The Roles of Amino Acid Chelates in Animal Nutrition

THE ROLES OF AMINO ACID CHELATESIN ANIMAL NUTRITION

THE ROLES OFAMINO ACID CHELATESIN ANIMAL NUTRITION

Edited by

H. DeWayne AshmeadAlbion Laboratories, Inc.

Clearfield, Utah

Reprint Edition

NOYES PUBUCATIONSWestwood, New Jersey, U.S.A.

Copyright 1993 by Noyes PublicationsNo part of this book may be reproduced or utilized inany form or by any means, electronic or mechanical,including photocopying, recording or by any informa-tion storage and retrieval system, without permissionin writing from the Publisher.

Library of Congress Catalog Card Number: 92-25242ISBN: 0-8155-1312-7Printed in the United States

Published in the United States of America byNoyes PublicationsFairview Avenue, Westwood, New Jersey 07675

1098 7 6 5 432

Library of Congress Cataloging-in-Publication Data

92-25242CIP

1992

The Roles of amino acid chelates in animal nutrition / edited by H.DeWayne Ashmead.

p. em.Includes bibliographical references (p. ) and indexes.ISBN 0-8155-1312-71. Amino acid chelates in animal nutrition. 1. Ashmead, H.

DeWayne.SF98.A38R64636.08'52--dc20

INTRODUCTION

Th i s book wi 11 be of great interest to anyoneconcerned with animal feeds and feeding programs whetherone is studying bovine, porcine, equine, avian or lowervertebrate (fish and eel) nutrition. This informationis critical to the success of an animal feeding program.Somet imes the di fference between a successful and afailing program can be traced to mineral deficiencieswhich cause either abnormal growth, reduced milkproduction, interrupted fertility and breeding,compromised immune system integrity and/or decrement innormal hemoglobin concentration. Increasedmorbidity/mortality rates can make a profitable animalfeeding program into a financial failure overnight whenthe replacement costs for a prize animal are considered.These abnormalities, and others, are addressed in thepages that follow.

From 25 controlled studies by 42 different authorsin five different countries a diverse array of data ispresented. These data val idate the effect i veness ofmineral nutrients presented as amino acid chelates whencompared with the ionic forms derived from the inorganicsal ts. These stud ies further support the resul ts ofnumerous laboratory experiments showing increasedabsorption, assimilation and reduced toxicity of theforms of minerals chelated to amino acids. With littlecost and effort animals can be supplemented with aminoacid chelates which will promote, with little risk ofoverdose, a fuller genetic potential achievement as faras mineral requirements are concerned. Results of thissupplementation are reflected in increased growth,immunological integrity, and more consistentreproduction (increased ovulation and conception afterfirst service) as a result of increased bioavailabilityof these chelated forms.

v

VI Introduction

Of novel interest are the reports showing aprotein sparing as a result of amino acid chelatesupp1ementat ion. In the face of dwi ndl i ng protei nsources for animal feeds, this effect of chelatedminerals needs further scrutiny in feeding programs inother species.

Darrell J. Graff, Ph.D.Weber State UniversityOgden, Utah, U.S.A.

A NOTE TO THE READER

In the late 1800's, many of the fundamentalconcepts of che1at ion chemi stry were evo1vi ng. Chemi stsbegan to recognize that certain atoms could exist inmore than one valence state, but could not comprehendhow atoms with more than one valence could form a highlystable compound.

Alfred Werner, a German chemist, was the first tobreak with traditional thinking and propose an entirelynew molecular structure to describe these highly stablemolecules. He noted that certain structural entities,which he called "complexes", remained intact through aseries of chemical transformations. In 1893, Wernerwrote, "If we think of the metal ion as the center ofthe whole system, then we can most simply place themo1ecul es bound to it at the corners of anoctahedron."(1) For the first time a chelate had beendescribed.

Werner further refined this revolutionary conceptin the succeeding years. He concluded that a metal ionwas characterized by two valences. The first, which hecalled the "principal valency", is now termed theoxidation state, or oxidation number, of the metal. Thesecond valency, which he called the "auxiliary valency",represents the number of ligand atoms associated withthe central metal atom. This is the same as thecoord inat i on number of the metal. (2-7) Werner's conceptswere fundamental to the comprehension of chelates.

The term, "chelate", was finally used by Morganand Drew, in 1920, to describe the molecular structurediscovered by Werner. As noted above, the fi rstchelating molecules that had been discovered were those

VII

VIII A Note to the Reader

with two points of attachment. It was this caliper-likemode of attaching the ligand (the chelating molecule) tothe metal atom that led Morgan and Drew to suggest theword "chelate" to describe the molecule.(8) The word isderived from the Greek word "chele", meaning lobster'sclaw. The word, IIchelate ll , was originally used as anadjective. It later became a more versatile word andtoday i s used as an adj ect i ve, adverb, or noun. Theligands are chelating agents, and the complexes theyform are metal chelates.

Because the claw, or ligand, held the cation, themetal was no longer free to enter into other chemicalreactions. Thus it quickly became evident that when ametal was che1ated, the chemi cal and phys i calcharacteristics of the constituent metal ion and ligandswere changed. This had far reaching consequences in therealms of chemistry and general biology. In spite ofthe knowledge of what chelation could do to and for ametal ion, it was not until the early 1960's that anyonethought seriously about using this molecule fornutritional purposes.

At that period, a handful of investigators,independent of each other, each conceived the idea thatif a metal ion could be chelated before feeding it toanimals, the ligand would sequester the cation andprevent it from entering into various absorptioninhibiting chemical reactions in the gut. Thetheoretical consequence was greater nutritional uptakeof the ions.

Two schools of thought quickly developed. One,led by the pioneering research of Albion Laboratories,Inc., proposed that amino acid chelates were the properchelates to enhance mineral absorption. As attested bya large number of research reports, lectures, andpublications based on the research efforts both

A Note to the Reader IX

coordinated and conducted by this organization, the useof amino acid chelates in animal nutrition were bothpositive and highly encouraging. At that point in timethese amino acids were called "metal proteinates"instead of chelates.

Concurrently, with the development of the aminoacid chelates, a second school of thought approachedanimal nutrition with synthetic chelates based onethylenediaminetetraacetic acid (EOTA). The theory wasthe same as before. The EOTA ligand would chelate thecation and protect it from chemical reactions in thegut. While it successfully accomplished its mission interms of protect ion, it genera11 y fa i1ed to enhancemineral nutrition because it formed chelates that weretoo stable. The biological ligands in the animals'bodies were incapable of extracting the cations from theEOTA chelates, even after they were absorbed into theblood. Thus, the EOTA chelates were returned to thelower bowels or excreted into the urine still protectingthe cations that the animal s were supposed to haveutilized. As Bates, et li., concluded, even thoughchelation plays a dominant role in mineral absorption,"chelation does not, in itself, insure efficient uptakebecause the absorption of the ferric chelates of EOTA,NTA, and gluconate were not significantly different thanthat of ferrous sul fate. ,,(9)

These synthetic chelates were heavily promoted inthe decade of the 60's and the early part of the 70's.When they could not deliver the enhanced mineralnutrition promised by the chelation concept, allnutritional products using the word "chelation" lostfavor with most animal nutritionists. The "c" wordbecame a word to avoid if one wished to amicably discussanimal nutrition.

x A Note to the Reader

It was for this reason metal proteinates became afavored description for the amino acid chelates. As aterm, the words evolved out of the concept of complexingmetal s wi th protei n. Metal protei nates becameacceptable terminology because they successfully avoidedmention of the "ell word. There was a problem with thatapproach, however. There was no official definition todescribe a metal proteinate.

By 1970, Albion Laboratories, Inc. had suppliedthe necessary research to allow the American Associationof Feed Control Officials (AAFCO) to officially definemetal protei nates as the product resul t i ng from thechelation or complexing of a soluble salt with aminoacids and/or hydrolyzed protein.

As greater numbers of manufacturers begancapital izing on the metal proteinate definition, itbecame evident that this definition was too broad toaccurately define Qllly those minerals that research hadproven were efficacious. Many companies were not makingchelates, but could still have their products defined asmetal proteinates. Other companies, who may have beenmaking chelates, were not making products that could beabsorbed. Thei r compounds were ei ther too bi g (achelate over 1,500 daltons can not be absorbed), or themineral was bonded to whole or partially hydrolyzedprotein (which had to be digested with subsequentrelease of the metal to competing reactions in the chymesimilar to those facing cations derived from any otherfeedstuff).

Because of the confusion among feed companies intrying to decide which metal proteinates were valuablesources of the added mineral nutrition, which metalproteinates were supported by scientific studies, andwhich were "me too" products that had no support data oftheir own, Albion Laboratories, Inc. applied to AAFCO

A Note to the Reader XI

for a new definition which accurately and morecompletely described an amino acid chelate. Realizingthe "e" word was still out of vogue among manynutritionists due to their earlier experiences withsynthetic chelates, Albion still decided to call theproducts by their true name - amino acid chelates.

After several years of debate within the AAFCOorganization, a debate which was primarily fueled bycompanies using Albion's research to promote dissimilarproducts ascribed to the proteinate definition, a newdefinition was ultimately approved. The new definitionfor a metal amino acid chelate rectified the loosenessof the metal proteinate definition by including absoluterequirements for molecular weights, molar ratios ofami no ac ids to metal s, and the abso1ute presence ofchelation. The amino acid chelate definition alsodisbarred the complexing of metals with protein orpeptides, both of which require further digestion beforeabsorption. The formation of chelates too large to beabsorbed was thus disallowed.

As defined by the American Association of FeedControl Officials, a metal amino acid chelate is litheproduct resulting from the reaction of a metal ion froma soluble salt with amino acids with a mole ratio of onemole of metal to one to three (preferably two) moles ofamino acids to form coordinate covalent bonds. Theaverage weight of the hydrolyzed amino acids must beapproximately 150 and the resulting molecular weight ofthe chelate must not exceed 800." (0 )

This book is about amino acid chelates. With fewexceptions, the research contained within it wasconducted by investigators independent of AlbionLaboratories, Inc. The organization with which eachinvestigator is affiliated is noted on the list ofcontributors and at the beginning of each chapter.

XII A Note to the Reader

The book is divided into several sections so thata reader, who may not wish to read the entire book, canquickly turn to his or her own area of primary interest.Separate sections are devoted to cattle, pigs, poultry,horses and fish. The beginning section discusses thefundamentals of amino acid chelation as they relate tothe various aspects of animal nutrition discussed ineach of the subsequent sections. It is stronglyrecommended that the reader who has primary interest inonly one species of animal still read this first sectionprior to addressing the species of interest. The firstsection will provide numerous basic concepts that willenhance the reader's comprehension of the data in thesubsequent sections.

For the animal nutritionist, veterinarian, andothers whose interests range further than a s i ngl especies, reading the book in its entirety isrecommended. As noted above, it is divided into fiveadditional sections beyond the introductory section plusa summary. The second sect i on deal s wi th severalaspects of dairy and beef cattle mineral nutrition.Some topics discussed include immunity, fertility,increased mi 1k product ion, greater growth rates, andimproved feed conversions. The third section addressesseveral important concepts of swine nutrition includingbaby pig anemia, improved reproductive capacity in oldersows, and leaner pork. Poultry is handled in the fourthsection. Topics include improvements in breeder/broileroperations, egg production and enhanced turkeyproduction. The next section deals with equinenutrition as it relates to fertility and proper growthand development of the legs. The last section dealswith enhanced performance in fish and eels.

Although the data are conclusive in most cases,the research reported in these sections is by no meanscomplete. In many instances the editor was faced with

A Note to the Reader XIII

making painful decisions as to whose research toinclude, or not to include, in order to avoid excessiverepetition. In spite of these efforts, some repetitionwas unavoidable, but hopefully not redundant.

The purpose of reporting this research in the formof a book has been two-fold. The first is to stimulateothers to piek up the torches that have been lighted bythe researchers who have contributed to this book and tocont i nue onward from where they stopped. The secondpurpose is to make the "e" word once again an acceptableword in animal nutrition circles.

H. DeWayne Ashmead

XIV A Note to the Reader

References

1. Werner, A., "Beitrag zur KonstitutionAnaorgan i scher Verbi ndungen," Z., anorg. u. all gem.Chern., 3:267, 1893.

2. Werner, A. and Miolati, A., Z. physik. Chern.(Leipzig), 14:506, 1894.

3. Werner, A. and Vilmos, Z. "Beitrag zur KonstitutionAnaorganischer Verbindungen," l. anorg. u. allegem.Chern., 21:153, 1899.

4. Werner, A., "Ueber Acetyl acetonverbi ndungen desPlatins," Ber. deut. chern. Ges., 34:2584, 1901.

5. Werner, A. ,Kobaltatoms.1911.

"ler Kenntnis des AsymmetrischenV," Sere deut. chern Ges., 45:121,

..

6. Werner, A., "Uber spiegelbild-isomerie beichromverbi ndungen. I I I ," Ber. deut. chern. Ges.,45:3065, 1912.

7. Werner, A., "lur Kenntris des AsymmetrischenKobaltatoms XII. Uber Optische Aktivitat beiKoh 1enstoffrei en Verbi ndugen, II Ber. deut. chern.Ges., 47:3087, 1914.

8. Morgan, G. and Drew, H., "Research on residualaffinity and coordination. II. Acetylacetones ofselenium and tellurium," J. Chern. Soc., 117:1456,1920.

9. Bates, G., et li., "Facil itation of iron absorptionby ferric fructose," Am. J. Cline. Nutr., 25:983,1972.

10. Haas, E., et li., eds., Official Publication 1989(Atlanta: American Association of Feed ControlOfficials, Inc.) 159, 1989.

CONTRIBUTORS

Ashmead, H. DeWayneAlbion Laboratories, Inc.Clearfield, Utah, U.S.A.

Ashmead, Harvey H.Albion Laboratories, Inc.Clearfield, Utah, U.S.A.

Atherton, DavidThomson & Joseph LimitedNorwich, England

Biti, F. RicciUniversity of BolognaBologna, Italy

Boling, James A.University of KentuckyLexington, Kentucky, U.S.A.

Bolsi, DanielleUniversity of ParmaParma, Italy

Bonomi, AlbertoUniversity of ParmaParma, Italy

xv

Cagliero, GermanoAgrolabo, S.P.A.Turin, Italy

Coffey, Robert T.Newton, Iowa, U.S.A.

Corradi, FulvioUniversity of BolognaBologna, Italy

Cuiton, LouisProductos QuimicoAgropecuarios, S.A.Mexico City, Mexico

Cuplin, PaulIdaho State Fish and GameDepartmentBoise, Idaho, U.S.A.

Darneley, A. H.Dorset, England

Ferrari, AngeloZoopropylactic Institute ofPiedmontLiguria and Valle d'AostaItaly

XVI

Forfa, Richard J.University of MarytandCollege Park, Maryland

Formigoni, AndreaUniversity of BolognaBologna, Italy

Guillen, EduardoProductos QuimicoAgropecuarios, S.A.Mexico City, Mexico

Hardy, Ronald W.University of WashingtonSeattle, Washington, U.S.A.

Herrick, John B.Iowa State UniversityAmes, Iowa, U.S.A.

Contributors

Jeppsen, Robert B.Albion Laboratories, Inc.Clearfield, Utah, U.S.A.

Kropp, Robert J.Oklahoma State UniversityStillwater, Oklahoma, U.S.A.

Lucchelli, LuiginaUniversity of ParmaParma, Italy

Maletto, SilvanoUniversity of TurinTurin, Italy

Manspeaker, Joseph E.University of MarylandCollege Park, Maryland, U.S.A.

Hildebran, SusanWapakoneta, Ohio, U.S.A.

Hunt, JohnSugar Creek Veterinary ServiceGreenfield, Indiana, U.S.A.

Iwahasi, YoshitoShizuoka Prefectural FisheriesExperimental StationLake Hamanako BranchShizuoka, Japan

Ming Lian, FengBeijing Agriculture ScienceInstituteBeijing, China

Parisini, PaoloUniversity of BolognaBologna, Italy

Quarantelli, AfroUniversity of ParmaParma, Italy

Contributors XVII

Robl, Martin G.University of MarylandCollege Park, Maryland, U.S.A.

Sabbiono, AlbertoUniversity of ParmaParma, Italy

Sacchi, C.University of BolognaBologna, Italy

Shearer, Karl D.University of WashingtonSeattle, Washington, U.S.A.

Superchi, PaolaUniversity of ParmaParma, Italy

Suzuki, KatsuhiroShizuoka Prefectural FisheriesExperimental StationLake Hamanako BranchShizuoka, Japan

Takatsuka, TakeharuShizuoka Prefectural FisheriesExperimental StationLake Hamanako BranchShizuoka, Japan

Volpelli, L. A.University of BolognaBologna, Italy

Wakabayashi, TakaakiEisai, Co., Ltd.Tokyo, Japan

Xian-Ming, CaoBeijing Agriculture ScienceInstituteBeijing, China

Van Ping, ZhouBeijing Agriculture ScienceInstituteBeijing, China

Zunino, HugoUniversity of ChileSantiago, Chile

Notice

To the best of the Publisher's knowledge the informationcontained in this publication is accurate; however, thePublisher assumes no responsibility nor liability for errors orany consequences arising from the use of the informationcontained herein. Final determination of the suitability of anyinfonnation, procedure, or product for use contemplated by anyuser, and the manner of that use, is the sole responsibility ofthe user.

The book is intended for informational purposes only. Thereader is warned that caution must always be exercised whendealing with chemicals, products, or procedures which mightbe considered hazardous. Expert advice should be obtained atall times when implementation is being considered.

Mention of trade names or commercial products does notconstitute endorsement or recommendation for use by thePublisher.

XVIII

Contents

INTRODUCTION . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. VDarrell J. Graff

A NOTE TO THE READER VII

CONTRIBUTORS XV

SECTION 1AMINO ACID CHELATION

1. MINERALS IN ANIMAL HEALTH 3John B. Herrick

2. FACTORS WHICH AFFECT THE INTESTINALABSORPTION OF MINERALS 21

H. DeWayne Ashmead and Hugo Zunino

3. COMPARATIVE INTESTINAL ABSORPTION ANDSUBSEQUENT METABOLISM OF METAL AMINO ACIDCHELATES AND INORGANIC METAL SALTS 47

H. DeWayne Ashmead

4. INCREASING INTESTINAL DISACCHARIDASEACTIVITY IN THE SMALL INTESTINE WITHAMINO ACID CHELATES 76

Silvano Maletto and Germano CaglieroXIX

xx Contents

5. EVALUATION OF THE NUTRITIONALEFFICIENCY OF AMINO ACID CHELATES 86

Silvano Maletto and Germano Cagliero

6. AN ASSESSMENT OF LONG TERM FEEDING OFAMINO ACID CHELATES 106

Robert B. Jeppsen

SECTION 2CATTLE

7. THE USE OF AMINO ACID CHELATES TO ENHANCETHE IMMUNE SYSTEM 117

Robert T. Coffey

8. THE USE OF AMINO ACID CHELATES IN BOVINEFERTILITY AND EMBRYONIC VIABILITY 140

Joseph E. Manspeaker and Martin G. Robl

9. THE ROLE OF COPPER IN BEEF CATTLE FERTILITY .... 154J. Robert Kropp

10. THE USE OF AMINO ACID CHELATES IN HIGHPRODUCTION MILK COWS 170

Andrea Formigoni, Paoli Parisini, and Fulvio Corradi

11. THE FEEDING OF AMINO ACID CHELATESUPPLEMENTS TO BEEF CALVES 187

James A. Boling

SECTION 3SWINE

12. THE ROLE OF IRON AMINO ACID CHELATE INPIG PERFORMANCE . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 207

H. DeWayne Ashmead

13. THE EFFECT OF IRON AMINO ACID CHELATE ONTHE PREVENTION OF ANEMIA 231

Cao Xian-Ming, Feng Ming Uan, and Zhou Yan Ping

14. THE EFFECT OF AMINO ACID CHELATED IRON INPREGNANT AND LACTATING SOWS 243

P. Parisini, F. Ricci Biti, L.A. Volpelli and C. Sacchi

Contents XXI

15. IMPROVING REPRODUCTIVE PERFORMANCE WITHIRON AMINO ACID CHELATE 251

A.H. Darneley

16. A NUTRITIONAL APPROACH TO MAXIMIZINGCARCASS LEANNESS 269

David Altherton

SECTION 4POULTRY

17. THE EFFECT OF AMINO ACID CHELATES IN CHICKMORTALITY 291

David Atherton

18. THE DYNAMICS OF FEEDING AMINO ACID CHELATESTO BROI LERS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 302

Alberto Bonomi, Afro Quarantelli, Paola Superchi,Alberto Sabbiono, and Luigina Lucchelli

19. GROWTH RATES AND FEED CONVERSION IN BROilERCt-IICKS FED AMINO ACID CHELATES 318

Louis Cuitun and Eduardo Guillen

20. THE USE OF AMINO ACID CHELATES IN GROWINGTURKEYS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 330

Alberto Bonomi, Afro Quarantelli, Paola Superchi,Alberto Sabbiono, and Danielle Bolsi

21. THE ROLE OF AMINO ACID CHELATES INOVERCOMING THE MALABSORPTION SYNDROMEIN POULTRY 349

Angelo Ferrari and Germano Gagliero

22. THE VALUE OF AMINO ACID CHELATES IN EGGPRODUCTION . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 366

Alberto Bonomi, Afro Quarantelli, Paoli Superchi andAlberto Sabbiono

23. THE ROLE OF AMINO ACID CHELATED MAGNESIUMIN EGG PRODUCTION 380

David Atherton

XXII Contents

SECTION 5HORSES

24. THE EFFECTS OF AMINO ACID CHELATES ONTHOROUGHBRED MARES 393

Martin G. Robl and Richard J. Forta

25. COPPER-RESPONSIVE EPIPHYSITIS AND TENDONCONTRACTURE IN A FOAL 400

Susan Hildebran and John Hunt

SECTION 6FISH

26. THE USE OF AMINO ACID CHELATES IN RAINBOWTROUT OPEN-FORMULA DIETS 413

Harvey H. Ashmead and Paul Cuplin

27. THE USE OF ZINC AMINO ACID CHELATES IN HIGHCALCIUM AND PHOSPHORUS DIETS OF RAINBOWTROUT 424

Ronald W Hardy and Karl D. Shearer

28. THE EFFECTS OF IRON AMINO ACID CHELATE INCULTURE EELS 440

Katsuhiro Suzuki, Yoshito Iwahasi, Takeharu Takatsukaand Takaaki Wakabayashi

SECTION 7SUMMARY AND CONCLUSION

29. SUMMARY AND CONCLUSION 457H. DeWayne Ashmead

NAME INDEX 473

INDEX 475

Section 1. AMINO ACID CHELATION

Chapter 1

MINERALS IN ANIMAL HEALTHJohn B. Herrick*Iowa State University

Sci ent i sts have long known that traces of mostelements exist in animal tissue, but in many cases theybelieved that those minerals were contaminants ratherthan functional entities. As analytical methods haveimproved, many elements that were once thought to becontaminants have been shown to be essential to the lifeand well being of the animals.(1) Thus, a mineral is nowbelieved to be essential if (a) it is present in allhealthy tissue, (b) its concentration from one animal tothe next is generally constant, (c) its withdrawal fromthe body results in reproducible physiological andstructural abnormalities, (d) its addition prevents orreverses those abnormal it i es, (e) the defi ci ency- inducedabnormalities are accompanied by specific biochemicalchanges, and (f) these biochemical changes can beprevented or cured with the addition of the mineral .(2)

The three major roles of essential minerals are todirectly or indirectly function in supplying energy, toindirectly and directly aid in growth and maintenance ofthe body tissues, and fin~lly to assist in theregulation of body processes.() The need for chromiumto potentiate insulin and the involvement of phosphorusin the ATP mol ecul e are two exampl es of the di verseroles of minerals in energy production. In their rolesof growth and maintenance of tissues, mineralscontribute to the rigidity of the bones and teeth and

* The original draft was written while associatedwith Iowa State U. Dr. Herrick is currentlyretired and working as a consultant.

3

4 The Roles of Amino Acid Chelates in Animal Nutrition

are an important part of protein and lipid fractions ofthe animal body. As regul ators of body processesminerals preserve cellular integrity by osmoticpressures and are a component of many enzyme systemswhich catalyze metabolic reactions in biologicalsystems. Most minerals function in more than one role.As an example, calcium is used in large amounts by thebody for synthesis of osseous tissue. Phosphorus alsocontributes structurally and yet is a key element in theuse of energy by the body. Furthermore, cobalt has aregulatory role (through vitamin 8-12) rather thancontributing quantitatively to tissue synthesis, but itseffect on growth i s as dramat i c as that of cal ci urn.Other elements play essential roles, as well.

Minerals which are involved in several metabolicprocesses are more likely to be interrelated with otherminerals than are those involved in a single or a fewfunct ions. (4.5) Knowl edge of these i nterre1at ionsh ipsbetween minerals is increasing rapidly. As thatknowledge expands in the field of mineral metabolism,many additional interrelationships will probably beelucidated.

Animals obtain essential mineral nutrition fromtwo pri mary sources: (1) through natural feeds and,possibly, water, and (2) through supplementation offeeds and water. Even though a 1arge port i on of therequired minerals may be provided by the vegetativeanimal feedstuffs, mineral supplementation is generallya necessary practice for properly nourishing the animalsdue to dep1et i on and imba1ances of mi nera1sin thesoils, and consequently in plants.(6) The mineralcontents of a plant depend primarily on the plantspecies, the season, the abundance of the element in thesoil, the type of soil, and the conditions (pH,moisture, etc.) which affect the plant's ability toabsorb the mi nera1s. (7) Because of the many factorsaffecting this absorption, the mineral contents ofplants vary both within and among the species.

Minerals in Animal Health 5

Furthermore, mineral requirements of plants are not thesame as for animals, so ratios of one mineral to anotherand the Quantities of minerals, being proportioned fordifferent biological functions, may not meet the needsof the animal when used in feeds. The availability ofminerals in plants is also affected by phytic acid andoxalic acid found in the cellulosic cell membranes asopposed to cytoplasm. It should be remembered that thepresence of a mineral in plant tissue used for feed doesnot guarantee its absorption into the animal's system.As stated by Underwood, "the evaluation of feeds andfeed supplements as sources of minerals depends not onlyon what the feed contains, i.e. the total content orconcentration as determined physio-chemically, but onhow much of the total mineral can be absorbed from thegut and used by the animal's cells and tissues."(8)

Before the development of isotopic techniques,absorption mechanisms of minerals were poorlyunderstood. Without isotopes the primary difficulty forconfusion of mineral metabolism was due to absorption,excretion back into the gut, and reabsorption, often asa standard cycle. Conventional balance studies wereunable to indicate the net utilization of minerals.Absorption of mineral ions is dependent upon numerousfactors, including the levels of the elements ingested,the age of the animal, Ph of the intestinal contents andenvironment, the state of the animal with respect todeficiency or adequacy of the element, and the presenceof other antagonistic minerals or nutrients as well asseveral other conditions. (9) Earl ier investigators wereunable to consider these variables due to lack ofadequate technology, and thus their reports often lackedagreement. With the use of isotopes it became easier tofollow the movement of trace elements through thebody. (8)

In a practical sense, all animals are subject tomineral deficiencies. These may be caused by: (a) asuboptimal amount of a specific mineral in the feed; (b)


an imbalance of another mineral or nutrient includingcertain vitamins, amino acids and fats, any of whichcould decrease absorption; (c) any condition whichincreases the rate of passage of the minerals throughthe intestine, such as diarrhea; and (d) the presence ofa metabolic antagonist which causes the animal torequ ire a greater quant i ty of the needed element. (4)Imbalances and deficiencies are not synonymousconditions, but either condition may lead to the other.The net result is less than optimum mineral nutritionfor the animal.

The pathways for excretion and rates of excretionof mineral elements vary. Some are excreted almostentirely in the feces via the lower bowel; others areeliminated almost entirely in the urine, while stillothers are excreted through both pathways. Certa inminerals are excreted in minute quantities through thesweat, and others are lost during the menstrual cycle.Integument losses from the animal's body may alsooccur. (4) Absorpt i on from the 1umen does not guaranteemineral usage in metabolism.(lO) In some cases mineralsare absorbed but later excreted in urine and feces asnon-metabolized wastes without ever being utilized inbiological processes.

Chelation of minerals (a process by which a metalatom is sequestered) is employed in some feedingreg imens in order to enhance the absorpt i on wi thoutregard to mineral metabolism. Ametal chelate is formedas a ring structure. It is produced by attractionbetween the positive charges of certain polyvalentcations and any two or more sites of highelectronegative activity in a variety of chemicalcompounds known co11 ect i vel y as 1igands. Ache1ategenerally requires both an ionic and a covalent bond.The covalent bond in particular, known as a "coordinate"bond, occurs because of peculiarities in electron shellsof transition metals and the capacity of the donatingatom of the ligand to contribute two electrons at the


same time. The word "chelate" is taken from the Greekword chele meaning "claw," a fairly good descriptiveterm for the manner in which polyvalent cations are heldby the metal bi nd i ng agents or 1igands. (12)

If any element is chelated by a ligand which willcarry the bonded mineral into the mucosal cell as anintact chelate, this chelate may indeed greatly enhanceabsorpt i on of that mi nera1. However, if ache1atemerely releases an ion at the intestinal wall, this isfrequently no more efficient than use of metal saltsbecause once the ion is released, it is subject to themi nera1 absorpt ion 1imi t i ng factors ment i oned above.Intact absorption is generally more efficient. However,due to high stability constants, some chelates which areabsorbed are never metabolized. cll ) If a chelate isabsorbed, it occurs because the chelate prevents thechemical reaction of the element with other substancesin the stomach and intestines to form insoluble chemicalcompounds. Che1at ion a1so prevents the strongadsorption of the mineral onto insoluble colloids in theintestine. This prevents the ion from being releasedback into the lumen. If a chelate is metabolized afterabsorption, it occurs because the ligand is capable ofeither releasing the cation to other metallic requiringcellular systems with subsequent metabolism of the freeligand, or the chelate is able to enter into a systemwhich requires both the metal and the ligand together.

There are basically three types of chelates whichare recognized as being essential in biological systems:

The first group includes chelates which transportand store metal ions. In these chelates the metal hasno current function of its own. It does not modify theproperties of the ligand, but instead requires the useof ligands with the chemical and physical propertieswhich will allow the metal to be absorbed, transportedin the bloodstream, and pass across cell membranes todeposit the metal ion at the site where needed. One


such chelate is transferrin. It chelates absorbed ironions which enter the blood and transfers them throughoutthe body. The presence of transferri n in the blood,however, does not guarantee that th i s wi 11 be theultimate destination of absorbed or otherwiseadministered iron. In the case of iron dextraninjections made to supplement inadequate body iron1eve1s , some of the iron i s i ncorporated intotransferrin, while the remainder is either eliminated inthe wastes or fixed in the connective tissues at thesite of injection. (13)

All amino acids are particularly effective metalbinding agents, and may be of primary importance in thetransport of minerals from the lumen into the mucosalcells as well as for storage of mineral elementsthroughout the an; rna1's body. As part of ache1atemolecule these amino acid ligands do not functionbiologically as individual amino acids, but as uniquetransfer molecules.

Ethylenediaminetetraacetic acid (EDTA) and similarsynthetic ligands may improve the availability of zincand certain other minerals for plants by protecting thecations from precipitating chemical reactions in thesoil. EDTA and similar variants are effectively used inmedicine to hasten the excretion of lead and other heavymetals from animals poisoned by these metal ions.(l4)Generally speaking, however, EDTA chelates and similaranalogs, do not enhance mineral nutrition in animals.(ll)

The second group of chelates are those which areessential to physiology. Many chelates exist in theanimal body in forms which allow the metal ion toperform its metabolic function(s). The chelated iron inhemoglobin and the chelated cobalt in vitamin 8-12 aresuch examples of this group of chelates. Without itsiron moiety, the hemoglobin molecule could not transportoxygen. On the other hand, if the i ron were notchelated, the hemoglobin could not effectively bind and


release the oxygen for metabolic use.(15) Metals whichare chelated into enzyme systems and function as part ofa metalloenzyme are other examples of metabolicallyessential chelates.(16)

The third group of chelates consist of those whichinterfere with utilization of essential cations. Manymetal chelates are probably formed "accidentally" andconsequently have no useful biologic value. In Table 1numerous enzyme systems are listed. Many can bedeactivated or inhibited when the wrong metal forms achelate within the enzyme.(l7) One should note thevariety of cations required for the catalytic functionsof these enzymes. Without them the enzymes will ceaseto function. This is a necessity which is frequentlyoverlooked by many who relegate mineral nutrition to itsstructural role in bones and teeth and are unaware ofthe importance of minerals as enzyme cofactors in basicmetabolism.

Table 1

Enzymes Whi ch Are Infl uenced by Mi nera1s (Modi fi ed from Schut te (lJ)Column I. The trace element (or mineral element) constitutes the

prosthetic group.Column II. The trace element (or mineral element) is an active part of the

prosthetic group, or is incorporated into the enzyme itself.Column III. Elements with integrating function(s) that are not understood,

as yet. El ements need not be speci fi c and may replace eachother.

Column IV. Facultative Activators.Column V. Inhibitors of enzyme activity.

ENZYME

Carbohydrases

II III IV v

Na,K,Li,Br, F,ISr,Mg,Ca,Ba

u-Amylase (animal) ClLysozyme,B-D-GlucosidaseHyaluronoglucos-aminidase

KS203, CN ,S I ,CuSK,Na,Ca,Ba, F,MgFe,Mn,Br,I,SO.,N03


(Table 1 continued)ENZYME II III IV V

Esterases

Deoxyribonucleases Mg,Mn,(Ca) Ca,BaZoolipase Ca,Mn,Cl Pb,Mn,NaLipoprotein lipase W,Mo,SiCholinesterase Ca Co,Ba,Mg,Cu, S F

MnAcetylcholinesterase NaClPhosphatidylcholin- Mgesterase

Alkaline phosphatase Zn,Co,Mn,Mg Ni , Fe++,Ca MgSH,CNAcid phosphatase Co Ca,Mg,Co,Ni F,MgAcid phosphomono- Mg Co Niesterase III

Fructose- Mg,Mn Co,Ni ,m,OJbisphosphatase

Nucleotidase Mg Zn,FeH-,A],Cu++

Ribonuclease FProstataphosphatase Ce,LaTropinesterase KC1,NaBr, F,CN

KCNS, MgSO.,CaC1 2 ,Na,Cl,NaI

Phosphoprotein Mophosphatase

Phosphatidate Mg C3,B3.,M],~phosphatase

Arginine deaminase FeArylsulphatase NO,ClDeoxyribonuclease Mg,Mn Ca FType I

Deoxyribonuclease Mg FType II

Micrococcal Ca Fendonuclease

Amidases

Defence proteinases S SH Sch-MeProteinases in general KCathepsins S,CN,SH, Fe Sch-Me

S203' S03 (Hg,Cu)Coagulation factor Xa Ca



(Amidases continued)Trypsin Ca, Mn, NH.,

MgSO.Chymosin Ca Rare EarthsEnteropeptidase CaPepsin A H,ClAminoacyl-histidine Zn,Mn PO., P20J , Fdipeptidase

Peptidases Mg,Mn,Zn, Zn,CoFe++,Co++

Dehydropeptidase I S,CNFolic acid conjugase SHg,CaTripeptide aminopeptidase MnAminopeptidase Mn,Mg Mn,Zn CN, S, P2OJ ,

Fe++, Pb++,1-9++, Cu++

Aminopolypeptidase Co,Zn Zn,CoCysteinyl-glycine Mn,Co,Fedipeptidase

Glycyl-l-leucyl- Mndipeptidase II

Glyclglycin- Co,Mn ZndipeptidaseGlycyl-l-leucine- Mn Zn, PO. Ca,(Zn-~.)dipeptidase I

Proline dipeptidase Mn,Cd po., PzOJ , F,S,CN,Ag

Prolyl dipeptidase Mn Sn,~,F,Fb++,Cd++,P2 0J

Tryptic carboxy- Zn Mgpolypeptidase

Catheptic carboxy- CNpolypeptidase

Histidine ammonia-lyase Cd++,KCNNAD(P)+ nucleosidase N0 3 , N0 2 , NH. ZnArginase Cd,Mn Fe++,Co,Ni Ca,Fe,Ni B,Zn

Cd,VAsparaginase Cu,Hg,AgGlycocarbaminase Mn



Phosphohydrolases

Pyrophosphatases Mg Mn Al,Mg,Zn,Zr, Ca,FTh,Pb,Fe,Co,La,Ce,Y,CN

Polyphosphatases MgAdenosinetriphosphatase Mg,K Mg Ca,NaTriphosphatase Mg,Fe,CoApyrase CaATP-Pyro- Cl,Brphosphatase

Oligometa- Mg,Mn,Co,Zn Ca,Ba,Al ,Ti, CN,Fphosphatase Fe,Ni ,Cu,Zr,

Th,Pb,La,Ce,Nd,Sm,Y,Pr

Polymeta- Mn,Mg,Zn Ag,Hg++phosphatase Ca,Pb

Phosphohalogenase Mn,Co Hg++,ZnCu++, Pb++(Mn)

Hydrolases with varyingsubstrate specificity

C-C-Hydrolases B6 -PO"Alkylhalidase Cl,BrIodine-tyrosine- Ideiodase

Di-isopropyl- Ca,Mg,Co,Mn Hg Hg++,Cu++fluorophosphatase

Transglycosylases

Phosphorylase Mg

Transphosphatases(Kinases)Glucose-l- AsO"phosphate --->amylose-trans-glucosidase

Minerals in Animal Health

(Table 1 continued)

13

ENZYME II III IV V

(Transphosphatases Kinases continued)Saccharase ---> As04ortho-phosphate-transglucosidase

Adenylate kinase MgCreatin kinase MgArginine kinase Mn Mg1,3-Diphospho- Mg K, NH4glycerate --->ADP-Trans-phosphatase

Pyruvate kinase K, Mg, NH 4 ,Rb

Hexokinase Mg6-Phosphofructo- Mg K, NH4kinase

Galactokinase Mg,MnPhosphoglucokinase Mg,MnGluconokinase MgRibokinase MgATP---> Nucleic Mg,F P04acid-trans-phosphatase

Riboflavin kinase Mg,MnAdenosine kinase Mg,MnPhosphoglucomutase Mg FFMN adenylyl- Mgtransferase

FMN adenylyl- Mgtransferase

ATP ---> NAD- Mg,MnTransphosphatase

Aminotransferases

Amino transferases Mg,NH4 ,C02Glutaminyl-peptide Mn, P04

-glutamyltransferaseAspartate aminotransferase Mn, P04Carbamoyltransferases Mg



Transmethylases

Transmethylase Mg,Ca CN,F,Ca

Acyltransferases

Acetyl CoA Mg K, NH., Rb Na,Cssynthase

Choline PO. ,Ca , Mg , Kacetyl transferase

Special Transferases

Transketolase Mg PO.Thiosulfate S203' Cu As03sulfurtransferase

Anaerobic Transhydrogenases

Succinate Fe PO. Ca,Al,Co,dehydrogenase Rare Earths

Oxalate Mgdehydrogenase

Choline Codehydrogenase

Thiamine Mgdehydrogenase

u-fJ-Unsaturated CuAcyl-CoA-reductase

Saturase Mn,ClMonodehydro- PO., AsO.ascorbatereductase

Alcohol Zndehydrogenase

Glutathione disulphide Mg, Mn, PO. NaClreductase (NAD(P)H)

Minerals in Animal Health

(Table 1 continued)

15

ENZYME II III IV V

Aerobic transhydrogenases

Amine oxidase Cu,Fe PO., Mo, Fe(flavin containing)

Amine oxidase Cu Co PO. CN,Ca(copper containing)

Xanthine oxidase Mo,Fe PO. CN,CuAldehyde oxidase Me NH., WAldehydmutase Mo

Anaerobic transelectronases

NADPH dehydrogenase PO.NADH dehydrogenase Fe++, PO. CN Cu,Zn,Mn,

Ca,~,P04'P2 0

"

V

Aerobic transelectronases

Cytochrome c oxidase Fe C1Monopheno1 Cu PO.,Ni ,CO,V K,Mg,Ca,Zn,monooxygenase Mn,A1,Fe

Urate oxidase Cu Mn CN,FLuciferin Mg PO., Mn P2 O,4-menooxygenase

Hydroperoxidases

Peroxidase Fe+++ NO), IDioxymaleic acid Mn,Fe+++ Foxidase

Ferro-peroxidase Fe++Lacto-peroxidase Fe+++Myclo-peroxidase Fe+++Catalase Fe

Special redoxases

Homogentisate Fe++1,2-dioxygenase

Lactonizing enzyme Mn


(Table 1 continued)ENZYME

Decarboxylases

II III IV V

Oxylacetate-,B-carboxylase

Malatedehydrogenase

Malonatedecarboxylate system

Succinatedecarboxylate system

Isocitratedehydrogenase

Pyruvatedehydrogenase

Triosephosphate-lyases

PO., Mn, Cd, MgCoMn Mg

PO. Mg,Mn

PO., Mn

PO., Mn, Co Mg

Mg Mn

Fructose-bisphosphatealdolase

Asparate ammonia- Mglyase

Hydratases and dehydratases

MeCuCo,Cu

Zn,Fe++,Co++,B

Aconitate hydrataseCN,S,F,Cu,Hg

Enolase MgCarbo-anhydratase Zn

Isomerases

Fe++

Mn,Zn F,HgCN,S

UDP-glucose-4-epimerasePhosphoglucomutasePhosphoglyceromutase

C-N- and C-S-lyasesand synthases

Cystathionine-lyase

Mg,Mn,Co

Zn,Mn,Mg

Mg


In summary, there are many types of chelates, bothnatural and synthetic. In addition to medicalfunctions, such as removal of certain isotopes orpoisonous metals from the animal's body, chelation canalso be used in the deactivation of bacteria throughmetal deprivation.(18) Nutritionally, amino acidchelates are used to enhance trace metal delivery to thebody. (19) For that to occur, the stab; 1; ty constants ofthe chelating bonds must be compatible for intactabsorption while maintaining availability fordegradation at the sites of metal usage in the body. (20)The molecular weight of the chelate must also be keptlow to promote intact absorpt ion. (21)

The science of chelation as it relates to thenutrition of domestic animals is coming of age. Theadvantage of using amino acids to chelate essentialminerals and render them more biologically available tothe animal offers greater possibilities to regulate theamount of a given metal ion at the cellular level thantechniques heretofore used.


References

1. Underwood, E., Trace Elements in Human and AnimalNutrition (New York: Academic Press) 1-10, 1977.

2. Mertz, W., IISome aspects of nutritional traceelement research," Federation Proceedings,

Federation of American Societies for ExperimentalBiology, Soc. Exp. Biol. 29:1482-1488, 1970.

3. Guthrie, H., Introductory Nutrition (St. Louis:C.V. Mosby Company) 11, 1975.

4. Dyer, I., "Mineral Requirements" in Hafez, E. andDyer, I., eds., Animal Growth and Nutrition(Philadelphia: Lea &Febiger) 313, 1969.

5. Suttle, N., "Trace Element Interactions inAnimals,1I in Nicholas, D. and Egan, A., eds.,Trace Elements in Soil-Plant-Animal Systems (NewYork: Academic Press, Inc.) 271, 1975.

6. Schutte, K., The Biology of the Trace Elements(Philadelphia: J.B. Lippincott Company) 132,1964.

7. Loneragan, J., "The Availability and Absorptionof Trace Elements in Soil-Plant Systems and their

Relation to Movement and Concentration of TraceElements in Plants," in Nicholas, D. and Egan,A., eds., Trace Elements in Soil-Plant-AnimalSystems (New York: Academic Press, Inc.) 109,A75.

8. Underwood, E., The Mineral Nutrition of Livestock(Slough: Commonwealth Agricultural Bureau) 15,1981.


9. Ashmead, D., and Christy H., "Factors interferingwith intestinal absorption of minerals," AnimalNutr. and Health, 40:10, August, 1985.

10. Ashmead, H., et tl., "Chel ation does notguarantee mineral metabolism," J. App. Nutr.,26:5, Summer, 1974.

11. Miller, R., "Chelating Agents in PoultryNutrition," A paper presented at DelmarvaNutrition Short Course, Delmarva, 1968.

12. Mellor, D., "Historical Background andFundamental Concepts [of Chelation]," in Dwyer,F. and Mellor, D., eds., Chelating Agents andMetal Chelates (New York: Academic Press) 1,1964.

13. Jones, L., "Antianemic Drugs," in Jones, L., etli., eds., Veterinary Pharmacology andTherapeutics (Ames: Iowa State University Press)283, 1965.

14. Goth, A., Medical Pharmacology (St. Louis: C.V.Mosby Company) 675, 1974.

15. Eichhorn, G., "The Role of Metal Ions in EnzymeSystems," in Seven, M. and Johnson, L., eds.,Metal-Binding in Medicine (Philadelphia: J.B.Lippincott Company) 19, 1960.

16. Hughes, M., The Inorganic Chemistry of BiologicalProcesses (London: John Wiley & Sons) 105, 1972.

17. Schutte, op. cit., 17-23.

18. Ashmead, D., "Chel ation in nutrition," WorldHealth &Ecology News, 7:10, 1976.


19. Ashmead, D. , "The needminerals," Vet. Med.jSm.69:467, 1974.

for chelated traceAnimal Clinician,

20. Kratzer, F. and Vohra, P., Chelates in Nutrition(Boca Raton: CRC Press, Inc.) 19-32, 1986.

21. Tiffin, L., "Translocation of Micronutrients," inDinauer, R., et li., eds., Micronutrients inAgriculture (Madison: Soil Science Society ofAmerica, Inc.) 207, 1972.

Chapter 2

FACTORS WHICH AFFECT THE INTESTINALABSORPTION OF MINERALS


Hugo ZuninoUniversity of Chile

The Periodic Table contains at lrast 104 elements,81 of which are considered minerals.() With certaintyseventeen of these minerals (and probably two others)are deemed essential for the vital functions of animals.The concept of determining if a mineral is essential ornot has evolved as a consequence to the development ofmore sophisticated analytical techniques andequipment.(2) It is probable that as scientificmethodologies are perfected and artificial diets becomemore sophisticated, additional mi~erals will be added tothis 1ist of essential elements. ( )

The primary source of essential mineral elementsfor all biological systems is the soil.(4) With theexception of animals retrieving minerals from thissource through natural salt licks, only some plants andcertain microorganisms are able to extract simpleorganic compounds and ions from the soil, withoutdepending on organic metabolites which have beenprefabricated by other organisms. Life forms having thecapability to extract soil ions for direct use (otherthan as salt licks) are termed autotrophic. For themost part, animals, which are heterotrophic, mustsecondarily find (or catch) their metal nutrients inprepackaged forms. Ultimately all animals are dependantupon plants as the primary source of theirunsupplemented mineral nutrition. Any deficienciesexperienced by plants have far-rea~hing consequences tothe animals which depend on them.()

21


Animal feedstuffs can be organized into six basicgroups: protei n, carbohydrates, 1i pi ds, vi tami ns,mi nera1s, and water. (6) The mi nera1 group exerc i sesthree bas i c funct ions. (7)

The first function relates to the role of mineralsin the growth and maintenance of both hard and soft bodytissues. Obviously, elements such as calcium andphosphorus as well as magnesium, contributesubstantially to the hardness of bones and teeth byformi ng mat ri xes or comp1exes that are fundamenta11 yinorganic in nature, while others such as phosphorus,sulfur, zinc, and magnesium make up important componentsof soft tissue; fluorine, zinc, and silicon play rolesin the formation of proteins and fats that compose thebody. (8)

Minerals also preserve cellular integrity throughtheir roles in maintaining the osmotic pressure betweenthe intra- and extracellular fluids, the acid-basebalance, membrane permeability and tissue irritability.Although not directly related to animal growth, one ofthe most dramatic examples of the types of rolesminerals can play in growth is seen in the developmentof the bacterium, Escherichia coli. A culture of thismicroorganism can double in size every 20 minutes in amedium containing only glucose and minerals. In thatperiod of time, the chemical components of the mediumbecome incorporated into the expanding protoplasmaticmass and are converted, through an intricate series ofbiochemical reactions, into approximately 2,500 proteinsof differing compositions including a wide range ofnucleic acids and over 1,000 organic non-proteincompounds. (9)

The second basic function played by minerals is inthe regulation of physiological and biological processesin the animal. For example, the same calcium which isessential for bone development, is equally necessary inthe proper functioning of the nervous system, for blood

Factors Which Affect the Intestinal Absorption of Minerals 23

coagulation, for regulating permeability in cellularmembranes, for the contraction of cardiac muscle, etc.Vanadium, as an essential trace element, regulatescholesterol and phospholipid synthesis. Copper isrelated to the synthesis of hemoglobin, regulatingthereby the oxidative processes in the animal.

In their role as regulators of body processes, theessential minerals function as catalysts in enzyme andhormone systems and as integral and specific componentsof metalloenzymes such as those seen in Table 1. Theymay also function as less specific activators withincertain metalloenzymes.


I Table 1 ISome Essential Metalloenzymes in Animals

Metal Enzyme Function

Iron Ferredoxin PhotosynthesisSuccinate dehydrogenase Aerobic oxidation of carbohydratesCytochromes Electron transferCatalase Protection against HzOz

Copper Cytochrome oxidase Terminal oxidaseLysyl oxidase Lysine oxidationCeruloplasmin Iron utilizationSuperoxide dismutase Dismutation of the superoxide free

radical (Oz -:)Zinc Carbonic anhydrase COz format ion

Alcohol dehydrogenase Alcohol metabolismCarboxypeptidases Protein digestionAlkaline phosphatase Hydrolysis of phosphate estersThymidine kinase Thymidine triphosphate formationRNA and DNA polymerases Synthesis of RNA and DNA chains

Manganese Pyruvate carboxylase Pyruvate metabolismSuperoxide dismutase (as above)

Molybdenum Xanthine oxidase Purine metabolismSulphite oxidase Sulphite oxidation

Selenium Glutathione peroxidase Remova1 of HzOz

The third major function of minerals lies in thegeneration of energy. This does not mean that mineralsof themselves are sources of energy; nevertheless, theyparticipate as essential co factors in enzymaticreactions which chemically transform foods into othermetabolites, thus freeing energy to be used in otherfunctions. To illustrate this concept in part, itshould be noted that calcium, magnesium, phosphorus,manganese, and vanadium are all utilized in one form oranother in the synthesis and formation of high-energybonds in compounds such as ATP. (11) In the case of


phosphorus, every physiological event involving gain orloss of energy and almost every form of energy exchangewithin all animal cells includes the making or breakingof high energy phosphate bonds and requires thatphosphorus be present. (e)

Accord i ng to the tota1 amount requ i red by theanimal, essential minerals are normally classified intotwo groups: macronutrients and trace elements.Although some believe that because of the low quantityof micronutrients required as compared tomacronut ri ents, the former are not important in thedaily diet. This is not true. For example, calcium, amacroelement, is used in great quantities in bonesynthesis for growth, but without the trace element,cobalt, growth is retarded as if there were a manifestdeficiency of dietary calcium. A cobalt deficiency canstart a chain reaction in the animal that can lead toinadequate metabolism of both protein and lipids whichi s further man i fested as a lower growth rate. (12)

For the above reasons, as well as others that areoutside the scope of this discussion, it is extremelyimportant that there be little or no interference in theintestinal absorption of essential minerals. While lackof interference would be desirable, this is generallynot the case. There are numerous antagonistic factorswhich cause less than optimal absorption of manyminerals. Consequently, there are numerous variationsin the absorption rates and levels of the same mineralunder different gastrointestinal conditions.(13)

It is commonly known that certain minerals caninteract with each other and mutually affect eachother's absorption and metabolism.(3) The more metabolicprocesses in which a certain mineral is involved, thegreater will be the possibility of its interacting withother minerals. Some of these interactions are shown inFigure 1.(3) The arrows indicate antagonisms betweenmi nera1s as they compete for intest ina1 absorpt ion.


These interactions may be grouped into six basiccategori es. (14)

p Co

Na

AgCd

BeCu

Figure 1. Mineral interrelationships in animalmetabolism. The arrows indicate antagonism betweenelements. For example, calcium is antagonistic tozinc. Magnesium and calcium are mutuallyantagonistic.

The first group consists of interactions whichproduce insoluble precipitates as a reaction product.


This may occur when two or more minerals in the lumencompete for the same anionic electron-bearing ligand.The ligand may be an organic compound, such as phyticacid, or an inorganic compound, such as phosphate. (15.16.17)Mineral competition for a specific dietary liganddepends on various factors including the associationconstants of the mineral-ligand compound and thesol ubi 1i ty of the product formed. (14)

When a soluble mineral salt is ingested, it isnormally ionized in the stomach. The acid pH of thestomach tends to encourage solubility. However, as thepH elevates in the intestines, the solubilitycharacteristic is lost, and the metal tends to bind withan an i on or 1igand. (13) Th is genera11 y occurs in thejejunum and ileum where the metal ion is sequestered bysuch molecules as metal-acid radical complexes which arevery stable and highly insoluble, thus rendering themineral unavailable for absorption. In order to beabsorbed, the metal ion must be soluble in theintestinal medium. (17) For example, in a precipitatedphytic acid salt state, the mineral cannot betransported by carri er protei ns across the cell ul armembrane of the mucosal ce11 s. (18) As the 1eve1 ofphytic acid increases in the feedstuffs, the absorptionof certain essential elements, especially calcium andzinc, proportionately decreases.(lg)

The same general principle discussed in relationto phyt i c ac id app1i es to other substances that arefound in the normal diet which can also form complexesor insoluble salts with various cations. For example,calcium, magnesium, zinc, manganese and iron all reactwith organic phosphates to form low solubility products.Some phosphates, such as calcium phosphate, which aresomewhat soluble in the acid environment of the stomachmay interfere with the uptake of other minerals when thedissociated phosphate anion reacts with another cation,such as iron, to form an insoluble precipitant: ironphosphate. In the particular case of iron, the


precipitation with phosphate can result in a drasticdecrease in absorption, and if severe enough, the animalcoul d exh i bi t signs of iron defi ci ency anemi a. (20.21.22.23)Table 2 demonstrates the influence of phosphates and toa lesser degree, calcium, on the absorption of iron. (24)

Table 2Influence of the addition of inorganic calcium andinorganic phosphorus on the absorption of iron

Mineral content of meal (mg)Ca P

59Fe absorpt i on*(%)

2424

202202

40414

40414

2.21.51.50.6

*All mean iron absorption rates tested weresignificantly different at the P


can occur between trace elements, macroelements, orboth. (27)

Figure 1 demonstrates these types of inter-actions.(3) The affinity of each essential mineral ionfor the electron-bearing atoms of the carrier proteindepends on their electronic configuration and theirpositions in the Periodic Table of Elements.(28,31,32)Thus, iron and copper are mutually antagonistic, sinceboth elements share the same carrier molecule in thecell membrane. (29) Norma11 y, there is a suffi ci entamount of the transport molecule, transferrin, to carryboth elements across the mucosal cells. However, ifiron and copper salts in the diet are excessivelyincreased (i.e. through a heavy intake of unbalancedmineral supplements), iron absorption is inhibited bythe copper because of a greater affinity of copper fortransferrin.(29) In this case the animal can displaysymptoms of iron deficiency anemia due to excessivedietary copper intake. This has been shownexperimentally in Table 3,(~) where both hemoglobin andhematocrit levels drop, and iron is sequestered in theliver.(30) In this particular experiment, a basal dietof 8.5% mixed grain protein was supplemented with ironalone, copper alone, or iron and copper together.

I Table 3 IEffect of supplementing the Basal Diet (8.5%mixed-grain protein) with Iron or Copper, orboth Iron and Copper

Basal +Fe +Cu Fe+CuHemoglobin (%) 10.4 9.2 11.3 9.8Hematocrit (%) 31 28 38 30Liver Fe (ppm) 183 198 187 211


The th i rd group of mi nera1 interact ions i nvo1vethe reduction in the capacity of body cells tosynthesize metal-binding proteins, due to interferencesproduced by spec i fi c react ions to some non-essent i a1heavy metal s. (33.34) The enzymat ic act i on necessary forthe building of a carrier protein can be blocked bydisplacement of a certain specific cation activated byanother exogenous metal. When this happens, the enzymemay function equally well, or may be completelyinhibited, depending on the particular enzymatic systeminvolved, and the mineral displaced.(lO) To illustrate,lead has an inhibiting effect on the anabolic routeregulating the synthesis of the porphyrin fraction ofthe hemoglobin molecule.(35) In the first stages inhemoglobin formation, the glycine is converted intoalpha amino levulinic acid, two molecules of whichcondense to form one molecule of pyrrol. Ultimately,two pa irs of pyrro1s bond together formi ng a 1argeporphyritic ring, which later undergoes a slight changein structure in one of the lateral groups of the ring.This change is a requirement for the reaction with iron.The most important enzyme catalyzing the condensation ofalpha-amino levulinic acid in pyrrol is activated byzinc, but inhibited by lead.(36) Excessive amounts oflead can result in a lower production of hemoglobin andpromote anemi a. (37)

A fourth group of mineral interactions is relatedto the previous one. In the previous group, the metalactivates the enzyme. In the fourth group, the metal isan integral part of the enzyme, thus forming ameta11 oenzyme. In these compounds, as the metal isreplaced or removed, the enzymatic action can either beaccelerated or blocked. For example, as shown in Table1, in the metalloenzyme, carboxypeptidase, zinc is anintegral part. The zinc may be inhibited from enteringinto the enzyme by cabal t . Wi thout the zinc, thepeptidase activity is reduced.(~) When cobalt replacesthe zinc in the enzyme, the peptidase activity of theenzyme will double. If either manganese or nickel


replace the zinc, peptidase activity is retarded.(39)Thus, the replacement of the zinc by other metals inthat particular metalloenzyme has the potential ofultimately affecting the protein nutrition of the animalbecause carboxypeptidase is proteolytic, catalyzing thehydrolyses of carboxy-terminal peptide bonds in peptidesand proteins.

The fifth group of mineral interactions is relatedto the transport and excretion of minerals which occurspecifically in the cells of the intestinal mucosa.Even though taken up by the intestinal cells, mineralsmay be returned to the lumen by those same cells withoutever being utilized by the body. This stagnation andexcretion can result in the replacement of a variety ofmetals at the same time.(40) The phenomenon usuallyoccurs only where specific interrelations exist betweenmetals promoting competition for specific transportmechan isms. (41)

The sixth group of mi nera1 interact ions i nvo1vechain reactions consequential to the previous groups.In the previous examples, each group of reactions wasconsidered as being separate. Generally, however, morethan one such interaction will be operating at the sametime. For example, if a certain cation is precipitatedby a given ligand making it insoluble in the intestine,then it cannot be absorbed, as has been indicated.Therefore, certain enzymatic reactions in which thatspecific metal is essential will be affected and may behalted or retarded. These enzymatic reactions may berelated to the production of other proteinaceoussubstances: hormones, carri ers, or enzymes that arerequired at the intestinal mucosa for the absorption ofsome other metals. At that point, the efficientabsorption of the other minerals is also affected. Inthis manner, the original precipitating ligand may blockthe absorpt i on of more than one essent iale1ement,although the 1igand only precipitated one mineral. (14)


Huisingh, et ~., demonstrated the complexity ofthese interactions while working with copper,molybdenum, and sulfur in ruminants and non-rumi nants. (.8) They cons idered three separateinteractions, the formations of unavailable CuMoO. andCuS and the i nh i bi t i on of MoO.2- Uptake by SO.2-- Theyshowed that these mechani sms are dependant upon eachother since the formation of either CuMoO. and Cu2+ andMoO.2- or S2-from SO.2-1 n the gut woul d 1imi t the abi 1i ty ofMoO.2- and SO.2- to precipitate in the 504 2 - x MoO.2-interact i on . (14)

Not only do interactions between mineralsinterfere with cation absorption, but vitamins may alsohave both negative and positive effects on mineraluptake. It is commonly known that vitamin D influencesthe absorption of calcium. (33) The effect of vitamin Con the absorpt i on of iron i sal so we11-known. (.3) Whenthese vitamins are absent, the absorption ofcalcium/iron, which are ingested as metal salts,significantly diminishes. On the other hand, the excessof another vitamin, such as niacin, can inactivatevitamin D which is necessary for the absorption ofcalcium.() Niacin can thus cause hypocalcemia, eventhough the levels of calcium from a salt and vitamin Din the diet appear to be adequate. Some of the clearlyelucidated synergistic relationships between vitaminsare shown in Fi gure 2. (.4)


A

PantothenIc

Niacin

K

B 12

D

BIotin

Figure 2. The synergistic relationships ofvitamins. Dietary increases in Vitamin E, Bl, andNiacin have no effects on Vitamin A, folic acid, andVitamin Bl, respectively. In all other cases adietary increase of a specific vitamin willinfluence body requirements for the other vitaminsconnected to that vi tami n by the 1i nes in th isfigure.

The quantity of fat in the feed can also affectthe absorption level of a given mineral. High fat dietspromote the formation of insoluble soaps of fatty acidsand calcium. This results in steatorrhea and areduction in calcium absorption.(46) Most of theseinterferences obviously depend on the quality of the fatin the diet and the chemical form in which the mineralelement i s found. (14,47)


Another important consideration in dietaryformulations which may affect mineral absorption is thequantity of non-digestible fiber in the feedstuffs. Ithas been demonstrated that fiber may reduce theabsorption of many minerals. In nutritional balancestudies, there were appreciable decreases in theintestinal absorption of calcium, magnesium, zinc andphosphorus in the presence of high fi ber diets. (49) Theloss of these elements through the feces correlated wellwith the increase in dry fecal material (which wasdirectly proportional to the increase of non-digestiblefi ber in the diet). These stud ies in non-rumi nantsshowed that the minerals were physically adsorbed andchemi call y bonded by the fi ber, and reta i ned in thefeces. Since some high-fiber feeds contain high levelsof phytic acid and, in some cases, oxalic acid, mineralabsorpt i on may be further reduced through theprecipitation of metal ions bonded to these organicacids as previously noted.

The chemical environments of the stomach andintestines are additional conditions affecting thepercent of mineral absorption. In unpublished research,it was shown that absorption of magnesium increased whenthe rumen was buffered wi th MgO. (49) Di fferent areas ofthe small intestine vary in their capacities to absorba given metal ion due to changes in pH. A solutioncontaining 45Ca was introduced into the intestinallumens of twelve individual rats. Thirty minutes laterthe intestinal segments were excised, ligated into nineequal segments (segment II includes the duodenum, fromthe pylobus to the ligament of Treitz), and assayed forcalcium uptake in a gas flow B-counter. The results areshown in Figure 3 and demonstrate the decreasedabsorption of calcium as it descends through the smalli ntest i ne. (51) The lower absorpt ion is a funct i on of pHand not morphological changes. (13)


80...---------------------..,

~ 70oC

641~C 5{JECDo 40Gi

D....c: 3(J.2a..o 2Gfl)..act: 10

xDCVIIIrvII01....----"-----"----1....---......10....----'------&--.....0....------"

I v VI VISegment Number

Figure 3. The absorption of calcium as it descendsthe small intestine.

With the exception of the al kal ine-earth ions (Na,K, Ca, Mg), the metallic ions tend to form insolubleprecipitates as the pH increases, which processincreasingly occurs in the distal portion of the smallintestine. Generally speaking, the more alkaline thechemical environment of the lumen, the lower is mineralabsorpt ion. (50,51) Certa in dietary components may increasethe pH of the gut to a higher than normal physiologicallevel, which further inhibits the absorption ofessential mineral elements when ingested as salts.Figure 4 demonstrates this concept. (52)


-

Strongly acid Neutral Strongly alkaline

I I-PHOSPHORUS

I I -POTASSIUM

I I I ISULFUR

I ICALCIUM

I I IMAGNESIUM

I IIRON

I IMANGANESE -.......

- I II IBORON -....I I

COPPER a ZINCI I I

MOLYBDENUM

I I-

Figure 4. The solubility of minerals at differentpH levels.

The absorption of a given mineral from the lumento the interior of the mucosal cells depends in part onthe capacity of the element to be bonded to thetransporting proteins embedded within the membrane ofthe intestinal cells. Any factor that inactivates thecarrier proteins or affects the chemical bondingcapacity of the cation, such as reducing its solubilityin the digestive tract, will cause a consequentreduction in the absorption of the cation. There are noexi st i ng general rates of absorpt ion that areuniversally accepted for essential elements in the formof salts.(lJ) Absorption varies in each particular case.According to Suttle,(14) these variations are primarilydue to the chemical form of the ingested mineral and thedegree of structural similarity it has to the effective


chemical form in which it is absorbed from theintestinal content. In other words, in the finalanalysis, the chemical interactions between the nutrientin the diet and the components of the intestinalenvi ronment are what determi ne the degree of absorpt ion.There is more than one mechanism available to transportan essential mineral through the intestinal wall towardsthe bloodstream. The system used wi 11 depend on thechemical form of the element when it reaches the mucosalmembrane of the intestinal cells.

This concept regarding the chemical form of themineral and its relative susceptibility to absorption isshown in Figures 5 through 8. In a series ofexperiments , metal sin di fferent chemi cal forms wereexposed to the intestinal mucosa for specific times.Absorptions of these different forms of the same metalwere compared as a function of time in vitro. (35,53) Inthis particular series of experiments, all potentiallyi nterferi ng factors normally found in the i ntest ina1environment were removed, thus allowing for optimumabsorption. The following figures clearly demonstratethe di fferent rates of absorpt i on of the di fferentchemical forms of the same metal.

38 The Roles of Amino Acid Chelates in Animal Nutrition350-----------------,

300Ea.E;250ZQ 200I--t:l.a:o 150enCD

~Z 100oa:

50

AAe

15 30

SECONDSFigure 5. The intestinal absorption of iron fromdifferent sources.

250

E200 Me0-SZo 150 -i=0-a:0CJ) 100 - co,CD so.(.) O2ZN 50 -

015 30 45 60

SECONDS

Figure 6. The intestinal absorption of zinc fromdifferent sources.

Factors Which Affect the Intestinal Absorption of Minerals 3935--------------------.

MC

e30 -a.0.~25 -oi=a.. 20 -cr:o

~ 15 -cr:W 10-a..0-S 5

15 30 45 60

SECONDSFi gure 7. The i ntest ina1 absorpt i on of copper f"omdifferent sources.

100,.....----------------.....,~

Ea.~ 80 -Z0

~a.. 60a:0enco 40::E::JCi5Wz 20C'~

015 30 45 60

AAC

SECONDS

Figure 8. The intestinal absorption of magnesiumfrom different sources.


These figures show the increased absorptionresulting from an essential mineral in the form of aminoacid chelate. The absorption of iron from the aminoacid chelate increased 1.7 times compared to ferrouscarbonate, 3.8 times compared to ferrous sulfate, and4.9 times compared to ferric oxide. The amino acid zincchelate was absorbed in the intestine 2.2 times morethan zinc as a carbonate, 2.3 times more than zinc aszinc sulfate, and 2.9 times more than zinc as zincoxide. In the case of copper, 4.1 times more metal wasabsorbed from the chelate than from the oxide, 2.7 timesmore than from copper carbonate and 2.8 times more thanfrom the sul fate. The magnes i urn from the ami no ac idchelate was absorbed from the intestine 1.2 times betterthan magnesium as a carbonate, 2.6 times better than asa sulfate, and 4.1 times better than as an oxide.Clearly the absorption rate of a metal is dependant onits chemical form.

It is important to understand the complexity ofmineral absorption before examining forms of mineralsthat optimize absorption and circumvent the majority ofthe problems discussed above. These amino acid chelateswill be examined in detail in the following studiesillustrating their potential and effectiveness both inthe therapeutic field as well as in the field ofprophylactic nutrition.


References

1. Phipps, D., Metals and Metabolism (Oxford:Clarendon Press) 1, 1976.

2. Davies, I., The Clinical Significance of theEssential Biological Metals (Springfield:Charles C Thomas) 1-15, 1972.

3. Dyer, I., "Mineral Requirements," in Hafez, E.and Dyer, I., eds., Animals Growth and Nutrition(Philadelphia: Lea &Febiger) 312, 1969.

4. Zunino, H., et li., "Measurement of metalcomplexing ability of poly functionalmacromolecules: Adiscussion of the relationshipbetween the metal-complexing properties ofextracted soil organic matter and soil genesisand plant nutrition," Soil Science 119:210,1975.

5. Egan, A., liThe Diagnosis of Trace ElementDeficiencies in the Grazing Ruminant, II inNicholas, D. and Egan, A., eds., Trace Elementsin Soil-Plant-Animal Systems (New York: AcademicPress, Inc.) 371, 1975.

6. Wilson, E., et li., Principles of Nutrition (NewYork: John Wiley &Sons) 4, 1979.

7. Guthrie, H., Introductory Nutrition (St. Louis:c.v. Mosby Company) 11, 1975.

8. Underwood, E., The Mineral Nutrition of Livestock(Slough: Commonwealth Agricultural Bureaux) 3,1981.

9. White, A., et li., Principles of Biochemistry(New York: McGraw Hill Book Company) 279, 1973.


10. Schutte, K., The Biology of the Trace Elements(Philadelphia: J.B. Lippincott Company) 17-23,1964.

11. Gallagher, C., Nutritional Factors and Enzym-ological Disturbances in Animals (Philadelphia:J.B. Lippincott Company) 12-38, 1964.

12. Ibid, 76-77.

13. Ashmead, H. D., et ~., Intestinal Absorption ofMetal Ions and Chelates (Springfield: Charles CThomas) 13-26, 1985.

14. Suttle, N., "Trace Element Interactions inAnimals," in Nicholas, D. and Egan, A., eds.,Trace Elements in Soil-Plant-Animal Systems (NewYork: Academic Press, Inc.) 271, 1975.

15. Williams, S., Nutrition and Diet Therapy (St.Louis: C.V. Mosby Co.) 137, 1977.

16. Cabell, C. A. and Earle, I. P., "Additive effectof calcium and phosphorus on utilization ofdietary zinc," J. Animal Sci., 24:800, 1965.

17. Vohra, P., et ~., "Phytic acid-metal complexes,"Proc. Soc. Exp. Biol. Med., 120:447, 1965.

18. Witt, W., Biology of the Cell (Philadelphia:W.B. Saunders Co.) 433, 1977.

19. Oberleas, D., et ~., "The Avail abil ity of Zincfrom Foodstuffs," in Prasad, A., ed., ZincMetabolism (Springfield: Charles C Thomas) 225,1966.

20. Pond, W. G., et ~., "Effect of dietary Ca and Plevels from 40 to 100 Kg body weight on weight


gain and bone and soft tissue mineralconcentrations," J. Animal Sci., 46:686, 1978.

21. Pond, W. G., et li., "Weight gain, feedutilization and bond and liver mineralcomposition of pigs fed high or normal Ca-P dietsfrom weaning to slaughter weight," J. AnimalSci., 41:1053, 1975.

22. Sell, J. L., "Utilization of iron by the chick asinfluenced by dietary calcium and phosphorus,"Poultry Sci., 44:550, 1965.

23. Waddell, D. G. and Sell, J. D., "Effects ofdietary calcium and phosphorus on the utilizationof dietary iron by the chick," Poultry Sci.,43:1249, 1964.

24. Monsen, E. R. and Cook, J. D., "Food ironabsorption in human subjects IV. The effects ofcalcium and phosphate salts in the absorption ofnonheme iron," Am. J. Clin. Nutr., 29:1142,1976.

25. Hill, C. J. and Matrone, G., "Chemical parametersin the study of in vivo and in vitro interactionsof transition elements," Fed. Proc., 29:1474,1970.

26. Ashmead, H.D., Ope cit., 103.

27. Starcher, B. C., "Studies on the mechanism ofcopper absorption in the chick," J. Nutr.,97:321, 1969.

28. Ahrland, S., et li., "The relative affinities ofligand atoms for acceptor molecules and ions,"Chern. Soc. London Quart. Rev., 12:265, 1958.

29. El-Shobaki, F. and Rummer, W., "Binding of copperto mucosal transferrin and inhibition of


intestinal iron absorption in rats," Res. Exp.Med., 174:187, 1979.

30. Caster, W. and Resurreccion, A., IIInfluence ofCopper, Zinc, and Protein on Biological Responseto Dietary Iron," in Kies, C., ed., NutritionalBioavailability of Iron (Washington, D.C.:American Chemical Society) 103, 1982.

31. Ashmead, H., "Tissue transport of organic traceminerals," J. Appl. Nutr. 22:42, 1970.

32. Little, P., "A Role of Chelated Minerals in theBody," in Ashmead, D., ed., Chelated MineralNutrition in Plants, Animals. and Man(Springfield: Charles C Thomas) 264, 1982.

33. Templin, V. M. and Steenbock, H., "Vitamin D andthe Conservation of Calcium in the Adult. II.The effect of vitamin D on calcium conservationin adult rats maintained on low calcium diets,"J. Biol. Chern., 100:209, 1933.

34. Blunt, J. and Deluca, H., "Biologically ActiveMetabol ites of Vitamin D," in Deluca, H., ed.,The Fat Soluble Vitamins (New York: PlenumPress) 69, 1978.

35. Ashmead, H., et li., "Trace Mineral Inter-relationships, New Techniques of Detecting leadand Other Heavy Metals in Animals, and The Roleof Organic Chelated Trace Elements Playas EnzymeCatalysts," Presented at Okla. Vet. Med.Convention, Tulsa, 1971.

36. Nieburg, P. I., et li., "Red blood cell-delta.-aminolevulinic acid dehydrase activity; an indexof body lead burden," Am. J. Dis. Child.,127:348, 1974.


37. Hoffbrand, A. and Konopka, l., "Haem synthesis insideroblastic anemia," in Porter, R. andFitzsimons, D., eds., Iron Metabolism (Amsterdam:Elsever) 269, 1977.

38. Deluca H. F., "Vitamin D and Calcium Transport,"Ann. N.Y. Acad. Sci., 307:356, 1978.

39. Hsu, J., "Biochemistry and Metabolism of Zinc,"in Zarcioglu, Z. and Sarper, R., eds., Zinc andCopDer in Medicine (Springfield: Charles CThomas) 70, 1980.

40. Hendri x, T., "The Absorpt i ve Funct i on of theAlimentary Canal," in Mountcastle, V., ed.,Medical Physiology (St. louis: C.V. Mosby) V2,1117, 1974.

41. Deluca, H., "The Control of Calcium andPhosphorus Metabolism by the Vitamin D EndocrineSystem," in Levander, o. and Cheng, L., eds.,Micronutrient Interactions: Vitamins, Minerals,and Hazardous Elements (New York: N.Y. Academyof Science) 12, 1980.

42. Huisingh, J., et li., Abstract #3833 "Sulfatereduction in mixed and isolated rumen bacteria,"Fed. Proc., 32:900, 1973.

43. Conral, M. and Schade, S., "Ascorbic acidchelates in iron absorption: A role forhydrochloric acid and bile," Gastroenterology,55:35, 1968.

44. Patrick, H. and Schaible, P., Poultry Feeds andNutrition (Westport: AVI Publishing Co., Inc.)144, 1980.

45. Nicolaysen, R., et li., "Physiology of calciummetabolism," Physiol. Rev., 33:424, 1953.


46. Guthrie, Ope cit., 117.

47. Fleischman, A. I., et li., "Effects of dietarycalcium upon lipid metabolism in mature male ratsfed beef tallow," J. Nutr., 88:255, 1966.

48. Reinhold, J. G., et li., "Decreased absorption ofcalcium, magnesium, zinc and phosphorus by humansdue to increased fiber and phosphorus consumptionas wheat bread," J. Nutr., 106:493, 1976.

49. Beede, D., Personal communications, Sept., 1988.

50. Wa1dron-Edward, D., "Effects of pH and counteri onon absorption of metal ions," in Skoryna, S. andWaldron-Edward, D., eds., Intestinal Absorptionof Metal Ions, Trace Elements, and Radionuclides(Oxford: Pargamon Press) 381, 1971.

51. Wa1dron-Edward, D., et li., "Effects of thecounter i on and pH on intest ina1 absorpt i on ofcalcium and strontium," Proc. Soc. Exp. Biol.Med. 123:532, 1966.

52. Hsu, H., "Trace Mineral Availability to Plants,"in Ashmead, D., ed., Chelated Mineral Nutritionin Plants, Animals and Man (Springfield: CharlesC Thomas) 60, 1982.

53. Graff, D., et li., "Absorption of mineralscompared with chelates made from various proteinsources into rat jejunal sl ices in vitro, IIPresented at Utah Acad. Arts, Letters, Sci., SaltLake City, April, 1970.

Chapter 3

COMPARATIVE INTESTINAL ABSORPTION ANDSUBSEQUENT METABOLISM OF

METAL AMINO ACID CHELATES ANDINORGANIC METAL SALTS


As noted in the previous chapter, when consideredin its most basic terms, animal nutrition is the optimalintake of protein, carbohydrates, fats, vitamins,minerals, and water for growth and maintenance of bodytissues, for energy, and to regulate all of the bodyprocesses. Health and well being of the animal aredependant upon the opt i mum mi x and intake of thesenutrients. An absolute deficiency of anyone of themfor an extended period will result in death. Minerals,function in all of the above nutrient roles. Thisnecessitates having an intake amount of the essentialmineral nutrients to carry out their multitude ofassigned functions. Optimal level is the key. Too muchor too little has an equally deteriorative effect on theanimal as illustrated in Figure 1.

47


HEALTH FUNCTION

100%

MARGINAL

OPTIMAL

MARGINAL

-~~ NUTRIENT INTAKE ~Figure 1. A dose response curve.

As seen in Figure 1, if there is an acutedeficiency or an extreme toxicity of an essentialmineral, death will occur. If the deficiency or thetoxicity is marginal, the health and well being as wellas the performance of the animal will be impaired. Thusit becomes absolutely necessary to provide minerals thatare "safe" and yet biologically available. The factthat a mineral is mixed in the feed and is chemicallypresent does not guarantee it wi 11 be absorbed andmetabol i zed. There are numerous factors that wi 11positively or negatively influence the bioavailabilityof essential minerals. Many of these intrinsic andextri ns i c factors have been revi ewed by Kratzer andVohra and are summarized in Table 1.(1)

Comparative Intestinal Absorption and Subsequent Metabolism 49of Metal Amino Acid Chelates and Inorganic Metal Salts

Table 1

Factors Affecting Mineral Bioavailability

Intrinsic factors:

1. Animal species and its genetic makeup2. Age and sex3. Monogastric or ruminant (intestinal microflora)4. Physiological function: growth, maintenance, reproduction5. Environmental stress and general health6. Food habits and nutrition status7. Endogenous ligands to complex metals (chelates)

Extrinsic factors:

1. Mineral status of the soil on which the plants are grown2. Transfer of minerals from soil to food supply3. Bioavailability of mineral elements from food to animal

a. Chemical form of the mineral (inorganic salt or chelate)b. Solubility of the mineral complexc. Adsorption on silicates, calcium phosphates, dietary fiberd. Electronic configuration of the element and competitive antagonisme. Coordination numberf. Route of administration. (oral or injection)g. Presence of complexing agents such as chelatesh. Theoretical (in vitro) and effective (in vivo) metal binding

capacity of the chelate for the element under considerationi. Relative amounts of other mineral elements

In the lumen:

1. Interactions with naturally occurring ligandsa. Proteins, peptides, amino acidsb. Carbohydratesc. Lipidsd. Anionic moleculese. Other metals

2. At and across the intestinal membranea. Competition with metal-transporting ligandsb. Endogenously mediating ligandsc. Release to the target cell


To review each of these factors is outside thescope of th i s chapter. The purpose of th i s presentdiscussion is to examine a single extrinsic factor inTable 1: the chemical form of the mineral as it affectsmineral bioavailability. It is well established that aninorganic metal salt has a different absorption levelthan a chel ate. (2) Even among chel ates, absorpt i on rateswill vary according to the ligand, stability constants,molecular weights, etc.()

Because there are numerous ligands including aminoacids, ascorbic acid, citric acid, gluconic acid,ethylenediaminetetraacetic acid, etc., for the purposesof this discussion the field of chelates will benarrowed to deal only with chelates resulting from thebinding of the polyvalent cation to the alpha-amino andcarboxyl moieties of an amino acid to form a five-membered ring. The structure of the ring consists ofthe metal atom, the active carboxyl oxygen atom, thecarbonyl carbon atom, the alpha-carbon atom, and thealpha-nitrogen atom. The bonding is accomplished byboth coordinate covalent and ionic bonding. At leasttwo and sometimes three, amino acids can be bound to asingle metal ion, depending upon its oxidative state, toform bicyclic (Figure 2) and/or tricyclic ringedmolecules. Even though the oxidative states of certaincations would allow for a fourth amino acid to bechelated to the cation, the bonding angles and theatomic distances required for chelation would tend topreclude its occurrence.

Comparative Intestinal Absorption and Subsequent Metabolism 51of Metal Amino Acid Chelates and Inorganic Metal Salts

Figure 2. A two dimensional drawing of a bicyclicchelate of iron with glycine and methionine asamino acid ligands.

As defined by the American Association of FeedControl Officials (AAFCO), such a metal amino acidche1ate as seen in Fi gure 2 is descri bed as, "theproduct resulting from the reaction of a metal ion froma soluble metal salt with amino acids with a mole ratioof one mole of metal to one to three (preferably two)moles of amino acids to form coordinate covalent bonds.The average weight of the hydrolyzed amino acids must beapproximately 150 and the resulting molecular weight ofthe chelate must not exceed 800."(4 ) An amino acidchelate is not the same as a metal proteinate which islithe product resulting from the chelation of a solublesalt with amino acids and/or partially hydrolyzedprotei n. 11(15) The 1atter does not descri be ei ther thestability of the chelate, the molar ratio of aminoacids, or the molecular weight, all of which will affectmineral bioavailability.(J) The looseness of the metalproteinate definition allows for loosely definedproducts which may not provide reproducible results fromusage to usage. Conversely, since the metal amino acidchelates are more tightly defined, research results andexpectations in practical usage can be expected to bemore reliable.


In an experiment comparing absorption capacity ofthe amino acid chelates versus inorganic sources of thesame metals, jejunal segments from adult male Sprague-Dawley albino rats beginning ten (10) cm below thepylorus and continuing for another twenty (20) cm werede1i neated and removed. The segments were placed inpetri dishes containing a buffer solution and maintainedat 5 C. Each intestinal segment was cut into twocentimeter segments and then severed longitudinallyalong the mesenteric line. The segments wererandomized, washed, rinsed, and incubated in KRB (KrebeRingers Bicarbonate) solution at 37 C while 95.5%oxygen and 4.5% carbon dioxi de bubb1e

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The Roles of Amino Acid Chelates in Animal Nutrition