Manipulation of the Estrous Cycle
-List of hormones used:
-GnRH Cystorelin (injectable), factrel
-Desorelin (GnRH analog) ovuplant (implant)
-Oxytocin
-Estrogens ECP
-Progesterons Regu-Mate (feed additive), MGA (oral, feedlot heifers),
Synchomate (ear implant), CIDR (vaginal implant)
-hCG PG600 (pregnant mare serum)
-PGF2a lutalyse, equinate, alfavet, estrumate, prosolyin, bovilene
-Synchoronization
-Regress the existing corpus luteum
-Simulate a corpus luteum
-Induction of estrus
-Non-cyclingcycle
-Estrus synchronization
-Cattle (can also be used in sheep, horses)
-PGF2a prostaglandins F
-Ludalyse- Natural compound 2-3 minutes half life
-Estrumate- Analogue 3-4 hour half life
-Prosolvin- Analogue 2 hour half life
-Bovilene- Analogue 18-24 hour half life
-Priniciple of use
-Regress active CL
-Only effective on day 7-18 CL
-Not effective on days 1-6
-Days 19-21 no CL
-In estrus 2-5 days after injection
-Average for heifers- 50 hours
-Average for cows- 72 hours
-Two methods
-Single random injections 60-65% will respond
within 72 hours
-Two injections will synchronize herd
-Injections given 14 days apart
-Cows responding to 1st injection have 6-9
day CL by 2nd injection
-Cows not responding to 1st injection
will have day 6-17 CL by 2nd
injection
-Breeding options
-Breed 80 hours after 2nd injection 31-80%
conception
-Breed based on estrus after PGF 67% conception
-Combination PGF2a + GnRH
-Developed by researchers at MSU and UofW
-Protocol Ovsynch
-Timed injections and AI
-Manipulation of Estrus
-Estrus synchronization in cattle (sheep and horses)
-Progestogens
-Principle: Maintain the cow under the influence of
progesterone until CL regresses, then remove progesteroneestrus 2-5 days later
-Addition of estradiol sometimes occurs
-Uses of PGF2a also seen
-Implants
-Vaginal implants
-Oral- MGA
-Estrus synchronization in sheep
-Prostaglandins
-Works only if ewes are cycling
-Best to use 2 injections 9 days apart
-Progestogen
-Implants
-Vaginal implants
-Oral- MGA
-12-14 days
-Give PG600 at removal of progestogen
-eCG and hCG combination
-Ewes come into heat 36-40 hours after removal
-Superovulating Sheep
-Why?
-For embryo transfer to recipient ewes
-Genetic recovery and proliferation
-Treatment Program
-Day one
-Expose donor and recipients to teaser rams
-Day 10
-Remove teaser rams from both groups
-Day 17
-Donor
-Inject folltropin (FSH)
-Replace CIDR with new CIDR
-Day 28
-Donor
-Folltropin injections am & pm
-Day 29
-Donor
-Folltropin injections am & pm
-Day 30
-Donor
-Folltropin injection am & pm
-PG600 (FSH-LH activity)
-Remove CIDR
-Recipient
-CIDR out
-PG600
-Day 31
-Donor
-Folltropin am
-AI pm
-Day 32
-Donor
-AI am
-Day 35
-Donor
-Reinsert 2nd CIDR
-Day 38
-Donor
-Surgical removal of embryos
-Recipient
-Surgical implantation
Manipulation of Estrus
-Estrus synchronization in swine
-Prostaglandins
-Not practical
-Progestogen
-MGA- will work but may cause ovarian cysts
-Regu-Mate approved for horses
-Dose for 18 days
-Estrus 4-8 days after stopping
-Minor ovarian cyst problems
-Expensive
-Why synchronize the estrous cycle?
-No experience or access to teasing stallion
-Estrus can be scheduled
-If AI- limited number of collections
-Maximize mare to be bred
-If frozen semen- timing improves conception
-If natural- reduces time at stud farm
-Synch recipients for ET
-Essential Elements
-Control the luteal phase
-Control follicle growth
-Cycling mares
-PGF2a
-Progestogen
-Progestogen + estradiol
-hCG and GnRH
-PGF2a
-Modifying the luteal phase
-Mare must have an active CL
-Estrus occurs 2-4 days post injection
-Ovulation occurs 7-12 days post injection
-Visible estrus may be reduced or non existent
-Cycling Mares
-Progestogen
-CIDR or Regu-Mate for 14-15 days
-CL regresses or use PGF2a
-Inhibits GnRH release
-Suppression of LH release
-Once removed ovulation occurs 7-12 days later
-Progestogen and estradiol
-Regu-Mate for 14-15 days
-Estradiol daily for same period
-Suppresses follicle growth (mild FSH suppression)
-Last day of Regu-Mate give PGF2a injection
-Results in more predictability or ovulation
-hCG (human chorionic gonadotrophin)
-Given during first 2-3 days of estrus
-80% ovulate within 48 hours
-GnRH
-Cystorelin or ovuplant
-highly effective
-Shortening the transition period
-Why is this useful?
-Registry derived time constraints
-January 1 birth date
-Market for early born foals
-Manipulation of Estrous Cycle
-Shortening of the transition period
-Artifical light
-Best choice
-Hormones
-Stimulating natural changes
-Attempts to fool the natural mechanisms
-GnRH
-Single doses- cystorelin
-Multiple doses
-Chronic infusions
-Implants- Ovuplant
-Progesterone priming holds promise
-LH and FSH
-FSH not normally the limiting hormone
-Normally cone rise 2-3 months before estrus
-Use of equine pituitary extract- LH and FSH
-Ovulation can occur with treatment
-hCG (human chorionic gonadotropin)
-LH-like activity
-Progestogens
-Will not hasten estrus alone
-Natural progesterone or Regu-Mate (synthetic
progesterone)
-Primes behavioral centers in brain
-Suppresses GnRH secretion- allow LH rebound
-Combination with estrogen- better results
-Trail mares treated with light estrogen +
progesterones 80% increase in foals born