A Review of Methods for
Detecting
Soreness
in Horses

Committee on a Review of Methods for Detecting Soreness in Horses

Board on Agriculture and Natural Resources

Division on Earth and Life Studies

A Consensus Study Report of

THE NATIONAL ACADEMIES PRESS
Washington, DC
www.nap.edu

THE NATIONAL ACADEMIES PRESS 500 Fifth Street, NW Washington, DC 20001

This activity was supported by contracts between the National Academy of Sciences and Tennessee Department of Agriculture, Tennessee Walking Horse Breeders Foundation, U.S. Department of Agriculture - Animal and Plant Health Inspection Service under contract numbers 10003803 and 10005226. Any opinions, findings, conclusions, or recommendations expressed in this publication do not necessarily reflect the views of any organization or agency that provided support for the project.

International Standard Book Number-13: 978-0-309-68374-6
International Standard Book Number-10: 0-309-68374-2
Digital Object Identifier: https://doi.org/10.17226/25949

Additional copies of this publication are available from the National Academies Press, 500 Fifth Street, NW, Keck 360, Washington, DC 20001; (800) 624-6242 or (202) 334-3313; http://www.nap.edu.

Copyright 2021 by the National Academy of Sciences. All rights reserved.

Printed in the United States of America

Suggested citation: National Academies of Sciences, Engineering, and Medicine. 2021. A Review of Methods for Detecting Soreness in Horses. Washington, DC: The National Academies Press. https://doi.org/10.17226/25949.

COMMITTEE ON A REVIEW OF METHODS FOR DETECTING SORENESS IN HORSES

Members

JERRY B. BLACK (Chair), Colorado State University (Emeritus), Texas Tech University

ROBIN FOSTER, Private Consultant, University of Puget Sound, University of Washington

PAMELA EVE GINN, University of Florida, Gainesville

SARAH LE JEUNE, University of California, Davis

BART SUTHERLAND, Private Practitioner, Oxford, Mississippi

TRACY ACE TURNER, Turner Equine Sports Medicine and Surgery, Stillwater, Minnesota

SUSAN L. WHITE, University of Georgia, Athens (Emerita)

Staff

CAMILLA YANDOC ABLES, Study Director

JENNA BRISCOE, Research Associate

SARAH KWON, Senior Program Assistant

Report Editor

ROBERT POOL

BOARD ON AGRICULTURE AND NATURAL RESOURCES

Members

CHARLES W. RICE (Chair), Kansas State University, Manhattan

ARISTOS ARISTIDOU (NAE), Cargill, Inc., Minneapolis, MN

SHANE C. BURGESS, University of Arizona, Tucson

SUSAN CAPALBO, Oregon State University, Corvallis

GAIL CZARNECKI-MAULDEN, Nestlé Purina PetCare, St. Louis, MO

BERNADETTE DUNHAM, Milken Institute of Public Health, George Washington University, Washington, DC

GEBISA EJETA, Purdue University, West Lafayette, IN

JAMES S. FAMIGLIETTI, University of Saskatchewan, Saskatoon, Canada

FRED GOULD (NAS), North Carolina State University, Raleigh

JOHN HAMER, DCVC Bio, San Francisco, CA

DOUGLAS B. JACKSON-SMITH, Ohio State University, Wooster

JAMES W. JONES (NAE), University of Florida, Gainesville

ERMIAS KEBREAB, University of California, Davis

STEPHEN S. KELLEY, North Carolina State University, Raleigh

JAN E. LEACH, Colorado State University, Fort Collins

ROBIN LOUGEE, IBM Research, Yorktown Heights, NY

JILL J. MCCLUSKEY, Washington State University, Richland

KAREN I. PLAUT, Purdue University, West Lafayette, IN

RICARDO SALVADOR, Union of Concerned Scientists, Washington, DC

V. ALARIC SAMPLE, George Mason University, Fairfax, VA

Staff

ROBIN A. SCHOEN, Director

CAMILLA YANDOC ABLES, Senior Program Officer

KARA N. LANEY, Senior Program Officer

JENNA BRISCOE, Research Associate

SARAH KWON, Senior Program Assistant

Acknowledgment of Reviewers

This Consensus Study Report was reviewed in draft form by individuals chosen for their diverse perspectives and technical expertise. The purpose of this independent review is to provide candid and critical comments that will assist the National Academies of Sciences, Engineering, and Medicine in making each published report as sound as possible and to ensure that it meets the institutional standards for quality, objectivity, evidence, and responsiveness to the study charge. The review comments and draft manuscript remain confidential to protect the integrity of the deliberative process.

We thank the following individuals for their review of this report:

Although the reviewers listed above provided many constructive comments and suggestions, they were not asked to endorse the conclusions or recommendations of this report, nor did they see the final draft before its release. The review of this report was overseen by Brian D. Nielsen, Michigan State University, and Barbara Schaal (NAS), Washington University in St. Louis. They were responsible for making certain that an independent examination of this report was carried out in accordance with the standards of the National Academies and that all review comments were carefully considered. Responsibility for the final content rests entirely with the authoring committee and the National Academies.

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Preface

The Tennessee walking horse (TWH) is an integral part of the American culture of the South, where its origins can be traced to the 18th century. The breed evolved out of necessities for horses used for transportation and utility on the farms and plantations of the southern United States and was known for its stamina, smooth gait, and even disposition. During the last century and today the horse has been used primarily for pleasure and show competition. As the popularity of the TWH grew, so did the desire among owners and trainers to showcase its beauty, quality, and athletic abilities at horse show competitions. Unique and natural to the breed is a smooth four-beat “running walk” gait. In the 1950s the accentuated or exaggerated running walk, known as the “big lick” became popular at high-level competitions. The combination of exaggerated high-action step in front and long stride behind is still considered desirable in today’s horse show competitions, and it is often achieved through soring. Soring is the practice of applying a substance or mechanical device to the lower limb of a horse that will create enough pain that the horse will exaggerate its gait to relieve the discomfort. Soring became popular at TWH shows in the mid-20th century, and by 1970 it became enough of a public concern for the welfare of the horse that Congress put into law the Horse Protection Act (HPA). The HPA specifically addresses the practice of soring by prohibiting the showing, exhibition, or sale of TWHs that are found to be sore. Progress has been made, but sadly soring is still being done even after 50 years of HPA enforcement. By all accounts from both the public and equine health and welfare professionals, soring is considered an inhumane practice and must be eliminated.

To the credit of the Tennessee walking horse industry and the U.S. Department of Agriculture (USDA), funding was provided for a National Academies of Sciences, Engineering, and Medicine (the National Academies) committee to conduct a review of the methods for detecting soreness in horses, in hopes of advancing the goal of ultimately eliminating the act of soring in horses and improving the welfare of TWHs.

I want to thank the experienced scientists and clinicians in a variety of equine disciplines who served on the committee for their remarkable dedication to the work involved in preparing this report. Those efforts include hours of literature reviews, multiple committee meetings, working with and learning from numerous presenters who have expertise in various aspects of health and welfare of the horse, and writing working drafts with many edits to make the report readable and of high quality. I also want to thank our wonderful team from the National Academies who worked diligently for many months to keep us on track and gave their total support throughout the entire process. On the committee’s behalf, I especially want to thank our study director, Camilla Yandoc Ables, for her assistance through virtually every aspect of the development of this report. Her leadership, knowledge, and determination to assist the committee in every way possible to produce a report that will significantly contribute to the scientific literature for the welfare of these great horses cannot be understated. The committee would also like to thank the rest of the National Academies team, Robin Schoen, Jenna Briscoe, and Sarah Kwon, for their invaluable assistance to the committee. Special thanks to Rachel Reed, representative of the SHOW HIO, for the horse inspection videos; Paul Stromberg and Lynne Cassone for the slides that helped greatly with the review of the scar rule; and the representatives of the study sponsors, Tom Blankenship and Aaron Rhyner, for all the information and assistance they provided to the committee. Last, I want to thank the numerous scientists, equine professionals, individuals previously with the Animal Care Horse Protection Program at

USDA’s Animal and Plant Health Inspection Service, and members of the public who contributed to the committee’s knowledge and understanding of issues important to the study and ultimately to the industry.

Contents

SUMMARY

1 INTRODUCTION

The Tennessee Walking Horse

The Horse Protection Act of 1970

Purpose of the Study and Committee’s Charge

Committee’s Approach to Its Charge

Organization of the Report

References

2 METHODS USED TO IDENTIFY SORENESS IN WALKING HORSES

The Inspection Process

Horse Inspectors’ Qualifications and Training

Methods Currently Used to Inspect Horses for Soreness

Methods for Detecting Soreness Not Currently Used in Horse Inspections for HPA Enforcement

Recommendations

References

3 NEW AND EMERGING METHODS, APPROACHES, AND TECHNOLOGIES FOR DETECTING PAIN AND ITS CAUSES

Introduction

Variability of Pain Expression

Behavioral Assessment of Pain

Behavioral Indicators of Pain

Physiological Assessment of Pain

Clinical Assessment of Pain

Recommendations

References

4 REVIEW OF THE SCAR RULE FOR DETERMINING COMPLIANCE WITH THE HORSE PROTECTION ACT

The Horse Protection Act and Application of the Scar Rule

Clinical Dermatologic Examination, Microscopic Anatomy of the Skin, and Pertinent Definitions

Microscopic Evaluation of Skin Biopsies of Tennessee Walking Horses Found to Be in Violation of the Scar Rule

Evaluation of the Scar Rule Criteria for Compliance with the Horse Protection Act

Recommendation

References

APPENDIXES

A BIOGRAPHICAL SKETCHES OF COMMITTEE MEMBERS

B OPEN SESSION AND WEBINAR AGENDAS

C THE HORSE PROTECTION ACT OF 1970 — REGULATIONS

LIST OF BOXES, FIGURES, AND TABLES

BOXES

S-1 Statement of Task

1-1 Horse Protection Efforts in the United States (1970 to 2019)

1-2 9 C.F.R. § 11.3 Scar Rule

1-3 Statement of Task

2-1 International Federation for Equestrian Sports Limb Sensitivity Testing Procedure

2-2 Committee’s Observations Based on Videos of Inspections Performed by Designated Qualified Persons

4-1 Ultrasonography to Study Pastern Tissue Injury in Tennessee Walking Horses

FIGURES

2-1a Horse inspection process when a designated qualified person (DQP) is present at a horse show (no veterinary medical officer)

2-1b Horse inspection process when a designated qualified person (DQP) and a veterinary medical officer (VMO) are present at a horse show

2-2 Horse inspection process when there is one VMO at a horse show

2-3 Horse inspection process when there are two veterinary medical officers (VMOs) at a horse show

2-4 Thermographic images of horse palmar pastern

2-5 Thermographic images of fore pasterns of two different horses

2-6 Radiographs showing hoof wall width and sole depth

2-7 Radiographs of illegal substances inside hoof packages

2-8 Radiograph showing a rotation of >5 degrees

2-9 Radiographs of a lateral view of an illegal metal pad and a legal weight on the sole of the package and a dorsal palmar view of an illegal metal pad and a legal weight on the sole of the package

3-1 Horse Grimace Scale

3-2 “Pain face” diagram for clinical use

3-3 Photographs captured from videotaped standing inspections by designated qualified persons before (left) and during (right) palpation

4-1 Diagram of the skin illustrating the types of endogenous and exogenous factors that can affect the integrity of the skin

4-2 Microscopic anatomy of the skin

4-3 Examples of primary and secondary lesions of the skin

4-4 Example of the evolution of a lesion over time

4-5a Photomicrograph of the caudal pastern of the skin of a horse included in the Stromberg study

4-5b Photomicrograph of the normal skin of the caudal pastern of a horse

4-6 Lichenified skin on the mane of a horse

4-7 Microscopic image of lichenification

4-8 Normal appearance of the skin of the palmar aspect of a horse

4-9 Pastern of a chronically sored horse in violation of the scar rule

TABLES

3-1 Score Sheet for the EQUUS-COMPASS Composite Pain Scale

3-2 Obel Laminitis Grades for Rating a Horse’s Withdrawal from Pressure/Palpation of Localized Area

3-3 Facial Features of Horses in Pain

3-4 Score Sheet for the Equine Utrecht University Scale for Facial Assessment of Pain (EQUUS-FAP) Scale

3-5 Behavioral Assessment Scales Basis, Pros, and Cons

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