Table Of Contenti
Ruminant Nitrogen Usage
Subcommittee on Nitrogen Usage in Ruminants
Committee on Animal Nutrition
Board on Agriculture
National Research Council
NATIONAL ACADEMY PRESS
Washington, D.C. 1985
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ii
National Academy Press 2101 Constitution Avenue, NW Washington, DC 20418
NOTICE: The project that is the subject of this report was approved by the Governing Board of the National Research Council, whose mem-
bers 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 report has been reviewed by a group other than the authors according to procedures approved by a Report Review Committee con-
sisting of members of the National Academy of Sciences, the National Academy of Engineering, and the Institute of Medicine.
The National Research Council was established by the National Academy of Sciences in 1916 to associate the broad community of sci-
ence and technology with the Academy's purposes of furthering knowledge and of advising the federal government. The Council operates in
accordance with general policies determined by the Academy under the authority of its congressional charter of 1863, which establishes the
Academy as a private, nonprofit, self-governing membership corporation. The Council has become the principal operating agency of both the
National Academy of Sciences and the National Academy of Engineering in the conduct of their services to the government, the public, and
the scientific and engineering communities. It is administered jointly by both Academies and the Institute of Medicine. The National
Academy of Engineering and the Institute of Medicine were established in 1964 and 1970, respectively, under the charter of the National
Academy of Sciences.
This study was supported by the Agricultural Research Service of the U.S. Department of Agriculture, by the Center for Veterinary
Medicine, Food and Drug Administration of the U.S. Department of Health and Human Services, and by the American Feed Industry Associ-
ation, Inc.
Library of Congress Cataloging in Publication Data
National Research Council (U.S.) Subcommittee on Nitrogen Usage in Ruminants.
Ruminant nitrogen usage.
Bibliography: p.
Includes index.
1. Nitrogen in animal nutrition. 2. Ruminants—Feeding and feeds. I. Title.
SF98.N5N37 1985 636.2 08 52 85–21682
ISBN 0-309-03597-X
Copyright © 1985 by the National Academy of Sciences
No part of this book may be reproduced by any mechanical, photographic, or electronic process, or in the form of a phonographic recording,
nor may it be stored in a retrieval system, transmitted, or otherwise copied for public or private use, without written permission from the pub-
lisher, except for purposes of official use by the United States government.
First Printing, October 1985 Second Printing, December 1991 Printed in the United States of America
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PREFACE iii
Preface
The Subcommittee on Nitrogen Usage in Ruminants of the Committee on Animal Nutrition was instructed to address the
increasingly apparent need to bring together the newer data and knowledge on ruminant nitrogen metabolism in such a way
that a systematic, quantitative approach to the rationing of ruminants for nitrogen could be set forth.
The charge to the Subcommittee included the need to produce a report that could be used by producers, technical service
people in the feed and related industries, as well as extension personnel, teachers, students, and research scientists. The
document was to serve as a base, upon which future refinement could be built, in such a way that continual improvement
would occur. Whereas many countries around the world have proposed nitrogen or protein systems for ruminants, this effort
was to evaluate each of those and incorporate those biological principles that are common to all ruminants.
During the course of the deliberations of this subcommittee, invaluable help has been provided by the staff of the Board
on Agriculture, especially Selma P.Baron and Philip Ross. This has been a most complex task, and without the
encouragement and assistance of these people, the document contained herein would not have emerged.
We especially appreciate the efforts of Werner G. Bergen who reviewed this report for the Committee on Animal
Nutrition and provided useful information for consideration by the authoring subcommittee. Also, the encouragement of
Joseph P.Fontenot and Robert R. Oltjen has been greatly appreciated; the former also served as the reviewer for the Board on
Agriculture. As a result, we feel that we have produced a document that meets the stated objectives of the original charge.
The assistance of Zaira Batchelder, Alice Jones, and Elaine Wylie in the preparation of drafts and manuscripts is gratefully
acknowledged.
Subcommittee on Nitrogen Usage in Ruminants
LEONARD S.BULL, Chairman
University of Vermont
WILLIAM CHALUPA
University of Pennsylvania
FREDRIC N.OWENS
Oklahoma State University
LARRY D.SATTER
USDA, Dairy Forage Research Center
CHARLES J.SNIFFEN
Cornell University
ALLEN H.TRENKLE
Iowa State University
DALE R.WALDO
USDA, Agricultural Research Service
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PREFACE iv
COMMITTEE ON ANIMAL NUTRITION
DUANE E.ULLREY, Chairman, Michigan State University
FRANK AHERNE, University of Alberta
RICHARD E.AUSTIC, Cornell University
JIMMY H.CLARK, University of Illinois
RICHARD D.GOODRICH, University of Minnesota
GEORGE E.MITCHELL, JR., University of Kentucky
JAMES G.MORRIS, University of California-Davis
ROBERT R.SMITH, USDI, Fish and Wildlife Service
DALE R.WALDO, USDA, Agricultural Research Service
SELMA P.BARON, Staff Officer
BOARD ON AGRICULTURE
WILLIAM L.BROWN, Pioneer Hi-Bred International, Inc., Chairman
JOHN A.PINO, Inter-American Development Bank, Vice Chairman
PERRY L.ADKISSON, Texas A&M University
C.EUGENE ALLEN, University of Minnesota
LAWRENCE BOGORAD, Harvard University
ERIC L.ELLWOOD, North Carolina State University
JOSEPH P.FONTENOT, Virginia Polytechnic Institute and State University
RALPH W.F.HARDY, Cornell University and BioTechnica International, Inc.
ROGER L.MITCHELL, University of Missouri
CHARLES C.MUSCOPLAT, Molecular Genetics, Inc.
ELDOR A.PAUL, University of California-Berkeley
VERNON W.RUTTAN, University of Minnesota
JAMES G.TEER, Welder Wildlife Foundation
JAN VAN SCHILFGAARDE, USDA, Agricultural Research Service
VIRGINIA WALBOT, Stanford University
CHARLES M.BENBROOK, Executive Director
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CONTENTS v
Contents
Introduction 1
Parameter Names for Describing Protein Metabolism 4
Comparison of New Protein Systems for Ruminants 7
Feed Evaluation 23
Degradation of Dietary Crude Protein in the Reticulo-Rumen 28
Microbial Growth 37
Digestion and Absorption in the Small Intestine 46
Nitrogen Metabolism in the Large Intestine 53
Nitrogen Metabolism in Tissues 57
Application to Ruminant Feeding 66
References 75
Appendix Tables 87
Index 137
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CONTENTS vi
Figures, Tables, and Appendix Tables
FIGURES
1. Schematic of nitrogen flow in the ruminant 2
2. Schematic diagram of nitrogen flow in the ruminant using symbols developed in this publica- 3
tion
3. Intake protein percentage in dry matter as a function of milk production 17
4. Undegradability of dietary intake protein as a function of milk production 18
5. Undegradability of dietary intake protein as a function of intake protein percentage in dry 18
matter
6. Protein flow into small intestine predicted from the system versus that expected based on the 19
digestible organic matter of the system and the equation of Tamminga and van Hellemond
(1977)
7. Protein flow into small intestine predicted from the system versus that expected based on the 19
digestible organic matter of the system and the equation of Rohr et al. (1979), etc.
8. Protein flow into small intestine predicted from the system versus that expected based on the 20
digestible organic matter plus undegraded protein intake of the system and the equation of
Journet and Vérité (1979)
9. Fecal protein as a function of intake protein percentage in dry matter 20
10. Fecal protein as a function of milk production 21
11. Urinary protein as a function of milk production 21
12. Milk protein as a function of milk production 22
13. Simplified model showing flow of amino acids in mammalian metabolism 58
TABLES
1. Assumed Factors in the Availability of Absorbed Protein to Ruminants 9
2. Assumed Factors in the Requirement of Absorbed Protein by Ruminants for Maintenance, 10
Milk Production, and Body Weight Change
3. Dry Matter Intakes and Energy Standards When Energy Concentration Varied as Used in 16
Comparison and Challenge of Protein Systems
4. Additional Assumptions of Protein and Energy Relationships 17
5. Interrelationship Among In Vivo Responses, Undegradability Assays, and Insolubility Assays 24
6. Tentative Estimates of Undegraded Protein for Common Feedstuffs When Total Dry Matter 33
Intake is in Excess of 2 Percent of Body Weight
7. Composition of Microbial Cells 38
8. Regressions for Dairy Cattle, Sheep, and Beef Cattle 42
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CONTENTS vii
9. Empirical Prediction Models of Microbial Nitrogen Flow 44
10. Equations Used for Predicting Microbial Yield or Efficiency 45
11. Summary of Apparent Absorption of Nonammonia Nitrogen and Amino Acids from the Small 47
Intestine of Ruminants
12. Proportionate Disappearance of Amino Acids from the Small Intestine 48
13. Supplies of Nonammonia Nitrogen and Amino Acids to the Proximal Duodenum and Termi- 49
nal Ileum, Apparent and True Digestibility of Nitrogen, and Endogenous Loss of Nitrogen
to the Small Intestine
14. Summary of True Absorption from the Small Intestine 50
15. Estimates of True Digestibility and Metabolic Fecal Nitrogen 54
16. Extraction of Amino Acids by Various Tissues 58
17. Estimated New Protein Requirements for Growth of Cattle of Different Body Weights and 64
Gaining at Different Rates
18. Protein Retention in Gain of Growing Sheep 64
19. Protein Retention in Fetus and Gravid Uterus of Cattle at Different Stages of Gestation 64
20. Protein Retention in Fetus and Gravid Uterus of Sheep at Different Stages of Gestation 65
21. Protein Content of Milk 65
APPENDIX TABLES
1. Numerical Data from the Protein Systems Used in Figures 3 Through 12 89
2. In Vivo Estimates of the Percentage of Undegraded Protein in Common Feed- 90
stuffs
3. Microbial Flow and Rumen Organic Matter Digestion 98
4. Urea Usefulness with Various Feed Intakes, TDN Levels, and Ruminal Diges- 108
tions of Dietary Protein Based on Equations from Dairy Cattle
5. Urea Usefulness with Various Feed Intakes, TDN Levels, and Ruminal Diges- 109
tions of Dietary Protein Based on Equations from Beef Cattle
6. Urea Usefulness with Various Feed Intakes, TDN Levels, and Ruminal Diges- 109
tions of Dietary Protein Based on Equations from Sheep
7. Production of Microbial Protein and Escape Protein Requirements for Beef Cat- 110
tle of Various Weights and Types
8. Requirements of Total and Escape Protein for Beef Cattle of Various Types, 111
Weights, and Rates of Gain
9. Factors Adopted for Transforming Feed Protein into Net Protein for Dairy Cattle 113
10. Factors Adopted for Transforming Feed Protein into Net Protein for Beef Cattle 123
11. Apparent Absorption of Nitrogen from the Small Intestine of Lactating Cattle 135
12. Apparent Absorption of Nitrogen from the Small Intestine of Nonlactating Cattle 135
13. Apparent Absorption of Nitrogen from the Small Intestine of Sheep 136
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viii
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ix
Ruminant Nitrogen Usage
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