Chăn nuôi gia cầm đẻ trứng

8/2/2019 Chn nui gia cm trng

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Bi Hu on

TRNG

V

P TRNG GIA CM

Trng g l k tch ca thin nhin, l mt trong nhng thc phm honthin nht m nhn loi tng bit n...

(Bch khoa ton thvThc n v Dinh dng Hoa K)

H NI - 2009


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LI GII THIU

Cc danh y i trc t tn cho trng g l k thong, mt loi thuc c tc

dng bhuyt, dng huyt. Nhiu bi thuc ng y sdng trng g nhmt loi

thc n bdng v thuc iu tr. n nay, theo nghin cu ca cc nh khoa hc, c

bit l cc nh dinh dng M xem trng g l mt v kh dinh dng tnhin, gp

phn nng cao sc khe cng ng. Trng g cn l ngun cung cp nhiu cht dinh

dng: protein, lipit, khong, vitamin... cho c th, axit amin cn thit v c li cho c

th. V chnh nnng cc axit amin trong trng g c xc nh l tiu chun nh

gi gi tr sinh hc ca cc loi thc phm khc.Trn thgii, cc nh khoa hc nh gi rt cao vai tr ca trng trong dinh

dng. Cng vi sa, lng trng tiu th bnh qun trn u ngi l mt trong nhng

chsquan trng nh gi mc sng ca ngi dn trong mt x hi vn minh. V c vai

tr to ln nhvy nn sn xut trng chim mt v tr quan trng trong ngnh chn nui

ni chung, chn nui gia cm ni ring. Sn xut trng v p trng gia cm ang l cc

hotng rt si ng trong ngnh chn nui gia cm nhm to ra sn phm p ng

cc nhu cu cp thitca i sng x hi.

Cun sch m bn c ang cm trn tay scung cp mt sthng tin cn thit v

tng i c h thng, tqu trnh hnh thnh trng, cu to, gi tr dinh dng, mt sphng php chbin trng... cc nhn tnh hng n sc sn xut trng: ging, thc

n, iu kin chm sc gia cm mi... n cc qu trnh pht trin phi, kthut p trng

gia cm nhn to v cng nghip...

Vi kinh nghim trn 30 nm ging dy v nghin cu trong lnh vc Chn nui

gia cm trong trngi hc Nng nghip, TS Bi Huon tc gi cun sch, dy

cng bin son v nht l a vo ti liu mt skt qu nghin cu mi ca nhiu nh

khoa hc trong v ngoi nc v ca chnh tc givnng cao nng sut trng v p

trng gia cm. Chng ti cho rng cun sch sl ti liu bch cho sinh vin, cn b k

thut, cc nh chn nui v cho tt c nhng ai quan tm n nhng ni dung m cunsch cp n.

Xinc trn trng gii thiu cng bn c! vi bn c ti liu k thut b ch

ny.

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Hy vng cun sch sgp phn nng cao nng sut trng v kt qup trng gia

cm.

Bn cnh nhiu u im, chc chn cun sch cng s khng trnh khi nhngnhc im v hn ch. Rt mong bn c ng gp kin cun sch hon thin hn.

NGT. GS.TS. ng V Bnh

MC LCLI GII THIU ....................................................................................................................iiChng I....................................................................................................................................5TRNG GIA CM ..................................................................................................................5I. Tng quan v tnh hnh sn xut v tiu th trng gia cm trn th gii v trongnc ............................................................................................................................................5

1. Trn thgii...........................................................................................................................52. Vit Nam .............................................................................................................................7II. Hnh thi, cu to v thnh phn ho hc ca trng ....................................................71. Hnh thi, cu to trng.......................................................................................................72. Thnh phn ho hc ca trng.........................................................................................10III. Cquan sinh dc ca g mi v qu trnh hnh thnh trng .................................111. Spht trin ca cquan sinh sn gia cm ....................................................................112. Srng lng v to trng gia cm. .............................................................................133. Qu trnh hnh thnh trng trong ng dn trng...........................................................145.iu ho qu trnh to trng v trng ........................................................................206. Tnh chu k ca strng ..............................................................................................237. Chu k rng trng...............................................................................................................238. Nhp iu trng hng nm ............................................................................................259. Phn xp trng.................................................................................................................2610.Thay lng.............................................................................................................................2611.Thnh thc sinh dc ca g mi - qu trng u tin .............................................2712. Tui v nng sut..............................................................................................................2813.Quy lut trng v thtrng ................................................................................28IV. Mt s yu tnh hng n sn lng trng ...........................................................291.nh hng ca hocmon n sn lng trng.................................................................292.nh hng ca nui dng...............................................................................................323.nh hng ca iu kin ngoi cnh...............................................................................334.nh hng ca phng thc chn nui. .........................................................................34V. Khi lng trng v cc nhn tnh hng n khi lng trng........................361.Quan h gia slng v khi lng ring. ....................................................................362.Nhit v khi lng trng..............................................................................................373.nh hng ca tui, thtrng v thi gian n...............................................................37

4. Xc nh khi lng trng.................................................................................................38VI. Cht lng trng .............................................................................................................391. Nhng tnh trngnh gi cht lng bn ngoi ca trng v cc phng php xc nh. 392.Xc nh cht lng lng trng v lng .......................................................................41VII.Trng l mt loi thc phm tuyt vi........................................................................43VIII. Dtr, bo qun v ch bin trng ..........................................................................451.Yu cu v cht lng trng ...............................................................................................46


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2.nh hng ca cc phng thc nui dng v chm sc n cht lng trng.....493. Bo qun trng....................................................................................................................514.Sn xut trng sch v cng nghip ho ngnh sn xut trng....................................55

IX.Vn an ton thc phm trong chn nui gia cm Viet GAHP.................................57...................................................................................................................................................59CHN LC, NUI DNG V CHM SC G MI ........................................592.1. ng dng mt s tin b di truyn trong cng tc ging i vi g trng ging...................................................................................................................................................592.2.Cch xc nh v nh gi nng sut ca g mi trng .......................................65Nhng c im bn ngoi ca g mi tt v xu tr-c khi ........................................65Nhng tnh trng bn ngoi ca g mi ........................Error! Bookmark not defined.Sn lng hng nm...............................................................................................................682.3.Thc n cho g cc loi ..............................................................................................702.3.1. Thc n cho g sinh sn hng tht...........................................................................70

Thnh phn dinh dng .......................................................................................................71KLCT ................................................................................................................................71

2.3.2.Thc n cho g hng trng (Leghorn, Goldlin, Hyline, ISA Brown...)................772.3.3. Thc n cho g th vn ........................................................................................80IV.Nhng yu t quan trng nht ca mi trng tiu kh hu chung nui g ...871.Khng kh..............................................................................................................................872. Nhit ................................................................................................................................913.Chm sc sc khogia cm trong iu kin kh hu nng m ......................................934. Chm sc g trong iu kin thi tit lnh..........................................................................955. nh sng...............................................................................................................................976. Lp n chung.................................................................................................................110V. Mt nui v ln ca n ......................................................................................113VI.Cc phng thc nui g mi ..................................................................................114VII. Hng dn chn lc v nhn ging c th ..............................................................1157.1. Chun bcc iu kin chn nui...........................................................................1157.2. Kthut chn ging.......................................................................................................116

7.2.1. Chn g con mt ngy tui ........................................................................................1167.2.3. Chn g 140 ngy tui................................................................................................1167.2.4. Chn ghp gia nh sau 258 ngy tui .....................................................................1167.3. K thut chn nui g ging........................................................................................1177.3.1. Kthut chn nui g con t0 21 ngy tui........................................................1177.3.2. Kthu t chn nui g con giai on 4 8 tun tui.............................................1187.3.3. Kthut nui dng g hu bt43 hoc 50 ngy n 140 ngy tui. ...............1197.4. V sinh phng bnh .......................................................................................................121VIII.Cng tc th y ..............................................................................................................122Chng III.............................................................................................................................125P TRNG NHN TO ....................................................................................................125I. Sinh l cquan sinh dc gia cm trng ........................................................................1251. Cquan sinh dc ca gia cm trng ..............................................................................1252.Sto tinh trng. ..............................................................................................................126

3.c im hnh thi v sinh l ca tinh trng gia cm ...................................................1284. Phn x sinh dc v ng tc giao cu ..........................................................................128II. Sth tinh........................................................................................................................129III. Tng quan vp trng nhn to.................................................................................1311.Lch spht trin ca p nhn to ..................................................................................131


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Chn nui gia cm thi hin i, nu nh ch da vo p t nhin th khng thp ngc s lng con ging cn thit. V vy con ngi nghin cu, th nghim to ra mitrng tng t nh ca gia cm khi p thay th chng lm nra t trng nhng c th

mi m khng cn s tham gia ca gia cm b m..............................................................1312.nh ngha vp nhn to ...............................................................................................1323. Mc ch ca p nhn to................................................................................................1324. Cu trc ca trm p nhn to........................................................................................132IV. My p trng..................................................................................................................1331. V my ................................................................................................................................1332. Bng iu khin, tn hiu .................................................................................................1333. Gi khay v khay ng trng .....................................................................................1344. H thng o trng ...........................................................................................................1355. H thng thng thong .....................................................................................................1356. H thng cp nhit ............................................................................................................1367. H thng to m ................................................................................................................1368. H thng bo v .................................................................................................................137V. Thu nht, chn v bo qun trng p..........................................................................1371. Thu nht trng v bo qun tm thi.............................................................................1372. Chuyn trng ti trm p .................................................................................................1373. Nhn trng v xng st trng ..........................................................................................1384. Chn trng p....................................................................................................................1395. Kthut xp trng vo khay p .......................................................................................1396. Bo qun trng trc khi p ...........................................................................................140VI.Qu trnh p v vn chuyn g con ............................................................................1411.a trng vo my p ......................................................................................................1412. Chuyn trng tmy p sang my n............................................................................1423. Ly g con ra khi my n...............................................................................................1444. Tim chng v bo qun g con mi n.........................................................................1455. Vn chuyn g con............................................................................................................146VII.Kim tra spht trin ca phi trong qu trnh p................................................147

1. Soi trng kim tra spht trin ca phi sau su ngy p (trn 144 gip) ............1472. Soi trng kim tra spht trin ca phi sau 11 ngy p (sau 264 gip) ...............1493. Soi trng nh gi spht trin ca phi sau 19 ngy p ...........................................1514. Kim tra khi g nv nh gi cht lng g n.........................................................1535. Kim tra gim khi lng ca trng trong qu trnh p.........................................1546.Theo di di ca qu trnh p......................................................................................155VIII. Mt s hin tng bnh l thng gp khi p trng cng nghip......................1561.p trng bo qun di ngy .......................................................................................1562. Bnh chn, cnh ngn (Micromelia) ..............................................................................1563. Bnh atexia ........................................................................................................................1574. Bnh khoo chn hay perosis ..........................................................................................1575. Bnh g con bdnh bt khi n........................................................................................1576.Phn tch t l phi cht ...................................................................................................1587. Nguyn nhn gy cht phi trong qu trnh p .............................................................163

8. Biu hin ca phi cht cc thi k khc nhau trong qu trnh p .........................1639. Gii phu phi cht ...........................................................................................................165IX.nh hng do thiu vitamin C, Ca, P ti spht trin ca phi ..........................166

Hp thu Ca......................................................................................................................167Canxi v pht pho v cht lng v trng .........................................................................168X.Cc nh hng ca chp i vi spht trin ca phi. ..................................170


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1. Chp v vic kim tra theo di .................................................................................1702.nh hng ca nhit i vi spht trin ca phi ...............................................1714.nh hng ca thng thong ti spht trin ca phi ........................................182

5.nh hng ca o trng i vi spht trin ca phi v vtr ca phi ..............184XI.Kim tra sinh hc...........................................................................................................1851. Cc nhu cu vmi trng phi pht trin trong cc giai on khc nhau.........1852. Cc bin php nhm iu chnh nhit ca trng.....................................................1863. Cc bin php nhm iu chnh bay hi nc ttrng..........................................1874. Cch xl khi ang p bmt in.................................................................................1875.Mt siu ch khi p trng thu cm, chim ct v iu.....................................1886.Mt sc im ring ca p trng thu cm, chim ct, iu ................................188TI LIU THAM KHO...................................................................................................195

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Chng I

TRNG GIA CM

1.1. Tng quan v tnh hnh sn xut v tiu th trng gia cm trn th giiv trong nc1.1.1. Trn thgii

Chn nui gia cm cng nh thng mi cc sn phm gia cm trn th gii pht trinmnh trong vng 35 nm qua. Sn lng tht v trng gia cm tng nhanh hn sn lng thtb v tht ln. Nm 1970, sn lng tht gia cm th gii cht 15,1 triu tn, tht ln l 38,3triu tn, tht b 60,4 triu tn nhng n nm 2005 sn lng ca cc loi tht ny tng lntng ng l: 81; 102,5 v 60,4 triu tn. Sn lng tht gia cm nm 1970 ch xp x 50%sn lng tht ln v bng 25% sn lng tht b nhng n nm 2005 sn lng tht gia cm tng cao hn 25% so vi tht b v bng 75% tht ln. Trng gia cm tng t 19,5 triu tnnm 1970 ln 59,2 triu tn nm 2005.

Sn lng tht v trng ca cc nc ang pht trin cao hn cc nc pht trin. Hinti, sn lng tht ca cc nc ang pht trin chim 55% sn lng tht th gii, sn lngtrng chim 68%. Mt khc, do tc pht trin nhanh nn to ra s mt cn i: Bc,Trung M v Chu u b chia s th phn bi cc nc chu , M La tinh nh: Trung Quc,Brazil.

Sn lng trng cc nc ang pht trin trong nhng nm u ca thp k 90 vttri so vi cc nc pht trin v chim 2/3 sn lng trng th gii. Nm 2005, sn lngtrng gia cm khu vc Chu chim hn 60% v ch yu l ng gp ca Trung Quc(sn lng trng ca nc ny chim 41% sn lng trng th gii), chu u gim xungcn 16,8%, khu vc Bc v Trung M chim 13,6%. Cc nc Nam M chim lnh cth trng t nm 1990 nhng h khng gi c th trng v h ch tp trung tngtrng v sn lng. Sn lng trng ca 10 nc ng u chim 72,4% tng lng trngth gii v tp trung khu vc c cc nc dn u v sn lng tht.

Ngc li vi nm 1970, c 6 nc chu u c sn lng trng cao nht nhng nnm 2005 ch cn li Php nm trong s cc nc c sn lng trng ln nht th gii. 5 v trcn li trong 10 nc l n , Mexico, Brazil, Indonesia v Th NhK.

Nh vy, sn lng trng th gii hu ht c sn xut t cc nc Trung Quc, n v Nht Bn. Nm 2005, trong 10 nc c sn lng trng cao nht th gii c 4 nc Chu v 2 nc thuc Chu M La tinh. iu cho thy chn nui gia cm cho trngchuyn t Chu u sang Nam v ng . Khu vc sn xut nhiu trng cng chuyn tChu u nm 1970 sang Chu nm 2005. C th l: nm 1970 c 6 nc chu u nmtrong s 10 nc c sn lng trng cao nht th gii v ch c 2 nc chu nhng nnm 2005 c 5 nc thuc khu vc Chu , trong sn lng trng ca 3 nc (TrungQuc, n , Nht chim gn 50% sn lng trng th gii).

Trong my thp k gn y, vng chn nui gia cm chuyn t Bc v Trung M,

Chu u sang khu vc Nam v ng . Nu nm 1970 ch c 2 quc gia chu trong 10quc gia ng u v chn nui gia cm l Trung Quc v Nht Bn, th n nay M vnng v tru (chim 22,9%), nhng Trung Quc v Brazil v tr th 2 v 3. Nm2005, sn lng tht gia cm cc nc ang pht trin chim 54,7% sn lng tht gia cmth gii. Th phn ca Bc, Trung M v chu u b chia s bi cc nh sn xut ln khc chu v Nam M l Trung Quc v Brazil. Nm 1970, sn lng tht ca khu vc Bcv Trung M, Chu u (EU) v Lin bang Nga chim hn 71% sn lng tht gia cm th

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gii, cn chu v Nam M chim t hn 24%. n nm 2005, t l ny l gn 50%, tc tng trng cao nht l khu vc chu gn 25 triu tn trong giai on 1975-2005, sau l Nam M 12 triu tn.

Tc tng trng ca thng mi gia cm tng nhanh hn so vi kh nng sn xut,c th l: nm 1970 ch c 521 tn tht gia cm c xut khu nhng n nm 2004 tngln 9,7 triu tn. Ngc li, nm 1970 tht gia cm ch chim 3,5% trong tng sn lng thtth n nay t l ny l 12%. Trong cng thi gian ny, thng mi trng gia cm tng t 0,4triu tn ln 1,4 triu tn.

Ngc li vi tht gia cm, trng gia cm ch xut khu c 12% nm 2004 v 1,8%lng trng gia cm sn xut ra c a ra th trng th gii do cc nguyn nhn nh: vnchuyn trng kh khn, trng thng c tiu thni a.

Xut khu trng gia cm tng t 400.000 tn nm 1970 ln hn 1 triu tn nm 2004.Th phn ca cc nc ang pht trin ch chim khong 10,5% n 24,5% ch yu l do nhucu tiu th cao hn so vi sn lng. Nm 1990, sn lng trng xut khu ca cc ncchu u chim 82% sn lng trng xut khu trn th gii nhng n nm 2004 gim xung

cn 68% nm 2004. Nm 1970, lng trng gia cm xut khu ca H Lan v B chim41,5%; 8 quc gia ng u v xut khu trng gia cm u thuc khu vc chu u v 2nc thuc khu vc chu . Nm 2004, H Lan v Ty Ban Nha ng v tr th 1 v 2chim 35,4% sn lng trng gia cm xut khu ca th gii., sau l Trung Quc. Ngoira, cn c mt s nc khng phi l nc xut khu trng gia cm ln nhng nm 1970nhng n nm 1970 trthnh nhng nc xut khu trng gia cm ln nht th gii nm2004 nh: Ty Ban Nha, M, Malaysia v n . Mc d nhu cu tiu th trng tng caosong th phn tiu th trng ca cc nc ang pht trin ch chim 24-35%. Bn cnh ,trong thp k qua Chu Phi trthnh th trng hp dn. Lng trng xut khu ca Chu Phiv cc nc Nam M c vai tr quan trng trong thng mi ca ngnh trng gia cm.

Trong giai on 1970-2004, s lng cc quc gia nhp khu trng gia cm tng ln.Nm 1970, 1/3 lng trng gia cm trn th trng c nhp khu tc v trong 3 thp kqua, quc gia ny vn lun v tr dn u (chim 25,4%). Nu nm 2001, c khng p

dng cc quy nh nhm hn ch nhp khu trng gia cm c nui ti cc trang tri chnnui tp trung trn chung lng nhiu tng th c tnh n nm 2012, lng trng nhp khust khong 10-100 t qu. Nm 2004, c nhng thay i v chnh sch ny, nn trng canhng gia cm c nui trong cc chung nh bt u pht trin. Mc d, cc quy nh nyngt ngho hn quy nh ca cc nc EU v c thnh hng ti s lng gia cm trng.Yu cu c th vi chung nui gia cm trng t nht cao 60cm v cch mt t 35cm. Nut 25cm cho ch thu phn th ch c tht c 2 dy chung thay v 3-4 dy nh thit ktrc y.

Ngnh chn nui gia cm c bin ng mnh trong vng 35 nm qua: sn lng tngmnh theo thi gian, sn lng tht v trng gia cm ca cc nc ang pht trin tng caohn so vi cc nc pht trin. Cc nc khu vc Chu v Nam Mc bit l TrungQuc v Brazil l nhng nc pht trin mnh v chn nui gia cm. Sn lng trng giacm nm 2004 ca cc nc ang pht trin chim 68% tng sn lng trng th gii, ch

ring Trung Quc chim 41,1%; Sn lng tht chim 55% sn lng tht th gii. Chn nuigia cm tng mnh mt s nc ng, Nam v Nam M nh Trung Quc v Brazil.Ngc vi Trung Quc, Brazil l quc gia c nhiu hn ch v kh nng cung cp ngunnguyn liu thc n cho gia cm nh kh du u tng. Do vy duy tr tc tng trngca ngnh chn nui gia cm nh hin nay c thy gi kh du u tng ln cao lm chogi gia cm th gii cng tng theo v y cng l bi hc ging nhi vi th trng thptrong my nm qua. Tuy nhin, ngnh chn nui gia cm c th b gim mnh nu dch cm


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gia cm khng c ngn chn. Dch xy ra ti Chu u v Chu Phi vo qu 1 nm 2006 lm cho ngi tiu dng lo ngi khng dm n tht v trng gia cm. Theo c tnh ca FAO,do dch cm gia cm nn lng tiu th tht gia cm nm 2006 gim 3 triu tn, l tn tht

nng ni vi cc nh ch bin cc sn phm gia cm xut khu.Tiu th tht, trng ca mt s nc trong khu vc: Trung Quc nm 2006 xut

khu 350 nghn tn tht gia cm, nhp khu 370 nghn tn, tiu th ni a 8 kg/ngi/nm,bnh qun 320 qu trng/ngi/nm.Thi Lan xut khu 280 nghn tn tht gia cm, khng nhp khu, tiu th 12 kg tht v 280qu trng gia cm/ngi/nm.

Malaysia tiu th 32 kg tht gia cm/ngi/nm....

Ngun: Worlds Poultry Science Journal, Volume 62, December 2006

1.1.2. Vit NamTrc khi xy ra dch cm gia cm, s lng gia cm ca nc ta hng nm tng

trng mc cao. Tng n gia cm c nc nm 2001 l 216 triu con, nm 2003 l 254

triu con v nm 2005 ch cn 220 triu con. Tc tng n 2001-2003 l 8,5% nm. BSHt 46,9 triu nm 2001 tng ln 65,5 triu nm 2003. S liu cc vng cn li tng ng nhsau: B 45,6; 41,64 triu, TB 6,8; 7,8 triu; BTB 27,2; 36,7 triu; DHMT 14,4; 16,2 triu, TN5,6; 10,1 triu; NB 24,9; 24,7 triu; BSCL 46,7; 51,5 triu con. T cui nm 2003, dodch cm gia cm lm gim tng n gia cm xung cn 219 triu con nm 2004, gim13,8%.. Mi tnh c s lng n gia cm ln l H Ty 10,8 triu con; Ngh An 10,9; ThiBnh 8,2; Hng Yn 6,50; Ph Th 7,9; ng Nai 5,2; H Tnh 4,9; Thi Nguyn 4,7; HiPhng 4,6 v Vnh Long 4,6 triu con.

Nng sut v sn lng tht, trng: sn lng tht trong giai on 2001-2005 t 372,7nghn tn, trng t 4,85 t qu. Bnh qun tht, trng gia cm trn u ngi ca nc tanm 2003 l: 4,5 kg tht hi/ngi/nm tng ng 2,94 kg tht x/ngi/nm, 60 qu trng,tng ng 3,4 kg trng/ngi/nm. Trc dch cm H5N1, sn lng tht gia cm hngnm chim 16-17% tng khi lng tht hi cc loi.

Cc s liu ni trn cho thy mc tiu th tht v trng bnh qun ca nc ta cn rtthp, nu bit rng hin nay mc tiu th bnh qun u ngi v trng gia cm ca ton thgii l khong 8,0 kg trng; cc nc pht trin l trn 300 qu th ngnh chn nui nichung, chn nui gia cm ca nc ta ni ring cn phi phn u rt nhiu mi c snphm cung cp cho nhn dn, nhm gp phn cung cp cho x hi mt lc lng lao ng c tr lc v th lc trong s nghip CNH, HH t nc.

Ngun: Bo co tng kt chn nui - Cc Chn nui, B NN&PTNT, 2006

Gi tht v trng gia cm nc ta hin nayt nht so vi cc nc trong khu vc.Gi g ta lm sn : 90-100 000 /kgG cng nghip lm sn ph bin 45.000- 50.000 ; .Trng g 1.200-1.300 /qu; Trng vt 1.600-1800 /qu.Trng th trng ni a Trung Quc: 800-950/qu.

Nhp khu 1 tn tht g i tM: 1.300 USD/tn.

1.2. Hnh thi, cu to v thnh phn ho hc ca trng1.2. 1. Hnh thi, cu to trng

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Deleted: Page BreakTiu th tht, trng ca mt s nctrong khu vc: Trung Quc nm 2006xut khu 350 nghn tn tht gia cm, nkhu 370 nghn t n, tiu th ni a 8kg/ngi/nm, bnh qun 320 qu trng/ngi/nm. Thi Lan xut khu 280 nghn t n thtcm, khng nhp khu, tiu th 12 kg tv 280 qu trng gia cm/ngi/nm. Malaysia tiu th 32 kg tht giacm/ngi/nm....

Deleted: Cc s liu ni trn cho th mc tiu th tht v trng bnh qun cnc ta cn rt thp, nu bit rng hinnay mc tiu th bnh qun u ngitrng gia cm ca ton th gii l kho8,0 kg trng; cc nc pht trin l tr300 qu th ngnh chn nui ni chungchn nui gia cm ca nc ta ni rincn phi phn u rt nhiu mi c phm cung cp cho nhn dn, nh m gphn cung cp cho x hi mt lc lnlao ng c tr lc v th lc trong nghip CNH, HH t nc.

Deleted: Cc s liu ni trn cho th mc tiu th tht v trng bnh qun cnc ta cn rt thp, nu bit rng hinnay mc tiu th bnh qun u ngitrng gia cm ca ton th gii l kho8,0 kg trng; cc nc pht trin l tr300 qu th ngnh chn nui ni chungchn nui gia cm ca nc ta ni rin

cn phi phn u rt nhiu mi c phm cung cp cho nhn dn, nh m gphn cung cp cho x hi mt lc lnlao ng c tr lc v th lc trong nghip CNH, HH t nc.


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Trng gia cm c hnh trng, l hnh bu dc khng cn i - hnh Kassini, tc lbu dc khng u, mt u t v mt u nhn. Trong thc tin, hnh dng trng c biuhin bng ch s hnh thi: l t s gia gia ng knh nh/ng knh ln, ch s ny

bin thin t 0,6 (hnh bu dc nhn) n 1 (hnh cu). Cng c th dng t l ngc li lng knh ln/ng knh nh, khi , CSHT dao ng t 1,0 n 1,45.

Cng nh mi i lng sinh hc khc, kch thc v khi lng trng c bin bin d kh ln. Romanofft cc ch tiu trung bnh sauy cho mt trng g lgo trng tiuchun l tng: ng knh ln (L) 5,7 cm, ng knh nh (chiu rng nht) (B) 4,2 cm;dung tch (V) 53 cm3, din tch mt ngoi (O) 68 cm2 v khi lng (G) 58g.

Trng gm 3 phn: v, lng trng v lng vi t l tng i gia cc phn l1/6/3. Trung bnh v cng chim 10%, lng 33%, lng trng 57% khi lng trng.

Lng chnh l t bo trng. T l khi lng gia cc thnh phn ny trong trngca cc g mi khc nhau cng nh ngay ca mt n g mi cng khc nhau. T ly cngtu thuc khi lng tuyt i ca trng, tui g mi v thnh phn thc n. Trng c vcng rt chc bao bc, b dy l 0,2 0,4mm, ngoi ph mt lp cht nhy trong sut (lpm sng) v trong c mng la gm hai lp chc. Mt ngoi v cng hi bng v c nhc bit vi mc khc nhau tu theo trng thi lp m sng v cu to ca v cng. Muca v trng thay i t trng (cc dng a trung hi) n vng nu (cc ging Chu ). Vtrng gm cht hu c, xen vo y l cc mui v c. Cht hu cdo protein ging nh keocolagen (4%) to thnh, cht v c l cacbonat canxi (94%), cacbonat magie v canxi fotfat(1%) to thnh.

Trn v cng c nhiu l kh, nhng l kh ny c ngha quan trng khi p trng.Trong thi gian phi pht trin, c s trao i kh gia phi v ngoi cnh qua nhng l khny. Khi mi p trng, phi c th b cht trong trng hp nu s l kh trn 1 cm2 v cngcc l kh qu hp v di (v dy) v thm nhiu nc t ngoi vo; trong nhng hon cnhy, trao i kh (th) thp hn mc bnh thng kh nhiu. Vo cui thi kp, s gim cccht cha bn trong trng do bc hi c vai tr quan trng. Khi y nu v trng c nhiu lkh qu v m khng kh trong myp thp th s c nh hng bt li i vi kt quptrng. nh hng ca mt l kh v b dy ca v trng i vi t l ncng nhmca khng kh bn ngoi c xc minh chnh xc. S l kh trn v trng dao ng nhiu,

trung bnh c n 10.000 l. u nhn ca trng, mt l hi t hn, cn u t thnhiu hn so vi phn gia ca trng. Bnh qun 1cm2 c 150 l kh.

Hnh 1. S cu to lp v cng ca trng gia cm

Di v cng c v la gm hai lp: lp trong gi l lp mng trng, v lp ngoidn cht vo v cng gi l lp mng v cng. Lp mng v cng nng gn 0,3g v c dy trung bnh l 0,07 mm.pha u t n hi dy hn v u nhn hi mng hn. Giahai lp ny, ngay khi trng va mi ra, hnh thnh bung khu t ca trng. Hin

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tng ny xy ra do sau khi, cc cht cha trong trng b ngui i v co li do nhit mitrng thp hn nhiu so vi thn nhit gi. Trong qu trnh bo qun, nc trong trng bchi nn th tch bung kh tng ln. Trong thc tin ngi ta li dng hin tng ny nh

gi trng ti hay c. Khi quan st lp v la bng knh hin vi c th thy mng ny lmt mng li gm cc si xp t ln xn, do 70% cht hu c(keratin, muxin), 10% chtv cv 20% nc to thnh.

Khong gia lng v v cha y lng trng, do nhiu lp c m c khcnhau to thnh (h.2). Ngay di lp mng trng l lp long ngoi (khong 23% th tch), sau l lp c gia (57% th tch) ri n lp long gia (17%) v lp c trong (3% th tch),lp cui cng ny bc ly lng . Dy chng nm dc theo trc di ca trng, nhc nhngu mt si mnh dn cht vo lp ny. Dy chng do nhiu si protitein to thnh, nhng siny xon li qung gia mt phn on thnh hnh xon c, cn theo hng ra pha ngoin i vo lp c gia ca lng trng, gi cho lng lun nm v tr trung tm. c bitlu rng, th tch ca cc lp lng trng c th chnh lch kh nhiu so vi cc s liu nu trn. V nh th tch lp c gia ca trng ti chnh lch t 20 n 80%. Lng trng trngti c mu vng nht, ngoi ra do c nhiu CO2 nn hi c. c tnh keo ca lp c giaca lng trng l do c nhiu si muxin, nhng si ny to thnh cu trc li. nh gitrng, vn xc nh cht lng v cu trc lng trng c c ngha ch yu. Khi cu trcli b hng, v d do chn ng th lng trng c trthnh long. N c phn ng kim, nhit 600C th ng li, bin thnh mt khi trng (lng trng trng). N cha gn 88%nc, 0,6% cht khong, cc cation K, Na, Mg, Ca v Fe, cc anion SO4 v Cl. Hm lngcc sunfat tng i cao l do c lu hunh trong lng trng. Trong s gluxit th c D glucoza (gn 0,9%). Cc cht protein (11%) l: albumin trng (6,5%), globulin trng (0,6%),muxin trng (1,1%), v mucoit trng (1,2%). Ngoi ra, trong lng trng trng cn c lavintrng (cht c mu vng cha nit), mt t fotfatit v cng c i cht clolexterin v keratin.

Lng nm trung tm trng, do mng lng, cn gi l mng mng bc ngoi, v vy,trong iu kin bnh thng lng khng ln vo lng trng. Mng lng mn cm i vi chnng v khi trng lu th n dn dn b yu i. nhng trng mi , nhcc dy chng xonc m lngc cnh gia trng.

Lng hnh cu (c

ng knh khong 3cm) ch yudo non hong to thnh. Trongcht ny cha tt c nhng chtdinh dng cn thit cho s phttrin ca g con. Trong lng sm c mt vi lp sng gi llng cu to, gia b lm vtheo hnh ci nm (latebra- rnhlng ), y v pha cc ngvt ca t bo trng c a phi,lun nm lp trn ca lng .

Quan st cu trc ca aphi c th phn bit c trngc trng hay khng. a phi ca

trng khng c trng (khng ththai) c nhng khoang hnh nang (cc khng bo vacuola); cntrng th thai th cu trcmt trn ca ngoi b (l phi ngoi) c dng ng nht. Ngoi ra, trong trng th thai cc qutrnh hot ng sng ca phi pht trin ta phi gy ra cc dng in, nu dng dng coin cc nhy c th xc nh c (Rauch, 1950). Trc v trong khi p trng, ngi ta nhnthy trong trng th tinh c in th khc nhau pht ra ta phi ang pht trin (hoc phi


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sng) (h.2). Trong cc trng hp cc hiu in th c th cao hn 30 mV. trng khngth tinh ch ghi c dng in yu khng bin i my (0-1mV).

Lng khng ho tan trong nc v c phn ng kim, thnh phn ho hc ca lng

phc tp hn lng trng.T l gia lng trng, lng v v trng thay i nhiu. Bng 1 a ra nhng s liu

trung bnh v vn ny. Trong trng vt, lng chim t l cao hn. Trng g, tri li c tl ca lng trng cao hn so vi trng vt v trng ngng.

Bng 1. T l (%) gia lng trng, lng v v trng ca mt s loi gia cm

Loi chim Trng khng v Lng trng Lng V

G 88,4 56,8 31,6 2,6

Vt 87,7 52,1 35,6 12,3

Ngng 88,6 50,2 38,4 2,4

Nh nu trong bng 2, lng do nc (48,7%), m (32,6%) v protein (16,6%)to thnh. Cn lu rng, hm lng mtrong lng cao lm cho cc cht dinh dng cnng lng cao cho phi pht trin.1.2. 2. Thnh phn ho hc ca trng

Bng 2.Thnh phn ha hc ca trng g (%)

Thnh phnTon qutrng (%)

Trng b v (%)

Lng (%)

Lng trng(%)

V v mngv (%)

Ton b trng 100 - 31,0 58,0 11.0Nc 65 75,0 48,0 87,0 2,0Protein 12 12,0 17,5 11,0 4,5M 11 11,0 32,5 0,2 -ng 1 0,5 1,0 1,0 -

Khong 11 1,5 1,0 0,8 93,5

Bng 3.Mt s axit amin thit yu trong trng g

Cc axit amin thit yu trong protein trng g (%)

Arginin Hystydin Isoloxin Lyzin Metionin Phenilalanin Treonin Tryptophan Valin

6,6 2,4 16,9 7,0 4,0 6,3 4,3 1,5 7,2

Vitamin

Bng 4.Hm lng vitamin trng g tnh trong IOOg vt cht(theo Bengard)Ton b Lng Lng trng

Vitamin A, mg 0,2 0,03-1,2 -Vitamin D, IU 200 100-400 -Vitamin E, mg 1 3 -Vitamin K, mg 0,02 - -


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Vitamin BI, mg 0,15 0,3 -Vitamin B2, mg 0,4 - -Niaxin (amit ca axit nicotinic), mg 0,1 0,05 0,01

Vitamin BI2, mg 0,05 18 0,1Axit pantotenic, mg 0,7 7,2 0,1

Trng cha rt nhiu vitamin (bng 4), nhng li thiu vitamin C.Trong lng trng ch c du vt mv 12,1% cht kh. Mc mu t vng nht

n vng thm v cha cc cht triglixerit ca cc axt bo: palmitic, stearic, oleic v c axitbo t do v axit glixerinophosphoric. Ngoi ra cn cha cholexterin khng b x phng hov c cc fotfatif- lextin v kefalin. Sc t vng ca lng (vitellolutein) khng phi l snphm ng vt ca trao i cht m cu to t cc cht mu c ngun gc thc vt. Nhngsc t vng v cha trong lng khng phi c tng hp trong c th g mi mchuyn t thc n vo trng. Tu theo s lng cc sc t m lng c mu m hay nht,nhng mu khc nhau ny l do tng quan s lng gia cc hp phn c mu ring bitquyt nh. Nhng hp phn ch yu l - lutein (hn hp cc cht carotinoit- xantofil vzeakxantin), carotin v flavin trng. Chng c hp th t thc n thc vt i qua mng rut

non qua ng bch huyt m vo h tun hon v tch lu li trong mca cth v lng trng.Nhng thnh phn ch yu ca cc cht protit lng l: vitellin (3/4 cht protit),

albumin nhn, livetin v c nhng cht c cha lu hunh ca hai protein ny dng snphm thu phn ca chng l tirozin, triptofan v cistin.

Trong s cc cht khong, thng gp nhiu fotfat, st v canxi c nhiu hn so vitrong lng trng.

1.3. Cquan sinh dc ca g mi v qutrnh hnh thnh trng

Trong qu trnh sinh sn ca gia cm, ngi tanhn thy nhng du hiu ging vi b st m tchng tin ho ln: th tinh trong v sinh sn bngcch trng. gia cm, trong qu trnh tin hocng vi vic tng kch thc trng xy ra vic thoiho phn bn phi ca h thng sinh dc, v vy chc bung trng tri v ng dn trng tri. S phttrin phi xy ra trong trng, c bo v bng vcng. Gia cm con mi n thng c kch thctng i ln.

1.3.1. Spht trin ca cquan sinh sn gia cmS hnh thnh mm ca tuyn sinh dc (h sinh dc) xy ra vo thi ku ca s

pht trin phi: phi g vo ngy th 3, vt v ngng ngy th 4 - 5. u tin h sinh dckhng c phn bit, c ngha chng khng c nhng du hiu ca ging, v tng phnc to thnh t 2 phn sinh trng v mt phn sinh dc.

Phn sinh trng ca h sinh dc c to thnh t np sinh dc l tng. Mt phnkhc, phn tu l nhng dy chng sinh dc v cht m, phn th hai - v to thnh t mphi. Phn sinh dc ca h sinh dc to ra nhng t bo sinh dc u tin (sinh dc bo) cdi chuyn theo mch mu vo vng np sinh dc trc khi hnh thnh b sinh dc (honada)vo cui ngy th nht hoc gia ngy p th hai. Thi k phn bit h sinh dc phi gc nhn thy vo ngyp th 6 - 9. Trong qu trnh pht trin h sinh dc, ging c t


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dy biu m lin kt pht trin ln, t bo c phn ho ra 2 dng: non nguyn bo vnang. Ti ngy p th 9, bung trng th hin s khng i xng, bung trng phi ngngpht trin v thoi ho dn. Trong bung trng tri pht trin lp v v lp tu. v xy ra

qu trnh sn sinh ra cc t bo sinh dc u tin - non bo. Vo ngy th 9, phi g mc 28 nghn, ngy th 17 - 680 nghn, n cui kp s lng chng gim cn 480 nghnnon bo.

n ngy p th 12, ng dn trng c phn thnh loa vi, phn tuyn v t cung.Vic hnh thnh tinh honphi g xy ra t b phn sinh dc trung tnh. Dy c

hnh thnh ngy th 7 trong b phn sinh dc, dn dn bin thnh ng. Trong chng xuthin lng ng, cn t bo thnh ng c phn ho thnh t bo sinh dc u tin (tinhnguyn bo) v nang (t bo sertoli). Tip tng to thnh cc ng dn tinh ngon ngoo, t tinh nguyn bo pht trin thnh cc t bo sinh dc, cn t bo sertoli thc hin chcnng m - dinh dng. Mm tinh hon ni vi thn nguyn thu, tng dn ca n (ngBolpha) sau khi ns trthnh ng dn tinh. Thn nguyn thu mt chc nng v thoi ho.T phn cn li ca n to thnh mo tinh hon.

Chc nng bung trng. Bung trng nm pha tri ca xoang bng, v pha trcv hi thp hn thn tri, c bng cc np gp ca mng bng t trn xung. Np gpkhc ca mng bng ni n vi ng dn trng. Kch thc v hnh dng bung trng phthuc vo trng thi chc nng v tui gia cm. g con 1 ngy tui, bung trng c dngphin mng, kch thc 1 - 2 mm vi khi lng 0,03g, cn 4 thng tui - phin hnh thoi ckhi lng 2,66g. G trong thi k mnh bung trng hnh chm nho, khi lng t 55g,vo thi k thay lng khi lng bung trng gim cn 5g.

Trong bung trng c cht v v cht tu. B mt vc ph bng mt lp biu mc lp t bo hnh tr hay lng tr thp. Di chng c mng lin kt mng, sau n c 2 lpnang vi cc t bo trng. Nm lp ngoi l nhng nang nh c ng knh n 400 m ,trong lp su c nhng nang ln hn vi ng knh 800 m v to hn.

Cht tu nm gia bung trng v c cu to t m lin kt vi cc mch mu vdy thn kinh ln. Trong cht tu c nhng khoang (l hng) c ph bng biu m dt vt bo k.

Sto trng

Qu trnh pht trin ca t bo sinh dc ci: trong s pht trin t bo trng c 3 thik: tng sinh, sinh trng v chn... Trong qu trnh pht trin t bo sinh dc ci (giao t)xy ra khng ch l s thay i cu trc v kch thc ca n m cn l s thay i c b thnhim sc ca nhn t bo trng.

Thi k tng sinh xy ra trong qu trnh pht trin phi thai ca bung trng v ktthc vo thi k g n. Nh k trn, do kt qu ca mt lot phn chia c tgim nhimcc t bo sinh dc u tin (non nguyn bo), s lng non bo trong bung trng t n480 nghn.

Trc khi bt u trng trong bung trng g mi m c 3500 - 4000 nonhong nhn thy c, thu cm l 1250 - 1500. Khc vi t bo sinh trng, trong nonbao c nhn to vi ht nhn nh v th nhim sc. Trong non bao khng c nhn t bo(trung th). Sau khi kt thc qu trnh sinh sn, cc t bo sinh dc c hnh thnh gi lnon bo ca hng th nht, tham gia vo thi k sinh trng.

Thi k sinh trng c chia thnh thi k sinh trng nh v thi k sinh trngln. Thi k sinh trng nh ko di t khi nn khi thnh thc sinh dc. u tin s phttrin ca non bo th hin yu. g 1 ngy tui ng knh non bol 0,01 - 0,02mm, ti45 ngy tui n t 1mm. Thi gian ny, nhn vn chim v tr trung tm trong t bo trng,chuyn cng tng bo sang bn cnh t bo v to a phi. g con 2 thng tui qu trnhtch lu lng trong tng bo ca non bo bt u. Lng c xp thnh nhng lpmu sng v mu sm. tm c lng sng hnh phu, t c vt nhi ra ra t bo


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S rng trng g xy ra mt ln trong ngy thng l sau 30 pht sau khi n trng. Nu g sau 16 gitrong ngy th s rng trng s chuyn sang bui sng ngy hmsau. Nu trng b gi li trong ng dn trng s lm ngng tr s rng trng tip theo. Nu

ly trng ra khi t cung, th cng khnglm tng nhanh s rng trng c. Srng trng g thng xy ra trong thigian t 2 giti 14 gihng ngy.

1.3. 3. Qu trnh hnh thnh tr ng trongng dn trng.

Chc nng ca ng dn trng. ngdn trng c hnh ng, xy ra s thtinh v hnh thnh trng, bt u gn bungtrng v kt thc l huyt.

Kch thc ng dn trng thay i

theo la tui v hot ho chc nng ca hsinh dc. Khi bt u thnh thc sinh dcng dn trng l mt ng trn, thng cng knh u trn ton bng. Sau khi qu trng u tin ng dn trng ca g c chiudi 68 cm, khi lng 77g. Vo thi k trng mnh, chiu di ca n tng ti 86cm, cnng knh n 10cm. g khng trng chiu di ng dn trng gim n 11 - 18cm,ng knh 0,4 - 0,7cm, cn thi k thay lng chiu di l17cm.

gia cm thnh thc sinh dc, trong ng dn trng c nhng phn sau: phu, phnlng trng, c (eo), t cung v m o.

Phu - phn mrng ca pha u ng dn trng, di 4 - 7cm, ng knh 8 - 9cm. Nnm di bung trng. Phu c chia thnh phn phu ring v c, n l phn chuyn tip.B mt nim mc phu xp np, trong n khng c cc tuyn. Trong nim mc c phu c cctuyn hnh ng, cht tit ra ca n tham gia vo vic hnh thnh v trng. Thnh phu chuynng nhs co bp ca lp v v dy ci t mp phu ti vch bng.

Chuyn ng nhu m ca phu c kh nng hng ly t bo trng rng. phu, t botrng dng li khng qu 20 - 30 pht. Lp lng trng u tin c bao bc xung quanh tbo trng c phu. Lng trng nhy, c c cc tuyn hnh ng tit ra qun ngay lng .Khi i qua phn u ca ng dn trng, lng xoay chm xung quanh trc ca n, khin cholp lng trng mi bc xung quanh lng cun xon li, to thnh dy chng. Chng gicho lng tm trng. Khi lng i tip pha di, phn long ca lng trng c titra quanh lng , to nn lp bn trong ca lng trng long

Phn to lng trng - phn di nht ca ng dn trng. Vo thi k mnh, n din 30 - 50cm. Nim mc c nhng np xp dc. Trong n c mt lng ln tuyn hnh ng,cu to ging nh tuyn c phu. Cht tit ra ca tuyn xung quanh lng u tin c,cn sau l lp long (ngoi) ca lng trng. Cc tuyn hnh ng phn to lng trng ckch thch bng estron v progesteron. Thi gian trng trong phn to lng trng khng qu3 gi.

Cng dn trng l phn hp ca ng dn trng di 8cm. Nim mc c nhng npxp nh. lp ngoi ca lng trng long c b sung v to mng v trng. Cc tuyneo tit ra cht ht ging nh keratin to nn lp si chc qun ly nhau hnh thnh mngchc. Cc l ca mng di v tit ra dung dch mui vo lng trng, lm tng khi lnglng trng trng. Qu trnh ny xy ra ctrong t cung. Trng nm trong on eo gn 1 gi.

T cung l on tip ca on eo, n l phn m rng hnh ti dy, chiu di 10 -12cm. Cc np nhn ca nim mc pht trin mnh, v xp theo hng ngang v xin. Tuyn





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ca vch t cung tit ra cht dch lng, thm qua cc mng di v trng vo lng trng.Trong thi gian trng t cung, khi lng trng tng gn gp i. V trng c hnh thnhcng do dch tit ca tuyn t cung.

V trng c cu to t ct hu c v cht trung gian. Ct c hnh thnh bngnhng si protein dng colagen nh chng cho ln nhau.

Cht trung gian cu to t nhng mui canxi dng hp nht khng tan - canxicacbonat (99%) v canxi photphat (1%). S tng hp cht vi c tin hnh trong sut thigian trng t cung (18 - 20 gi).

Do thm thu mt lng nc ln t dch tit ca tuyn t cung vo trng nn khilng ca n c tng dn, lc ny b mt ca cc mng di vc bm cht vo thnht cung, do cc mng ny gin ra. Trng lc ca c t cung tng ng thi, n c khnng tip xc ln vi trng v tit khong to v ln b mt trng.

u tin lp v ngoi c to thnh lp trong nh v trng, lp ny c cu to tnhng nh, u trn ca nh cm su vo b mt ngoi ca lp di v, cn phn chn rngth hng vo vch d con. Nh cu to t tinh th canxi cacbonat (canxita), nhng tinh thhp tip bng protit. Lp nh chim 1/3 dy v. T bn ngoi lp nh c ph mt lpbn chc. Nn mng ca lp ny l cc si collagen c to bi cht dch ca tuyn phntrc t cung. Phn trung gian gia cc si cha mui canxi, lp bn chc ny lm cho vtrng c gi vng.

Khong khng gian gia nn cc nh khng cha cht vi, y c cc l kh, ccmch ny xuyn qua dy cht bn chc v c mra trn b mt ca v trng bng ccl. S lng cc l ph hp vi s lng lng ca tuyn d con. Cc l phn b trn b mtv trng khng u: phn nhiu l tp trung trn u t ca trng, vng bung kh v t hnc l u nhn ca trng. Trong mt v trng g c ti 8 nghn l hi. Tuyn d con snxut ra cc sc t lm cho v trng c mu khc nhau.

T bn ngoi v trng c ph mt lp trn v mng nh, mng nyc to bngcht tit ca t bo biu m t cung.

Men cacbonanhydraza v photphataza kim tham gia tch cc vo trong qu trnh hnhthnh v trng, Cacbonathydraza xc tc cho s hnh thnh anion cacbonat t cacbonic vnc. Phophataza kim xc tc vo qu trnh chuyn ion ho canxi tng hp cc cht v c

ca v. Ngi ta rt ra kt lun rng g , trong biu m t cung cha mt lngcacbonanhydraza nhiu hn hn g khng . Cc cht c ch cacbonanhydraza(sulfanilamit) ph hu qu trnh hnh thnh v trng... Nu tha cht th trng ra khngc v.

m o l on cui cng ca ng dn trng, sau khi hnh thnh trng ri vo .T d con m o c tch ra bng phn thu hp c t cung, ni c van c. Phn cuicng ca m o c mra vo on gia nhp gn niu qun tri. m o di 7 - 12 cm.Nim mc nhn, tuyn ng khng c. Lp biu m ca m o theo mt s tc gi cho bit lc sn xut ra dch tit, dch tit ny tham gia vo s hnh thnh lp mng trn v, lp cphttrin tt, nht l lp cvng, nhs co bp ca lp cny m qu trng c y ra ngoi.

Shnh thnh cc lp v trng. Ngay khi trng va vo n phn eo th u trcca n bt u hnh thnh lp v la. Trng chuyn ng kch thch cc thnh phn ca phneo lm cho cht ht ta nh keratin tit ra t cc ng dn ca nhng tuyn nm trn thnh eo.

Cht ny c hnh si nhy c v dnh. Cc si y xon vo nhau thnh lp v chc bn trongca lng trng. Khi trng hon ton vo phn eo th mt lp v la rt mng dnh cht, bcly n. Trng lu li y mt thi gian ngn, sau y tip tc t t di chuyn, lc y cc tuynpha di phn eo tit ra cc cht cu to lp v la ngoi. Lp ny do cc bi si th hnv xp hn cu to nn cng ging nh lp si ca lp v trong. Da vo nhng tnh trngny, khi soi knh hin vi rt d dng phn bit lp v trong vi lp v ngoi.


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Lc u lp v la ca thnh trong dnh cht vo trng, v sau n gin ra v khi trngchuyn n pha cui phn eo th n hi tch khi trng. V la mu hng nht c cha mt tcht oporfirin.

Trng c cc lp v la bc ngoi, i vo t cung lm cho t cung tit ra cht dchcha nhiu nc. Cc lp v la ban u c c tnh thm nc cao nn nc v mt s muiho tan thm vo trng, lm cho lng trng b trng ln, tng khi lng, li dn cht vocc lp v la. Trn mt rn li t nhiu ca v la hnh thnh lp vi tc l lp v cng.

Lp v cng hnh thnh trong t cung. Nhng trng ri khi ng dn trng qua ngr nm cui t cung c lp v cng cu to hon chnh; mt khc nu ct bt t cung mton th cu to v cng trnn thiu hon chnh, cha hm lng vi v protit thp.

Trong qung thi gian ba giu khi trng lu li t cung, nguyn liu hnh thnhv vi tch t li rt chm. Sau hin tng tch t trnn ng u v nhanh. Trong qungthi gian 17 gicui cng, khi lng lp v cng tng ln theo t l thi gian trng lu litrong t cung. Lng cc cht cu to nn v cng tit ra tu thuc vo ln ca lng vkhi lng lng trng tch t trong trng.

Khi lp v cng hnh thnh, nhng ni no tip xc vi biu m t cung th sinh racc l kh. Nhng l ny ging nh l mao mch b, mra mt trn lp v cng.

Khng nn khng nh rng, vi l do mt on c bit no ca t cung hoc do mttuyn c bit no y tit ra, v cc m t cung ca g mi ang r cha t canxi hncc m thuc nhng phn khc ca ng dn trng. V khi hnh thnh v cng trong vng 20gi, c n 5g cacbonnat canxi tch lutrng, do c th don l ngoi t cung ra cnc ngun canxi khc na. Hm lng canxi trong mu g miang cao hn kh nhiu sovi g mi khng . V khi v trng hnh thnh th lng mu dn v t cung tng ln, nnc th ginh rng, cc mui canxi dng ho tan t mu chy vo t bo cc tuyn t cung,sau cc t bo tuyn ny li tit dung dch y vo ng t cung. Canxi khng li mt duvt no ta c th theo y m xcnh ni tit ra n hoc qung ng n chy qua. Chc hin tng l trong cc tuyn tip xc vi trng, hm lng canxi c cao hn mt t.

Trong thi gian hnh thnh cc lp v trng, cht oporfirin c phn b vo lp vcng c mu. y l cht mu ch yu, do hemoglobin ca hng cu phn hu m to ra. Khiv cng hnh thnh xong c th c cc cht mu khc b sung thm thnh hnh lm tm,

hnh cc sc vn hoc cc nt sn b.Lp v mng trng ngoi (lp m sng) hnh thnh trong qung thi gian t khi trngcu to hon chnh cho n khi trng ra ngoi. V thnh phn ho hc, n cng ging nhcc lp v la.

1.3.4. Ti sao trng c u to, u nh?Trng gia cm sdc mt u to mt u nh l do trong qu trnh hnh thnh b

pha trn ca ng dn trng dn p tng on mt n i xung di. u trng ny b dnp, lng trng v mng v by sang phi ri li sang tri, v th m pha u ny phnh to,sau khi v hnh thnh xong th c c nh li. Ngc li, u kia ca qu trng hngxung on di ca ng dn, do va i n va chn vo ng dn trng, lm cho ng nymrng trng d di chuyn xung t cung. Lc dn p ca ng dn vo qu trng lm chou nh hnh thnh ri nh hnh dn. Khi trng vo n t cung, u nh hng v pha uig, cn u to th hng ngc li.

Cho n nay vn cha r iu g quyt nh thi gian cho ln rng trng u tin cagia cm, nhng c hai yu t h thn kinh v cch hormon l quan trng hng u. Ln rngtrng th 2 l s tip din ca ln rng trng trc v xy ra 15-40 pht sau khi qu trngu tin i qua l huyt. Nhng ln rng trng tip theo xy ra vo cng khong thi gian saukhi trng c .

Nhng qu trng ra lin tc khng nghc gi l trng hay l chu k trng.Kt thc chu k ny, gia cm s khng trong mt s ngy tip theo. ln ca mt



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trng c th t 1 n hn 200 qu (k lc c ghi nhn l 235 qu). Nhng loi g trng tt t 3-8 trng mi trln v u n. Khong thi gian mt rt c trng chotng c th: nhng con kh nng sn xut ngho nn c nhng ngn hn, ngc li

nhng con c kh nng sn xut tt c trng ln hn. Khi thi gian cho mt , g mis dng rng trng v dng c sn xut t rng trong mt ngy hoc nhiu hn, v sau litip tc cho tip theo. Nhng con g sn xut trng km c thi gian ngh di hn nhng gsn xut tt.

Thi gian cn thit sn xut mt trngThi gian cn thit cho mt qu trng di chuyn trong vi trng rt khc nhau mi

c th. Hu ht g mi trng lin tip sau nhng khong thi gian t 23-26h. Nu thi gianny di hn 24h, mi qu trng trong giai on lin tip nhau sc trong ngy khc.Nhng qu trng vo bui chiu s nm trong ng dn trng lu hn nhng qu trng vo bui sng. Nhng qu trng cui cng c mun khi chui s b gin on v mtchu k rng trng s chm dt.

Thi gian cho rng trngG mi c nhng trng di qu trng u tin ca trong thi gian sm ca

ngy, 1-2 h sau khi mt tri mc hay sau khi h thng nh sng nhn to c bt ln. Srng trng ca ln hnh thnh lng tip theo n rt nhanh sau khi mt qu trng c vo ngy tip theo, ch sau mt khong thi gian ngn. Nhng con g mi c thi gian chomt ngn hn qu trng u tin ca vo thi gian mun hn trong ngy, s rng trngcho ln hnh thnh lng l chm hn, v khong thi gian chcho s trng di hn.Hu ht qu trnh rng trng xy ra trong sut khong thi gian bui sng, s bt bnh thngnu qu trnh rng trng din ra vo bui chiu.

Qu trnh sn xut trng vo thi im bt u Trong tun trng u tin, s rng trng rt khng bnh thng, cch hormon ca

g mi l khng cn bng. Thng ch c 2-4 trng c sn xut. Nhng n nhng tun th2-3 qu trnh rng trng s c nhng tin bng k, v ch gim st rt chm trong tun vinhng qu trng cn li trong mi chu k.

nh sng v srng trngnh sng, d l t nhin hay nhn to, s c nhng tc ng kch thchn tuyn yn,

kch thch n tng lng hocmon FSH tit ra, v ngc li s kch hot bung trng. C hai yu tthi gian v cng nh sng u quan trng. Qu trnh iu khin lng chiu sng cho phhp trong chung g l rt phc tp v sc ni r hn trong cc phn sau.

Lm tnhl mt tn hiu ca vic rng trngTrong hu ht cc trng hp, g mi s tm khong 24h trc khi rng trng, v nhiu

nh khoa hc coi tn hiu ny l quan trng hn cho vic xc nh vic rng trng hn c qutrnh trng. Bng chng l s xut hin ca mt qu trng hon chnh trong l huyt chng cg lin quan n n lc i tm ca g mi. Mt s g mi rng trng v t bo trng khng tic vi trng v nhng con g mi ny s tm mun hn mt ngy.

T cung v cbn l tuyn v, di khong 10-12cm g . Trng ang hon thintn ti trong t cung khong 18-20h, lu hn nhiu so vi cc giai on khc trong vi trng.

Lp lng trng mng pha ngoi c lng ng sau mng vKhi trng ln u vo t cung, nc v mui sc b sung qua mng v bi qu

trnh thm thu bm ra khi lp mng v lng lo v lm lng ho mt s lng lng trng

mng hnh thnh nn lp th 4, chnh l phn lng trng mng pha ngoi. trngng tc trng l mt phn x phc tp. Nhng th cm nim mc m o c kch

thch bng qu trng nm trong n. Nhng xung ng t th cm lm cho cm o v d con cobp mnh. Lc thnh d con cng vi trng qua m o vo nhp. Nhc co bp ng thi


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Phn protit 3 12,8

Phn eo 1,17 5,0

T cung 19 80,8m o Rt ngn

Cng 23,5 100,0

Trc khi hnh thnh trng, xy ra hng lot cc bin i c th trng thy v khngtrng thy trong cc cquan sinh dc v trong cc chc nng ca cth.

Trc thi k sinh sn, mu cha nhiu cht m v sau chuyn vo trng. Nng lngchi ph vo qu trnh bin ho ny l do hm lng glucoza trong muc tng thm v clin quan vi vic tng cng trao i cbn.

Khi bt u trng, hm lng m, protein, gluxit v cc cht khong trong mu gmi c tng thm. Tng cao nht l hm lng m(n 255%), trong s cc cht khongth hm lng fotfo tng cao nht (n 202%), tip theo l cc cht hu ccha trong fotfatit,

cn hm lng fotfo v cch tng 26%, canxi tng 68%. Mu g mi ang nhiu proteinhn mu g mi khng 62%. hnh thnh trng ni chung v tng phn ca trng ni ring, nh lng , lng

trng, v g mi cn chuyn ho mt lng ln cht dinh dng nn tt nhin i hihot ng kh cng thng khng ch ca cc cquan sinh dc m cn ca ton b cth.

Bng 6. Chiu di v khi lng ng dn trng v khi lng bung trng thuc cc latui khc nhau cc giai on c nng sut khc nhau.

ng dn trngTui

Khi lng, g Chiu di, cmKhi lng

bung trng, g

G con mt ngy tui 0 0,45 0,03

G mi tlc ba thng tui 0,18 6,60 0,31

G mi tlc bn thng tui 1,10 9,69 2,66

G mi tlc nm thng tui 22,0 32,21 6,55G mi tsau khi qu trng u 77 68 38

G mi tngay sau khi ngng 74 65 34

G mi trong thi k thay lng 4 17 3

G mi li sau khi thay lng 75 68 49

G mi gi ang 78 69 52

G mi gi vo lc ngngmang 5 30 4

G mi gi trong thi gian p 6 30 3

Cc qu trnh xy ra khi hnh thnh trng

Bng 7. S lng t bo trng nhn thy trong bung trng ca g mi thuc cc gingkhc nhau

(theo ti liu ca Pirle v Shoppe v Romanoff)Ging g S nang Nang di T bo trng nhn thy Tng s




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pht trin 1mm T1mmn 1cm

Trn 1cm

Lgo trng (Loghorn) 87 2268 124 5 2484G lai i mt 46 2257 64 7 2374

Plymouth Rock 31 1486 88 6 1608

G chi n 54 1323 167 6 1550

G Brama nht 28 1074 119 9 1130Bng 8. Sthay i thnh phn ho hc ca lng(%) trong qu trnh hnh thnh trng

(theo Romano ff)

Trng c ng knh

T2 n 6mm T6 n 35mmNc 86 45

Protein 44,4 35,1

M 23,1 42,3Folfalit 11,0 12,7

Cht dn xut khng m 8,6 3,9

Tro 12,9 6,0

Tnh chu k ca s rng trng ph thuc vo nhiu yu t: iu kin nui dng vchm sc, la tui v trng thi sinh l ca gia cm... vic nui dng km, khng nhsng v nhit khng kh trong chung cao cng lm chm s rng trng v trng.Ngi ta bit c mi lin quan gia vic rng trng v ch ngy chiu sng. Nunui g ban ngy trong nh ti, cn ban m cho nh sng nhn to, th s rng trng v trng s chuyn sang ban m.

1.3.5.iu ho qu trnh to trng v trngS rng trng gia cm chu siu khin ca cc hocmon. Cc hocmon hng sinhdc ca tuyn yn FSH v LH kch thch sinh trng v chn ca cc t bo trng. Phn mnh,cc t bo nang tit estron trong khi trng rng, kch thch hot ng ca ng dn trng.Estron nh hng ln tuyn yn, c ch vic tit FSH, nh vy s lm chm vic chn t botrng bung trng. xc nh c l hocmon luteinostimuli (LH) kim tra vic rngtrng ca gia cm. Tuyn yn ngng tit n khi trong ng dn trng c trng. Do c chs rng trng ca t bo trng chn tip theo. Ngoi ra LH chtit vo bui ti, s chiu snglm ngng tr vic t it n, do vy, s rng trng s b ngng li. Ngi ta cho rng g tlc bt u tit LH n lc rng trng ko di khong 6 - 8 gi. V vy vic chiu sng thmvo cc gibui chiu v ti lm chm vic tit LH, vic trng v rng trng 3 - 4 gi.Nh vy, cch ca qu trnh rng trng gia cm ph thuc vo mc tit cc hocmonhng sinh dc trong ngy.

Trong vic iu ho qu trnh rng trng, c cc vng ca h thn kinh cp cao thamgia, k c v bn cu i no. gia cm, to nn phn x c iu kin tc dng ln cc nhnt khc nhau ca mi trng bn ngoi m n kch thch hayc ch qu trnh rng trng v trng.

Chu ktrng. trng l bn nng ca qu trnh sinh sn. Chim rng th hin rhot tnh sinh dc c chu k theo ma v do chu k trng ph thuc vo iu kin ngoicnh. mt s ging g cng nghip cao sn, tnh trng theo ma khng th hin. iu

Formatted: Condensed by 0.6 pt


Deleted:


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chnh ch nui dng th duy tr c sn lng trng cao trong thi gian di. G cao snc th 300 v hn 300 trng trong mt nm.

Phn ln l g mi ngy 1 qu, khng ngh trong thi gian ngy di hay ngn. G

km thng cch nht; my ngy, sau ngh khong 2, 3, 4, 5 ngy v c th hn,sau li tip. Thi gian ko di ca chu k trng ph thuc vo thi gian hnh thnh 1qu trng. g thi gian cn thit hnh thnh 1 qu trng l 24 n 28 gi(trung bnhl 25 gi). Nu trng c hnh thnh di 24 gith g lin tc (ngy mt) v chu ktrng c th ko di (4 - 6 trng v hn). Nu nh trng c hnh thnh trn 24 ting, th g cch nht. S ko di qu trnh hnh thnh trng g s lm cho trng nm trong dcon lu. Nu nh vo na ngy th hai m khng c hin tng rng trng, th qu trnh trng s cch nht. V d, qu trng hnh thnh trong 26 gith trng vo nhng ngy saus lch sang 8, 10, 12, 14 gica ngy, v sau l cch nht. Nh vy, thi gian cn thit hnh thnh qu trng cng nhiu th chu k trng cng ngn v cng ko di thi gian cchnht. Ngc li, chu k cng di th thi gian ngh cng ngn.

Chu k trng ca g c c trng rt nhp nhng, ngha l chu kc nhcli. Chu kc chia ra: chu kng, khi thi gian trng ko di qua mt s ngy nhtnh v chu k khng ng. Tnh nhp nhng ca chu k thay i khi ph viu kin nuidng. G trng tt c chu k cnh v ko di. Nhng g km chu k thng ngn,thi gian ngh gia cc chu k di, t.

Chu k sinh hc trng l thi k t khi bt u pht dc v qu trng u tinn khi bt u thay lng, trong thi gian g thay lng n khng. Sau khi thay lng snlng trng c hi phc v ko di n khi thay lng ln sau. g 2 nm tui v gi hn,chu k sinh hc trng bao gm c thi gian gia 2 t thay lng. S bt u v kt thcca chu k sinh hc trng nhng g ny c th xy ra trong thi gian khc nhau trongnm v ph thuc vo thi gian nca g. Thng l chu k ko di 1 nm. Chu k ko dic quan st thy g c kh nng pht dc sinh l cao, trng cnh v u.

G ty, vt v ngng chu k trng khc hn ch ko di hn v theo ma. G tt trong mt nm ti 220 - 250 qu, vt 120 - 180 qu, g ty 100 - 150, ngng 50 - 80qu.

Yu t ma trng ca vt v ngng lin quan n chu k nm ca hot tnh hocmon

(B.G.Novicop). Nng FSH v LH v hot tnh ca chng ph thuc vo s lng Rilizing- hocmon c to thnh trong vng di i th.Vt bt u t 7 - 8 thng tui v trong thi gian 6 thng cho n thi k thay

lng. Trong thi gian (chu k sinh hc u tin) vt bnh qun 120 - 130 qu trng. Saut thay lng, kh nng trng c khi phc (cui k th II) v ko di 5 thng, trongthi gian ny vt cho 80 - 90 qu trng. Vt rt sm, v d vo 3 - 4 gisng. n 6 gisng c ti 70% vt , cn n 9 - 10 givt xong.

S pht trin v chc nng cc cquan sinh sn ca g mi c kim tra bng cchthn kinh hocmon phc tp, di nh hng ca iu kin ngoi cnh. Tc nhn kch thchu tin ti s pht trin h thng sinh dc gia cm non l s sn xut hocmon hng tuynsinh dc ca tuyn yn, nhng hocmon ny kch thch s pht trin v trng thnh ca trngtrong bung trng. Cng vi s sinh trng ca trng xut hin hot ng ni tit ca bungtrng; t bo nang trng tit ra oxtron, cht ny kch thch s sinh trng v hot ng cang dn trng. Di nh hng ca oxtron d tr cc cht dinh dng c di chuyn, nhng

cht ny cn thit cho s hnh thnh mng v trng, tng mc trao i cht, tng tch lucanxi trong mu g , s tch lu ny di s iu tit ca hocmon tuyn cn gip. Cntuyn cn gip chu nh hng ca hocmon tuyn yn. Sau khi rng trng cc t bo nangtrng v, tit ra progesteron duy tr trng thi hot ng ca ng dn trng khi hnh thnhqu trng v cng lc tuyn yn tch li hocmon thc (oxitoxin). Qu trnh nyc chhot tnh vn ng ca ng dn trng v d phng trc thi gian. Tuyn yn tit ra


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Rng trng thng din ra sau na gi k t khi qu trng trc. Khi trng vophn sau ca ng dn trng, phn ny li c mu dn vo v chuyn qua trng thi hot ngtch cc tip thu qu trng mi thnh thc.

Vn ti sao nang trng vvn cha c sng r. Ngi ta khng th cho rng, dop lc ln bung trng ngoi vo t pha phu cng khng phi do p lc xy ra bn trongnang t pha lng hoc t dch nang. V vy ch cn c th ginh rng, hin tng nangvcng nh phn ln cc qu trnh sinh sn khc cng do cc hocmoniu tit.

S c mt ca g trng v hin tng p mi khng nh hng n tn s rng trng.i vi b cu th vn c hi khc. b cu, ng tc p mi lm kch thch trng rng.Sau khi p mi khong tm hm th trng rng. Khi trong t c hai trng th b cu mi btu p. Hin tng trng rng b ngng li v b cu mi khng thm na. Tuy nhin nuly trng ra khi t th li c th tip tc c s rng trng. C th buc g mi thm nhiutrng bng cch ly trng ra khi . Nhng khng nn cho rng, ch dng ring bin phpnhn to ny l c th nng cao sn lng trng ln n 300 qu hng nm, m mun t nnng sut y cn cn phi to ra hng lot cc iu kin khc na.

Cc iu kin bn trong v bn ngoiu c th d dng iu tit vic rng trng. nhsng kch thch rng trng, cn bng ti th c ch n. V vy, nu hin tng rng trng cnphi hon thnh xong ngay trc lc ti tri th n s b gi li cho n sng hm sau. Trongiu kin chiu sng lin tc th s trng v tip l s rng trng din ra c ngy lnm. Vo cui ma h tri qu nng bc lm gim tc rng trng. Sn lng trng lc bygicng gim.

Nu quy ry g mi khi th trng b gi li trong ng dn trng v s rng trngtip theo s b chm li.

C nhng trng hp c nhng qu trng n hai ba lng , v ngi ta ghi lic qu trng c nhiu nht l 9 lng . G mi t khi lin mt lot ton trng c hailng . Ngi ta xem nguyn nhn ca hin tng ny l do s ri lon ca chu k rngtrng, trong mt s lng rng gn nh cng mt lc. Hin tng ny xy ra g trng ging hng tht nhiu hn g hng trng.

Cng vn thng xy ra nhng trng hp m Sterky nu l g mi vn rngtrng u n, nhng lng thnh thc khng ri vo ng dn trng m ri vo khoang c

th v y mt thi gian th b tiu ht i, sau chng khng bao gi na. Nhng gmi ny b ngoi thy rt bo v p, khi dng sp th thy chng khng bao gi trng.G mi trng theo nhp l my ngy lin tc sau y ngng mt hoc vi

hm. V vn ny, gi thit ca Bastian v Zarrow rt ng ch . V nguyn tc, gigic trng vo bui sng i vi cc quu chu k, cn qu cui cng i khi vo lc qu tra rt lu. Phn ln gia cc chu k c mt ngy khng v mi chu k c th tmt n trm qu trng, c khi cn nhiu hn na nhng a s trng hp g t hai n baqu. Cc tc gi trn cho rng, c hai chu k hon ton c lp vi nhau, tc ng tng hln nhau v cng to thnh chu k rng trng in hnh ca g mi. Chu ku l s thay ingy m k tip nhau, chu k hai l nhp iu thnh thc cc nang trng. Tin quan trng gii thch vn ny l thi gian t bo trng thot khi nang trng din ra ban m vocng mt giging nhau v ko di kh lu gn tm gi; ngoi ra li cn do cc nang uthnh thc sau cng mt thi gian tng i bng nhau.

Th nghim Bastian v Zarrow chng minh rng, chiu sng ban m dn n trng

thi hot ng ca g mi s lm cho trng thi rng trng ca nang u tin trong chu k bchm li. V cc tc gi cho rng, nhp iu ban ngy thy g mi khi rng trng, c th giithch bng tc ng u th giai on sng trong ngy v hot ng ban ngy c tc ngn rng trng.


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mi tt. Thi gian ngt qung thng xy ra vo lc tm ngh ma ng ko di t ngymng mt thng mi n ngy mng mt thng ba. Khong thi gian tm nghng phthuc vo c tnh di truyn v nh hng ngoi cnh. vng kh hu nng, hin tng tm

ngh ma nng thay cho tm ngh ma ng.C th c nhiu cch xc nh thi gian ko di trng. Heis v Saninborn (theo

trch dn ca Hutt) xc nh: l s ngy k t khi bt u trng n khi bt u tm nghma ng. Cc tc gi ny gi thi ky l nm trng sinh hc. C th ly ngy thng g qu trng cui cng hoc tui ca g mi vo lc y lm mc o c th thi gian ko di trng. Mun th phi ghi chp ngy g n. Trong thc tin c th dng s lng trng vo thng tm v thng chn tc l trong hai thng trc khi tm ngh lm mc o. Huttcho rng nng sut chung cng vi nng sut tng thng l mc o gi tr kinh t ca g mitrc tip hn v thch hp hn bt k mt kiu xc nh no khc. Chng ta c th nht tr viquan im ny. Nghin cu cn thn s trng ca g mi ta c th c ngay n tng rrng v thi gian ko di v tnhn nh ca s trng.

1.3.9. Phn xp trng

Bn nng p trng lin quan n kh nng trng v phn x khng c iu kin. mts g thng l ma xun sau khi th bt u p trng. Sp ca g nh c th hin dng nm l trong , ngng ; g ku cc cc. c bit sp th hin r g ty, thng lsau khi c 15 - 17 trng. Bn nng p trng xut hin sau khi 12 - 15 trng, cnnhng mi so sau 6 - 10 trng. vt bn nng ny xut hin trong trng hp, nu nhngtrng ra vn trong . g dng trng bn nng p trng khng cn. iu to iukin cho n c nng sut trng cao. g ging tht, sp trng lm gim sn lng trng.Thi gian p ca g l 21 ngy. khng ch khng cho g p, ngi ta lm cng tc chnging, chn nhng g t p hoc khng p.

Trong iu kin t nhin, g mi rng sau khi trng t u th chuyn qua giaion p trng ri nui con v ch sau mi gt u t th hai

Hin nay do chn lc, bn nng p trng mt s ging g chuyn trng gim inhiu. Thc ra, ngi ta vn cha t n mc xo b n hon ton. Bn nng ny biu hinmnh nht cc ging g tht (ln) chu . Mt vi ging g chu u v chu M lai vi g

mi chu vn gi bn nng ny mc tng i. Thm ch nhng ging g b (gingg trng) a trung hi, ni chung khng cn bn nng ny na, nhng i khi vn thy thhin. C th hiu mt cch d dng v sao bn nng ny li c duy tr qua nhiu th h, nuta nhrng y l do vn bo tn ni ging m c. Nhng g mi khng p th mt khnng duy tr ni ging, con ci ca chng ch c th c c bng cch p trng nhn to nhs can thip ca con ngi. Vic tin hnh tuyn chn g theo hng khng c bn nng ptrng cng d dng v iu ny lin quan n vic tuyn chn theo nng sut cao hng nm:ni chung cc mi p th t trng (y cng vn c nhng trng hp ngoi l).

Heis v Sainborn chng minh rng nhng g mi c bn nng p trng th cng trng gia hai kp cao hn nhng g mi khng c bn nng ny. Tuy nhiniu y cngkhng th b p ton b trng b mt (do khng ) trong khi p v do trong mi trng hpnhng g mi c bn nng p thng c nng sut trng hng nm thp hn.

c ch bn nng y, ngi ta nht g mi vo gi hay vo lng t ngoi tri. Bngcch y thng sau vi hm g mi c th qun p c.

Thi gian gn y ngi ta dng dng in h th rt ngn thi k g mi p trng.Cng c th rt ngn thi gian p ca g mi bng cch: h st (c th dng thuc gim st),cho n tt, nht chung vi g trng, t lng g ni khng yn tnh v c nh sng y ,lm nh vy, sau 2-3 ngy g s bp (Bi Hu on v CTV).

1.3.10.Thay lng




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Thi gian g ngh lu khng phi vo lc p trng m vo lc thay lng. Chonnay ngi ta vn cha to c ging g khng thay lng hoc khi thay lng m vn . Thaylng vgia cm l hin tng sinh l t nhin tng ng vi hin tng thay lng mao

ng vt c v.Hin tng thay lng ko di bao lu v tin hnh vo lc no l hon ton tu thuc

vo cc i thay ln ca c th. Trong mt s trng hp, cc lng chnh ln lt b thay th,do quanh nm chim c lp lng v gn bo v ton thn. Trong nhng trng hpkhc, do ton b lng cng rng bt ngnn c lc g mi hu nh b tri lng. Thay lngihi cth loi chim hot ng gp i, khi gia cm rt mn cm vi mi trng v bm. Mt mt yu cu chi ph nhiu th cn thit phc hi lp lng mi, mt khc g b trilng d b tc ng nh hng bt li ca thi tit hn.

Thi gian bt u thay lng gn vi hot ng gim st ca cquan sinh dc. Khi btu thay lng, trnh cho cth khi hot ng qu sc, g ngng trng. Ngi ta phnbit thay lng hon ton vi thay lng b phn hoc thay lng c. Khi thay lng hon ton thg mi thay ton b lng v v trong thi gian t hai n nm thng, n khng. Trong iukin kh hu ph bin, thay lng hon ton phn ln bt u vo cui thu hay vo mang,nh ta bit cc nh hng thun li hoc bt thun li u c th lm chm hoc lmnhanh hin tng thay lng v trong cc trng hp hn hu c th hon ton lm nh chhin tng y. Trong thi gian ny nu thay i v tr hoc chung tri, thay i thi tit btng, thay i thc n t ngt th c th dn n thay lng chp nhong. Nhng g mi ttbt u thay lng mun hn v mt t thi gian hn cc g mi khc to ra b lng mi. Cnhng g mi c bit trong hai nm lin hoc lu hn na, vn m khng c cc du hiuthay lng hon ton. V vy, gia thi gian ko di thay lng v sn lng trng hng nm cmi lin quan cht ch.

Khi thay lng b phn th g khng thay ton b lng m thng ch thay lng c.Trng hp ny, thi gian g ngng rt ngn v khng c tnh quy lut nh thay lng honton. Nu cho g n v chm sc c bit cn thn th c th lm cho chng trnh c thaylng ton b. Nhng g mi trng thnh i khi bt u thay lng b phn vo ma ng,sau thi gian trng cng thng.

Heis v Sainborn pht hin rng, khong thi gian ngh ma ng khng tu thuc

vo qu trnh thay lng v khng c mi quan h no gia khong thi gian thay lng vkhong thi gian p trng. Ngc li, cng trng, tnh cht n nh ca s trng,sn lng trng c nm v sn lng trng trc khi thay lng c tng quan nghch vikhong thi gian thay lng. G mi c nng sut cao v lu bn th cng c thi gian thaylng ngn nht.

Hin tng thay lng cng do cc qu trnh hocmon iu tit v c quan h vi hotng ca tuyn gip. Khi tuyn gip pht trin qu mc th lng thay sm. Mt khc, hotng tuyn gip li b chi phi bi kch t do tuyn yn tit ra. Tim kch t gip trng s lmcho g thay lng sm. Nh Buddenbrock chng minh, khi tim hormon ny 3 ln, g btu thay lng.

1.3.11.Thnh thc sinh dc ca g mi - qu trng u tin cht dinh dng to thnh trng, trong cth g mi c tc trao i cht rt

cao. Nhng ging g mi ngy nayc to ra qua chn lc, bt u trng rt sm khi thnh thc sinh dc nhng c th th cn lu na mi trng thnh. G mi t bt u trng th th trng cht gn 2/3 trng lng bnh thng khi trng thnh. G mi vntip tc ln khi trng do cth phi lm vic gp i.

Chim rng bt u trng vo ma xun, vo thi gian thun li trong nm, phn lnkhi c mt nm tui. G mi thuc cc ging trng hin nay bt u trng vo cui hhoc vo ma thu lc nm n sau thng tui (tu theo thi gian n). Ni chung tnh thnh thc



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sinh dc sm c quan h vi nng sut trng cao. Nu v mi con nra vo thi gian bt thngtrong nm th chng c th thnh thc sinh dc rt sm nhng s c nng sut thp.

Ngi ta nhn thy rng, g con nvo ma xun v u ma h thnh thc sinh dc

mun hn, v vy khi thnh thc th cn nng cao hn g nvo thu ng.Mc d g nvo ma xun trng mun hn nhng tng s trng chng ra li

nhiu hn. G mi c nng sut cao nht trong ma thu l nhng g nvo thng hai v btu trng vo thng by, nhng trong thng mt v thng chp, chng cng thng hayngng v bt u thay lng cc b. Trong c hai trng hp k trn, giai on trngthc t trong nm u b rt ngn rt nhiu.

Theo quan im sinh hc th trong cc iu kin nui dng bnh thng, nhng gcon n ra trc ngy mt thng t khng c u im g tri hn. G mi n vo thi gianthng thng trong nm bt u trng vo thng mi mt, thi gian trng khng bngt qung v khng thay lng. Trongiu kin chm sc v nui dng theo phng phphin i c th cho g nquanh nm v ngi ta phn b s trng lm sao c hiu qukinh t nht.

Heis nghin cu vn ny s ln g mi Rhode Island nvo thng ba v thng t.Nhng g mi n sm qu th nh hn nhng g mi nvo thi gian trung bnh hoc nmun. Khi lng khc nhau ny khi 14 thng tui trln khng cn na. Tui g mi tkhibt u trng c nh hng n trng lng trng: nhng mi thnh thc mun ni chungc nm ra trng nng hn nhng mi thnh thc sm. Nhng mi thnh thc rt sm thnng sut cao hn nhng mi thnh thc mun nhng khng cao hn s mi thnh thc trungbnh.

Heis cho rng, ng v quan im kinh t m xt th tt nht l nui g mi thnh thcsinh dc t bn thng ri n su thng tui.

1.3.12. Tui v nng sutTui cng cao th nng sut g mi cng gim. iu y khc vi cc loi gia sc khc

nh b, ln. B ci t sn lng sa cao nht vo la th t hay la th nm, ln ni nhiu con nht vo la ba hay la bn. Trong c hai trng hp trn, chng ta u gp nhngqu trnh sinh trng ko di, ch sau khi cc qu trnh ny hon thnh th sau gia sc mi

c kh nng t nng sut y . Sau khi bt u trng, g mi cng cn tip tc ln, tuynhin cng trng t c trong nm u tin s l cao nht.Nng sut ca gia cm mi theo tui c trnh by trong bng sau:

Bng 9. Nng sut ca gia cm mi theo tuiNm G Vt Ngng G ty

12345

100%85%706050

100%105807055

100%12516015075

100%105957585

Cn c vo s bin ng ca t l trng qua cc nm m ngi ta xc nh thi gian sdng thch hp i vi tng loi, ging gia cm.

i vi g nn s dng ht nm u, vt 2 nm, ngng 4 nm, g ty 3 nm. Nu tip tc nui, tiutn thc n tng ln nhng t l thp.

1.3.13.Quy lut trng v thtrng




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Cn c vo tc ng ny ca cc hocmon i vi cc cquan to trng, ngi ta hyvng c th d dng nng cao nng sut trng khi tim hocmon cho g. Tuy nhin, v vn ny chon nay vn cha c iu g sng t.

Trong thc t din ra hng lot cc cng trnh nghin cu m kt qu hon ton tringc nhau. Qua y ngi ta thy rng, loi chim vic xc nh quan h tng h ca cchocmon v tcng ring bit ca tng hocmon kh hn ng vt c v.

Buddebrock nu r cc c im sinh hc ca loi chim v c bit v s tn ti cabung trng th sbn phi. Sau khi ct bung trng ang hot ng bn tri th bung trngbn phi bt u pht trin v bin thnh mt tinh hon y . C th v vy m g mithin, mo v tch pht trin mnh lm cho b ngoi trng ging nh g trng. Nh chng tathy phn ng ca bung trng th sbn phi rt rt c o. Ngi ta khng r n phnng nh th no khi tim cc hocmon t ngoi vo v c ly l nguyn nhn ca mi khkhn trong vic xc nh quan h tng h gia cc hocmon v ca nhng mu thun v ccti liu thu c khi tim hocmon cho g mi. V vn dng hocmon nng cao snlng trng, Hutt nu nh sau: trong cc thng bo v 31 th nghim dng cc cht tuynyn, bung trng, tuyn gip hoc dng cazein c hot tnh tiroit v dng th vng u khngc mt bng chng no chng t rng, d da vo mt trong s cc cht th nghim li cth buc g mi nhiu trng hn so vi i chng. Trong hon cnh hin nay, chng tacha th nng cao nng sut trng bng cch dng bin php hocmon c th ng dngrng ri trong thc tin.

Tuyn gip. Tuyn gip gy nh hng quyt nh i vi qu trnh trao i cn thitcho vic sn xut trng, v vy v mt l lun dng phng php cho g n cc ch phmtuyn gip nng cao nng sut trng l c thc. Cc th nghim ni ting trc y caDjiakming (1922 1923) nghin cu tc ng ca cc ch phm t tuyn gip khi cho chimn. Trong cc th nghim ny trao i cht tng rt cao, n mc, mc d cho n y , chimvn hon ton khng tch lu m. Trng thi ny dn n tnh trng tuyn c (timus) b b li,cn tuyn l huyt th b teo sm; b lng trnn ri v c. Lng pht trin nhanh nmc lm cho thi gian thay lng ko di v lng mt sc t. Khi cho n cc ch phm ttuyn gip vi liu lng cao th sau qung thi gian ngn li c thay lng v c th dn nrng lng hon ton.

Turner xc nhn rng, g mi gi tiroxin t hn cc g mi tkh nhiu. Bng cchcho n ko di cht tireoprotein tuyn gip c th duy tr mc cha tiroxin trong mu vnhth ngn chn vic gim st sn lng trng.

Tuy nhin, nhng kt qu thu c trong cc th nghim dng ch phm t tuyn gipvn cn nhiu mu thun, v vy cha nn s dng cc ch phm y vo thc t sn xut.

Tuyn c (timus). So vi tc ng ca tuyn yn, tuyn gip v tuyn sinh dc th tcng trc tip ca tuyn c i vi nng sut trng l khng ng k. Greenvoad v Blythxc minh rng, sau khi ct tuyn c th hm lng canxi trong mu g mi cn non vn mc bnh thng v chng vn trng c v vi bnh thng. Do , tri vi nhng ti liutrong cc th nghim khc, timus hnh nh khng gy nh hng g i vi vic hnh thnhlp v vi. Paron v Kagan (theo trch dn ca Buddenbrock) cho bit rng, vt c khi ctb tuyn c s c hin tng ngng pht trin cc dch hon. Tc ng ca s ct b tuyn cvt mi yu hn, tuy nhin s pht trin tuyn sinh dc v ng dn trng ca chng s bchm li. Buddenbrock gi thit rng, c ltimus lm cho cc tuyn sinh dc pht trin nhanh,

cc tuyn sinh dc pht trin li gy nh hng c chi vi timus bng cc hocmon cachng. Tuy th ng ta cho rng, trong s tt c cc cquan ni tit th tc ng ca timus cnang c tranh lun nhiu hn c. V th khng c g ng ngc nhin khi khng mt nhno nh ng dng timus vo thc tin.

nh hng ca cc hocmon i vi sp trng


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Skoglund, Thomhave v Manfodr nghin cu khi lng trng nhng g mi nvothi gian khc nhau. Nhn thy nhng g mi ntrong thi gian t thng mi n thng ba.Cc tc gi gii thch vn y l do khi g mi nv ma ng bt u trng th gp phi

thi gian nng trong nm, lc ny khi lng trng b gim, cn g mi nvo ma h th btu trng vo cc thng mt tri. Ngoi ra, hnh nh nhng g mi c khi lng trngthp hn th thnh thc sinh dc sm hn nhng g mi khc. Nhng g mi nvo mang bt u khi t 180 ngy tui, trong khi y nhng mi khc cht mc thnh thcvo lc 202 ngy tui. Do s ph thuc ca khi lng trng i vi thi gian g nc thgii thch bng nh hng ca nhit bn ngoi.

1.5.4. Xc nh khi lng trng c n tng chnh xc v khi lng trng ca mi g mi cn phi cn ton b trng

n sp trong ton nm trng. Theo cchy, khi lng trng sn xut l tng s ton bcc trng em cn. Phng php ny c p dng trong cc cng trnh nghin cu v khi kimtra quc gia v nng sut. Nhng trong thc tin ngi ta khng dng cchy v tn nhiu sc laong. V vy, y ngay tu vic xc nh khi lng trng da trn cscc mu chn lc.

Hin nhin l chnh xc khi xcnh nh th cng cao nu cc mu chn lc c tin hnhthng xuyn v phn bu trong nm. Do khi lng trng tu thuc vo tui g mi cngnh vo nhit bn ngoi nn c th nhn thy nhng s liu khc nhau kh nhiu trong s ghichp qua tng thng.

Martimo kim tra chnh xc ca cc phng php cn c chn lc khi xc nhkhi lng ca c khi trng, so snh cc kt qu thu c vi s liu thc t. Tc gi thy nhng nhm g mi c nng sut thp th ngay c nhng phng php t chnh xc hn vnmang li nhng kt qu thong, tuy nhin nng sut cng cao th s khc nhau cng ln.

Tc gi ngh mt phng php ng tin cy l cn mt qu trng (quu tin) cami thi k bt u t ngy mng mt, ngy mng mi, 20 mi thng, tnh khi lng trngca mi thi k thnh kilogam ri cng cc kt qu li. Nhng nu ch cn mt qu vo ngymng mt v ngy mi lm mi thng th cng vn cha t c cc s liu chnh xc.

Rauch so snh lch trung bnh v lch ti a trong cc phng php xc nhkhi lng trng khc nhau. V d nh trong ngnh nui g ging c ngi ta cn nhng

qu trng ra t ngy 26 mi thng cho n lc ht thng v trn csy tnh khi lngtrng c nm. Phng php y cho sai s trung bnh 0,7g v sai s ti a l 2,0g.Nhng i vi tng g mi th khng bao gic th ni l c sai s trung bnh hay ti

a, v vy iu gy kh khn cho ngi nui g trong lc chn lc theo khi lng trng.Trong thc tin phng php thun tin nht l phng php khng i hi phi cn nhiu,m ch cn khi a s g mi . Tt nhin thi gian thch hp nht l ma ng l nhngthng cng vic khng bn rn lm. Nhng v ma ng khng phi lc no cng c th theodi ht ton bn mi, v d vy s phi tn kh nhiu thi gian thu c s trng cami g mi tnh ch tiu trung bnh vo thng nm hu ht g mi u . Ngoi ra nh ni trn, trong thi gian ny khi lng trung bnh ca trng tng i gn ging khilng trng trung bnh c nm. Cn trng vo thng nm, ta c 54% tng s mi c lchn 1,0g, 85% khng qu 2,0g v ch c 15% l c lch cao hn 2,0g (quan string). Trong thng y ch c 0,5% tng s mi cha kim tra c v chng cha bt u .Tuy nhin, trong thng nm ngi nui g c nhiu cng vic nhp trng, nui g con nnkhng c thi gian cn trng.

Trng hp khng th t chc cn trng mi thng trong nm ngy, th kim tra nmngy trong cc thng chp, ging, hai, bn, nm, su cng c kt qu kh chnh xc. Cn nhvy trong 75% mi c th c lch n 1,0g, 96% n 2,0g v ch c 40% l trn 2,0g.Ngoi ra c th trong su thng ny t nht mi g mi cng c mt ln vo ngy kimtra v nh vy c th c s liu hu ht ton n.



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khng qu 1g. Hnh dng trng c th c kiu, khc vi hnh dng thng thng nhngiu y khng nh hng n gi tr dinh dng ca trng. Tht vy c th gp nhng qutrng ging nh hnh qu thn, c nhng ch li, lm khng u, c nhng mu tha hnh

giun v c nhng nt khc thng khc. Tt c nhng trng k hnh y l do ri lon chcnng ca ng dn trng, khng c v, trng v mng qu hay dy qu hoc thiu v. B dyca v cng khng c di 0,32mm, nhng trng c v mng hn th khng thch hp vn chuyn v c nguy cv. Ch s hnh thi ca trng bnh thng phi bng 0,7 0,8, vnu hnh dng c nhng chnh lch ln hn th c th gy kh khn trong p trng nhn to(t l nthp).

V trng phi sch, trn, khng b h hng v ng mu. Vn ra trng ht scquan trng trong trng hp bo qun trng. Nht l khi bo qun trong cc nh m t,trng ra ri chng b hng hn cc trng khng ra, v lp m sng b h hi trong lc ra.V vy, ch nn bo qun nhng trng vn sch t nhin, cc trng bn cn ra th phi lptc chuyn i tiu th. Ngi ta nghin cu hng lot cc bin php phn bit trng ra ri nhng vn khng n gin.

xc nh tui trng, ngi ta dng hin tng pht quang, hin tng ny hin ratrn v cng khi chiu tia t ngoi vo trng. c tnh pht quang ca trng l do trn lp msng c cc cht pocfirin, khi di cc tia t ngoi vo th nhng cht ny pht ra nh sngmu sm. Thng thng mu sm ca trng cha ra tu theo thi gian di hay ngn(tu theo iu kin bo qun) m nht dn, lc u bin thnh mu tm hoc sau y thnhmu trng xanh lam nht. Tuy nhin, khi di tia t ngoi c th nhng trng ti i khi cngc mu khng ging bnh thng m hi khc thng, c trng hp sau t mt n hai ngynhng trng ti c mu tm xanh lam hoc trng xanh lam nht. Mt khc, nhng trng hn mi ngy i khi cng c pht quang mu , do chnh xc ca phng phpny khng cao.

nh gi mc ti ca trng nguyn (cha dp v), i khi trong thc tinngi ta dng phng php th theo t trng. Nh bit, nhng trng mi (trng lngring bnh qun gn 1,08g/cm3) khi y l nc th nm ngang. Cc cht cha trong trngb kh dn th trng lng ring ca n cng b gim theo. V vy, nhng trng b kh inhiu th s lm cho u to ng dn ln v trng c xu th ni ln trn mt nc. ng dng

phng php ny, ngi ta b trng vo dung dch NaCl 10% v quan st th ni ca n trongdung dch. Th theo cch ni khng ng tin cy lm, v trng lng ring ca trng ti binthin rt ln (t 1,06 1,11g/cm3), do khng th xc nh chnh xc tui ca trng.

C thnh gi mc kh ca trng theo ln (chiu cao v ng knh) ca bungkhc to thnh gia cc lp v la ngay sau khi trng mi ra. Bung kh sinh ra trctin l do cc cht cha trong trng b co li khi trng ngui (t nhit trong cth g mi410C xung nhit mi trng chung nui). nhit 200C ng knh ban u cabung kh vo qung 14mm. Kch thc ca bung kh tip tc ln ln, sau y ch yu l docc nhn t nh nhit , m, trao i khng kh trong phng v thi gian bo qun kodi. Vic xc nh ln ca bung kh khi nh gi cht lng trng c ngha ln trongvic bun bn. Trong thc tin, ngi ta dng loi n c bit n soi trng, nhn nyngi ta cng c th xc nh nhng bin i din ra trong qu trng, v d thay i v trca lng , s h hng do vi sinh vt gy nn, ngoi ra cn thy c cc vt nt b trn vcng m mt thng khng thy c, v.v V vy, khi kim tra trng cn dng phng php

soi trng. Phng php ny khngi hi thit b phc tp.Chiu cao ca bung khtrng ti c cht lng cao ch l mt vi milimt. Chiu

cao ti a ca bung kh c tiu chun ho. Tiu chun ny cc nc khng gingnhau. Bung kh thng nm u t ca trng v c hnh bn cu. i khi nhng trngem bn, do vn chuyn khng cn thn bung kh b chia thnh nhiu mnh. Trong nhng qu


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nu chn th vn tiu ho tt nh nhau. iu y l do cc ht mnm trong lng trngthi keo (nh tng). Trong lng cng c cha cc fotfatit (nh lexitin) c tc dng i vih thn kinh v s trao i gluxit v lin kt mt cch hu cvi st (2mg), do trng c

ngha c bit bi dng cho sc kho. Trng l ngun cung cp fotfo hu cd hp thu,99% cht ny (mi qu trng c 116mg) nm trong lng .

Bng 10. Gi tr dinh dng ca trng thc phm, sa v tht(theo ti liu ca Grossfeld v Romanoff)

Thnh phn ho hc, % Vitamin

Thc phmNc Protit M gluxit

Nhitnng,kcal

A,IU B1, mg B2, mg

Axitnicotinic,

mgC, mg

Ccvitamin

khcTrng khng c v 74 13 12 1,0 158 1140 0,12 0,34 0,1 - D;1,1mgBt trng 2 48 43 2,6 593 4460 0,35 1,23 0,2 - D; ELng ti 49 17 33 1,0 355 3210 0,32 0,52 - - D; ELng trng ti 88 11 - 1,0 47 - - 0,22 0,08 - -

Sa b ti 87 3 4 4,9 69 280 0,04 0,17 0,1 1,7 D; 0,12Tht b cbo mg ETrung bnh 60 17 21 - 218 20 0,20 0,29 7,0 - -

Hot tnh ca vitamin l do tc ng ca vitamin A + carotenMt IU (n v quc t) vitamin A = 0,0006 mg - caroten.Ngoi st v fotfo cn phi kn canxi (2mg mi qu - trong 99% nm v cng),

magie (27mg, trong 90% lng ), kali (82mg), clo (76mg), natri (66mg), lu hunh (67mg),lu hunh ch yu lin kt xixtin v metionin v cc nguyn t vi lng km (khng qu 1mg mi trng), ng (0,3mg), brom (di 0,2mg), mangan (di 0,02g) v iot (t 0,004 n0,01mg).

Cc danh y i trc t tn cho trng g l k t hong, mt loi thuc c tcdng b huyt, dng huyt. Nhiu bi thuc ng y p dng trng g nh mt thc n bdng v thuc iu tr. n nay, theo kt lun ca cc nh khoa hc, c bit l cc nh dinh

dng M xem trng g l mt v kh dinh dng t nhin, gp phn nng cao sc khecng ng. Trong trng g HDL-Cholesterol cn thit v c li cho c th cng nhiu chtdinh dng khc nh vitamin B12, D, E, Riboflavin, Folate... c bit vitamin E, acid boOmega-3 ca trng khi lin kt vi nhau s to thnh mt hp thc ha hc c kh nng lmgim nguy c mc bnh tim mch. Acid bo Omega-3 c tc dng gim t l nhi mu ctim, gim ng mu, ci thin tnh trng bnh i tho ng, gim s hnh thnh cc bnhtc mch. C tc dng tch cc trong nhiu bnh tim mch, cao huyt p, stress, suy nhc,kch thch tiu ha, chng to bn, chng vim xng khp, tng kh nng thi c ca gan,b no, nng cao tr lc, phng nga suy no, nng cao nng lc tr tu, chng dng, gimung th ...

Trng g cn l ngun cung cp nhiu acid amin cn thit v c li cho c th. Vchnh nng cc axit amin ny trong trng g c xc nh l tiu chun nh gi gitr sinh hc ca cc loi thc phm khc. c bit, trng g cha nhiu Lysin, l mt trong 8

axit amin c bit cn thit cho c th. Trong 100g trng g c cha 1.070mg Lysin, nhiugp 9 ln so vi sa m. y l mt axit amin tham gia tch cc vo s pht trin ca cth.Ngoi ra Lecithin c nhiu trong lng trng c c tnh kt hp vi cht bo thm quathnh rut vo mu i nui cth, lm cho cholesterol khng tng trong huyt tng.

Trng c ngha ln v mt thc phm trc ht l do c cc axit amin v cc chtdinh dng khc c nng v h s tiu ho cao. Cng nhtt c cc i tng sinh hc,tnh trng cht lng ca trng rt d thay i. V vy, vic xc nh cht lng trng c


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tin hnh da trn vic xc nh cc tnh trng bn ngoi, bn trong v nng cc cht dinhdng trong trng. Bn cnh , ngi ta cn nh gi trng ln cscc c tnh l hohc: mi v trng khng c hon ho hoc c cc v khc thng d nhn thy bn ngoi

( ln, hnh dng), bn trong (cc th l, cc ht mu trong lng trng v lng ).1.7.2. V vn cholesterol trong trngCholesterol c cng thc l C27H45OH, thuc nhm lipit c tn l sterols,c tng

hp trong c thng vt, chim v ngi, l sn phm ca qu trnh trao i cht t bo,khng c trong thc vt. Cholesterol c tm thy nhiu trong mu ngi b xcng ngmch v cao huyt p. Nm 1974, Cc Nng nghip Hoa K cng

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