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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?