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Committee on Nutrient Requirements of Horses
Board on Agriculture and Natural Resources
Division on Earth and Life Studies
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THE NATIONAL ACADEMIES PRESS • 500 Fifth Street, N.W. • Washington, DC 20001
NOTICE: The project that is the subject of this report was approved by the Governing Board of the National Research
Council, whose members are drawn from the councils of the National Academy of Sciences, the National Academy of
Engineering, and the Institute of Medicine. The members of the committee responsible for the report were chosen for
their special competences and with regard for appropriate balance.
This study was supported by grants from the American Feed Industry Association, the American Paint Horse
Association, the American Quarter Horse Association, the Equine Science Society, the North American Equine
Ranching Information Council, general support of The Animal Nutrition Series provided by The Department of Health
and Human Services (U.S. Food and Drug Administration) under Award No. 223-01-01-2460, and internal National
Research Council funds. Any opinions, findings, conclusions, or recommendations expressed in this publication are
those of the author(s) and do not necessarily reflect the views of the organizations or agencies that provided support
for the project.
Library of Congress Cataloging-in-Publication Data
Nutrient requirements of horses / Committee on Nutrient Requirements of Horses,
Board on Agriculture and Natural Resources, Division on Earth and Life Studies,
National Research Council of the National Academies. — 6th rev. ed.
p. cm.
Includes bibliographical references and index.
ISBN-10: 0-309-10212-X (cloth)
ISBN-10: 0-309-66096-3 (pdf)
ISBN-13: 978-0-309-10212-4 (cloth)
ISBN-13: 978-0-309-66096-9 (pdf)
1. Horses—Nutrition—Requirements. 2. Horses—Feeding and feeds. I. National
Research Council (U.S.). Committee on Nutrient Requirements of Horses.
SF285.5.N37 2007
636.1′0852—dc22
2006030795
Additional copies of this report are available from the National Academies Press, 500 Fifth Street, N.W., Lockbox 285,
Washington, DC 20055; (800) 624-6242 or (202) 334-3313 (in the Washington metropolitan area); Internet,
http://www.nap.edu.
Copyright 2007 by the National Academy of Sciences. All rights reserved.
Printed in the United States of America
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www.national-academies.org
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COMMITTEE ON NUTRIENT REQUIREMENTS OF HORSES
LAURIE M. LAWRENCE, Chair, University of Kentucky, Lexington
NADIA F. CYMBALUK, Linwood Equine Ranch, Brandon, Manitoba, Canada
DAVID W. FREEMAN, Oklahoma State University, Stillwater
RAYMOND J. GEOR, Virginia Polytechnic and State University, Middleburg
PATRICIA M. GRAHAM-THIERS, Virginia Intermont College, Bristol
ANNETTE C. LONGLAND, Institute of Grassland and Environmental Research, Ceredigion,
Wales, United Kingdom
BRIAN D. NIELSEN, Michigan State University, East Lansing
PAUL D. SICILIANO, North Carolina State University, Raleigh
DONALD R. TOPLIFF, West Texas A&M University, Canyon
EDUARDO V. VALDES, Disney’s Animal Kingdom, East Bay Lake, Florida
ROBERT J. VAN SAUN, The Pennsylvania State University, University Park
Staff
AUSTIN J. LEWIS, Study Director
JAMIE S. JONKER, Study Director*
DONNA LEE JAMEISON, Senior Program Assistant**
RUTH S. ARIETI, Project Assistant
External Support
MICHAEL C. BARRY (AgModels, LLC), Computer Programmer
PAULA T. WHITACRE (Full Circle Communications), Editor
*Through June 2004
**Through January 2006
v
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BOARD ON AGRICULTURE AND NATURAL RESOURCES
W. REG GOMES, Chair, University of California, Oakland
SANDRA J. BARTHOLMEY, University of Illinois at Chicago
ROGER N. BEACHY, Donald Danforth Plant Science Center, St. Louis, Missouri
H. H. CHENG, University of Minnesota, St. Paul
BRUCE L. GARDNER, University of Maryland, College Park
JEAN HALLORAN, Consumer Policy Institute/Consumers Union, Yonkers, New York
HANS R. HERREN, Millennium Institute, Arlington, Virginia
KIRK C. KLASING, University of California, Davis
BRIAN W. MCBRIDE, University of Guelph, Guelph, Canada
TERRY L. MEDLEY, E. I. duPont de Nemours & Co., Wilmington, Delaware
ROBERT PAARLBERG, Wellesley College, Watertown, Massachusetts
ALICE N. PELL, Cornell University, Ithaca, New York
BOBBY PHILLS, Florida A&M University, Tallahassee
SONYA B. SALAMON, University of Illinois, Urbana-Champaign
HAL SALWASSER, Oregon State University, Corvallis
PEDRO A. SANCHEZ, The Earth Institute at Columbia University, Palisades, New York
B. L. TURNER, II, Clark University, Worcester, Massachusetts
LAURIAN UNNEVEHR, University of Illinois, Urbana-Champaign
TILAHUN D. YILMA, University of California, Davis
JAW-KAI WANG, University of Hawaii, Honolulu
Staff
ROBIN A. SCHOEN, Director
KAREN L. IMHOF, Administrative Assistant
AUSTIN J. LEWIS, Program Officer
PEGGY TSAI, Research Associate
RUTH S. ARIETI, Project Assistant
vi
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Preface
The domesticated members of the genus Equus (horses, ing of horses since the publication of the previous edition in
ponies, donkeys, mules) are used for many purposes includ- 1989. New information, previously existing information,
ing competition, recreation, entertainment, transportation, and previous recommendations have been considered in the
farm and ranch work, and even therapy. Several nondomes- process of determining requirements. In some cases, authors
ticated species of Equus are maintained in zoological parks of papers on specific subjects were contacted for clarifica-
or are the focus of conservation efforts. The demand for in- tion. In addition a few data sets were obtained for some
formation relating to the nutrition and feeding management areas (growth) to augment existing values. In most cases
of horses, ponies, and their relatives has grown with the pop- these data sets were from a graduate thesis so were pub-
ularity of these animals and with the increased interest in lished in some format. Some areas of equine nutrition have
nutrition in general. received little study from the scientific community.
The Sixth Revised Edition of the Nutrient Requirements Therefore, data from other animals were reviewed for appli-
of Horses is a project of the Board on Agriculture and cability when studies using horses were not available. Most
Natural Resources of the National Academies. This docu- recent research has used horses of light horse breeding (such
ment was produced from the work of a committee appointed as Thoroughbreds, Quarter horses, Standardbreds, and
in February 2004. The committee accepted input from stake- Arabians). Several older studies used ponies. Very little re-
holders and sponsors during several public information ses- cent information is available for draft breeds, and, similarly,
sions and from a public website. The purpose of this publi- few studies have compared draft breeds, light horse breeds,
cation is to review the existing scientific literature relating to and pony breeds. Users should recognize that many recom-
the nutrition and feeding of horses and to summarize the in- mendations for ponies and draft horses have been extrapo-
formation relating to nutrient requirements of horses of var- lated from data obtained using light horses. Therefore, it is
ious physiological classes. The publication is accompanied suggested that the recommendations for ponies and draft
by a web-based computer program. The computer program horses be applied with discretion. Several sections of the
will calculate nutrient requirements of domestic horses and text provide information on how body size might affect re-
ponies of specific weights and physiological classes. quirements for specific nutrients.
Included in this edition of this publication is a discussion of A central purpose of this publication was to evaluate the
the nutrition and feeding of donkeys, mules, and captive recommendations in the previous edition in light of new in-
equids. formation about the nutrient requirements of horses and
A complete review of information pertaining to the di- to revise nutrient requirements when appropriate. Several
gestive physiology of the horse was outside of the charge mathematical equations have been derived to provide more
given to this committee for this report. However, an under- dynamic estimates of requirements for some physiological
standing of the anatomy and physiology of the equine di- states including growth, gestation, and exercise. The re-
gestive tract will be helpful in interpreting and applying quirements shown in the tables provide recommendations
many of the recommendations contained in this publication. for broad classifications of horses, whereas the computer
Reviews of various aspects of equine digestive physiology program allows some flexibility in calculating the nutrient
may be found in veterinary and animal science texts cited in requirements for a specific animal. The values listed in this
this publication. document represent the committee’s best estimates of the
A great deal of new information has appeared in the sci- nutrient requirements of horses of different physiological
entific literature on topics related to the nutrition and feed- states. The required amounts of many nutrients have been
vii
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determined using average values for nutrient availability in quirement, such as individual variation, breed, feed composi-
common horse feeds. Users of the document and the associ- tion, and environment. It is not possible for the committee to
ated computer program may choose to recalculate require- predict every combination of variables that could influence
ments when they possess specific information on nutrient the nutrient requirements of a specific animal. Therefore, it is
availability for the rations being fed in practice. The com- incumbent upon the user to accurately assess the factors that
mittee recognizes that the values suggested here may not could alter requirements and then apply appropriate adjust-
meet the need for all horses in all situations and that adjust- ments accordingly.
ments may be needed for individual horses or to meet spe-
cific production goals. Users of this document will find a
more detailed review of the literature on equine nutrition than Laurie M. Lawrence
in previous editions. The committee has attempted to sum- Chair, Committee on Nutrient
marize information on the factors that might modify a re- Requirements of Horses
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Acknowledgments
This report has been reviewed in draft form by persons to endorse the conclusions or recommendations, nor did
chosen for their diverse perspectives and technical expertise they see the final draft of the report before its release. The
in accordance with procedures approved by the National review of this report was overseen by R. L. Baldwin, Jr.,
Research Council’s Report Review Committee. The purpose University of California, Davis. Appointed by the National
of this independent review is to provide candid and critical Research Council, he was responsible for making certain
comments that will assist the institution in making its pub- that an independent examination of this report was carried
lished report as sound as possible and to ensure that the re- out in accordance with institutional procedures and that all
port meets institutional standards of objectivity, evidence, review comments were carefully considered. Responsibility
and responsiveness to the study charge. The review com- for the final content of this report rests entirely with the au-
ments and draft manuscript remain confidential to protect thor committee and the institution.
the integrity of the deliberative process. We wish to thank The committee on Nutrient Requirements of Horses
the following for their review of this report: would like to express deep appreciation to all of the spon-
sors that contributed the funds to support this effort.
Joseph J. Bertone, Western University of Health Sponsors for the Sixth Revised Edition of the Nutrient
Sciences, Pomona, CA Requirements of Horses included the American Feed
Manfred Coenen, University of Leipzig, Leipzig, Industry Association (www.afia.org), American Paint Horse
Germany Association (www.apha.com), American Quarter Horse
Patricia A. Harris, Waltham Centre for Pet Nutrition, Association (www.aqha.com), Equine Science Society
Leicestershire, United Kingdom (www.enps.org), general support of The Animal Nutrition
Kenneth W. Hinchcliff, Ohio State University, Series provided by the Department of Health and Human
Columbus, OH Services (U.S. Food and Drug Administration) under Award
Rhonda M. Hoffman, Middle Tennessee State No. 223-01-01-2460 (www.fda.gov/cvm/), and North Amer-
University, Murfreesboro, TN ican Equine Ranching Information Council (www.naeric.
James H. Jones, University of California, Davis, CA org). The funding for this project was necessary to support
Edgar A. Ott, University of Florida, Gainesville, FL the travel and communications costs of the committee dur-
(retired) ing the course of its work, as well as the work of the Na-
Joe D. Pagan, Kentucky Equine Research, tional Research Council staff who organized meetings,
Versailles, KY maintained the website, and compiled the draft and final
Sarah L. Ralston, Rutgers University, New documents.
Brunswick, NJ The committee would also like to thank all of the indi-
Judith A. Reynolds, ADM Alliance Nutrition, viduals who helped to make this project a reality. Charlotte
Quincy, IL Kirk Baer, former Board on Agriculture and Natural
Virginia Rich, Rich Equine Nutritional Consulting, Resources (BANR) director, was instrumental in developing
Eads, TN the original proposal that received approval from the Board
Ronald E. Rompala, Blue Seal Feeds, Londonderry, NH on Agriculture and Natural Resources in August of 2003.
Ms. Baer was also integrally involved in developing the
Although the reviewers listed above have provided many funding for this project, as were Dr. Donald Topliff, West
constructive comments and suggestions, they were not asked Texas A&M University, and Dr. Randy Robbins, chairman
ix
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x ACKNOWLEDGMENTS
of the American Feed Industry Association (AFIA) annual meetings in 2004. The committee also thanks Dr.
Specialty Committee. Austin Lewis was a tireless manager Mary Beth Hall and Dr. George Fahey, who provided advice
as the program officer assigned to this committee. The com- on topics related to carbohydrate classification and analysis.
mittee sincerely appreciates the wealth of experience and We would also like to thank the American Feed Industry
perpetual optimism that Dr. Lewis brought to this project. Association for providing input at an open session of the ini-
The work of this committee could not have been completed tial meeting of our committee. The committee is indebted to
without the able assistance of Donna Jameison, senior pro- Michael Barry, who compiled the computer program that ac-
gram assistant and Ruthie Arieti, project assistant. Finally, companies this report and provided invaluable advice to the
we would like to thank Robin Schoen, who replaced Ms. committee. Finally the committee would like to thank their
Baer as BANR director in 2004. families, students, colleagues, and home institutions. Without
In the process of planning, researching, and writing this their patience and willingness to accept additional responsi-
document, the committee obtained input and advice from sev- bilities, this project would not have been accomplished. This
eral sources. We would like to thank Kentucky Equine list of acknowledgements would not be complete without the
Research, Inc. and the American Society of Animal Science recognition of the work of previous committees. We hope that
for allowing us to present public information sessions at their our efforts will do justice to the tradition of excellence estab-
lished by those who came before us.
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Contents
SUMMARY 1
1 ENERGY 3
2 CARBOHYDRATES 34
3 FATS AND FATTY ACIDS 44
4 PROTEINS AND AMINO ACIDS 54
5 MINERALS 69
6 VITAMINS 109
7 WATER AND WATER QUALITY 128
8 FEEDS AND FEED PROCESSING 141
9 FEED ADDITIVES 183
10 FEED ANALYSIS 203
11 FEEDING BEHAVIOR AND GENERAL CONSIDERATIONS
FOR FEEDING MANAGEMENT 211
12 UNIQUE ASPECTS OF EQUINE NUTRITION 235
13 DONKEYS AND OTHER EQUIDS 268
14 RATION FORMULATION AND EVALUATION 280
15 COMPUTER MODEL TO ESTIMATE REQUIREMENTS 285
16 TABLES 293
NUTRIENT REQUIREMENT TABLES 294
FEED COMPOSITION TABLES 304
xi
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xii CONTENTS
COMPOSITION OF MARE’S MILK TABLES 311
TABLE OF CONVERSIONS 315
APPENDIXES
A COMMITTEE STATEMENT OF TASK 317
B ABBREVIATONS AND ACRONYMS 319
C COMMITTEE MEMBER BIOGRAPHIES 323
D BOARD ON AGRICULTURE AND NATURAL RESOURCES PUBLICATIONS 325
INDEX 327
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Tables and Figures
TABLES
1-1 Summary of Studies that Measured Heat Production in Horses at Maintenance 8
1-2 Three Proposed Levels of Digestible Energy Intake for Maintenance Mcal/d
in Adult Horses as Compared to the Previous Recommendation 9
1-3 Lower and Upper Critical Temperatures in Horses 11
1-4 Effect of Age on the Amount of Digestible Energy (DE) Required per
Kilogram of Gain for Growing Horses 14
1-5 Summary of Estimates of the Relationship Between Age and Percentage of
Mature Body Weight in Growing Horses 14
1-6 Body Weight Predicted by Equation 1-3 and Expected Mature Body Weight
and Body Weight Estimated in the Previous NRC (1989) for Growing Horses 15
1-7 A Condition Scoring System for Horses 21
1-8 Estimated Oxygen Consumption and Net Energy Utilization of a 500-kg
Horse Ridden by a 50-kg Rider at Various Heart Rates 24
1-9 Hypothetical Weekly Net Energy Expenditure (above maintenance) of a
500-kg Horse Used for Recreational Riding 25
1-10 Example Weekly Workloads of Horses in the Light, Moderate, Heavy,
and Very Heavy Exercise Categories 26
1-11 Estimated Increase in Digestible Energy (DE) Intake Necessary to Change
the Condition Score of a 500-kg Horse from 4 to 5 28
2-1 Neutral Detergent Fiber (NDF), Nonfiber Carbohydrate (NFC), and Nonstructural
Carbohydrate (NSC) Composition of Selected Feedstuffs on a Dry Matter Basis 35
2-2 Carbohydrate Composition (dry matter basis) of Selected Feed Ingredients 36
7-1 Estimated Water Needs of Horses 131
7-2 Guidelines for Total Dissolved Solids (TDS) or Total Soluble Salts (TSS) 135
7-3 Water Hardness Guidelines 136
7-4 Generally Considered Safe Upper Level Concentrations (mg/L) of Some
Potentially Toxic Nutrients and Contaminants in Water for Horses 137
8-1 Estimated Voluntary Fresh Matter Intake (VFMI) and Voluntary Dry Matter Intake
(VDMI) of Fresh Herbage 145
8-2 Contents of Digestible Energy and Protein and Apparent Dry Matter and
Protein Digestibilities of Various Fresh Forages by Horses 146
8-3 Estimated Voluntary Dry Matter Intake of Various Hays by Horses and Ponies 151
8-4 Apparent Dry Matter, Organic Matter, Energy, Protein, and Fiber Digestibilities
of Various Hays in Horses 153
8-5 Voluntary Dry Matter Intakes (VDMI) of Ensiled Forages by Ponies and Horses 155
xiii
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xiv TABLES AND FIGURES
8-6 Apparent Dry Matter, Organic Matter, Protein, and Energy Digestibility of
Ensiled Forages by Ponies 155
8-7 Fatty Acid Composition of Some Fats and Oils Available for Use in
Equine Feeds 163
8-8 Amino Acid Contents of Some Horse Feed Ingredients and Forages 164
8-9 Supplemental Vitamin Sources: Chemical Form, Vitamin Activity, Physical
Form, and Applications 168
8-10 Comparison of Small Intestinal Starch Digestibility of Processed Corn 169
8-11 Comparison of Small Intestinal Starch Digestibility of Processed Oats 170
8-12 Comparison of Small Intestinal Starch Digestibility of Processed Oats
and Barley 170
8-13 Comparison of Small Intestinal Starch Digestibility of Grains 171
8-14 Comparison of Small Intestinal Starch Digestibility of Grains Fed at
Moderate Intakes 171
8-15 Comparison of Small Intestinal Nitrogen Digestibility of Diets Containing
Micronized and Crimped Oats and Sorghum 172
8-1A Selected Terminology Related to Feed Identification and Processing 173
9-1 AAFCO Feed Ingredient Definitions for Organic Mineral Products 195
11-1 Summary of Ranges of Reported Average Voluntary Dry Matter Intakes
(AVDMI) of Selected Feedstuffs 214
11-2 Foraging Criteria by Horses Provided Various Feeds 215
12-1 Guidelines for Feeding Horses during Cold Weather 238
12-2 Guidelines for Feeding Horses during Hot Weather 239
12-3 Grasses That May Contain Excessive Amounts of Oxalates 251
13-1 Comparative Energy Expenditures in Horses and Donkeys 271
13-2 Chemical Composition (g/100 ml) of Milk of Donkeys and Other Animal Species 273
13-3 Daily Rations for Adult Donkeys 273
13-4 Estimated Nutrient Intakes for Adult Donkeys Consuming Diets Based on
Poor or Good Quality Forage (dry matter basis) 273
13-5 Wild Equids Found in Zoological Parks 274
13-6 Diet Ingredients and Nutrient Composition (dry matter basis) of Typical Diets
Fed to Wild Equids in Zoological Parks 275
13-7 Digestibility Coefficients, Organic Matter (OM) Intake, OM Extraction, and
Cell Wall Extraction by Wild Equids 276
14-1 Feed Ingredient Nutrient Composition (dry matter basis) 281
14-2 Example Estimates of Nutrient Requirements 281
14-3 Comparison of Nutrient Intake and Estimated Requirements 282
14-4 Feed Ingredient Nutrient Composition 282
14-5 Example Intake Limit (as-fed basis) and Estimated Nutrient Requirements 282
14-6 Comparison of Nutrient Intake and Estimated Requirements 282
14-7 Targeted Nutrient Concentration of the Example Concentrate (dry matter) 282
14-8 Nutrient Composition of Feedstuffs (100% dry matter basis) 283
14-9 Nutrient Concentration of an 80:20 Mix of Grain One and Grain Two 283
14-10 Comparison of the Grain Mix and Protein Supplement
with the Targeted Nutrient Densities for the Concentrate 283
14-11 Comparison of the Grain Mix, Protein Supplement, and
Mineral One with the Targeted Nutrient Densities for the Concentrate 283
14-12 Comparison of the Final Formulation with the Targeted
Nutrient Densities for the Concentrate 284
14-13 Formulated Concentrate Constituents on a Dry Matter and As-Fed Basis 284
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xv
TABLES AND FIGURES
16-1 Daily Nutrient Requirements of Horses (Mature Body Weight of 200 kg) 294
16-2 Daily Nutrient Requirements of Horses (Mature Body Weight of 400 kg) 296
16-3 Daily Nutrient Requirements of Horses (Mature Body Weight of 500 kg) 298
16-4 Daily Nutrient Requirements of Horses (Mature Body Weight of 600 kg) 300
16-5 Daily Nutrient Requirements of Horses (Mature Body Weight of 900 kg) 302
16-6 Nutrient Composition of Selected Feedstuffs 304
16-7 Compositions of Inorganic Mineral Sources on a 100% Dry Matter Basis 308
16-8 Research Findings on Composition of Mare’s Milk (1989 NRC) 311
16-9 Research Findings on Composition of Mare’s Milk (Since 1989 NRC) 313
16-10 Conversion Factors 315
FIGURES
1-1 Energy flow diagram 3
1-2 Comparison of digestible energy (DE) intakes of growing horses as predicated
by NRC (1989) and actual intakes reported in the literature 11
1-3 Effect of age on digestible energy for maintenance (DEm) (Kcal/Kg BW)
in growing horses 12
1-4 Relationship between age (in months) and the amount of digestible energy
(DE) required above maintenance per kilogram of gain in growing horses 13
1-5 Digestible energy (DE) intakes of growing horses as predicted by equation 1-4
and actual intakes reported in the literature 16
1-6 Fetal weight during gestation as a percentage of birth weight 17
1-7 Comparison of two equations (1-5b and 1-5d) that predict fetal weight as a
percentage of birth weight 18
4-1 Regression of means from nitrogen digestibility studies for sedentary horses 56
4-2 Regression of means from nitrogen digestibility studies evaluating foregut
vs. total tract digestibility of nitrogen 56
4-3 Relationship between calculated available protein (AP) intake and digestible
protein (DP) intake 57
4-4 Linear and nonlinear regression for nitrogen balance for horses at
maintenance 58
10-1 Fractionation of plant carbohydrates and related compounds 206
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