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What are 5 advantages to using estrus synchronization in beef herds?
1) More efficient use of A.I.
2) Groups time of parturition
-long sleepless hours, nice to group
3) Uniform crop of offspring
4) Utilizes labor more efficiently
5) Can shorten breeding season
*dairy cattle are easier to handle
Why do we want to have a uniform crop of offspring?
Want uniformity so they can all go into same lot, a buyer's best day would be to find 80 calves that are all the same size, color, sex, all dehorned & castrated- looking for uniformity bc when go into stock or feedlot operation they can be handled in a similar fashion
What are 3 advantages to using estrus synchronization in a dairy herd?
1) Reduces need for heat detection
2) "circumvents" cystic ovarian disease
-synchronization is a treatment for cystic ovarian disease
3) May induce fertile ovulation in anestrous cows
What are 4 disadvantages to performing estrus synchronization?
1) Requires skilled labor and periods of intensive management
2) Requires adequate facilities
3) Higher input costs
-need to examine economics first!
-costs balanced by increased returns
-may have lots of shots
4) Cannot be used in organic/ natural herds
What are the 3 drugs used to pharmacologically control the estrous cycle?
1) Prostaglandins (PGF)
2) Progestins (CIDR, MGA)
3) Gonadotropins (GnRH, hCG)
-causes FSH & LH release--> stimulates new waves of follicles so ovulate when we want
What are the 3 general strategies for estrous synchronization?
1) Control length of luteal phase
-prolong or shorten/ induce luteolysis
2) Initiate a new follicular wave emergence
3) Control time of ovulation
What drug do we give to control the time of ovulation?
Gonadotropins (GnRH, hCG)
-hCG: LH- like activity in animals, used to induce ovulation
-GnRH--> FSH--> emergence of new follicular waves OR if dominant follicle then GnRH--> LH--> ovulation
What are 3 drugs that are used to shorten the luteal phase?
What are 2 drugs that are progestins used to prolong the luteal phase?
1) MGA: melengesterol acetate
-approved for feedlot heifers
2) EaziBreed CIDR*****
What is the EaziBreed CIDR?
Has progesterone, it goes into vagina and a little plastic purple string hangs out so can pull it out
-CIDR: controlled intravaginal drug release**
How does PGF2alpha shorten the luteal phase?
Causes regression of CL
-by inducing luteolysis the "progesterone block" is removed--> allows follicles to grow and ovulate
What happens if a CL is present (days 6-17) and PGF2alpha is administered?
Ovulation occurs in 2-5 days
If a group of randomly cycling heifers are all cycling and are all given a shot of PGF2alpha, how many would be in heat within 2-5 days?
Estrus cycle is 21 days and the CL responds to PGF2alpha after day 6, so this means that cows are responsive to PGF 15/21 days. 15/21= 71% should come into heat within 5 days
How does GnRH control the time of ovulation?
-causes synthesis and release of LH & FSH
-stimulates follicular growth
-Induces maturation and ovulation of large follicles
What is the result of giving a group of heifers a shot of PGF2alpha?
-synchronizes end of luteal phase, resulting in synchronized estrus
-expect 75% of cycling females to come into estrus within 2-5 days
-results in variable time to estrus (bell curve with majority coming into heat at day 3 & 4)
-heat check and AI at day 5
If you see a heifer in heat in the morning, when should you breed her?
In the evening
-if in heat in evening then breed in morning
What are the results of giving a PGF2alpha injection at day 0 (heat check & AI day 5) and at day 14 (heat check and AI 16-19 days)?
-femalesmust be cycling to be successful
-need good animal handling facilities
-Time breeding not recommended (not synched enough for AI)
-good heat detection
What are the 4 steps involved in the protocol of "Ovsynch"?
1) GnRH at day 0
-synchronize emergent follicles
2) PGF2alpha at day 7
3) GnRH at day 9
-LH surge -ovulates follicles in 28 h***
-gives us ovulation associated with AI***
4) time AI at day 10
Why do we perform AI 16-24 hours after the second GnRH (day 10) using Ovsynch when the mares don't actually ovulate until 28 hours after the GnRH?
bc want semen in there prior to ovulation so sperm can be transported to site of fertilization and undergo capacitation (takes 6-8 hours) so breed well before ovulation so when ova released sperm are waiting and ready
Why is it so important to be able to predict the timing of ovulation?***
how long semen lasts depends on how processed
- fresh is like 2-3 days, frozen is probably 12-13 hours
What are 5 advantages to Ovsynch?
1) Shortened time to AI
-10 days after start of treatment
2) No heat checking needed
3) Reduced days to first service
4) First service conception rates same AI at estrus
5) "treats" cystic ovarian disease
Why do dairy cattle only have a 20% first conception rate compared to 50% in beef cattle using Ovsynch?
Dairy cattle are stressed out= cortisol= hard to get pregnant
What are 5 disadvantages of Ovsynch?
1) Drug cost
2) Multiple injections required
3) Less time spent observing animals
-can miss detecting non-cyclers in herd
4) Response is variable depending on day of cycle when started********
-synchrony of ovulation improves if there is a dominant follicle when Ovsynch is started
5) High semen costs
-all animals inseminated
Synchronization of ovulation using Ovsynch is most successful when there's a dominant follicle when the protocol is started. Emergence of a new wave is most reliable when Ovsynch is started when?
On days 5 & 10 of cycle =most likely to get emegence of new follicular wave, all programs developed after ovsynch were developed to get cow in that 5-10 day window to where we start
What are 2 reasons that starting Ovsynch mid-cycle (day 5-10 of cycle) improves the results of Ovsynch?
1) If started prior to day 5 first GnRH injection does not alter follicular development since follicles are too small to respond
2) If started in late diestrus follicles may/ may not respond to first GnRH. Endogenous PGF release from the endometrium causes luteolysis and premature ovulation
How is the Pre-synch Ovsynch program different from Ovsynch?
Give 2 shots of prostaglandin preceeding the Ovsynch
What are the 6 protocols involved in the pre-synch Ovsynch program?
1) PGF2alpha day 0
2) PGF2alpha day 14
-if see heat after these 2 inj they breed
3) GnRH day 26
4) PGF2alpha day 33
5) GnRH day 35
6) Timed AI day 36
How long is the voluntary waiting period (period after calving before breeding)?
Usually 2 months (50-60 days)
-so ignore if come into heat before this
What are 3 advantages to the Pre-synch Ovsynch program?
1) Enhances health of reproductive tract
2) Places cows at day 5-10 of cycle so the Ovsynch will work better
3) More presynch cows ovulate in response to first GnRH injection
How long after calving do cows enter the Pre-synch Ovsynch program?
In order to breed after voluntary waiting period we calculate back and start 36 days prior to the end of the 60 day waiting period.
60-36 days= 24 days, so enter program 24 days after calving
How does the Pre-synch Ovsynch program result in GnRH administration being in that 5-10 day window of the cow's cycle?
if give PG at day 14 then will ovulate 2-5 days later, say average 3 or 4 days till they ovulate at ~day 18 and then if start GnRH at day 26 we're 8 days later which is in the 5-10 day window we want to get good response
What is the Co-synch program used in beef cattle? (3 protocols)
1) GnRH day 0
2) PGF2alpha day 7
3) GnRH & Timed AI day 9
Compare the pregnancy rate of the Co-synch program in beef cattle with that achieved with Ovsynch.
Pregnancy rate is 5-8% less than Ovsynch, but some people report no difference
When using the Co-synch program in beef cattle, about 8% of cows will exhibit estrus, what should you do with these cows?
What should you do if you are using the co-synch program on beef cattle and the cow has a calf?
Separate calves from their dam when give PGF= increases preg rate 9%
What are the 5 protocols of the Pre-synch/ co-synch program?
1) PGF2alpha day 0
2) PGF2alpha day 14
3) GnRH day 26
4) PGF2alpha day 33
5) GnRH & timed AI day 35
How can the Co-synch program be modified to increase the conception rate?
Normally give the GnRH & timed AI 48 hours after PGF2alpha, but if give GnRH & AI 56 hours after PGF then higher rates of conception
Explain the postpartum anestrus in beef cows.
In a period of anestrus for about 45-50 days and then undergo a "short cycle" where progesterone doesn't get very high, then around day 60 they have their first fertile cycle
Explain the protocol used for Melengesterol acetate (MGA) synchronization.
1) Start MGA day 0
2) Stop MGA day 14
3) PGF2alpha day 33
4) Breed day 35-37
When does the first estrus occur after MGA administration?
estrus that occurs about 5-7 days after MGA withdrawl is not fertile do NOT breed
When should you inseminate a cow if you are using MGA and and she's not bred on observed estrus?
Inseminate all females 72 hours after PGF2alpha (37 days into program)
When do you want to start the MGA synchronization program?
Best used on heifers
-start 33 days before breeding season
What are the 4 steps involved in the controlled intravaginal drug release -based synchronization program?
1) Insert CIDR (day 0)
2) PGF2alpha (day 6)
3) Remove CIDR (day 7)
4) Observe heat and breed day 9+
-can also remove CIDR and give PGF on day 7
True or false. CIDRs can be used 2 or 3 times.
False, can be reused just rinse them off and put in a bag but only 2 times not 3
What is the purpose of adding a CIDR to a synchronizing program?
pregnancy rates and AI are correlated with serial progesterone levels in the cycle preceding one in which they're bred so can boost progesterone w/ CIDR in the cycle before the one they're bred in
-increases conception rate
How many follicular waves occur in heifers over their 21 day cycle?
3 follicular waves, 3rd wave is the one that is responsive to GnRH so 12/21 days of cycle= 57% chance of having non-optimal response to GnRH (12= when 3rd wave starts)
What is the 5-day CIDR synch?
Give GnRH day 0 and put in CIDR, then remove CIDR at day 5 and give PGF, then day 8 give GnRH and timed AI
What is the G-6-G synch program? (5)
1) give PGF2lpha (day -8 from ovsynch)
2) GnRH (day -6 from ovsynch)
3) start the ovsynch program day 0 give GnRH (hence name G-6-G)
4) Give PGF2alpha day 7
5) GnRH & bred day 9
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