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Estrus Detection Dr. Allen Bridges details methods for detection
of estrous in beef cattle, part of an efficient breeding program.
Hello this is Dr. Allen Bridges, Assistant Professor in the Department of Animal Science
at Purdue University and a member of the Purdue Beef Team. Continuing with our video series
on reproductive management in beef cattle. Today we will be discussing estrous detection
in beef cattle. Estrous, or heat detection efficiency, can greatly impact pregnancy success
in an estrous synchronization program. Pregnancy rate is the product of the proportion of animals
detected in estrous times conception rate. As this table illustrates, as estrous detection
rate increases at a constant conception rate, pregnancy rate will also increase. Therefore,
poor estrous detection results in poor pregnancy rates. When detecting heat or estrus in beef
cattle, remember it is important to observe for estrus for at least one hour in the morning
and one hour in the evening. Most commonly, cows will exhibit estrus in the early morning
hours and just before dark. Several factors can impact the efficiency
of estrous detection in a group of beef cows. These include the influence of herd mates
such as social interactions between dominant and submissive cows and the number of cows
in estrus at a given time. Whether the estrus is a synchronized estrus following an estrus
synchronization program or a spontaneous estrus. Environmental temperature can impact the intensity
of the estrus or heat period. Breed can impact estrous detection efficiency in the expression
of estrus by cows. As can the footing surface and leg and foot problems in the cows. Additionally
nutrition and level of milk production can also influence estrous detection expression
in a group of cows. The primary sign of a cow in heat is for her to stand to be mounted
by another animal. This is the only to sure way to know whether this cow is in estrus,
and is ready to be inseminated. Remember, it is the cow being mounted that is in heat,
and not the cow that is mounting her. Often cows that are in estrus will congregate
into a sexually active group, as demonstrated in this video.
Prior to behavioral estrus, cows will often display secondary signs of estrus. Also, cows
can exhibit secondary signs of estrus after behavioral estrus. As demonstrated in this
video, secondary signs of estrus include increased physical contact between cows, such as, resting
the chin on another cow, increased head butting, and circling. Other secondary signs of estrus
include females mounting other females. A female which mounts another female indicates
this animal may be coming into estrus or may be coming out of estrus. Remember, however,
that only the female that stands to be mounted is in standing heat.
As demonstrated in this picture, another secondary sign of estrus is clear mucus discharge coming
from the ***. Prior to exhibiting behavioral estrus, cows
often have increased activity, such as; increased restlessness, increased walking the pasture
or lot, and increased bawling. Additionally, due to rising estradiol concentrations, the
*** often swells. Another secondary sign of estrus is dirt on the flanks, and a roughed
up tail head. These are indications that a cow has previously been mounted. If bloody
mucus is observed from the ***, this indicates that estrus likely occurred 2-3 days prior
to this observation. There are several estrous detection aids available
to assist in detecting behavioral estrus in cattle. These include: estrus alert patches
as demonstrated on the left hand side of the slide, Bovine beacons and k-mars, and tail
paint and tail chalk. These aids serve to indicate when a cow is in estrus. However,
it is important to realize that these aids do not compensate for visual observations
of cows in estrus. Another estrous detection aid is the Heat Watch Electronic detection
system. This system involves an electronic relay patch
on the tail head of the cow, thus when she gets mounted, it sends an electronic signal
to a computer indicating the time at which she was mounted as well as the duration of
that mount. So once a cow is observed in behavioral estrus,
when is the appropriate time to inseminate her? The most common strategy used is referred
to as the AM/PM rule. If estrus is observed in the AM, the cow is inseminated in the following
evening in the PM. If estrus is observed in the evening during the PM hours, the cow is
then inseminated the following morning, in the AM.
Using this AM/PM strategy, often yields the most consistent pregnancy rates following
estrous detection and AI. This slide depicts the events associated with estrus, ovulation,
and fertilization in beef cattle. The duration of behavioral estrus or heat, averages around
15 hours in a beef cow. However, it can range from 6 hours to24 hours in some animals. The
interval from estrus to ovulation is typically between 2 and 6 hours. From the beginning
of estrus until ovulation is typically 27 hours and can range from 24 hours to 32 hours
in cows. As will be depicted in the subsequent slide,
the best time to breed a cow, following her first mount of behavioral estrus, is from
4 to 16 hours later after estrus is initially observed. Breeding before this time, or after
this time period, results in reduced pregnancy rates. It is important to remember that the
lifespan of *** in a cow’s reproductive tract is 24 to 30 hours. However, the lifespan
of the ovulated oocyte, is only 6 to 10 hours. Thus, it is important to have *** at the
site of fertilization and ready for the oocyte. Rathar than have the oocyte there waiting
on the ***. This graph illustrates conception rates achieved when artificial insemination
occurred at various intervals after the onset of estrus. As demonstrated in this study,
when insemination occurred between 4 and 16 hours after the onset of estrus, conception
rate was similar. However, if insemination occurred prior to 4 hours after the onset
of estrus, or after 16 hours after the onset of estrus, conception rates were reduced.
Therefore, the optimal time to inseminate cows, following the onset of estrus is between
4 and 16 hours later. For additional information on estrous detection,
estrous detection aids, and artificial insemination, please contact Dr. Allen Bridges at the Department
of Animal Sciences at Purdue University.