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AN INV EST IGATION INTO THE MECHAN ISMS INVOLVED IN THE DEPRES S ION OF OVULATION RATES IN EWES GRAZING OESTROGENIC LUCERNE
A thes i s p r e s en t ed in pa rt ial ful f il ment of the requ iremen t s for
the degree o f Ma s t er of Agr icul ture Sc ienc e in An ima l S c i ence at
Ma s sey Un iver s i ty
BERNARD JOSEPH McLEOD 1 9 7 8
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A B S T R A C T
The r eproduc t ive per f o rmance o f 123 Romney and Border Leic e s t er x Romney ewe s wa s compar ed a f t e r they gra zed o e s t rogenic l uc erne or non -oestrogen ic ryegra s s / c lover pa s t ur e .
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T o synchron ize oestrus pr ior to t h e exper imen tal t r ea tmen t ,
progestagen-impr egna t ed in t ravag inal sponges wer e inser t ed in a l l ewes for 14 days . In Exper imen t I , wh ich invo lved 42 Romn ey and Border Leic ester x Romney ewes , the an imal s gra z ed trea tmen t pa stures for one comp l e t e oes trous cyc l e . B lood samples wer e taken a t interva l s
thro ughout t he cyc l e and l u t ein i z ing ho rmone concen t ra t ions wer e d e t e rmined . Ovula t ion r a t e s and the numbers o f fol l ic l es presen t on the surface of the ovaries wer e r ec orded a t laparotomy , three days po s t - oes trus .
In Exper iment I I , which invo lved 81 Romney ewes , oes trogen ic lucerne or non-oes trogenic ryegra s s / c lover pa s tu r e wa s grazed for a comp l e t e o e s trous c yc l e , or t ea tmen t s wer e int erchanged i n mid-cyc l e . Al l ewes wer e slaugh tered three days po s t -oes trus and their r eproduc t ive trac t s wer e r ecovered and individual ly id en t i f i ed . Ovula tion r a t e s and the
numbers o f fo l l ic les on t he sur face of t he ovar i e s were r ecorded . Af t er sec t ioning the ovar ies , a l l fo l l icles of a d iame ter gr eater t han 2.0mm wer e recorded . Sec t ions o f t i ssue from t he vag ina , c ervix , u t erus and fa llopian tubes of each ewe were moun t ed , sta ined wi th ha ema toxyl in and eosin , and the height of their ep i thel ial cel l s mea sur ed .
The inge s t ion o f oes trogenic lucerne for one comp l e t e oes trous c yc l e depr e s s ed ovula t ion r a t e s by 29 per c en t (0.67 ovula t ions per ewe) in Exper imen t I and by 22 percent (0.40 ovulat ion s per ewe) in Exper iment II. The inge s t ion o f o es trog enic luc erne for pa r t o f the o e s t ro u s c yc l e ,
depr essed ovulat ion r a t e s only i f i t wa s consumed for the l a t t er hal f o f t h e cyc l e .
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O e s t ro genic luc erne d id no t sign i f ican tly in f luence t h e s ec r e t ion of l u t e in i z ing hormone over the pre-ovula tory per iod , or a t any o ther s tage of t h e oestrous cyc l e .
The r e wer e no s ignificant d i f f erenc es in t he to tal numb ers o f ovar ian f o l l icles presen t , i n the numbers o f fol l ic l es o n the sur fac e o f the ova r ie s , o r in the numbers o f large f o l l ic l e s (wi t h a d iame ter o f gr ea t er than 3 .5mm) p r e s en t , b e tween the trea tmen t group s .
The inges t ion of o e s t ro g enic lucerne did no t inc r ea s e sign i f ican tly , the h eight o f epi thel ia l c el l s in gen i ta l trac t t issue , when compared with tha t in ewes graz ing non -oest rogenic ryegra s s / c l ov er pa s ture . S imilar l y , there was no sign i f icant d i f f erence in u terine we ight s . Th is i s in contrast to pub l i shed da ta where luc erne i s f ed to speyed ewe s .
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A C K N 0 W L E D G E M E N T S
The author is spe c ia l ly indeb ted to his supervisor
Dr . M . F. McDona l d for his invaluab l e gui dance and a s s i s tance in
expe r ime n t a l work and adv ice dur ing the preparat ion o f this manu s c r ip t .
Special thanks are due t o D r . K . R. Lapwood for assis t ance with radio immunoassays and for his he l p fu l d i s cuss ions and adv ice ; t o Mr . M . J . Bir t les for a s s i s t ance with histo logica l preparat ions ; and
to Dr . R . W . Ke l ly , Inve rmay Agricu l t ural Research Centre , for the coume s tan assays . Special apprec iat ion for t e chnical assis tance is due to Mr. C . Mu i r , Mr . M. Wyc h e r l ey and Mr . B. Tha t cher and t o a l l those who assisted with the co l l e c t ion o f b lood samp l e s , especi a l l y my f e l l ow s t udents o f reprod u c t ive physio logy , Ma rk Fishe r , S t ua r t Mc C u t cheon , Bi l l McMi l lan and Al a s t a i r Gibson .
Acknowl edgement i s mad e t o Mr . P.H. Whi t ehead and farm s t a f f and to Miss J . McKegg for the typ ing o f t h i s manus crip t .
Financial assistance f rom the D . J . McGowan Tru s t and the J . Hur ley Trus t , is gra t e f u l ly acknowledged .
Final ly , special t hanks a r e due t o my fami ly for s upport and encouragement throughout this s t udy .
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P R E F A C E
This inv e s t iga t ion wa s c onduc t ed a t the Fer t il i ty Cen tr e , par t o f the Depa r tmen t of S heep Hu sband ry , Ma s s ey Univer s i t y . The
experimen tal work wa s c a r r i ed out in April and May of 1 9 77 and represen t s or ig ina l r es earch b y t h e au thor under the supervis ion o f Dr . M . F .
McDona ld , Reader , Sheep Husbandry Depa r tmen t , Ma s s ey Univer s i ty .
T A B L E 0 F C 0 N T E N T S
ABSTRACT • . . .
ACKNOWLEDGEMENTS PREFACE
LIST OF TABLES LIST OF FIGURES INTRODUCTION . .
CHAPTER I REVIEW OF LITERATURE .
(A) PHYTO-OES TROGENS
( i ) Phyto-oestrogen s in Pas ture Plants
( i i ) Fa c tors Inf luenc ing Phy to-oest rogen Levels
(iii) The Me tabo l ism o f Phy to-o e s t rogens in Sheep ( iv ) Phyto-oes trogens and Repro duc t ive Fa i lure
in Sheep . . . . . . . . . . . . . . . ( B ) THE MECHANI SM O F ACTION OF OES TROGENS
( C ) EXOGENOUS OESTROGENS AND REPRODUCTION IN THE EWE
( i ) The Oes t rous Cyc l e
( i i ) Gonado trophin S ec r e t ion ( ii i ) The Reproduc t ive Trac t
( iv) Oes t rogen Recep t o r s
( D ) FOLLICLE MATURATION I N THE EWE
( i ) Pat terns of Fol l ic l e G rowth and Atresia ( i i ) Hormonal Con trol o f Fo l l i c l e Ma tura t ion
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1 1 1 4 6
8 12
13 13 1 5
1 8 19 2 0 20 21
( E )
( F )
OVULATI ON I N THE EWE . . ( i )
( i i ) ( i i i )
Fac to r s Influenc ing Ovulat ion Ra tes P o s tulated Mechanisms of Ovula t ion Blockade of Ovulation
THE PURPOSE AND SCOPE OF THE INVESTIGATION CHAPTER I I
MATERIALS AND METHODS . (A) EXPERIMENTAL PLAN ( B )
( C ) ( D ) ( E ) ( F ) ( G ) ( H ) ( I )
LUCERNE AND CONTROL PASTURES AN IMALS
OESTRUS SYNCHRONI ZATI ON HORMONE ANALY S ES . CERVICAL MUCUS ANALY S I S UTERINE AND OVARIAN WEIGHTS FOLLI CLE POPULATI ONS .
REPRODUCTIVE TRACT HISTOLOGY ( J ) ANALY S I S OF DATA
RESULTS . . . .
CHAPTER Ill
(A) LUCERNE OESTROGENIC POTENCY
( i ) Luc erne Coume s tan Con t ent ( i i ) Daily Coumes tan Intake ( B ) EWE LIVEWEIGHTS AND OESTRUS ( i ) Ewe Livewe igh t s . . . . ( i i ) Oes trus Synchroni z a t ion ( i i i ) Oe s t rus-Ovulat ion Interval
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30 3 0 3 1 3 1 3 2 3 2 33
34 3 4 3 4 3 4
36 36 36 36 37 37 39 39
(C) LUTEINIZ ING HORMONE S ECRETION ( i ) Dur ing Oes t rous Cyc le ( i i) Pre-Ovul atory LH Peak (D) OVULAT ION RATES
( i ) Experiment I ( i i ) Experimen t I I
( i i i ) Corpora Lu tea Diame t e r (E) FOLLICLE POPULATIONS
( i ) Surface Fol l i c l e s
( i i ) To tal Fo llicle Popula t ions
(F) OVARIAN AND REPRODUCTIVE TRACT RESPONSES ( i ) Ovar ian and Ut erine Weigh t s
( i i ) Tra c t His tology (G) SUMMARY . . . . . .
DI SCUSS ION
(A) OES TROGENIC LUCERNE ( B ) OES TRUS PHENOMENA .
CHAPTER IV
( i ) Synchron iza t ion of Oes trus ( ii ) Oes trus To Ovula t ion Int erval ( C ) LUTEINIZING HORMONE S ECRETION ( D ) DEPRESS ION O F OVULATION RATES (E) FOLL ICLE POPULATIONS
(F) P ROGESTERONE S ECRETION
( G ) COUMESTANS AND THE REPRODUCTIVE TRACT ( H ) CONCLUS IONS
BIBLIOGRAPHY . .
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Tabl e 1 - 1
Tabl e 1-2
Tab l e 3- 1 Table 3-2
Table 3-3 Table 3-4
Table 3-5
Table 3-6
Table 3-7
Table 3-8
Tabl e 3-9
Tabl e 3- 1 0
Tabl e 3- 1 1
L I S T 0 F T A B L E S
The relat ive po t enc ies o f phyto-oes t rogens admin i s tered orally or intramuscularl y . Oestrogenic luc erne and repro duc t ive per formanc e
Lucerne coume s tan conten t
The daily coume s t an intake (mg/day) o f ewes inges t ing 1 kg ( DM) of lucerne .
Mean ewe l iveweights (kg) . .
Mean plasma LH concentrations (ng/ml ) during the oes trous cyc l e , in ewes graz ing pas ture or
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3
1 1 3 6
3 7 3 8
oe s t rogenic luc e rne . 4 1
P re-ovulatory LH concentrations (ng/ml ) in ewes graz ing pas ture or o e s t ro genic luc erne . 42 Mean ovula t ion ra t e s for ewe s grazing pas ture
o r oes trogenic luc erne - Experiment I . . 43 Mean ovulation ra t e s for ewe s grazing pas ture
o r oes t ro genic lucern e - Experimen t II
Compar i sons o f the d i f f er enc e s in ovulation rates be tween t r ea tmen t group s - Experimen t II
Mean corpo ra lutea d iame ter (mm) three days po s t-oe s trus
Surface f o l l i c l e s o f greater than 3 . 5mm d iamet e r, corpora lutea and follicles p e r ovula t ion for ewes grazing pas ture o r o e s t ro genic lucern e -
44
44
4 5
Exp erimen t I . . . .. 46 Sur face f o l l i c l e s of grea t er t han 2 . 0mm
d iamet er , corpora lutea and fol licl e s p e r ovula t ion f o r ewes graz ing pas ture o r
o e s t rogenic lucerne - Experiment I • • • • • • 4 7
Tabl e 3- 12
Tab l e 3- 1 3
Tab l e 3-14
Tab l e 3- 15
Tabl e 3- 1 6
Tabl e 3- 1 7
Page Ovar ian fol l ic l e populat ions of ewes graz ing
pasture or oestrogenic l ucerne - Experimen t I I 4 9 To tal number o f f o l l i c l e s o f greater t han
3 . 5mm diameter , corpo ra l u t ea and f o l l i c l e s p e r ovula t ion - Exper imen t I I
To tal numb er o f f o l l i c l e s o f grea ter than 2.0mm diameter , corpo ra l u t ea and f o l l i c l e s p e r ovulat ion - Experiment I I
Fo l l i c l e s grea t er than 2.0mm d iame t er , p e r gram o f ova rian t issue
Ovarian and uterine we ight s (g) of ewes grazing pa s ture or o e s t ro gen ic lucerne Ep ithel ial cell he igh t (�) o f reproduc t ive t rac t t issue f rom ewe s graz ing pa s ture or o e s t rogenic lucerne . . . . . . . . . . .
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5 1
48
52
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Fig . 1 - 1 Fig . 1 - 2 Fig . 1 - 3
Fig . 2 - 1 Fi g . 2-2 Fig . 3- 1
F i g . 3-2
Fig . 3-3 Fig . 3-4 Fig . 3-5 Fig . 3-6 Fig . 3-7
L I S T 0 F F I G U R E S
Phyto -o e s t rogens . . . . . . .
The metabol ism of fo rmononet in in sheep Po stulated mechan ism o f o e s t rogen a c t ion wi thin tar get cel l s
Exper imen tal plan - Exper imen t I . Exper imen tal plan - Exper imen t I I D i s t r ibut ion o f t he onset o f oes t rus- Exp er imen t I . . . .
Dis t r ibut ion o f t he onset o f oestrus- Exper imen t II . . . .
Onset of Oest rus-LH peak int erval LH secre tion over the oes trous cyc l e Pr e-ovula tory L H s ecretion
Ovulat ion rates
Po s t-ovula t ion fo l l i c l e popula tions
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