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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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The National Academy of Sciences is a private, nonprofit, self-perpetuating society of distin- guished scholars engaged in scientific and engineering research, dedicated to the furtherance of science and technology and to their use for the general welfare. Upon the authority of the char- ter granted to it by the Congress in 1863, the Academy has a mandate that requires it to advise the federal government on scientific and technical matters. Dr. Ralph J. Cicerone is president of the National Academy of Sciences. The National Academy of Engineering was established in 1964, under the charter of the National Academy of Sciences, as a parallel organization of outstanding engineers. It is auton- omous in its administration and in the selection of its members, sharing with the National Acad- emy of Sciences the responsibility for advising the federal government. The National Academy of Engineering also sponsors engineering programs aimed at meeting national needs, encourages education and research, and recognizes the superior achievements of engineers. Dr. Wm. A. Wulf is president of the National Academy of Engineering. The Institute of Medicine was established in 1970 by the National Academy of Sciences to se- cure the services of eminent members of appropriate professions in the examination of policy matters pertaining to the health of the public. The Institute acts under the responsibility given to the National Academy of Sciences by its congressional charter to be an adviser to the federal government and, upon its own initiative, to identify issues of medical care, research, and educa- tion. Dr. Harvey V. Fineberg is president of the Institute of Medicine. The National Research Council was organized by the National Academy of Sciences in 1916 to associate the broad community of science and technology with the Academy’s purposes of furthering knowledge and advising the federal government. Functioning in accordance with gen- eral policies determined by the Academy, the Council has become the principal operating agency of both the National Academy of Sciences and the National Academy of Engineering in provid- ing services to the government, the public, and the scientific and engineering communities. The Council is administered jointly by both Academies and the Institute of Medicine. Dr. Ralph J. Cicerone and Dr. Wm. A. Wulf are chair and vice chair, respectively, of the National Research Council. 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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TABLES AND FIGURES xv 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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