency
is lacking and there is much room for improvement to provide
truly effective, multimodal analgesia. The same cannot be said

5

with large animals, where it remains customary to perform many
procedures without anesthesia or analgesia, particularly in North
America (Hewson et al., 2007b; Fulwider et al., 2008). However,
in some countries analgesia is legally required when carrying out
certain husbandry procedures. For example, all the Scandinavian
countries now have regulations governing the use of anesthesia and
analgesia for procedures such as dehorning and castrating calves
(Thomsen et al., 2010). In New Zealand, analgesia is required for
castration of cattle over 6 months and for dehorning in those over
9 months (Laven et al., 2009).

Surveys that have compared attitudes toward, and frequency of,
pain alleviation in different species pointed out large differences
among different animal species undergoing similar operations and
among clinical conditions that received equal pain ratings (Hellyer
et al., 1999; Raekallio et al., 2003). Even though there is no physiological basis for this differentiation, the discrepancy between practice in companion and production animals is pronounced (Stookey,
2005).
Roadblocks to Treating Pain in Farm Animals
There are many practices carried out routinely in the management
of livestock and poultry that cause pain and distress (e.g., castration,
tail docking, dehorning, branding, beak trimming). Many of these
husbandry procedures are carried out on very young animals (e.g.,
tail docking in piglets and lambs, beak trimming in poultry); yet
there is mounting evidence that such tissue damage early in life may
program the animal to a lasting state of somatosensory sensitization
and increased pain (Vi˜nuela-Fern´andez et al., 2007).
Cost–benefit analyses of performing such procedures as an aid
to management have too often ignored the costs to the animals
themselves in terms of pain and suffering (Hewson, 2006). Increasingly, the public expects pain relief to be provided to farm animals
(Phillips et al., 2009; Whay & Main, 2009), yet there are economic,
practical, and regulatory constraints, such as the cost of treatment
relative to the monetary value of the individual animal, limited
availability of licensed analgesic drugs in food animals, and concern about drug residues and food safety (Vi˜nuela-Fern´andez et al.,
2007; Mellor et al., 2008a).
In considering a harm/benefit analysis of husbandry procedures,
we should first attempt to minimize the harm (Weary et al., 2006)
by asking questions such as:
1. Is the procedure necessary? Is it justified in terms of direct benefit to the animals and/or to the farming enterprise? For example
hot iron branding is a cause of avoidable pain to animals and
yet, since 2005, a US trade rule has required that all feeder cattle
entering the United States from Canada be branded, despite

the fact that Canadian cattle for export already bear an ear tag
traceable to the farm of origin through the Canadian Cattle Identification infrastructure (Whiting, 2005). Is there another way of
achieving the same end, for example, the development of polled
breeds to eliminate the need for dehorning calves or immunocastration in calves, piglets, and lambs (Stafford & Mellor, 2009)?
2. What harms are caused, how bad are they, can they be avoided
or reduced (e.g., through treatment of pain)?
3. What are the availability, cost, effectiveness, and ease of administration of pain-relieving drugs? Are there adverse effects or
residues? Is administration by a veterinarian required?

www.pdfgrip.com


6

Section 1 / Introduction and Anatomy, Physiology, and Pathophysiology of Pain

Husbandry practices with no benefits for animals or farmers may
become entrenched. For example, studies have shown no benefits
of tail docking in dairy cows, and yet this practice, which has been
shown to cause acute and chronic pain, as well as increased fly numbers, and to which the American and Canadian Veterinary Medical Associations are officially opposed (AVMA, 2009, CVMA,
2010), is still widespread in the United States (Fulwider et al.,
2008).
The recognition of pain in species such as cattle and sheep
may be more difficult because, as prey species, there was strong
evolutionary pressure to mask signs of pain and associated weakness (Phillips, 2002; Rutherford, 2002). A large European survey
describing pain management practices in cattle (Guatteo et al.,
2008) showed very high variability among veterinarians in the
knowledge of and sensitivity to pain in cattle. Again, awareness
of and ability to assess an animal’s pain were critical to the decision on whether to treat pain. In a similar survey in the United
Kingdom, cattle practitioners who did not use analgesics assigned

significantly lower pain scores to painful procedures or conditions
(Huxley, 2006).
In such studies, veterinarians expressed the concern that producers would be unwilling to pay additional costs of providing
analgesia (Whay et al., 2005; Huxley, 2006; Hewson et al., 2007a;
Guatteo et al., 2008). However, a follow-up study (Huxley & Whay,
2007) showed that, for a significant minority of cattle farmers, the
cost of providing analgesia may not be a barrier. For castration
and dehorning, for example, 40% and 25% of respondents, respectively, were prepared to pay additional fees sufficient to cover the
cost of appropriate analgesic drugs (local anesthesia and NSAIDs).
Fifty-three percent of farmers surveyed agreed with the statement
“Veterinary surgeons do not discuss controlling pain in cattle with
farmers enough.”
As well, there are costs to NOT providing analgesia. Apart from
causing animal suffering, pain can cause significant economic
losses (Denaburski & Tworkowska, 2009; Whay & Main, 2009;
Grandin, 2009). Yet, a UK study (Leach et al., 2010) showed that,
despite a high prevalence of lameness in dairy cows (36% in farms
surveyed in 2006–2007), the majority of farmers did not perceive
lameness to be a problem on their farm, and underestimated the
cost of pain to production.
Management of pain is dependent on the stockperson (or animal
caregiver) and the veterinarian. Effective pain management requires
recognition of the pain, provision of an environment where the animal can recover, and knowledge about and provision of appropriate
analgesic drugs. The ways in which an animal is handled and cared
for can exacerbate or mitigate pain and distress. Studies in all major
farm animal species have confirmed a strong relationship between
the methods used in handling animals, the degree of fear the animals show toward people, and the productivity of the farm (Rushen
& Passill´e, 2009). For example, a large study of US dairy farms
showed lower somatic cell counts in the milk and tendencies to
lower percentages of lame cows and shorter calving intervals on

farms where the cows were more willing to approach the observer
(Fulwider et al., 2008).
A special issue of Applied Animal Behaviour Science, “Pain in
Farm Animals,” summarizes current knowledge about addressing
many of the major causes of such pain, for example, disbudding and
dehorning in cattle (Stafford & Mellor, 2011a), castration in pigs
and other livestock (Sutherland & Tucker, 2011), identification and

prevention of intra- and postoperative pain (Walker et al., 2011),
and pain issues in poultry (Gentle, 2011).
THE WAY FORWARD
There have been many advances in the understanding of and ability
to treat pain in animals in recent decades. We have the knowledge to
effectively manage perioperative pain through multimodal analgesia and there are practical resources available to assist veterinarians
to do so (Tranquilli et al., 2004; Cracknell, 2007; Flecknell et al.,
2007; Lemke & Crook, 2011). There are published recommendations for managing painful procedures in large animals (Lemke
et al., 2008; Stafford & Mellor, 2011b), although there are still
many constraints. The management of chronic pain continues to
present a challenge.
The widespread finding that a veterinarian’s perception of pain
is a significant predictor of analgesic usage is a major concern,
especially considering pain ratings vary so markedly. A persuasive
case is made in pediatric medicine against allowing personal beliefs
about the experience of pain to prevent “optimal recognition and
treatment of pain for all children” (Hagen et al., 2001). Veterinary
practitioners must adopt the same approach for animals.
Veterinarians commonly feel their knowledge of issues related to
recognition and management of pain is inadequate, and are interested in continuing education opportunities to address this lack.
There is a great deal of information available on assessment and
management of pain, which needs to be better communicated to

veterinary students and veterinarians.
So what can veterinarians do to better manage pain in animals?
Veterinarians working with all species should avail themselves of
continuing education regularly to ensure they have current knowledge about recognizing, assessing, and managing pain. Veterinarians working with large animals should ensure that they inform
farmers of the strategies available to mitigate pain associated with
production practices and with chronic conditions, and of the resulting benefits to the animal and to the bottom line. And veterinarians,
as a profession, can work with other stakeholders, as expected of
them by society as advocates for animals, to address regulatory,
technological, and economic constraints.
REFERENCES
ACVA (1998) American college of veterinary anesthesiologists’ position paper on the treatment of pain in animals. Journal of the American Veterinary Medical Association, 213(5), 628–630.
AVMA (2009) Tail Docking of Cattle [Homepage of the
American Veterinary Medical Association], />issues/policy/animal_welfare/tail_docking_cattle.asp (accessed July
24, 2013).
AVMA (2011) Animal Welfare Policies [Homepage of the American Veterinary Medical Association], />Policies/Pages/Pain-in-Animals.aspx (accessed July 24, 2013).
Bermond, B. (2001) A neuropsychological and evolutionary approach
to animal consciousness and animal suffering. Animal Welfare, 10,
S47–S62.
Capner, C.A., Lascelles, B.D.X., & Watermann-Pearson, A. (1999)
Current British veterinary attitudes to perioperative analgesia for
dogs. Veterinary Record, 145(4), 95–99.
Cracknell, J. (2007) Analgesia in Exotics: A Review and Update, British
Veterinary Zoological Society, Romford, UK.

www.pdfgrip.com


1 / Introduction: Pain: An Issue of Animal Welfare
CVMA (2010) Tail Docking of Dairy Cattle [Homepage of
the Canadian Veterinary Medical Association], http://www.

canadianveterinarians.net/documents/tail-docking-of-dairy-cattle#.
UfANWG0U0ms (accessed July 24, 2013).
CVMA (2007) Pain Control in Animals [Homepage of the
Canadian Veterinary Medical Association], http://www.
canadianveterinarians.net/documents/pain-control-in-animals#.
UfAN3W0U0ms (accessed July 24, 2013).
Denaburski, J. & Tworkowska, A. (2009) The problem of pain in farm
animals and its effects on animal welfare and certain economic
results. Polish Journal of Veterinary Sciences, 12(1), 123–131.
Dohoo, S.E. & Dohoo, I.R. (1996) Postoperative use of analgesics in
dogs and cats by Canadian veterinarians. The Canadian Veterinary
Journal. La Revue V´et´erinaire Canadienne, 37(9), 546–551.
Farm Animal Welfare Council (2009) Five Freedoms [Homepage of
FAWC], (accessed July 24.
2013).
Flecknell, P., Gledhill, J., & Richardson, C. (2007) Assessing animal
health and welfare and recognising pain and distress. ALTEX, 24,
Spec No 82–83.
Flower, F.C., Sedlbauer, M., Carter, E., von Keyserlingk, M.A., Sanderson, D.J., & Weary, D.M. (2008) Analgesics improve the gait of lame
dairy cattle. Journal of dairy science, 91(8), 30103014.
Făollmi, J., Steiger, A., Walzer, C., et al. (2007) A scoring system
to evaluate physical condition and quality of life in geriatric zoo
mammals. Animal Welfare, 16(3), 309–318.
Fulwider, W.K., Grandin, T., Rollin, B.E., Engle, T.E., Dalsted, N.L.,
& Lamm, W.D. (2008) Survey of dairy management practices on
one hundred thirteen north central and northeastern United States
dairies. Journal of dairy science, 91(4), 1686–1692.
Gentle, M.J. (2001) Attentional shifts alter pain perception in the
chicken. Animal Welfare, 10, S187.
Gentle, M.J. (2011) Pain issues in poultry. Applied Animal Behaviour

Science, 135(3), 252–258.
Grandin, T. (2009) The Importance of Measurement to Improve the
Welfare of Livestock, Poultry and Fish, CABI, Wallingford, UK.
Guatteo, R., Holopherne, D., Whay, H.R., & Huxley, J.N. (2008).
Attitudes et pratiques actuelles des v´et´erinaires praticiens dans la
prise en charge de la douleur des bovins [Attitudes and practices of
veterinary practitioners in the management of pain in cattle]. Bulletin
des GTV, 44, 57–64.
Hagen, J.F., Coleman, W.L., Foy, J.M., et al. (2001) The assessment
and management of acute pain in infants, children, and adolescents.
Pediatrics, 108(3), 793.
Heleski, C.R. & Zanella, A.J. (2006) Animal science student attitudes
to farm animal welfare. Anthrozoăos, 19(1), 316.
Hellyer, P.W., Frederick, C., Lacy, M., Salman, M.D., & Wagner,
A.E. (1999) Attitudes of veterinary medical students, house officers, clinical faculty, and staff toward pain management in animals.
Journal of the American Veterinary Medical Association, 214(2),
238–244.
Hewson, C.J. (2006) “Eat well, spend less.” The costs of cheap food to
animals and humans. Canadian Veterinary Journal, 47(1), 38–41.
Hewson, C.J., Dohoo, I.R., & Lemke, K.A. (2006a) Factors affecting
the use of postincisional analgesics in dogs and cats by Canadian
veterinarians in 2001. Canadian Veterinary Journal, 47(5), 453–459.
Hewson, C.J., Dohoo, I.R., & Lemke, K.A. (2006b) Perioperative use
of analgesics in dogs and cats by Canadian veterinarians in 2001.
Canadian Veterinary Journal, 47(4), 352–359.
Hewson, C.J., Dohoo, I.R., Lemke, K.A., & Barkema, H.W. (2007a)
Factors affecting Canadian veterinarians’ use of analgesics when

7


dehorning beef and dairy calves. Canadian Veterinary Journal,
48(11), 1129–1136.
Hewson, C.J., Dohoo, I.R., Lemke, K.A., & Barkema, H.W. (2007b)
Canadian veterinarians’ use of analgesics in cattle, pigs, and horses
in 2004 and 2005. The Canadian Veterinary Journal. La Revue
V´et´erinaire Canadienne, 48(2), 155–164.
Hugonnard, M., Leblond, A., Keroack, S., Cadore, J., & Troncy, E.
(2004) Attitudes and concerns of French veterinarians towards pain
and analgesia in dogs and cats. Veterinary Anaesthesia & Analgesia,
31(3), 154–163.
Huxley, J.N. & Whay, H.R. (2006) Current attitudes of cattle practitioners to pain and the use of analgesics in cattle. The Veterinary
Record, 159(20), 662–668.
Huxley, J.N. & Whay, H.R. (2007) Attitudes of UK veterinary surgeons
and cattle farmers to pain and the use of analgesics in cattle. Cattle
Practice, 15(2), 189–193.
IASP (1994) Pain terms, a current list with definitions and notes on
usage in Classification of Chronic Pain, 2nd edn (eds H. Merskey &
N. Bogduk), IASP Press, Seattle, WA, pp. 209–214.
Johnson, C.B. (2008) Lessons learned from pain management in
humans, in Scientific Assessment and Management of Animal Pain,
(eds D.J. Mellor, P.M. Thornber, D. Bayvel, et al.), OIE (World
Organisation for Animal Health), Paris, pp. 184–194.
Kielland, C., Skjerve, E., & Zanella, A.J. (2009) Attitudes of veterinary
students to pain in cattle. Veterinary Record, 165(9), 254–258.
Lascelles, B.D.X., Capner, C.A., & Watermann-Pearson, A. (1999)
Current British veterinary attitudes to perioperative analgesia for cats and small mammals. Veterinary Record, 145(21),
601–604.
Laven, R.A., Huxley, J.N., Whay, H.R., & Stafford, K.J. (2009) Results
of a survey of attitudes of dairy veterinarians in New Zealand regarding painful procedures and conditions in cattle. New Zealand Veterinary Journal, 57(4), 215–220.
Leach, K.A., Whay, H.R., Maggs, C.M., et al. (2010) Working towards

a reduction in cattle lameness: 1. Understanding barriers to lameness
control on dairy farms. Research in Veterinary Science, 89(2), 311–
317.
Lemke, K.A. & Crook, A.D. (2011) Examples of Anaesthetic and
Pain Management Protocols for Healthy Cats and Dogs, 2nd edn
[Homepage of the Canadian Veterinary Medical Association],
/>panels_0.pdf (accessed July 24, 2013).
Lemke, K.A., Hewson, C.J., & Crook, A.D. (2008) Examples of
Anaesthetic and Pain Management Protocols for Large Animals
[Homepage of the Canadian Veterinary Medical Association],
/>20Pages.pdf (accessed July 24, 2013).
Levine, E.D., Mills, D.S., & Houpt, K.A. (2005) Attitudes of veterinary students at one US college toward factors relating to farm
animal welfare. Journal of Veterinary Medical Education, 32(4),
481–490.
Mathews, K.A. (2000) Pain assessment and general approach to management. The Veterinary Clinics Of North America Small Animal
Practice, 30(4), 729.
McMillan, F.D. (2003) Maximizing quality of life in ill animals. Journal of the American Animal Hospital Association, 39(3), 227–235.
Mellor, D.J., Fisher, M.W., & Stafford, K.J. (2008) A Cost-benefit
Analysis of Pain Relief for Farm Animals, in Scientific Assessment
and Management of Animal Pain, (eds D.J. Mellor, P.M. Thornber,
D. Bayvel, et al.), OIE (World Organisation for Animal Health),
Paris, pp. 47–55.

www.pdfgrip.com


8

Section 1 / Introduction and Anatomy, Physiology, and Pathophysiology of Pain


Mellor, D.J., Thornber, P.M., Bayvel, D., & Kahn, S. (2008) Scientific
Assessment and Management of Animal Pain, OIE (World Organisation for Animal Health), Paris.
Melzack, R. (1993) Pain: past, present and future. Canadian Journal
of Experimental Psychology, 47(4), 615.
Morton, C.M. (2005) Application of a scaling model to establish and
validate an interval level pain scale for assessment of acute pain in
dogs. American Journal of Veterinary Research, 66(12), 2154–2166.
Phillips, C. (2008) Pain As An Animal Welfare Issue, in Scientific
Assessment and Management of Animal Pain, (eds D.J. Mellor,
P.M. Thornber, D. Bayvel, et al.), OIE (World Organisation for Animal Health), Paris, pp. 38–46.
Phillips, C. (2002) Environmental perception and cognition in Cattle
Behaviour and Welfare, 2nd edn (ed. C. Phillips), Blackwell Science,
Oxford, pp. 49–61.
Phillips, C.J., Wojciechowska, J., Meng, J., & Cross, N. (2009) Perceptions of the importance of different welfare issues in livestock
production. Animal, 3(8), 1152–1166.
Raekallio, M., Heinonen, K.M., Kuussaari, J., & Vainio, O. (2003) Pain
alleviation in animals: attitudes and practices of Finnish veterinarians. Veterinary Journal, 165(2), 131–135.
Roughan, J.V. & Flecknell, P.A. (2003) Evaluation of a short duration
behaviour-based post-operative pain scoring system in rats. European Journal of Pain (London, England), 7(5), 397–406.
Rushen, J. & Passill´e, A.M.D. (2009) The Importance of Good Stockmanship and Its Benefits for the Animals, CABI, Wallingford, UK.
Rutherford, K.M.D. (2002) Assessing pain in animals. Animal Welfare,
11, 31–53.
Stafford, K.J. & Mellor, D.J. (2009) Painful Husbandry Procedures in
Livestock and Poultry, CABI, Wallingford, UK.
Stafford, K.J. & Mellor, D.J. (2005) The welfare significance of the
castration of cattle: a review. New Zealand Veterinary Journal, 53(5),
271–278.
Stafford, K.J. & Mellor, D.J. (2011) Addressing the pain associated
with disbudding and dehorning in cattle. Applied Animal Behaviour
Science, 135(3), 226–231.

Stookey, J.M. (2005) The veterinarian’s role in controlling pain in farm
animals. The Canadian Veterinary Journal. La Revue V´et´erinaire
Canadienne, 46(5), 453.
Sutherland, M.A. & Tucker, C.B. (2011) The long and short of it: a
review of tail docking in farm animals. Applied Animal Behaviour
Science, 135(3), 179–191.
Thomsen, P.T., Gidekull, M., Herskin, M.S., et al. (2010) Scandinavian bovine practitioners’ attitudes to the use of analgesics in cattle.
Veterinary Record, 167(7), 256–258.
Tranquilli, W.J., Grimm, K.A., & Lamont, L.A. (2004) Pain Management for the Small Animal Practitioner, 2nd edn, Teton NewMedia,
Jackson, WY.
Vickers, K.J., Niel, L., Kiehlbauch, L.M., & Weary, D.M. (2005) Calf
response to caustic paste and hot-iron dehorning using sedation with

and without local anesthetic. Journal of Dairy Science, 88(4), 1454–
1459.
Vi˜nuela-Fern´andez, I., Jones, E., Welsh, E.M., & Fleetwood-Walker,
S.M. (2007) Pain mechanisms and their implication for the management of pain in farm and companion animals. Veterinary Journal
174(2), 227–239.
Walker, K.A., Duffield, T.F., & Weary, D.M. (2011) Identifying and
preventing pain during and after surgery in farm animals. Applied
Animal Behaviour Science, 135(3), 259–265.
Weary, D.M. & Fraser, D. (2008) Identifying Pain in Farm Animals,
in Scientific Assessment and Management of Animal Pain, (eds D.J.
Mellor, P.M. Thornber, D. Bayvel, et al.), OIE (World Organisation
for Animal Health), Paris, pp. 157–171.
Weary, D.M., Niel, L., Flower, F.C., & Fraser, D. (2006) Identifying
and preventing pain in animals. Applied Animal Behaviour Science,
100(1–2), 64–76.
Webster, A.B. & Fletcher, D.L. (2004) Assessment of the aversion of
hens to different gas atmospheres using an approach-avoidance test.

Applied Animal Behaviour Science, 88(3), 275–287.
Whay, H.R., Webster, A.J., & Waterman-Pearson, A.E. (2005)
Role of ketoprofen in the modulation of hyperalgesia associated with lameness in dairy cattle. Veterinary Record, 157(23),
729–733.
Whay, H.R. & Huxley, J.N. (2005) Pain relief in cattle: a practitioner’s
perspective. Cattle Practice, 13(2), 81–85.
Whay, H.R. & Main, D.C.J. (2009) Improving Animal Welfare: Practical Approaches for Achieving Change, CABI, Wallingford, UK.
Whiting, T.L. (2005) Hot iron branding - not a reasonable requirement for international trade in live ruminants. Canadian Veterinary
Journal, 46(11), 1042–1046.
Williams, V.M., Lascelles, B.D.X., & Robson, M.C. (2005) Current
attitudes to, and use of, peri-operative analgesia in dogs and cats
by veterinarians in New Zealand. New Zealand Veterinary Journal,
53(3), 193–202.
Wiseman-Orr, M., Nolan, A.M., Reid, J., & Scott, E.M. (2004) Development of a questionnaire to measure the effects of chronic pain on
health-related quality of life in dogs. American Journal of Veterinary
Research, 65(8), 1077–1084.
Wiseman-Orr, M., Scott, E.M., Reid, J., et al. (2006) Validation of a
structured questionnaire as an instrument to measure chronic pain in
dogs on the basis of effects on health-related quality of life. American
Journal of Veterinary Research, 67(11), 1826–1836.
Wojciechowska, J.I., Hewson, C.J., Stryhn, H., Guy, N.C., Patronek,
G.J, Timmons, V. (2005) Development of a discriminative questionnaire to assess nonphysical aspects of quality of life of dogs.
American Journal of Veterinary Research, 66(8), 1453–1460.
Yazbek, K.V.B. & Fantoni, D.T. (2005) Validity of a health-related
quality-of-life scale for dogs with signs of pain secondary to cancer.
Journal of the American Veterinary Medical Association, 226(8),
1354–1358.

www.pdfgrip.com



2
Anatomy, Physiology, and Pathophysiology
of Pain
Yael Shilo and Peter J. Pascoe

Projection : the conveyance of nociceptive information through the
spinal cord to the brain (to the brainstem and thalamus and then
to the cortex).
Perception: the integration of the nociceptive information by the
brain, or, in other words, the overall conscious, emotional experience of pain (Muir & Woolf, 2001; Westlund, 2005; Muir,
2009).

Pain in animals has been defined as “an aversive sensory and emotional experience representing an awareness by the animal of damage or threat to the integrity of its tissues; it changes the animal’s
physiology and behavior to reduce or avoid damage, to reduce the
likelihood of recurrence, and to promote recovery” (Molony &
Kent, 1997).
The ability to react to environmental change is crucial for the
survival of an organism, and an essential prerequisite is the capacity to detect and respond to aversive stimuli. Primary afferent nerve
fibers provide information to the central nervous system (CNS)
about the environment and also about the state of the organism
itself. Incoming non-noxious input from the periphery is important
for discerning fine discriminative touch, pressure, and position in
space. Most animals have dedicated sensory afferents that respond
to noxious stimuli. These nociceptive afferents are described by the
International Association for the Study of Pain (IASP) as “preferentially sensitive to a noxious stimulus or to a stimulus which would
become noxious if prolonged” (Wall et al., 2006; Smith & Lewin,
2009). Information about a noxious event in the periphery can initiate a protective reflexive withdrawal event (Westlund, 2005; Smith
& Lewin, 2009).
Nociception, derived from the Latin nocere meaning “to

hurt/harm,” is the name given to the process by which organisms
detect potentially or actually damaging stimuli and the transmission of that information to the brain. It is important to differentiate
nociception from pain, which always encompasses an emotional
component. Nociceptor activation in and of itself does not necessarily result in pain (Julius & Basbaum, 2001; Muir & Woolf, 2001;
Smith & Lewin, 2009; Basser, 2012).
Noxious input is transmitted to the brain through specialized
receptors, fibers, and neurons, and processing occurs at many levels
(Figure 2.1). Sensory processing includes

NOCICEPTORS
Activation of nociceptors requires that adequate stimuli depolarize
peripheral terminals (producing a receptor potential) with sufficient
amplitude and duration. This ensures that despite any attenuation
and slowing of the action potential (by passive propagation), information such as stimulus intensity will be encoded in the resulting
train of impulses (Dubin & Patapoutian, 2010).
Nociceptive neurons that detect chemical stimuli have a distinct
expression of ion channel systems or transduction channels, including transient receptor potential (TRP) ion channels, acid-sensing ion
channels (ASIC), purinoceptors, serotonin receptors, and sodium,
calcium, and potassium channels (Wall et al., 2006). Agents such
as protons or capsaicin directly depolarize nociceptive neurons by
triggering the opening of cation channels permeable to sodium
and/or calcium. In contrast, agents such as bradykinin and nerve
growth factor (NGF) act on G protein-coupled receptors and receptor tyrosine kinase, respectively, to initiate intracellular signaling
cascades that, in turn, sensitize depolarizing cation channels to their
respective physical or chemical regulators. Other agents, such as
glutamate, acetylcholine (ACh), and adenosine triphosphate (ATP),
activate ion channels and G-protein-coupled receptors to produce
a spectrum of direct and indirect effects on nociceptor membrane
potentials (Caterina et al., 2005). This chapter will focus on several
important transduction channels; however, it is beyond the scope

of this chapter to discuss all of these.

Transduction: the conversion of noxious stimuli into an action
potential at the level of the specialized receptors or free nerve
endings.
Transmission: the propagation of the action potentials by primary
afferent neurons to the spinal cord.
Modulation: the process by which nociceptive information is augmented or inhibited.

Transient Receptor Potential Ion Channel
The TRPs have emerged as a family of principal transducing channels on sensory neurons, and are classified according to their primary amino acid sequence (rather than according to their selectivity
or ligand affinity), as their properties are heterogeneous and their

Pain Management in Veterinary Practice, First Edition. Edited by Christine M. Egger, Lydia Love and Tom Doherty.
C 2014 John Wiley & Sons, Inc. Published 2014 by John Wiley & Sons, Inc.

9

www.pdfgrip.com