PHYSIOLOGICAL PRINCIPLESPHYSIOLOGICAL PRINCIPLES

UNDERLYINGUNDERLYING

SYNCHRONIZATION OF ESTRUSSYNCHRONIZATION OF ESTRUS

M.F. Smith, G.A. Perry, J.A. Atkins, E.M.M.F. Smith, G.A. Perry, J.A. Atkins, E.M.

Jinks, K.G. Pohler, and D.J. PattersonJinks, K.G. Pohler, and D.J. Patterson

Division of Animal Sciences, University of Missouri,Division of Animal Sciences, University of Missouri,

ColumbiaColumbia

Department of Animal and Range Sciences, SouthDepartment of Animal and Range Sciences, South

Dakota State UniversityDakota State University

OverviewOverview

•• Physiology of the bovine estrous cycle Physiology of the bovine estrous cycle

•• Hormones utilized for estrus synchronization Hormones utilized for estrus synchronization

•• Estrus synchronization products Estrus synchronization products

•• Hormonal management of the luteal phase Hormonal management of the luteal phase

•• Hormonal management of follicular waves Hormonal management of follicular waves

•• Management considerations Management considerations

Characteristics of the Estrous CycleCharacteristics of the Estrous Cycle

•• Length of the estrous cycleLength of the estrous cycle

Average 21 days (range 17 to 24 days)Average 21 days (range 17 to 24 days)

Two follicular waves Two follicular waves –– 17 to 20 days 17 to 20 days

Three follicular waves Three follicular waves –– 21 to 24 days 21 to 24 days

Estrus (standing heat)Estrus (standing heat)

12 to 18 hours (range 8 to 30 hours) 12 to 18 hours (range 8 to 30 hours)

OvulationOvulation

Approximately 30 hours after the beginning of Approximately 30 hours after the beginning ofstanding estrusstanding estrus

Duration of Estrus

0

10

20

30

40

0-5 6-10 11-15 16-20 21-25 >25

Duration of Estrus, h

Perc

enta

ge o

f co

ws

Influence of confinement area on the numberInfluence of confinement area on the number

of mounts per estrus (P > 0.5)of mounts per estrus (P > 0.5)

30.6

27.9

0

5

10

15

20

25

30

35

Drylot Pasture

Mo

un

ts

Influence of the number of cows in estrus onInfluence of the number of cows in estrus on

number of times cows are mounted in drylot ornumber of times cows are mounted in drylot or

pasturepasture

11.0a

27.7a,b

30.9b

50.4c

0

10

20

30

40

50

60 Pasture Drylot

Nu

mb

er

of

mo

un

ts

1 2-3 4-6 7 +

Number of Cows in Estrusa,ba,b superscripts differ P < 0.07 superscripts differ P < 0.07

b,cb,c superscripts differ P < 0.002 superscripts differ P < 0.002

Variation in Ovulation Time

0

2

4

6

8

10

12

14

16

18

20 22 24 26 28 30 32 34 36 38 40 42

Time of Ovulation (h)

Perc

enta

ge o

f C

ow

s

Ovarian StructuresOvarian Structures

•• Graffian follicle Graffian follicle

•• Corpus luteum Corpus luteum

5 10 15Estrus

OvulationOvulation

Ho

rmo

ne

con

cen

tra

tio

n

SelectionSelection

DominanceDominance

AtresiaAtresia

Estrus

OvulationOvulation

The Estrous CycleThe Estrous Cycle

CLCL ProgesteroneProgesteroneRecruitmentRecruitment

Stages of the Estrous CycleStages of the Estrous Cycle

•• Follicular Phase Follicular Phase

•• Estrus Estrus

•• Luteal Phase Luteal Phase

Follicular and Estrus PhasesFollicular and Estrus Phases

Growth

Selection

Dominance

Estrus

LHSurge

Ovulation

Estrogen

• Maturation of the preovulatory follicleMaturation of the preovulatory follicle

•• Estrous behavior Estrous behavior

•• Ovulation (induced by the LH surge) Ovulation (induced by the LH surge)

P4

Luteal PhaseLuteal Phase

0 2 4 6 8 10 12 14 16 18 20 0

Est

rus

Est

rus

Growth Regression

PGF

•• P P44 = Progesterone = Progesterone –– CIDR and MGA CIDR and MGA

•• PGF = Prostaglandin F PGF = Prostaglandin F –– Lutalyse, ProstaMate, In Synch, Lutalyse, ProstaMate, In Synch,

Estrumate, estroPLANEstrumate, estroPLAN

Est

rus

Corpus Luteum and PregnancyCorpus Luteum and Pregnancy

Day of the Estrous Cycle

•• Maternal recognition of pregnancy Maternal recognition of pregnancy –– day 15 to 16 day 15 to 16

•• Caution Caution –– PGF can induce abortion in pregnant cows PGF can induce abortion in pregnant cows

PGF

Maintenance

0 2 4 6 8 10 12 14 16 18 20 0

Embryo

Growth

Physiology of Follicular WavesPhysiology of Follicular Waves

Day of the Estrous Cycle

0 2 4 6 8 10 12 14 16 18 20 0

Est

rus

Est

rus

OvulationDominance

FSH FSH

Selection

Recruitment

Problem of Anestrus!Problem of Anestrus!

0

1

2

3

4

5

6

Pro

gest

ero

ne (

ng

/ml)

0

15 31

Day

42

Problem of Anestrus!Problem of Anestrus!

0

1

2

3

4

5

6P

ro

gest

ero

ne (

ng

/ml)

0

15 31

Day

42

GnRH

CIDR

OrOr

Hormones utilized in EstrusHormones utilized in Estrus

Synchronization ProtocolsSynchronization Protocols

•• Progesterone/Progestins Progesterone/Progestins

•• Prostaglandin F Prostaglandin F22!!

•• GnRH GnRH

ProgesteroneProgesterone

Biological FunctionsBiological Functions

•• Inhibit estrus/ovulationInhibit estrus/ovulation

•• Preparation for pregnancyPreparation for pregnancy

•• Maintenance of pregnancyMaintenance of pregnancy

Progestins/ProgesteroneProgestins/Progesterone

Role in SynchronizationRole in Synchronization

•• Inhibit estrus/ovulation Inhibit estrus/ovulation

•• Induce cyclicity Induce cyclicity

•• Dominant follicle turnover Dominant follicle turnover

Prostaglandin FProstaglandin F22!!

Biological FunctionBiological Function

•• Luteal regression in nonpregnantLuteal regression in nonpregnant

animalsanimals

Role in SynchronizationRole in Synchronization

•• Induce premature luteal regressionInduce premature luteal regression

Gonadotropin Releasing HormoneGonadotropin Releasing Hormone

(GnRH)(GnRH)

Biological FunctionBiological Function

•• Control secretion of LHControl secretion of LH

•• Induces gonadotropin surgeInduces gonadotropin surge

Role in SynchronizationRole in Synchronization

•• Induce ovulationInduce ovulation

•• Synchronize follicular wavesSynchronize follicular waves

Estrus Synchronization ProductsEstrus Synchronization Products

ProgestinsProgestins

•• Melengestrol AcetateMelengestrol Acetate

•• EAZI-BREED CIDREAZI-BREED CIDR

Prostaglandin FProstaglandin F22!!

•• LutalyseLutalyse

•• ProstaMateProstaMate

•• In SynchIn Synch

•• EstrumateEstrumate

•• estroPLANestroPLAN

Estrus Synchronization ProductsEstrus Synchronization Products

GnRHGnRH

•• CystorelinCystorelin

•• FertagylFertagyl

•• FactrylFactryl

•• OvaCystOvaCyst

Hormonal management ofHormonal management of

the luteal phasethe luteal phase

•• Progestins Progestins

•• Prostaglandin F Prostaglandin F22!!

Role of Progestins in EstrusRole of Progestins in Estrus

SynchronizationSynchronization

•• Synchronization of estrus inSynchronization of estrus in

•• beef heifers & cowsbeef heifers & cows

•• dairy heifers & cowsdairy heifers & cows

•• Advances onset of puberty in heifersAdvances onset of puberty in heifers

•• Advances return to estrus after calving in Advances return to estrus after calving in cowscows

ProgestinsProgestins

•• Melengestrol Acetate - MGAMelengestrol Acetate - MGA

•• Controlled Internal Drug ReleaseControlled Internal Drug Release

- CIDR- CIDR

ProgesteronePregn-4-ene-3, 20-dione

OC

O

CH3

CH3

CH3

MGAMGA(melengestrol acetate)

6-methyl-17-alpha-acetoxy-16-methylene-pregn-4, 6-diene-3, 20-dione

C

O

CH3

O

CH3 CH3

CH3

CH3

O

OC

CH2

Inhibition of Ovulation FollowingInhibition of Ovulation Following

Long-term Progestin TreatmentLong-term Progestin TreatmentProgestin Treatment

MGA for 14 days

18161412108642

CLRegressed

Estrus

(less fertile)

18161412108642

18161412108642

18161412108642

18161412108642

18161412108642

Persistent FolliclesPersistent Follicles

Persistent Follicle (PF) vs. Growing Follicle (GF)

4

8

12

16

20

24

-12 -10 -8 -6 -4 -2 0

Days Relative to Estrus (day 0)

Fo

llic

le D

iam

ete

r (m

m)

PFGF

•• Causes CL regressionCauses CL regression

•• No effect on noncycling cattleNo effect on noncycling cattle

•• No induction of cyclicityNo induction of cyclicity …… No Jump-start No Jump-start

•• Effective days 6 to 16 of the estrousEffective days 6 to 16 of the estrouscycle (day 0 = estrus)cycle (day 0 = estrus)

Prostaglandin FProstaglandin F22!! (PGF) (PGF)(Lutalyse, ProstaMate, Estrumate, In Synch, estroPLAN)(Lutalyse, ProstaMate, Estrumate, In Synch, estroPLAN)

Day of the Estrous Cycle

0 2 4 6 8 10 12 14 16 18 20 0

NO NO

YESEstrus Estrus

PGFPGF2a 2a –– Effect of stage of the cycle Effect of stage of the cycle

Hormonal management ofHormonal management of

follicular wavesfollicular waves

•• GnRH GnRH –– Induces dominant follicle to Induces dominant follicle to

ovulateovulate

•• Estradiol Estradiol –– dominant follicle turnover dominant follicle turnover

((!!FSH)FSH)

•• Progesterone Progesterone –– dominant follicle dominant follicle

turnover (turnover (!!LH)LH)

•• Induces ovulationInduces ovulation

•• Synchronizes follicular wavesSynchronizes follicular waves

•• Induces formation of a CLInduces formation of a CL

GnRHGnRH(Cystorelin, Factrel, Fertagyl, Ovacyst)(Cystorelin, Factrel, Fertagyl, Ovacyst)

0

GnRHInjection

2 to 3

Hours after GnRH injection

24 to 30

OvulationLH Surge

GnRH – Induced Surge of LH

NONO

0 2 4 6 8 10 12 14 16 18 20 0

Estrus

Day of the Estrous Cycle

GnRH-Induced Ovulation During

a Follicular Wave

YESYES

Estrus

Management considerationsManagement considerations

for selecting heifers and cowsfor selecting heifers and cows

for synchronization of estrusfor synchronization of estrus

Before you start an estrous synchBefore you start an estrous synch

and AI program and AI program –– Heifers Heifers

What has the pregnancy rate of your heifersWhat has the pregnancy rate of your heifersbeen over the past few years?been over the past few years?

Have your heifers received growth promotingHave your heifers received growth promotingimplants?implants?

Have you selected an appropriate targetHave you selected an appropriate targetweight?weight?

Heifers-contd.Heifers-contd.

Have your heifers attained 65% of their matureHave your heifers attained 65% of their mature

body weight?body weight?

What proportion of your heifers have aWhat proportion of your heifers have a

reproductive tract score of reproductive tract score of "" 4? 4?

Before you start an estrous synch andBefore you start an estrous synch and

AI program AI program –– Postpartum Cows Postpartum Cows

What has the pregnancy rate in your cowsWhat has the pregnancy rate in your cows

been over the past few years?been over the past few years?

What is the current length of your breedingWhat is the current length of your breeding

season?season?

Postpartum Cows Postpartum Cows –– contd. contd.

What proportion of your cows are cyclingWhat proportion of your cows are cycling

by the start of the breeding season?by the start of the breeding season?

What was the body condition score of yourWhat was the body condition score of your

cows at calving?cows at calving?

Postpartum Cows Postpartum Cows –– contd. contd.

What is the current body condition score ofWhat is the current body condition score of

your cows?your cows?

How many days postpartum will your cowsHow many days postpartum will your cows

be when estrus synchronization isbe when estrus synchronization is

initiated?initiated?

Postpartum Cows and HeifersPostpartum Cows and Heifers

How much time can you devote to estrusHow much time can you devote to estrus

detection?detection?

Considering your handling facilities, howConsidering your handling facilities, how

many cows can you breed in an hour?many cows can you breed in an hour?