This document discusses estrus synchronization, which uses hormones to control and reschedule the estrous cycle in cattle. It describes the estrous cycle and hormones involved like LH, FSH, progesterone, and prostaglandin. Several synchronization methods are outlined, including protocols using prostaglandins, gonadotropins like GnRH, and progestins administered via a CIDR. Synchronization allows for a shortened calving season with improved herd management, health, and uniformity of calves. The Ovsynch protocol is also summarized, which uses GnRH and PGF2α injections to synchronize ovulation for timed artificial insemination without heat detection.

1. 20.09.2023
PK/academics/Germany/ES
Estrus Synchronization

2. Time of increased sexual desire, activity and receptivity
During estrus female will stand and accept male. At other times,
female rejects mating advances of male
There is one period in each estrus cycle when male is accepted
ESTRUS CYCLE
Sequence of events between two cycles.
Inter-estrus interval- The time between beginning of one
estrus to the beginning of second estrus
ESTRUS

3. The time between these two estrus events averages 21 days but
can vary between 17 to 24 days. The estrous cycle has four
stages: estrus, metestrus, diestrus, and proestrus.
The most obvious and visual of these stages is estrus.
During estrus, the female is in standing heat, which means she
is visually receptive to the male and stands still to be mounted.
Ovulation follows the start of standing estrus by approximately
27 hours
Estrous cycle

4. Hormones associated with reproduction
LH & FSH
Progesterone
Estrogen
Prostaglandin
Hormones

5. A management technique that
makes use of hormones to
control or reschedule the estrous
cycle
Estrus Synchronization

6. A shortened calving season
improved management and observation of the cow herd, which should result in fewer
losses at calving
Shortened calving periods also facilitates improvements in herd health and
management
Nutrition can be improved by grouping cows according to stage of gestation and
feeding each group accordingly
All calves will be more uniform in age and size which can lead to an advantage in the
market place
WHY?

7. Basis for Synchronization of Estrus
Manipulate life span of CL
Manipulate growth of follicles and
timing of ovulation

8. Gonadotropins(GnRH protocols)
• Naturally occurring hormone that
stimulates the release of LH and FSH that
stimulates follicular development
• Protocols include Ovsynch and Cosynch
Synchronization methods

9. Synchronization methods
Prostaglandins
– Naturally occurring hormone that causes
regression of the CL (luteolysis) and
decreases progesterone secretion which
results in a return to estrus
– Can expect estrus within two days following
injection
– Protocols include PGF one-shot method and
PGF two-shot method

10. Progestins
• Form of progesterone that extends the
period of time progesterone is present and
prevents animal from coming into heat
• Protocols include MGA (melangestrol
acetate) + prostaglandin and CIDR
Synchronization methods

12. One Injection of PGF
• Advantages
– Useful for detection of
estrus in heifers and
cows
– Decreased drug cost
– Limited animal
handling
• Limitations
– 10-25% of females
may not be detected in
estrus during days 0 to
10
– Poor degree of
synchrony on females
that return to estrus
– Must have CL
– Length of estrus
detection
– Abortion

14. Two Injections of PGF
• Advantages
– Useful for detection of
estrus in heifers and
cows
– Tighter synchrony than
one injection method
– Can use fixed
insemination time after
2nd injection
• Limitations
– Females must have
functional CL
– Length of estrus
detection
– Administration of PGF
will cause abortion in
pregnant animals

15. Controlled internal drug release
CIDRs are inserted intra-vaginally using a specialized applicator
Once inserted, CIDRs provide slow-release administration of
progesterone, which artificially extends the luteal phase
Plasma progesterone levels rapidly increase upon insertion,
when removed the progesterone levels decrease rapidly
This is normal and does not impact the effectiveness of the
device or the animal’s performance
CIDR

17. A CIDR is a vaginal insert that releases
progesterone and can be used with either of
these Ovsynch protocols. The CIDR is inserted
at the time of the first injection of GnRH and is
removed at the time of the injection of PGF2α
The use of a CIDR can increase conception
rates but will also increase the cost of the
protocol
CIDR Synch

18. CIDR
• Advantages
– Useful for detection of
estrus in heifers and
cows
– Induces cyclicity in a
percentage of
anestrous cattle
– High pregnancy rates
• Limitations
– Possible retention
failure of CIDR
– Cost per treatment
may be higher than
other methods
– An additional day of
processing for
hormone treatment
would be required to
facilitate fixed time AI

19. For the use of timed artificial insimination (TAI)
TAI has two major advantages:
it does not require detection of estrus, which
decreases labor
it ensures all females are inseminated, which
increases the total number of cows that
become pregnant
Ovsynch

20. There are two main variations of Ovsynch; they
differ only in the timing of the final injection.
The first, Ovsynch48
requires an injection of GnRH on day 0 and an
injection of PGF2α 7 days later
A second injection of GnRH is administered 48
hours later, and the cow is inseminated 8 to 24
hours after the final injection of GnRH.
Ovsynch

21. The second Ovsynch protocol is Ovsynch56
This protocol also starts with an injection of GnRH on day 0
and an injection of PGF2α on day 7
The difference is the timing of the last injection of GnRH
In Ovsynch56, the GnRH is administered 56 hours after the
PGF2α and TAI is performed 16 hours later
These are both great protocols for synchronizing large groups
of animals at a minimal cost
Ovsynch