Below is a text only preview of this Word document,
Click here to open the full Word document.
Click here to go to the PowerPoint associated with this document.
B123 Estrus Synchronization and Heat Detection
Name _____________________________ Date __________
What is Estrus Synchronization?
Reduced _______________________
____________________________ efforts and management time can greatly be reduced
during the breeding season.
It also narrows the ____________________________________, which reduces labor
for the producer.
Increased ____________________________ rates
Cows that come into estrus early will have _____ opportunities to conceive
during the first 45 days, while those who do not cycle early will only have
_____ or less. Estrus synchronization results in fewer _______________________.
Increased _________________________________________
Beef cows that conceive early in the breeding season will produce calves that
weigh more at weaning simply because they are ______________________.
A calf conceived on the first day of a 60-day breeding season will be worth more
than one conceived on the last day.
A more _________________ calf crop is produced. Calving seasons that are shorter
produce calves that are closer in age and weight at weaning. Buyers will pay
more for uniform cattle.
Economic returns like these can more than pay the cost of the average
synchronization program.
Increased time for post calving ________________________________.
Cows require time (________ days) to recover from the stress of calving before
they can be expected to rebreed.
Cows that calve early will have more days postpartum to reproductively recover
and resume normal estrus cycles before the beginning of the next breeding
season.
Reproductively Sound Replacement Heifers
Replacement heifers kept from early calving cows will be older at the
beginning of their first breeding season and more likely to have reached
____________________ and targeted breeding ________________________.
Replacement heifers kept from late calving cows will be younger and smaller at
the beginning of their first breeding season and are predisposed to reproductive
problems.
Estrus synchronization allows virgin heifers to be bred ______ weeks prior to
the cow herd. This early breeding is especially important because it allows the
first-calf heifer additional _____________________________ after calving before
the next breeding season begins.
Management Considerations
The economic benefits of estrus synchronization apply to every herd,
regardless of how the animals are bred (Al or natural service). However, natural
service with estrus synchronization is usually cost prohibitive because of the
number of ___________ required to breed cows during a short period of time. Al
becomes the logical, cost-effective alternative.
Management Goals
The goal of synchronization programs is to get all animals to conceive
within a reasonable amount of time after calving (______ to ______ days).
Because the estrous cycle is _______ days long, only about ________ of the
cycling animals are in heat during the first week of the breeding period/season
if estrus synchronization is not used.
Breeding the natural estrus
Regardless of whether the animals are inseminated naturally or artificially,
only _____ to _______ % of them will conceive to a given insemination or
breeding.
Thus, after a week of breeding to natural heats, only about _______ % of the
eligible animals may be pregnant (33% in heat x 65% conception rate).
Many of the estrus synchronization methods can induce _____ to ______ % of the
cycling animals to display estrus within a _____ day period.
Additionally, many methods can induce a fertile heat in as much as 50% of the
anestrous (non-cycling) cows.
Thus it is typical for many of these synchronization protocols to result in ____
to _____ % of the animals being pregnant by the end of the first week of the
breeding period. (compared to 21% with non synchronized cows)
Several fixed-time Al options can result in 40 to 50% of the cows becoming
pregnant following one single day of breeding with _______ hours spent for heat
detection.
Synchronization Methods
There are four main methods to synchronize cattle.
1.
2.
3.
4.
Prostaglandin Injection
Administering the hormone ________________________ is sometimes used to
synchronize cattle.
Prostaglandin is a natural hormone which destroys the __________________ and
stops the production of progesterone which causes the animal to come back into
heat.
Administering a shot of prostaglandin simultaneously destroys the CL from all
cycling animals at a predetermined time, causing them to come into heat in 5 to
7 days later.
_______________, Estrumate, Prostamate, and In-Synch are all commercial
prostaglandins.
The major limitation of prostaglandin is that it is not effective on animals
that do not possess a CL. This includes animals within _____ to _____ days of a
previous heat, young _______________________, and _______________________ non
cycling cows.
Despite these limitations, prostaglandins are the simplest method to synchronize
estrus in cattle.
Prostaglandin Injection
Draw the chart for administering prostaglandin injections.
Gonadotropin injection
The interval from an injection of prostaglandin to when estrus and ovulation
occurs is highly variable between cows due to differences in the stage of
________________________ development at the time of the injection.
Using ____________________________ with progesterone minimizes the differences
in follicular development. The result is a higher estrus response rate and much
tighter synchrony of estrus when compared to prostaglandin alone.
Each gonadotropin system involves an injection of __________________________,
followed _____ days later with an injection of ______________________________.
The following are all different commercial estrus synchronization programs
utilizing gonadotrophin and prostaglandin:
MGA System
Metengestrol Acetate (MGA) is a synthetic form of the hormone
_______________.
MGA is a proven method for synchronizing estrus in beef and dairy _____________.
MGA is mixed with 3 to 5 lbs of a _______________ fed at a rate of 0.5
mg/head/day for ________ days.
Within 3 to 5 days after MGA feeding, most heifers will display standing heat.
DO NOT BREED at this heat because conception rates are reduced. Wait ______ to
______ days after the last day of MGA feeding and inject all heifers with a
single dose of _________________________________. For the next ______ to ______
days, inseminate animals _____ to ______ hours after detected estrus.
Draw the chart showing the MGA system.
Cattle Synchronization Implants
CIDRs (The Eazi-Breed) are a ______________________ that delivers the
natural hormone progesterone throughout the seven-day implant period. This
progestin stimulation helps to induce cyclicity in anestrous cows and advances
___________________ in heifers.
Animals may either be bred to detected estrus for _________ or __________ days
after CIDR removal or fixed-time inseminated at 48 to 54 hours after implant
removal.
Research has shown the CIDR to be an effective means of synchronizing estrus in
virgin beef and dairy _____________________ and in ___________________ beef
cows.
Heat Detection and Breeding
A cow in heat is one that is receptive to the bull or ready to be
artificially inseminated. This time usually occurs every ________________ days
and lasts for_______________ hours. Most cows should be bred _____________ hours
after being observed in standing estrus. The following table demonstrates part
of a cow’s estrous cycle and when the proper time to inseminate a cow occurs.
Heat Detection and Breeding
Heat Detection
It is important to physically observe the herd or group of animals at least
__________ a day. This is because most cows show signs of heat in the
____________________ (6 a.m. to noon), ____________________ (6 p.m. to
midnight), or during the night. In fact, many animals (approximately 45%) show
heat during the hours of midnight to 6 a.m.
Heat Detection Tools
A ______________________________ - This device is placed under the chin of a
detector animal. When the animal mounts, the device leaves a mark on the back of
the animal being ridden.
_________________________ cows - These are female cows that are given
_____________________ to cause them to show male-like behavior. These animals
are great candidates for the chin-ball marker.
Heat Detection Tools
Surgically ____________________ bulls - (Gomer Bull) These animals are
surgically altered in a way that prevents the penis from entering the cow. These
bulls still have the sexual drive to mount, but cannot reproduce.
Heat Detection Tools
_____________________ devices (Kamar) and paint - These devices are glued
onto the tail-head of the cow. Pressure on the device when the cow is mounted,
causes the marker to change color. In the case of the Kamar device, the white
marker changes to red when the cow is ridden. Paint sticks can also be used in a
similar manner. The paint can be applied in areas on the hooks, pins and
tail-head. When the cow is ridden, the paint will rub and __________________.