Download - Estrous Cycle & Estrus Sychronizaton
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To understand the different parts of the estrous cycle.
To understand the hormonal changes during the estrous cycle.
To understand how the estrous cycle coordinates the events of female reproduction so it can be successful.
Learning Objectives
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Proestrus
Tertiary follicle(s) and oocytes undergo final maturation Estrogen levels
Female starts to become receptive - Estrogen prepares uterus and oviducts for sperm transport and fertilization - Estrogen initiates uterine changes for later embryo development
Anestrus
Female is not cycling (No expression of heat over time)
Cow has a 21 Day Estrous Cycle: Day 0 first Day of Standing Heat
Day 17-20 (Follicular Phase)
Prior to estrus, CL is undergoing regression, progesteronelevels fall below 1 ng/mL which allows final follicular development
One dominant follicle - Graafian StageStimulated to final maturation by FSH and LH
Estrogen
Smooth muscle contractions and cilia movement
Uterine glands and oviduct secretion
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ESTRUS
Picture provided by Dr. Robert P. Wettemann
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Estrus
Female in heat
High estrogens cause LH surge
LH surge causes ovulation
LH surge initiates corpus luteum formation
- Day of Standing heat! Day 0 of estrous cycle Lasts 12 to 20 hours in cow
Estrogen from the Graafian follicle stimulate increase in GnRHwhich stimulates increase in LH
GnRH increases to cause a large increase in LH (surge release)Ovulation occurs during estrus in ewe, sow and mare but metestrus in cow
Following ovulation - LH stimulates development of luteal cellsfrom the granulosa and thecal cells of the ovulated follicle wall.Theca and granulosa cells luteinize by LH stimulation to differentiate in luteal cells
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Metestrus
Estrogen levels have decreased
Corpus luteum is forming
Progesterone levels start to
Progesterone begins preparing the uterus for the embryo Embryo partially develops in the oviduct and moves into the uterus
Day 2-4 of Estrous Cycle
In cow, ovulation occurs after the end of estrus
Graafian follicle has ovulated
Developing from Corpus Hemorrhagicum
Second increase in FSH occurs to stimulate anotherwave of follicular development
Moves into uterus on Day 4 - 5 depending on species
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Diestrus
Maximum corpus luteum size High progesterone levels inhibit final follicular development, ovulation and estrus
Embryo continues to develop in the uterus Embryo signals the uterus it is present - no CL regression
If embryo is not present - uterus releases PGF2 to cause CL regression If CL regresses, progesterone in blood decreases and Graafian follicle(s) begin final development that occurs in proestrus for ovulation at estrus.
Day 5 - 17 of Estrous Cycle
Mature at Day 12 of estrous cycle
Inhibits final maturation of follicle and estrusNegative feedback on GnRH
Estrous Cycle starts over!!!!
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Hormonal Profiles During the Estrous Cycle
ng = nanogram 10-9 grams LH, FSH, Progesteronepg = picogram 10-12 grams Estrogen, PGF2
Follicle will become atretic and regress as a new follicle grows to ovulate with CL regression
Increases for CLregression Second increase of FSH for
follicle development. Inhibinis low as is progesterone
When progesterone is less than 1 ng/ml it usually means the cowhas regressed the CLand is coming into heatduring the estrous cycle
Estrus
LH surgefor ovulation
First FollicularWave
Second FollicularWave
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Estrus Estrus
Adapted from Ginther, O.J. 1992. 2nd EditionReproductive Biology of the Mare. p288
Mare
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Phases of the Estrous Cycle
Follicular
Luteal
Phase of the female estrous cycle when she is underestrogen stimulation Proestrus and Estrus
Phase of the female estrous cycle when she is underprogesterone stimulation Metestrus and Diestrus
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Species Variation in Estrous Cycle Characteristics
Estrous Cycle EWE SOW COW MARE
Length ofEstrous Cycle 14 - 19 Days 18 - 22 Days 18 - 24 Days 16 - 24 Days
Length of Estrus 24 - 36 hours 48 - 72 hours 12 - 19 hours 2 - 11 Days
Time ofOvulation
24 - 36 hoursAfter the onset
of estrus
35 - 45 hoursAfter the onset
of estrus
10 - 11 hoursAfter the end
of estrus
1 - 2 DaysBefore the
end of estrus
Time of AI12 - 18 hours
After the onsetof estrus
16 - 14 hoursAfter the onset ofestrus and again8 - 24 hours later
7 - 18 hoursAfter onsetof estrus
Second day andevery other day
in estrus
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To understand how estrus synchronization works and how to use it successfully.
Learning Objective
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Estrus synchronization:
Why
1. Group females for parturition:
a. Labor, Calving period
b. More uniform weaning weights.
2. Reduce time required for estrus detection.
3. Eliminate estrus detection with timed insemination:
Reduce calving season
Hopefully in future, not always most efficient!!!
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Cattle:
Prostaglandins: PGF2
Lutalyse - Natural compound 25 mg dose I.M.
Estrumate - Analogue 500 g dose I.M.
Prosolvin - Analogue 15 mg dose I.M.
Bovilene - Analogue 1 mg dose s.q.
Equimate - Analogue used in Mare
Half-life in blood 2-3 min
3-4 hrs
2 hrs
18-24 hrs
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Principle - Regress active corpus luteum
Regresses Day 5-17 corpus luteum. In estrus 2-5 days after injection heifers ~50 hours cows ~72 hours
~60-65% of herd should respond to injection. To get whole herd synchronized, give 2nd injection 11 days after 1st Cows responding to 1st injection have day 6-9 corpora lutea Cows which did not respond to 1st injection now have day 6-17 corpora lutea
PGF2 is not effective between Day 0 - 4 of Estrous Cycle
To single one time injection
11 Days following 1st injection
Therefore, all cows now have a CL which will respond to PGF2 on day 11
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Reasons for variation of response. Young and old corpora lutea may respond different
Heifers react sooner than cows
Animal may be pregnant - Abortion
Females do not have a corpora luteum, i.e. are anestrus
Older CL have a larger mass Day 6-9 CL in heat within 40-50 hrs Day 10 -16 CL in heat within 60-72hrs
Difference in body weightCan adjust dosage based on body weight for largerbreeds - standard dose Lutalyse 25 mg/1100 lbs give additional 5 mg/500 lbs over 1100 lbs
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Brahman cattle respond poorly to the two injectionsystem of PGF2
Recommended:
Inject and breed all responders
Inject 2nd treatment 11 days later to all those not bred to 1st injection and breed on estrus detection
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Management Consideration:
Have proper facilities to handle animals Good reproductive records
Have enough A.I. technician help
Be sure cows & heifers cycling
Use good fertility semen
One technician/100 cows will cause problemsShould be around 30-50 cows/technician
Anestrus cows don’t respond to PGF2
No CL!!!!!!
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Breeding with prostaglandins:
Conception Rate 1. Breed 80 hours after 2nd injection 31 - 80 %
2. Breed based on estrus after PGF2 67%
3. Control cows bred based on estrus 75%
Based on estrus - Breed 12 hours after the 1st observed estrus activity
Timed AI - variation in response over 2-5 days
AM/PM rule - Twice daily heat detection
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Improving ovulation synchronization
48 hours after PGF2 -Give GnRH Cause LH surge; achieved slight increase in conception rates
Cystorelin (GnRH Analogue)
Maybe a better quality CL.Improve conception rate 3-4%
Used mostly in problem breeding cows
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Use of progestogens for Estrus synchronization
Principle:
Maintain the cow under the influence of progesterone until corpus luteum regresses, remove progesterone -animal respond to progesterone with estrus 2-5 days later.
Administration:
Injection
Feed
Implant
Pessary or Control Internal Drug Release (CIDR)
Time Consuming
Mix in ration
Place in ear
Place in Vagina
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Synchromate B system:
Inject 5 mg estradiol valerate & 3 mg norgestomet Implant Norgestomet (Progestagen) 6 mg
Remove implant 9 days later
Breed 48 to 60 hours later or 54 hours later
Estradiol - Luteolytic to d 3-9 corpora lutea Norgestomet - Inhibits early C.L. development
Day 1
Injection allows for rapid increase in progestin in bloodwhile the implant initiates its release over several hours
Rapid decrease in progestin in blood allows animal to return to heat 2 to 3 days
If you use timed AI at 54 hoursBetter to heat check and breed
Therefore treatment blocks proestrus,estrus and early CLdevelopment. Wait 9 days for diestrus cows to regress CL
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Sychromate B System can be used on noncyclingcows which may induce them to come into heat.
System is not dependent on having a CL as with the prostaglandin system.
However, cows need to be in good condition and close to cycling to respond
Brahman cattle recommend to implant norgestometNo Injection - Estradiol causes a problemInject PGF2 on Day 8 and pull implant on Day 9
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Feed progestogen for 9 days
Prevents estrus in diestrus and proestrus animals
Give PGF2 on Day 8 to regress C.L.'s
Remove progestogen on Day 9 Cows are in heat in 2-5 days
Melengesterol Acetate (MGA) System
(0.5 mg/head/day)
AlternativeFeed MGA for 14 days - Don’t breed on first heat (poor fertility)Inject PGF2 16 days after withdrawal of MGA and breed onestrus detection
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EAZI-BREED CIDR System
Insert CIDR (progestin) with CIDIROL capsule (estrogen)in vagina
Day 6 inject with PGF2
Remove CIDR Day 7 and breed on heat detection
Can inject with CIDIROL on Day 8 and breed by timedinsemination 50 hours from CIDR removal
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EAZI-BREEDEAZI-BREEDCIDRCIDR
Insert CIDRInsert CIDRwith CIDIROLwith CIDIROLcapsulecapsule
Day 6Day 6
RemoveRemoveCIDRCIDR
Detect EstrusDetect Estrusor or
InseminateInseminateFixed-timeFixed-time50 hours50 hours
Inject PG
Day 7Day 7Beef Cow
Day 9-11Day 9-11Day 8Day 8
InjectInject2mL2mL
CIDIROLCIDIROL
7 Days
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Ewe estrus synchronization:
Implant progestogen for 12-14 days Remove implant, ewes in heat in 36-60 hours
May use PMSG at implant removal to stimulate follicular growth
Fertility good 1 ram/10 ewes
Use 1/2 of a new norgestomet implant
400 - 800 IU
Procedure will also work with CIDR and Pessary (Vaginal Sponge
Can use PGF2 if during the breeding season Give 20 mg Lutalyse 9 days apart - No Effect If Anestrus
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Sow estrus synchronization:
PGF2 will not cause C.L. regression until day 12 of the cycle
Common progestogens will synchronize estrus but cause ovarian cysts
Progestogen -
Allyl trenobolone fed at 20 mg/head/day for 18 days - remove from feed - in heat in 4-8 days. Fertility normal - a minor incidence of cysts.
Reason - LH binds to luteal cell receptor with strongaffinity following ovulation and is not released until day 12Repeated injections over two to three days will regress CLbefore Day 12 but is not practical
In Horse tradename Regumate is effective
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Prepubertal gilts (noncycling) can be effectivelysynchronized with P.G. 600
P.G. 600 400 IU PMSG (eCG) and 200 IU HCG
Gilts cannot be cycling
Need to be greater than 51/2 months of age
Gilts should express heat 3-4 days following treatment
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Mare estrus synchronization:
Luteolytic PGF2 in diestrus, in heat in 4-5 days
Use of prostaglandins in horses:
Equimate (Fluprosterol)
~1/5 cow dose
Mare CL more sensitive than cow, ewe
Will only work during diestrus when CL is presentRemember heat is over 5-11 days
Give 250 g
If you use Lutalyse or Estrumate
Problems with smooth muscle stimulatingproperties of PGF2 which occur within 15 mins
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Side Effects:1. Sweating in neck, shoulders and central abdominal region2. Increase Heart rate and Respiration3. Increase motility of GI Tract (Colic)
These should disappear within 1 hourTreatments with PGF2 Mares can exhibit what is called Prolonged Diestrus Caused by persistent luteal function- CL form after ovulation fails to undergo luteolysis during normal diestrus - remains 3-4 weeks-CL maybe deep - unable to produce enough progesterone for stimulation of endometrial PGF2 release or caused by low grade uterine infectionFailure of embryo to survive but extended CL lifespan as innormal pregnancy Equimate can be used to induce estrus
when mares arrive to be bred by a stud
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Use of progestins in horses Regumate
.044 mg/Kg body weight in feed Feed for 12 days or 15 days without equimate injection Remove from feed; give equimate In heat 3-4 days later
Can inject progesterone daily 150-200 mg i.m.
Liquid Regumate 1 mL/110lbs
Remember will not ovulate until day 8 of estrus
Utilization:
1. Can use on show mares to suppress heat during events2. Transport mare to breeding farm to time estrus3. Regulate number of mares in heat to utilize a stallion over time. Synchronize mating