nitrogen balance in lambs after weaning
著者 Fujihara Tsutomu journal or
publication title
三重大学大学院生物資源学研究科紀要
volume 37
page range 31‑43
year 2011‑02‑01
その他のタイトル 育成メンヨウの増体および窒素出納に及ぼす給与飼 料中蛋白含量の影響
URL http://hdl.handle.net/10076/11522
Introduction
Rumi nantani mal sl ettohabi tal otofmi crobes,
i.e. ,thesel f - nutri ti ousmi crobes,i nthei rstomach,so cal l edthereti cul o- rumen,andthen,thei rprotei nmetabol i sm i sl argel ydi f f erentf rom othermammal s
1）. Thei ngesteddi etaryprotei ni sdegradedtoammoni abymi crobes,andf urthertheyprol i f erateusi ngthe el aboratedammoni ai ntherumen,
i.e. ,synthesi sofmi crobi alprotei n.Then,themi crobi alprotei ni s di gestedi nthel owerguts,andf urtheruti l i zedasmetabol i zabl eprotei ni nthebody. Furthermore, rumi nantani mal saredi f f erentf rom mono- gastri cani mal s,andtheyareabl etousenon- protei nni trogen
（NPN）
tosynthesi zeprotei n,
i.e. ,theywi l lbeabl etosynthesi zehi ghqual i ty- protei nf rom poorprotei n, suchasroughages
2）.So,thepartofi ngestedprotei n,suchasprotei nescapedmi crobi alf ermentati on,and di gestedbutnotuti l i zed,wi l lbeexcretedi ntof aecesasun- absorbedprotei n.Ontheotherhand,mostof absorbedami noaci dsareusedi nthel i vertosynthesi zeprotei ntobereservedasbodyprotei n,andthen, theunabsorbedami noaci dsand/ ordri venthroughdegradati onofti ssueprotei ni nthebodywoul dbe
Effectofdietaryproteinlevelongrowth andnitrogenbalanceinlambsafterweaning
TsutomuF
UJIHARAFacultyofBioresources,MieUniversity,1577Kurimamachya-cho,Tsu-shi514-8507,Japan
Abstract
Inthepresentstudy,theeffectofchangesindietaryproteinlevelonthegrowthrateandnitrogen balancewereinvestigatedinlambsafterweaning.Using2twinsoflambsweanedat55daysafterbirth, eachoftwinswereallocatedintotwogroups,whichtheywerefedhighprotein（HP）orlowprotein（LP） diet;1.8or1.2timesofmaintenancelevelrespectively.Thedietwasconsistedwithtimothyhay,rolled barleyandsoy-protein.Feedintakeandbodyweightweremeasureddailyandweekly,respectively,and thenitrogen（N）balancetrialwasconductedat1,2and3week,and2,3and5monthafterweaning.The dailygain（DG）throughtheexperimentalperiodwas153and142（g/d）inHPandLPgroupsofJapanese Corriedalelambs,andthatwasalso235and145（g/d）inHPandLPgroupsofcrossbred（Japanese CorriedaleX Suffolk）lambs,respectively.TheN consumptionwasmoreinHPgroupthaninLPgroup duringtheperiod,andthen,NretentioninthebodywasalsogreaterinHPgroupthaninLPgroup,and thesephenomenawouldreflectonthegrowthrateintwogroupsdescribedabove.OnthechangesinN balanceduringtheperiod,theintakeincreasedbuttotalexcretionalsoincreasedalongwithaging,and consequently,theratioofretentiontoabsorptiontendedtodecreaseasawhole.TheN retentiontended todecreaseinLPgroup,althoughthattendedtoincreaseinHPgroupalongwithaging.TheretainedN permetabolicbodyweight（KgW0.75）didnotchangeinLPgroupthoughitdecreasedinHPgroupafter 2month. ThesefindingssuggestthatthechangeintheDG oflambingrowingstageisobviously influencedbychangesinretainedN causedbychangesindietaryproteinlevel.
KeyWords:Dietaryproteinlevel,Growthperformance,N balance,Lambs, February，2011
2010年9月28日受理
convertedtoureathroughammoni ai nthel i ver,andf urtherexcretedthroughki dneyi ntouri ne
3）. Thedi etaryprotei nabsorbedi susedtosynthesi zebodyprotei n,andtheothersi de,thebodyprotei ni s al sodegradedandexcretedi ntouri neasni trogen
（N）,
i.e. ,thebodyprotei ni si ndynami cstate;synthesi s anddegradati onwi l lbedonesi mul taneousl y.Then,i nadul tani mal sbodyprotei ni smostl ymai ntai ned atcertai nl evel ,socal l ed・dynami cbal ancedsi tuati on・,andsothei rNbal ancewi l lbezero,
i.e. ,theywi l l beatmai ntenanceperi odi nprotei nnutri ti on.Ontheotherhand,theNbal ancei nani mal sundergrowi ng stagecoul dbeposi ti ve
（plus
）,andi ntheperi odofhi gherdegradati onthansynthesi sofbodyprotei n,N bal ancewi l lbesurel ynegati ve
（minus
）.Sothi sN bal ancei sshowi ngi ncreaseanddecreaseofbody protei n,andwi l lbeani ndextoj udgeacondi ti onofprotei nnutri ti on,whi chwoul dbeaf f ectedwi thagi ng, bodywei ghtandtotalnutri ti on.Thesynthesi sandaccumul ati onofbodyprotei naresurel yamai nevent duri ng growi ng ofbody,and then theaccumul ati on ofprotei n obvi ousl y i ncreasesal ong wi th a devel opmentofbodyti ssuesand organs,and consequentl y,theprotei nrequi rementshoul d cl earl y i ncreasesi nthegrowi ngani mal s.
Then,i nrumi nantsthedevel opmentofshapeand/ orf uncti oni nthereti cul o- rumenshoul dberel atedto ani ncreasei ni ntakeofsol i df eedaf terweani ng
4）.Inyoungrumi nants,ani nsuf f i ci enti ntakeofsol i df eed resul tedi nani mperf ectsi tuati onofreti cul o- rumenf uncti onascomparedwi ththati nadul trumi nants, andtheni nthi sci rcumstance,mostofthei rprotei nrequi rementtomeetthegrowthand/ ortomai ntai nthe physi ol ogi calf uncti ons,coul d be suppl i ed di rectl y through di etary protei n f ormi crobi alprotei n synthesi zedi ntherumenasmaturerumi nants.Consequentl y,thequanti tati veand/ orqual i tati vechanges i ndi etaryprotei ncoul dhaverel atedtothechangesi nabsorpti on,metabol i sm ordeposi ti onofprotei ni n thebodyofyoungrumi nants,i nparti cul aratweani ngstage.Thereare,however,sti l lmanypoi ntstobe cl eared abouttheef f ectsofthechangesi n system ofnutri enti ntakef rom mono- gastri ctypeto rumi nant- typeonprotei nnutri ti on,andal sothedevel opmentoftherumenal ongwi thgrowth.Ingeneral , i ti swel lknownthatthedi f f erencei nl evelofnutri ti onf edtotheyoungani mal scl earl ygi veri seto di f f erencei ngrowth,
i.e. ,thedi f f erencei nbodywei ghtthroughani ncreaseoradecreaseofgrowthrate, aroundmaturestageexternal l y
5）.
Inthepresentstudy,thegrowthrateandni trogenbal anceduri nggrowi ngstagehavebeeni nvesti gated af terweani ngi nl ambsf edthedi etswi thdi f f eri ngprotei nl evel .
MaterialsandMethods Animals,dietsandmanagement
JapaneseCorri edal etwi nf emal e
（nos.4& 5）andcrossbred（JapaneseCorriedal eX Suf f ol k
）twin f emal el ambs
（nos.9&10）wereusedi nthepresentexperi ment.Theywererearedwi ththei rdamsduri ng suckl i ngperi od,andtheyweregradual l yal l owedtoeathays,concentrateand/ orstarter
（pell ets
）f orcal ves f rom 2weeksaf terbi rth.Then,theywereseparatedf rom thei rdams,andweanedon55daysaf terbi rth, andi ndi vi dual l ykepti nametabol i sm cratewi thwi re
（net）f l oorduri ngtheenti reexperi mentalperi od.
Af terweani ng,eachtwol ambsofthetwotwi nsweredi vi dedtwogroupsandf edhi ghprotei ndi et
（HP:nos.4& 9
）orl ow protei ndi et
（LP:nos.5& 10）accordingtotheNRC
（NationalResearchCounci l
）standard
6）.Thetwol evel sofdi etaryprotei nwereasf ol l ows:HP:1. 8andLP:1. 2ti mesofmai ntenance l evel ,respecti vel y.
Ti mothyhayandrol l edbarl eywasusedasmai ndi etaryconsti tuents,andsoybeanprotei nwasusedto
adj ustadi etaryprotei nl eveldel i catel y
（Table1
）.Theti mothyhayandconcentrate
（barleyandsoybean
protei n
）wereoff eredseparatel y. Freshwaterwasf reel yavai l abl e,andeachl ambhadaccesstoa
mi neral i zedsal tl i ckatal lti me.Theani mal swerewei ghedonceaweekbef orethemorni ngf eed.Thef eed i ntake
（roughage& concentrateseparately
）,f eedresi due
（orts）,f aecesanduri newerevol umetri cal l y measured,andkeptonrecorddai l yduri ngenti reexperi mentalperi od.
Experimentalprocedure
Onthe1- ,2-and3- weeksaf terweani ng,andal so2- ,3-and5- month- ol dofl ambs,dai l yf eedi ntake,and f eedresi dueweremeasuredduri ng5- 7days,andal socol l ectedf aecesanduri nef orchecki ngdi gesti bi l i ty ofthedi etandN bal ance.
Theni trogen
（N）inthedi et,orts,f aecesanduri newasanal yzedbytheKj el dahlmethod,andthe contentsofcrudef at,crudef i breandashi nthedi etweredetermi nedaccordi ngtoAOAC
（Associati onof Of f i ci alAnal yti calChemi sts
）method
7）.Theuri naryNwasanal yzeddai l yi neachani mal ,andtheval ues wereaveragedi neachperi od.TheNi ntheortsandf aeceswasmeasuredusi ngthemi xedsampl esofeach peri od.
ResultsandDiscussion Feedintakeandgrowthrate
InFi gure1,thechangesi nbodywei ghtofl ambsaf terweani ngareshown,andtherewerecl earl ysome di f f erencei ngrowthratebetweentwogroupsofdi etaryprotei nl evel .Onthef i rstweekaf terweani ng, therewasnodi f f erencei nbodywei ghtoftwi nl ambs;therewerecl eardi f f erenceofbodywei ghti nHP groupandLPgroupat5monthaf terbi rthasf ol l ows;nos.4&5:5kg,nos.9&10:12kg,
i.e. ,hi ghprotei n di etsurel yi ncreasedthebodywei ght.Thi sresul tcl earl yconf i rmedthati nani mal srearedwi thhi gh
Fig.1 Thegrowthcurvesoflambsduringtheperiod.
Table1.Chemicalcompositionoffeed
1）
Ni trogenf reeextract.
2）Totaldi gesti bl enutri ents.
Timothyhay Rolledbarley Soyprotein
Drymatter（％） 89.4 87.8 89.1
Crudeprotein（％） 8.4 11.2 85.1
Crudefat（％） 2.3 1.4 0
Crudefibre（％） 26.6 1.3 0
NFE1）（％） 42.8 71.3 0
Crudeash（％） 9.3 2.6 4.3
TDN2）（％） 62.1 86.4 85.0
concentratedi et,
i.e. ,hi ghnutri ti onall evelf eedi ng,obvi ousl yi ncreasestherateofgrowth
8,9）.
Asshowni nFi gure2,theaveragedai l ygai n
（ADG）i neveryweekaf terweani ngwas153,142,235and 145gi nNo.4,No.5,No.9andNo.10l ambs,respecti vel y.Thedi f f erencei nADGbetweenHPandLP groupswerehi gheri ncrossbredl ambsthani nJapaneseCorri edal el ambs,andi twoul dbecausedbythe di f f erenceoftypeofbreed,
i.e. ,meattype
（nos.9&10）andwooltype
（nos.4&5）.Theaveragedai l ygai n i nJapaneseCorri edal etwi nwasrel ati vel ysteadyascomparedwi ththati nanothertwi nal ongwi ththe growth,andi nparti cul artheval uei nNo.9l ambwasf ai rl yhi ghratherthantheotheraf ter11
thweek.The ADGofNo.10l ambwasrel ati vel ybi gvari ancethroughtheenti reexperi mentalperi odascomparedwi th thati notherl ambs.Thechangei nDG ofNo.9l ambsduri ng9
thto15
thweekswasgreaterthanthosei n otherl ambs,andi twoul dbeduetodecreaseofroughagei ntakei nani mal sexceptNo.9duri ngsummer
Fig.2 Thedairygainoflambsduringtheperiod.
Fig.3 Thefeedintakeinlambsduringtheperiod.
Fig.4 Thefeedintakepermetabolicbodyweightinlambsduringtheperiod.
season.Then,monthl yf eedi ntakei ni ndi vi dual ,andal sothatpermetabol i cbodywei ght
（MBW）duri ng theenti reexperi mentwereshowni nFi gures3and4,andso,f eedi ntakeofNo.9l ambswassuperi orto thoseofotherl ambs.Thi speri odwasal mostthesametotheperi odsof9
thto15
thweeksofexperi ment.
Thequi tebi gdi f f erencei nroughagei ntakebetweenNo.9andotherl ambscoul dcausetodi f f erencei n DG.Ingeneral ,therewi l lbeacl oserel ati onshi pbetweenadevel opmentofthereti cul o- rumenandan i ncreaseofDGi nyoungrumi nants.Brownl ee
10）andWarner
etal.
11）haveshownthatadevel opmentofthe rumencoul dbecl earl yi nf l uencedwi thchemi calpropertyofsol i df eedi ngested,andf eedi ngofahi gh energyconcentrate- di ethasanef f ectonthedevel opmentofmucosalpapi l l ai ntherumen.Tamate
etal.
4）hasal soreportedaphysi calpropertyofroughagesi ngestedobvi ousl ycontri butetoi ncreaseof vol umei nreti cul o- rumenanddevel opmentofmuscl el ayerofrumenwal l . Furthermore,Hari sson
etal.
12）andStobo
etal.
13）havedemonstratedthatthechangei naqual i tyofsol i df eed
（suchasaratioof roughageandconcentrate
）hasbeenadaptedtoamorphologi calchangeofthereti cul o- rumen. As
Table2.Theaveragebodyweightandfeedintakeinlambsduringtheperiod
1）
Week.
2）month.
3）LambNo.i nHPgroup.
4）LambNo.i nLPgroup.
5）
Rol l edbarl ey+soyprotei n.
Periodafterweaning
1 2 31） 2 3 52）
Bodyweight（kg）
No.43） 12.5 13.8 15.2 21.0 23.8 33.0 No.54） 11.7 12.6 13.8 17.8 21.2 28.2 No.93） 16.6 18.0 20.0 27.2 31.8 42.8 No.104） 13.8 15.8 17.0 23.6 26.2 30.8
Feed/nutrientintake（g/d/h） Timothyhay
No.4 167 179 162 214 283 418
No.5 150 166 163 155 181 330
No.9 174 201 243 300 700 694
No.10 177 247 249 242 433 433
Concentrate5）
No.4 396 396 452 676 676 746
No.5 388 388 388 528 668 708
No.9 536 536 571 716 816 886
No.10 528 528 528 668 708 758
Drymatter（g/d/h）
No.4 500 510 528 788 843 1022
No.5 477 492 489 606 753 922
No.9 625 648 716 894 1329 1365
No.10 616 688 690 808 1014 1058
Crudeprotein（g/d/h）
No.4 189 190 196 227 233 250
No.5 124 126 125 134 141 153
No.9 213 215 221 241 278 273
No.10 136 142 142 146 162 163
menti onedabove,therei sacl oserel ati onshi pbetweenasol i df eedi ntakeandgrowthrate,
i.e. ,dai l ygai n i nrumi nantani mal .IntheTabl es2and3,theADG,f eedi ntake,di gesti bi l i tyofdrymatter
（DM）and crudeprotei n
（CP）,and totaldi gesti bl enutri ents
（TDN）i ntakei n each twi n l ambswi thi n the experi mentalperi odareshown.Asdescri bedabove,i twasveryhotsummeri ntheyearwhenthe experi menthasbeendone,andsoexperi mentalani mal sresul tedi ntobeexposedtothehotenvi ronment f oraqui tel ongperi od.Rumi nantani mal swi l lbegeneral l ythoughttobenotstrongunderahot envi ronment,andsoadecl i neoff eedi ntakel eadi ngal owergrowthrateaf terweani ngi srel ati vel y commonunderthosecondi ti ons.Inthepresentstudy,asdescri bedbef ore,roughagei ntakeofl ambsexcept No.9werei nf l uencedunderthehotenvi ronment,butthei ntakeofconcentratei ncreasedal ongwi than i ncreaseofbodywei ghti ndi vi dual l y.Asaresul t,theref ore,thetotali ntakesofCPandTDN i nal lthe ani mal smi ghtbei magi nedtobei ncreasedtotal l yi nthepresentstudy.Inthepresentexperi ment,al lthe ani mal shadcompl etel yconsumedtheconcentrateof f eredduri ngtheperi od,
i.e. ,thei rprotei ni ntake i ncreasedal ongwi ththestageofgrowi ng,andconsequentl y,averagedCPi ntakei nHPgroupwas1. 6 ti meshi gherthanthati nLPgroup.OntheTDN i ntakeduri ngtheperi od,therewasnodi f f erence betweentwogroupsatoneweekaf terweani ng;however,onthe5monthaf terweani ng,thetotali ntake i nHPgroup
（100& 250g/d:nos.4& 9
）wasgreaterthanthatinLPgroup
（nos.5& 10）.TheDM di gesti bi l i tyi nnos.4&5i ncreasedunti l3monthaf terweani ngandat5monthi tdecreased,andthati n nos.9& 10i ncreasedonl yunti l3weeksaf terweani ngandthereaf teri tdecreasedunti ltheendofthe experi ment.Thedi f f erenceofDM di gesti bi l i tybetween2groups
（withi ntwi ns
）wouldbeduetoan i ncreaseofroughagei ntakei nHPgroupduri ngtheperi od,i nparti cul ari nNo.9l amb,theconti nuous i ncreaseofroughagei ntakeresul tedi narel ati vel yl owDM di gesti bi l i tyduri ngtheperi od.Therewasa l i ttl edi f f erencei nDM di gesti bi l i tybetween2ani mal sofeachtwi n.Asdescri bedabove,adevel opment ofreti cul o- rumensti mul atedthroughani ncreaseoff eedi ntakecoul dbethoughttoi ncreasei nbody wei ghti nl ambs.
Table3.DigestibilityofdrymatterandcrudeproteinandTDN1）intakeinlambs
1）
Totaldi gesti bl enutri ents.
2）Week.
3）Month.
4）LambNo.i nHPgroup.
5）
LambNo.i nLPgroup.
Periodafterweaning
1 2 32） 2 3 53）
Drymatter（％）
No.44） 75.6 77.5 76.6 79.0 78.6 74.8 No.55） 76.0 74.9 78.7 75.7 79.5 72.6 No.94） 78.8 78.9 82.2 81.1 73.6 71.7 No.105） 75.9 76.6 79.7 77.5 73.9 69.3 Crudeprotein（％）
No.4 88.7 89.1 88.5 86.8 87.4 85.3 No.5 84.9 82.6 86.0 81.4 81.9 78.4 No.9 87.9 86.9 88.7 87.3 82.0 76.2 No.10 80.5 82.4 82.4 78.6 78.0 72.5 TDN intake（g/d/h）
No.4 362.5 379.2 401.3 600.1 642.2 740.0 No.5 348.5 353.6 369.5 441.6 577.1 641.5 No.9 477.2 495.6 570.0 701.7 945.0 947.2 No.10 456.3 505.6 527.0 601.2 715.7 701.5
ThechangesinNbalanceduringgrowth
Thechangei nNbal anceofeachl ambduri ngtheexperi mentalperi odi sshowni ntheTabl e4,andthe Nbal anceofi ndi vi dualat1,2and3weeksandat1,2,3,and5monthsaf terweani ngareshowni nFi gures 5and6,respecti vel y.
TheN i ntakeobvi ousl yi ncreasedal ongwi thi ncreaseofbodywei ght,andtheval uewasgreateri nHP groupthani nLPgroup. Therati oofN absorpti on
（AbsorbedN/consumedN
）andtheratioofN retenti on
（retainedN/ consumedN
）wereal sohi gheri nHPgroupthani nLPgroup.IntheLPgroup
（Fi
gure5
）,at3weeksaf terweani ngaveragedN i ntakewas30g/ dand20g/ di nNo.4andNo.5l ambs, respecti vel y,andN excreti oni ntof aeceswereal mostthesamei nal lani mal sregardl essi ndi vi dualN i ntake.Inuri naryN excreti on,therewereal i ttl echangeat1and2weeksaf terweani ng,andthen,at3
Table4.NitrogenbalanceinlambsfedonLPorHPdiet.
1）
Week.
2）Month.
3）LambNo.i nHPgroup.
4）LambNo.i nLPgroup.
Periodafterweaning
1 2 31） 2 3 52）
Intake（g/d/h）
No.43） 30.2 30.3 31.4 36.3 37.3 40.0 No.54） 19.9 20.1 20.0 21.5 22.6 24.5 No.93） 34.0 34.4 35.5 38.6 44.5 43.6 No.104） 21.5 22.7 22.7 23.4 25.9 25.5 FecalN（g/d/h）
No.4 3.36 3.30 3.56 4.84 4.71 5.93 No.5 3.00 3.48 2.77 4.04 4.15 5.26 No.9 4.15 4.52 4.04 4.89 8.00 10.40 No.10 4.23 4.03 4.03 5.02 5.73 7.05 UrinaryN（g/d/h）
No.4 3.18 2.74 5.58 4.55 6.63 6.16 No.5 2.33 2.21 2.59 4.04 5.03 5.86 No.9 5.86 6.00 4.52 7.31 10.33 5.01 No.10 2.38 2.48 2.05 3.06 5.49 3.71 RetainedN（g/d/h）
No.4 23.6 24.3 22.2 27.0 26.0 27.9 No.5 14.6 14.4 14.6 13.5 13.5 13.4 No.9 24.0 23.9 27.0 26.4 26.2 28.2 No.10 14.6 16.2 16.7 15.3 14.7 14.7 RetainN/IngestedN（％）
No.4 78.1 80.2 70.7 74.4 69.7 69.8 No.5 73.4 71.6 73.0 62.8 59.7 54.7 No.9 70.6 69.5 76.1 68.4 58.9 64.7 No.10 69.3 71.4 73.6 65.4 56.8 57.6 RetainedN/absorbedN（％）
No.4 88.1 90.0 79.9 85.6 79.7 81.8 No.5 86.5 86.7 84.9 77.1 72.9 69.8 No.9 80.3 80.0 85.8 78.4 71.8 84.9 No.10 86.1 86.7 89.3 83.2 72.8 79.5
weeksaf terweani ng,theuri naryNexcreti onofNo.4l amb
（5.58g/ d
）wasabout2ti meshi gherthanthat ofNo.5Lamb
（2.59g/ d
）.Consequentl y,i nNo.4l ambtheNi ntakedi dnotcl earl ychangeduri ng3weeks af terweani ng,andsoretai nedN al sodecreasedl eadi ngal owerN uti l i zati on
（retainedN/ absorbedN
）. Therati oofNabsorpti oni nLPgroupaf terweani ngdi dnotchangeduri ng3weeks,andthef i gureswere hi gheri nNo.4l ambthani nNo.5l amb.Intherati oofN retai ned,theval uedecl i nedat3weeksaf ter weani ngi nNo.4l amb.TheNuti l i zati on
（retainedN/ absorbedN
）wasal wayshi gheri nNo.4l ambthan i nNo.5l ambduri ngtheperi odexcepttheval ueat3weeksaf terweani ng.IntheHPgroup,therewasno changei nN i ntakeoftwi nl ambs
（No.9:34g/d,No.10:22g/ d
）duri ng3weeksaf terweani ng,andthe val ueofNo.9l ambwas1. 6ti meshi gherthanthati nNo.10l amb.Thef aecalN outputwasal mostthe samei nbothl ambs,andtheval uesareal mostconstantduri ngtheperi od.Uri naryNexcreti on,however, i nNo.9l ambwasal ways
（ineveryweeks
）morethan2ti meshi gherthanthati nNo.10l amb.Therati o ofN absorpti ondi dnotchangei nbothl ambsduri ng3weeksaf terweani ng,andtheval uewashi gheri n No.9l ambthani nNo.10l amb.Therati oofretai nedN wasal moststeadyduri ng3weeksexceptval ue ofNo.9l ambat3weekaf terweani ng.TheNuti l i zati onwasdi f f erentbetween2twi ns,andtheval uei n No.10l ambwashi gherthanthati nNo.9l amb,andal sotheaveragedval uesweretheopposi tei ntwo groups.InNo.9l amb,hi ghNi ntake,hi ghuri naryNexcreti onandal sohi ghNretenti onwereobserved, howevertherati oofNuti l i zati onwasl owerthanthati nNo.10l amb.TheureaN
（NPN）synthesi zedi n thebodywi l lbethoughttobeanendproductofprotei nand/ orami noaci dsmetabol i sm,andexcreted throughtheki dney.Inadul trumi nants,i ti swel lrecogni zedthatwhentheyrecei vedhi ghprotei nf eedthe uri naryexcreti onofureamarkedl yi ncrease,andcontrarywhentheyweref edal owprotei nf eed,theywi l l beabl etocontroltheuri naryureaexcreti on,andshi f ttosecreteureai ntothegut
（reticul o- rumen
）f or sti mul ati ngthemi crobi alprotei nsynthesi s
14）.Obara
etal.
15）reportedthattherumenwi l lbeamai npl ace f orusi nganendogenousureai nrumi nantsf edl owprotei ndi et,andal sowhenthedi etcontai nsenough
Fig.6 Nitrogenbalanceoflambsduring5monthsafterweaning.
Fig.5 Nitrogenbalanceoflambsduring3weeksafterweaning.
ni trogentobeabsorbedanendogenousureawi l lbesecretedi ntothel owergut.Then,i nthepresentstudy, ni trogeni ntakei ncreasedthroughhi ghprotei ndi eti nNo.9l amb,andaprovi dedl argeamountofprotei n woul dbetoomuchf orprotei nuti l i zati oni nthebody,andsoexcessni trogenmi ghtbeusedf orurea synthesi stobeexcretedi ntouri ne.
Asshowni ntheFi gure6,i nthemonthl ychangesi nN bal anceaf terweani ngi nnos.4and5l ambs, monthl yNi ntakesofNo.4and5werei ncreased1. 3and1. 2ti mesduri ng5months.Thef aecalNexcreti on al soi ncreasedal ongwi ththel apseofti meaf terweani ng,thoughtherewasl i ttl edi f f erencei ni ndi vi dual s.
Uri naryNexcreti oni nNo.4l ambwas2ti mesmorethanthati nNo.5l ambatonemonthaf terweani ng, andthereaf ter,theextentofi ncreasei nuri naryNi n2l ambswasal mostthesameduri ngtheperi od.The retai nedNat5monthi nNo.4l ambi ncreased1. 3ti mesascomparedtothatatonemonthaf terweani ng, al thoughi nNo.5l amb,theN retenti ondecreasedsl i ghtl yduri ngtheperi od.Asshowni nFi gure2,the DG i nNo.4l ambduri ngexperi mentalperi odwas233,300,33and267g/ dat1,2,3and5monthaf ter weani ng,andal sothati nNo.5l ambswasal so200,133,33and133g/ dat1,2,3,and5monthaf ter weani ng,respecti vel y.TheN retenti onatthesameti medescri bedabovei ncreasedal mostthesamerate i nNo.4and5l ambs,andsoani ncreasei nN retenti onwasroughl yref l ectedonani ncreasei nDG,
i.e. , ani ncreaseofprotei nsynthesi si nthebody.Inthenos.4and5l ambs,absorbedN i ncreasedal ongwi th growi ngstage,thoughNretenti oni nNo.5l ambdecreasedsl i ghtl y.Inthenos.9and10l ambs,Ni ntake i nNo.9l ambwashi ghascomparedtoother,andi twoul dbeduetomorei nconcentratei ntakeas comparedwi ththati nNo.10l amb.TheN i ntakei nnos.9and10l ambsi ncreasedunti l3monthaf ter weani ng,andtheni ttendedtoberel ayedat5monthaf terweani ng.Thef aecalN excreti oni ncreased al ongwi ththel apseofti meaf terweani ngi nbothl ambs,al thoughtherewasadi f f erencei ndi vi dual l y,and then,i ttendedtoi ncreasei nNo.9l ambat3monthaf terweani ng.Thi scoul dbeduetonoref l ecti onof ani ncreasei nf eedi ntaketodi gesti onandabsorpti onofdi etaryni trogen. Theuri naryN excreti on i ncreasedi nbothl ambsal ongwi ththel apseofti me,andtheval uei nNo.9l ambwasal most2ti mes hi gherthanthati nNo.10l ambunti l3monthaf terweani ng,andthentheval uesi nbothl ambsdecreased i nsi mi l arextentat5monthaf terweani ng.Inthebothl ambsofnos.9and10,thei rbodywei ghti ncreased, al thoughtheNi ntakeofthemwasrel ati vel ydel ayedat5monthaf terweani ng.At5monthaf terweani ng, i tcanbepresumedthatthei rprotei nsynthesi si nthebodywasgreatresul tedi ncontroluri naryurea excreti on,andconsequentl y,theuri naryNexcreti ondecreasedi nnos.9and10l ambs.Ni trogenretenti on i nNo.9l ambi ncreasedas27. 0,26. 4,28. 2
（g/d
）,andthati nNo.10l ambrel ati vel ydecreasedas16. 7,15. 3, 14. 7and14. 7
（g/d
）at1,2,3and5monthaf terweani ng,respecti vel y.TheDGi nNo.9l ambduri ngsame peri odwere333,200,333and533
（g/d
）,andi twasi nproporti ontoani ncreasei nN retenti on.
InbothgroupsofHPandLP,anabsorbedN i ncreasedal ongwi thani ncreasei nN i ntakedueto
i ncreasei nbodywei ghtthroughagi ngofl ambs. However,i nthi sstudy,N retenti oni nHPgroup
i ncreasedal ongwi thagi ng,al thoughtherewasal i ttl edecl i nei nLPgroup.Theref ore,i ti sthoughttothat
thedi f f erencei ndi etaryprotei nl evelwi l li nf l uencetoNretenti on,andtheni tshoul dhavesomeef f ecton
thegrowthratei ngrowi ngl ambs.TheN i ntakei nl ambwasrel ati vel yhi gheri nHPgroupthani nLP
group,andsubsequentl y,therewereal sohi ghabsorbedandretai nedN i nHPgroupascomparedtothat
i nLPgroup.However,asshowni nTabl e4,thedi f f erencesi ndi etaryprotei nl evelcl earl yi nf l uencedon
theabsorpti onandretenti onratesofN i nl ambs.Thati s,theabsorpti onandretenti onrateswere
si gni f i cantl yhi gheri nHPgroupthani nLPgroup.Theratesofabsorpti onandretenti onofni trogen
decreasedal ongwi thagi ngofl ambsaf terweani ngi nbothgroups.Inparti cul ar,i twasthoughttothatN
absorpti onwashi ghandal soprotei nsynthesi shasbeendoneacti vel yi nNo.9l amb.Ontheotherhand,
uri naryN excreti onwasal sohi gh,andconsequentl ytheretai nedN i ncreasedbutN uti l i zati onwasnot
al waysi mprovedi nNo.9l amb.Innos.5and10l ambs,Nuti l i zati onratewasnotal waysl ower,al though thei rabsorbedN wasrel ati vel ynotsomuch.Then,thedi f f erencei ndi etaryprotei nl eveli sthoughtto havenobi gef f ectonN uti l i zabi l i tyi nl ambs.Onesi de,theN uti l i zabi l i tyi nl ambswasrel ati vel yhi gh unti l3weeksaf terweani ng,andthereaf teri ttendedtodecrease.
Forcompari sontheresul tofi ndi vi dual s,thechangesi nN bal ance
（perBW0.75）ofl ambsunti l3weeks af terweani ngwereshowni nTabl e5,andthati n1,2,3and5monthsaf terweani ngwereal soshowni n Tabl e6,respecti vel y.TheN retenti oni nNo.4and5l ambswas3. 6,2. 2and2. 9,and2. 3,2. 2and2. 0at 1,2and3weeksaf terweani ng,respecti vel y.Theref ore,theretai nedNperkgBW
0.75decreasedal ongwi th agi ng,andthentheval uetendedtohi ghi nHPgroupthani nLPgroup.Inthetwi nofNo.9and10,there
Table5.Nitrogenbalanceindicatedaspermetabolicbodyweightinlambs fedonLPorHPdiet
1）
Af terweani ng.
2）g/ kgBW
0.75LambNo. 5 4 10 9
1stweek1） Fecal 0.462） 0.50 0.58 0.49 Urinary 0.34 0.49 0.34 0.70 Retained 2.26 3.46 2.06 2.86
2ndweek Fecal 0.52 0.46 0.50 0.53 Urinary 0.33 0.39 0.31 0.68 Retained 2.12 3.32 2.06 2.46
3rdweek Fecal 0.38 0.46 0.48 0.43 Urinary 0.35 0.72 0.24 0.44 Retained 2.08 2.88 1.96 2.90
Table6.Nitrogenbalanceindicatedaspermetabolicbodyweightinlambs fedonLPorHPdiet
1）
Af terweani ng.
2）g/ kgBW
0.75LambNo. 5 4 10 9
1stmonth1） Fecal 0.402） 0.46 0.48 0.45 Urinary 0.36 0.72 0.24 0.44 Retained 2.08 2.92 1.96 2.92
2ndmonth Fecal 0.47 0.50 0.48 0.41 Urinary 0.47 0.46 0.28 0.60 Retained 1.54 2.72 1.46 2.14
3rdmonth Fecal 0.40 0.44 0.50 0.60 Urinary 0.51 0.57 0.47 0.76 Retained 1.36 2.48 1.24 1.92
5thmonth Fecal 0.43 0.44 0.55 0.64 Urinary 0.47 0.46 0.27 0.30 Retained 1.10 2.04 1.18 1.68
wasasi mi l artrendi nNretenti onunti l3weeksaf terweani ngthatobservedi nthetwi nofNo.4and5.It i sthoughttobethatani ncreasei ntheretai nedN perBW
0.75mi ghti nducetheN uti l i zati onf orbody protei nsynthesi sperBW
0.75,whi chwoul di mprovegrowthrateofl amb.IntheDGduri ng3weeksaf ter weani ng,i tref l ectedontheretai nedN perBW
0.75i nbothtwi nsofnos.4and5,and9and10l ambs.
Furthermore,onthechangesi nN bal anceduri ng5monthsaf terweani ng,theretai nedN perBW
0.75tendedtodecreaseal ongwi thagi ngi nbothgroups,andi nparti cul artheval uesofNo.9l ambvari edmore thanthoseofotherl ambs.Theretai nedNperBW
0.75duri ngthewhol eperi odofthi sstudywasqui temore unti l3weeksaf terweani ngi nal ltheani mal s,al thoughthati ncreasedal ongwi thagi ng.Ontheother hand,thechangesi ndi etaryprotei nl evelmi ghti nducetheretai nedN perBW
0.75rel ati ngthechangesi n protei nsynthesi zedi nthebody.
Conclusion
Inthepresentstudy,i twasobvi ousl ysuggestedthatthechangei ntheDGofl ambi ngrowi ngstagei s obvi ousl yi nf l uencedbyachangesi nretai nedNcausedbyachangesi ndi etaryprotei nl evel .Inthel amb f edonhi ghprotei ndi et,therati oofabsorpti onandretenti onofN tendedtohi ghascomparedwi ththat i nl ambsf edonl ow protei ndi et.Further,N retenti onperBW
0.75tendedtodecreaseal ongwi thagi ng, al thoughi twi l lbemorei ntheearl ystageaf terweani ng.
Acknowledgement
Theauthorsareverygratef ultoMr.K.Hashi yamaf orhi sassi stanceduri ngthecourseofthe experi ment,andtoDrT.Ban- Tokudaf orhertechni calassi stanceonthemanuscri pt.
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育成メンヨウの増体および窒素出納に及ぼす 給与飼料中蛋白含量の影響
藤 原 勉
三重大学大学院生物資源学研究科
要 旨
反芻動物の成長に伴う反芻胃の発達や単胃動物型から反芻（複胃）動物型への栄養摂取形態の変化が 蛋白質栄養に及ぼす影響については未だ十分に明らかではない。本研究では，離乳後の育成メンヨウに 蛋白質レベルの異なる飼料を給与し，増体および窒素出納に及ぼす影響について比較検討した。
生後55日齢で離乳した2組の双子（雌）メンヨウを供試し，各双子内で高タンパク飼料区（HP区）
と低タンパク飼料区（LP区）に振り分けた。市販のチモシー乾草を基礎飼料とし，圧ぺん大麦と大豆 たんぱくを用いて，蛋白含量をHP区で維持要求量の1.8倍，LP区は1.2倍になるよう調整した。各 個体の採食量は毎日，体重は週齢ごとに測定した。また，離乳後1，2および3週齢と2，3および5カ 月齢の6期間を試験期として，各期間中の残飼量，糞および尿を毎日採取し，それらの窒素（N）量を 測定してN出納を算定した。全実験期間中の平均日増体量は，日本コリデール種の双子において，HP 区で153g，LP区で142gであり，交雑種（日本コリデール種Xサフォーク種）の双子において，HP 区で235g，LP区で145gであった。飼料摂取量については，濃厚飼料は各個体ともほぼ全量を摂取し たが，粗飼料は交雑種のHP区以外は，夏季の暑熱環境下で摂取量が一時減少した。HP区におけるN 摂取量はLP区におけるそれよりも多く，結果としての体内蓄積N量もHP区でLP区よりも多くなっ た。また，週齢に伴いN摂取量は増加したが，排泄N量も増加したことから，体内蓄積N量の割合は 低下した。週齢に伴う体内蓄積N量はHP区では増加したが，LP区ではやや減少する傾向にあった。
代謝体重当たりの体内蓄積N量は，各双子のLP区で変化は認められなかったが，HP区では離乳後2 カ月以降における交雑種（nos.9 & 10）の減少が顕著であった。
これらの結果は，育成時のヒツジにおける日増体量の変化が，給与飼料中のタンパクレベルの変化に 起因する蓄積窒素量の差によって明らかに影響されることを示唆している。
