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Artificial Insemination of Swine Improving Reproductive

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									                     Artificial Insemination of Swine:
           Improving Reproductive Efficiency of the Breeding Herd

                                   Robert V. Knox, Ph.D.
                           Swine Reproductive Extension Specialist
            Department of Animal Sciences, University of Illinois, Urbana-Champaign
                                    Phone: 217-244-5177

Artificial Insemination and Profitability
        The reasons for developing and implementing a successful swine A.I. program are
numerous. However, the primary reason for utilizing this technology must relate to improving
the overall profitability of the swine herd. In many ways, profitability is linked with reproductive
Analysis of the impact of altering some measures of reproductive performance so that the new
herd average is somewhere near the top 1/3rd of the current herd records, (i.e. ~one standard
deviation) has been shown to have tremendous impact on producer profit (Table 1)

Table 1.
Trait                  Increase in Profit (%)
Number Born Alive             40.0
Conception rate               20.0
Age at puberty                  4.5

It therefore appears that methods that can improve reproductive efficiency in the herd will aid in
improving and increasing the sustainability of the production system.

Reproductive Records of North America
        PigCHAMP records (~90% from North America, 1999), indicates that average herd size
is now 664 sows. Of these sows most are weaned at 19 days, and ~84% are bred within 7 days of
weaning. More than 85% receive more than one insemination during estrus. Typical herds
average 80 open-days/sow annually. This number is significant since it has been estimated that
each open sow day costs $1.50 /sow/day. With these numbers in mind, early breeding after
weaning and reduced incidences of return to estrus following breeding, will be critical for
returning profit to producers.
        One of the most important measures of reproductive performance is farrowing rate.
Unfortunately, farrowing rates are highly variable and are influenced by a variety of factors that
include season and farm differences in management. The average farrowing rate in the USA is
reported to be 77% with each sow farrowing ~2.3 times/year. The value of improvement in
farrowing rate has been estimated using the Illinois Hog Herd Simulator (Mueller, 1995). This
simulator indicates that for each 1% improvement in farrowing rate, returns above feed costs
improve 1.5 to 2% for farms with 1000 and 440 sows, respectively.
        Litter size in swine is one of the traits that has the greatest impact on economic return to
producers and so deserves adequate attention. Evaluation of average litter size within a herd is

related to herd genotype. Standard measures to assess the current genetic status of the herd can
help make decisions about the next breeding and management actions (Table 2).

Table 2.
Litter Size Assessment       Born alive
Poor                          9.0
Typical (worldwide)           9.4
Good (target)                11.0
Excellent (Target)           12.5

1999 PigCHAMP data indicates an average of 11.2 total pigs born, with 10.2 of these born alive,
0.8 stillborn, and 9 pigs weaned per sow, for a total of 20.6 pigs per weaned per sow per year.
All of previous measures of reproductive performance are important and related, especially when
we associate these with profit. It can be seen from Table 3 that measures for improving
farrowing rate (litters /year and weaning age) and pigs born alive can help producers remain

Table 3.
Reproductive Measures and Profit Percentile
Measure             50th 75th 90th
Litters/sow/year    2.24 2.39 2.43
Weaning Age (days) 20      18      17
Number Born Alive 10.2 10.7 11.0

Current Status of AI Use
Worldwide Perspective
        In all of the Americas, of the 12.2 million sows, ~39% are bred artificially (Weitze,
2000). The Asia-Pacific region maintains 44.1 million sows, of which only 28% are bred by AI.
Europe, on the other hand, with an estimated 9.4 million sows, breeds 69% using AI. These
numbers become important when considering where expansion in technology use and resultant
increases in swine production efficiency and magnitude can occur after adoption of certain
        The USA swine breeding herd has been reported to include 3.9 million sows.
Approximately 60% of these sows were mated by artificial insemination. Each sow received 6.5
doses of semen annually, for a total of 25 million doses utilized in a single year (Burke, 2000).
The majority of sows are housed in crates. Estrus is detected once to twice daily. Most of the AI
is performed using two doses given 24 h apart and containing 3 billion motile sperm in 80 cc of a
3 to 5-day liquid extender. The semen is typically stored at 15-18 ° for 4 days. Bottles (tubes)
and bags are used for storage in single doses at a similar frequency. Although frozen boar semen
is currently available, there appears to be some limitations since insemination must occur within
8 h prior to ovulation to achieve results comparable to liquid extended semen for farrowing rates
and litter sizes.

Improving Reproduction
        There are a number of maternal traits with great economic importance but unfortunately
many of these are lowly heritable. The expression of a trait depends not only the presence of the
gene itself, but also on the effects of environmental influences both inside and outside of the
animal. This means that direct selection for a trait will not necessarily produce the desired
results due to the low heritable nature of the trait and the great influence of environmental factors
on expression of that trait. A list of some maternal line traits and their heritabilities are shown in
Table 4.

Table 4
Heritabilities of Maternal traits
Trait                     % heritability
Structural soundness            40
Age at puberty                  30
Birth weight                    20
Weaning weight                  20
Number of teats                 15
Longevity                       10
Number born alive               10
Number weaned                   10
Pig survival to weaning           0

Despite the low heritability, these traits can often be improved by crossbreeding and by
management. Heterosis results when pigs that are genetically unrelated are mated. This can be
accomplished by mating unrelated animals across lines and even across breeds. However, more
important is the fact that expression of the trait is most dependent upon management factors.

Advantages of AI
 Worldwide Access to the Best Genetics
        Although there are numerous reasons to utilize AI, its use is most attractive due to the
economic benefits associated with access to the best genetics and the resulting improvements in
animal performance. The greatest economic benefit resulting from AI occurs with carcass trait
improvement in the terminal hog. Advantages in the highly heritable carcass traits, such as
backfat, percent lean, and carcass yield, are all associated with the value of the animals at
slaughter. Advantages are also observed in the moderately heritable production traits such as
feed efficiency and average daily gain. These traits are valuable since the greatest cost to
producers is the amount of feed consumed per hog until reaching market weight. Another area
for economic potential from improved genetics occurs with selection of sires for their maternal
line traits such as litter size, lactation ability, spermatogenetic potential (testis size), and age at

Scheduling & Records
        One of the frequently overlooked benefits of AI is the precision gained in the assessment
of reproductive status of females within the breeding herd. For example, AI allows the formation

of tight breeding groups, which facilitates more precision in managing females. This can include
pregnancy detection occurring at specific days post-breeding, culling, and observation for both
regular and irregular returns to estrus

       One of the facts of natural mating is that size mismatches frequently result since new
boars and gilts are introduced into existing breeding groups. These mismatches can cause
problems for mating of young boars to older sows since the boars are often not physicality tall
enough to achieve intromission.

        AI breeding of females allows personnel to perform a greater number of matings per unit
time when compared to natural service. Flowers and Esbenshade, (1993) reported that as the
number of sows bred per day increased (from 1 to 8 sows) the time to inseminate each sow
decreased for AI (34.6 min vs. 17.3 minutes/sow, respectively) but did not change for natural
service, regardless of number served (23 minutes/sow). The time requirements will be
substantially less when semen is purchased from a semen supplier.

 Boar use needs
        Artificial insemination allows much more effective boar utilization with AI than with
natural service. One ejaculate may contain between 40-100 billion sperm cells. This will result in
10-40 AI doses and will cover the mating of 5-20 females. In contrast, with natural service, two
natural services consecutively in a 24-h period will deplete sperm reserves for a singe boar. This
allows only 4-5 services per boar per week maximally before fertility is reduced.

Herd Health & Disease Transmission
         Artificial insemination can be beneficial for limiting disease transmission provided that
the source of the semen has high health certification. Most reliable sources of semen have high
health and management standards for their boars in stud. They often observe strict quarantine
and acclimation procedures, limit both animals and human contact with the animals. These
facilities also perform routine monitoring for certain diseases. Although even this system cannot
completely eliminate the risk of disease introduction into a herd by way of semen, it does limit
the chances when compared to the risk associated with that originating from the introduction of
disease with new animals.

Boar Evaluation
         AI facilitates frequent evaluation of the boar’ potential fertility. This is critical since of
all sires that are culled from boar studs, most of these fail because of reproductive problems.
Collection of semen, whether by the semen supplier or on farm, allows evaluation of the boar’         s
fertility based on ejaculate quality. This can include a gross evaluation of volume, opaqueness,
turbidity, color and odor. An ejaculate that does not meet standard criteria for all of these
indicators can indicate a potential problem or disease. Further evaluation of the collected sample
allows assessment of sperm numbers, motility and abnormalities. All of these characteristics are
associated with boar fertility.

Improvements That Facilitate AI Use

        Adoption of AI is even easier and more practical today than it was at any time over the
last two decades. Improvements have been made in insemination equipment. This includes the
use of disposable supplies that greatly reduce the risk of disease transmission or infections
resulting from contaminated equipment. Improvements have also been made in the design of AI
catheters, which allow choices to be made based on preference, price, and ease of insemination.
Although the storage form of semen is liquid, improvements have been made in the semen
containers which facilitate ease of insemination, provide more efficient temperature control, and
reduce cost of shipping due to reduced bulk of container.
        Semen extenders have also been improved over the years with semen fertility extended
from 2 to 5 days. Choices are still available for purchase of a short-term extender or a long-term
extender with cost savings associated with the short-term extender. Even semen storage units
have been improved with the development of precise temperature control units that can maintain
semen temperatures to within ±1°of desired storage temperature. Even semen shipping has been
improved with overnight and next-day delivery service available. Shipping containers are also
better able to protect and insulate liquid semen in a variety of climates. The semen collection and
delivery services today can put semen on the farm within 24 h of collection.

AI Compatible Applications
        There are certain management procedures that are uniquely suited for use with artificial
insemination in pigs. One of these is the ability to induce a synchronous estrus in animals to be
mated. Synchrony of estrus allows groups of sows to be mated and then farrow at the same time.
Since each female will require two services within an estrous period, each estrus will require two
semen doses (with A.I) or one boar (natural service) for females that come into estrus within a
given day. Natural service can obviously produce a need for a great number of boars on the farm.
However, with AI, numerous doses of semen can be extended from a single collection and
therefore, breeding females expressing estrus at the same time becomes important for cost, time,
and space management.
        One method of synchronizing estrus in gilts results from regrouping, relocation, and boar
exposure near the age of puberty. This procedure can usually induce 30-40 % of gilts within 10-
15 d of the procedure. Another method of inducing gilts into estrus is with the drug, PG600® .
This drug, when administered to gilts near the age of puberty, can often induce estrus in 50-80%
of females in five days. In fact, most of these females express estrus within 1-2 days of each
other. Synchronization of estrus in sows occurs with weaning after females have lactated
between 15 to 30 days after farrowing. This procedure allows sows to express estrus within 4-7
days after weaning. All of the estrous synchronizing techniques will require access to a large
number of boars in order to accomplish natural service or adequate numbers of semen doses to
accomplish this task with AI.

Keys to Reproductive Success
       The ability to achieve and maintain a high level of reproductive performance in a swine
herd is not an easy task, especially when considering the genetically lean composition of the
animals, the confinement type of housing, and the rate at which they reproduce annually. The
measures of reproductive performance are determined by the genetic nature of the pig. Although
some measures appear limited by the genotype of the pig and may be beyond the control of
producers for improving reproductive rate, others can be influenced, even if only slightly.

However, these slight changes can have dramatic impact on profit return to the producer. Many
factors that are under the direct influence of the producer include: the feeding and nutrition plan,
the housing and environmental management system, the animal health and disease prevention
program, and the level of the reproductive management system. Methods for assessing the
efficiency of these programs can help determine management systems that can improve the
productivity of the swine breeding herd.

General recommendations
   • Maintain a healthy, fertile breeding herd by effective and properly administered vaccines,
      high levels of sanitation, and properly operating biosecurity systems.
   • Detection of estrus should involve trained personnel, high quality boar exposure, and
      adequately exposing gilts and sows to boars once to twice daily.
   • Semen quality and boar libido should be assessed on a routine basis.
   • Proper insemination times and techniques should be optimized for herd reproductive

A Healthy Fertile Breeding Herd
        Reproductive efficiency is not possible if problems exist in the breeding herd.
Reproductive records indicate an annual 40-50% culling rate for sows. Of these losses, 30% are
attributable to reproductive failure (Koketsu et al., 1997).
The failure breakdown is as follows:
    1. 25% anestrus
    2. 37% fail to conceive
    3. 1.5% fail to remain pregnant
    4. 15% of pregnant sows fail to farrow
    5. 7.4% abort

        Identifying poor performance is not difficult but identifying the cause of poor
performance can be a formidable task. However, some methods do exist to aid in problem
solving. Determining the cyclic nature of estrous behavior in the female pig is one method to
ensure reproductive processes are occurring normally. Deviations from the normal 20-21 day
average or in the length or symptoms of estrus should give warning of a potential problem.
        Utilizing production records in hindsight will also be essential in reproductive problem
solving. The more accurate and detailed the record reports, the more precise will be insight into
the causes of failure. For example, poor litter size is related to many factors, starting with the
number of eggs ovulated and ending with the number of pigs that die during farrowing.
However, detailed record analysis can yield important information revealing when and where
some problems may be originating. For example, record analysis indicating that the number of
single services has exceeded a certain value can indicate improper estrous detection and number
of inseminations during estrus as a cause of low litter size.
        Ultrasound can provide additional information on the early establishment or loss of
pregnancy and help in pin pointing additional causes of reproductive loss, since these units can
have accuracies of greater than 95%. New technologies such as real-time ultrasound can be used
to evaluate the reproductive status of the ovaries and uterus. This procedure can determine the
reproductive status of any female at known ages after birth for gilts, after last estrus, at weaning,

breeding or following hormone treatment. The technology can also be essential for reducing non-
productive days, through identifying early reproductive failure. The top 10% of producers
average 36 non-productive days (non-lactating and non-gestating days). Excessive cases of early
reproductive failure can warrant reproductive management intervention and warrant breeding,
housing or health management adjustments. These types of failures can also alert herdsmen to
early disease signs. General animal observation can help identify animals that go off feed or
that fail to get up or act normal. These signs can be the best and earliest indicators of potential
reproductive failure.

Detection of Estrus
         The accurate detection of estrus for all animals in the breeding herd is probably the most
critical factor linked to reproductive success when using AI. Estrus is a gradual response to
estrogen released from follicles on the ovaries. The behavior that results ensures that mating
takes place near the time when eggs are ovulated from the ovary. The time period that a female
will stand is variable and can be short or long depending upon environmental circumstances.
         There are aspects of boar exposure that are essential in eliciting the estrous response in
females. It has been shown that by just applying back-pressure alone in the absence of the boar,
approximately 48% of females will exhibit the standing response (Signoret, 1970). When back-
pressure and boar vocalizations are used together, 70% of females are detected. When odor is
used in place of boar vocalizations, 80% are detected in estrus. When all stimuli are applied
together with visual stimulation from the boar, 97% of all females in estrus are detected. This
indicates that humans cannot detect 100% of all estrus females without direct physical contact of
females with a boar. But this also indicates, that boar vocalizations, sight of the boar, and boar
odor emissions are critical in accurate detection of estrus and should be optimized in a fence-line
estrous detection regimen.
         From the previous data it can be seen that almost half of the females will exhibit estrus in
the absence of a boar. However, because of the high failure rate this will not be useful in on farm
application. Studies have shown that over 90% of pigs actually go through recognizable phases
during estrus. These include an initial period of refusal to stand for a boar and for back-pressure
applied by humans. Hours later however, the female will allow only a boar to mount but will still
refuse back-pressure from humans. As estrus advances approximately 4-8 hours, the female will
exhibit estrous symptoms in response to the boar and also to human stimulation. This phase will
last about 20 hours for humans alone and about 44 hours for the boar. In the late stages of estrus,
the female will again refuse to stand for the human but will accept the boar. After this period, the
female will refuse stimuli from both (Boender, 1966). In application of these observations for
improved mating, the failure of 10% of females to stand for humans without a boar will preclude
this methodology without modification to enhance the response to humans alone (Uemoto et al.,
2000). However, the time a female will stand for only a human is much more precise and closer
to the time of ovulation.
         It has been shown that detection of estrus for gilts housed in crates or gilts housed in pens
using a boar located in the alleyway, takes longer (0.5–1 minute longer) and detects only 68% of
estrous gilts compared to 87% when detecting estrus after moving the gilts to the boar pen or
100% detected from actual physical boar contact (Zimmerman, 1997). Housing the gilts away
from boar or opposite the boar with a distance of 3 feet or more will allow 95% of gilts to be
detected in estrus, compared with only 75% when females are housed adjacent to boars. Even
when the boar has physical contact with the gilts after being housed adjacent, he is only able to

induce standing in 95% of gilts compared to 100% when the boar is housed away (Tilbrook and
Hemsworth, 1990). It is also worthy to mention that housing boars too close to females can
reduce the intensity of estrus and the duration of the standing period.
        The duration of time that a gilt will express estrus depends upon where the female is in
her period of estrus, and how long the exposure to a boar has been when the standing response is
tested. Some females that are in estrus and stand when they receive initial boar exposure at time
0, will fail to stand after 5 minutes, and at later times. This appears to be related to whether it is
the first or second day of estrus. For example, on the second morning of estrus, 100% of gilts
stand at 0 minutes, 94% at 5 minutes, 88% at 10 minutes, and only 77% at 15 minutes.

Quality of Semen & Boar Fertility
        Another critical aspect for implementing a successful AI program involves maximizing
the fertility of the semen utilized. New estimates indicate that in the US there are 19,500 boars in
AI centers. Each of these boars produces 1,617 doses of semen annually, which is approximately
31 doses per week or 15 doses per collection. It has been suggested that based on the trend for
increased AI usage over the next 10 years, there will be an increased need for boar stud
expansion (Burke, 2000).
        Whether semen is purchased from outside the farm or collected on farm, most needs are
based on the number of sows weaned on a certain day of the week. Also one must take into
account the number of services from each ejaculate, which can fall anywhere between 10-50.
The number of ejaculated sperm depends upon the age of the boar but also on the collection
frequency and rest period between collections. For example, boars collected every 12 h
consecutively fall to below 50% of 1st output value at the time of the third collection, whereas
this level of depletion doesn’ occur until the 5th collection when boars are collected every 24 h.
This is not to say that boars should be collected this many times consecutively but illustrates that
boar semen reserves can be quickly be depleted without adequate rest.
        In data from USA boar studs, annual boar culling is high (Colenbrander, 1993). The
primary reason for boar culling is related to reproductive problems (61%). These factors involve
sperm quality, quantity, and boar libido problems. In identifying boars with problems, evaluation
is essential. Evaluation begins with records on the boar, such as his age, and collection history.
The history can include all records on the boar’ past ejaculate characteristics. The evaluation
typically includes a gross and a microscopic evaluation. The gross evaluation characterizes the
volume, color, opacity, odor, and turbidity. The microscopic evaluation may include the motility,
the structural abnormalities, and the concentration.

Evaluation of Boar Fertility
       Levis (1997) reported the effects of individual boars with different rates of abnormalities
and their interaction with age in extender on subsequent farrowing rate. Important considerations
were identified, in that boars with high incidences of abnormalities such as boars J, and I, had
lower farrowing rates. Additionally, boars with moderate rates abnormalities such as boar H,
showed one of the highest farrowing rates after four days of storage. Other boars, with even low
abnormalities however (such as boar D), showed significant reduction in farrowing rates from 2
to 4 days in storage. What this indicates is that abnormality rate alone may not be the best
indicator for fertility, but can be used with some degree of confidence to identify potential

sources of fertility problems. Further, duration of storage for extended boar semen has a large
effect on farrowing rate and certain boars should be evaluated for their fertility after storage.
        Flowers (1996a) has shown the effect of sperm motility on both farrowing rate and litter
size in swine. Semen with a motility estimate below 62% shows significant drops in both
farrowing rate and litter size. However, this measure was not precise in assessing fertility
differences between boars when motility was above this value. This does indicate at what levels
poor samples should be discarded. Some general recommendations for semen handling and
storage involve daily rotation (1-2 times). This is for dispersing the toxic waste products and for
providing sperm access to nutrients. Semen should be protected from temperature changes
outside of the 15-18 ° range. Semen should be used within 4 days of collection and should be
protected from sunlight and shock.

Proper AI Technique
        Once estrus has been identified, proper AI involves making sure the female receives
adequate stimulation from the boar. This should involve head to head stimulation of females with
a mature, vocal boar in good lighting and low (not poor) ventilation. To stimulate sows to self
inseminate, apply firm back-pressure, side rubbing, and udder stimulation for ½ to 2 minutes.
This can induce semen to be sucked into the uterus. The presence of the boar at mating has been
reported to induce an oxytocin surge (through pheromone) and appears to reduce the amount of
sperm lost at insemination by 18%, but this leakage, nor the presence or absence of the boar
seems in itself do very little to improve fertility or semen retention over time. However, the
presence of the boar does initiate rigid standing and limits the female from moving at the time of
insemination and prevent semen loss.
        The actual technique of artificial insemination involves the deposition of approximately
80-100 cc of liquid extended semen into the cervix-uterus of the female. Eighty cc has been the
standard volume, and amounts less than 60 cc typically do not result in high reproductive rates.
The catheters used are for the most part commercially manufactured, disposable, and low cost.
The catheters are made out of foam, rubber, or plastic. Some are grooved or spiral-shaped and
lock into the cervix of the female. It has been observed that some catheters may be advantageous
in locking into the cervix in certain situations, as when some older sows tend to lock onto either
one better than another. This suggests that having some of both types could prove beneficial for
optimizing inseminations.
        The standard procedure for A.I. involves cleaning the area of the vulva with a clean
disposable paper towel. The tip of the catheter should be lubricated with a non-spermicidal
lubricant. The lips of the vulva should be gently separated. The foam catheter can be inserted
with no angle adjustment, but the spiral catheters, which have a pointed end, should be inserted
at an upward angle because they can have a tendency to enter the opening of the bladder with
their pointed tip. This can be damaging and painful for the female and can cause bleeding and
refusal to be served. Catheters should be gently inserted about 6-8 inches until some resistance is
felt. The catheter made of foam can be pushed firmly to lock into the first or second set of
cervical pads. On the other hand, the spirette should be rotated counterclockwise until it can no
longer turn as it penetrates 3 to 4 pads deep. To release some pressure, rotate clockwise about
one turn to aid in ease of insemination.
        The semen containers are generally cochette bags, sealed tubes, or bottles made out of
collapsible plastic. Once the semen container is attached to the catheter, some of the semen can

gently be deposited by gentle slow pressure, and then letting the sow or gilt inseminate herself
with stimulation, or through employing combination of both gentle pressure and female
stimulation. The catheter can be left in place after insemination or can be removed to minimize
backflow. This apparently makes little or no difference on overall fertility or leakage over time.
However, if catheters are left in, they should be bent so that semen cannot leak directly out of the
        Before insemination, the semen should be mixed gently as it has a tendency to settle to
the bottom with time. Recommendations for time to inseminate are generally about 3-5 minutes.
Approximately 75% of the sperm are lost in back-flow over an 8-hour period, with 66% lost in
the first 45 minutes after AI. Although billions of sperm are deposited into the uterus, only
thousands actually reach the site of fertilization. Many sperm are lost but those that survive
develop into a sperm reservoir in the oviduct. This reservoir will be important for fertilization
when eggs arrive.
        Flowers (1996b) has reported the effects of AI technician on farrowing rate and litter
size. Large effects were observed for technicians especially in farrowing rates. This accounted
for great variation pigs produced per technician. The reasons for these technician effects are not
clear, however the data indicates that technicians performing more than 10 inseminations before
taking a break have farrowing rates that are reduced from ~85% to 78%. More services than 15
without a break, show a further reduction in farrowing rate to 71%. Determining the required
number of technicians for adequate personnel to accomplish breeding in a timely fashion can
alleviate this problem. Determining the time needed for services, for example; 8 minutes/
service, is desired to accomplish moving to the female, moving the boar, checking records, set up
of equipment, and actual insemination and recording. Eight minutes per service is desired and
one technician should not perform more than 13 services in a 2-hour period. In a 2-hour period,
10 sows can be bred in 80 minutes. This leaves 15 minutes for a break before resuming to breed
3 more in the remaining 25 minutes. In an example, we have 30 sows to breed in a 2-hour period
of time. How many technicians will we need? To determine technician needs, based on the
formula: 1 Technician /13 services/2 hours = X Technicians /30 services/2 hours. In this case we
are solving for X or number of technicians. The answer is 2.3 technicians to accomplish this task
in a 2-hour period. If we rearrange the formula and now include 3 technicians as being available,
we can determine how long the task will take with the 3 technicians. For example: 1 Tech/13
services/2 hours = 3 Tech/30 services/ X. Solving for X we determine this task can now be
accomplished in 1.5 hours.
        In examining the effect of the technician on fertility, it has been reported that fast
inseminations, occurring in less than 30 seconds, have a 33% drop in conception rates compared
to slow inseminations taking 10-15 minutes. The exact speed of insemination that produces
optimal results is not known but should take over 3 minutes ideally. Leakage at the time of
insemination is reported to be related to conception rates. Leakage at insemination is undesirable
because potential fertilizing sperm never have a chance reach the egg. It should be noted that
leakage after insemination is normal, and approximately 2/3 of the volume and sperm will be lost
in the 4 hours following insemination. The amount of leakage at the time of insemination is most
likely related to the technician’ ability to securely seat the catheter in the cervical pads,
technician proficiency for slowly depositing semen, amount of technician pressure applied to the
semen container, amount of sow stimulation arising from back-pressure, side and belly rubbing,
level of boar contact, and strength of the standing response of the female.

AI Timing
        During estrus, egg release occurs approximately 66-85% of the way through the duration
of standing estrus. The timing of this event is highly variable and may depend upon wean to
estrus interval, parity, and season. The duration of ovulation, or the time it takes all of the eggs to
ovulate within a female, is not very variable and lasts only 3 hours. Following insemination,
sperm can survive in the female tract for 24-36 hours (depending upon the time since collection).
However, eggs may only be fertilized normally and develop into fetuses up to 8 hours after
ovulation. Conception and litter size is most influenced by the time of insemination relative to
ovulation (optimal time is within 12 h before ovulation) and the inherent fertility of the boar’      s
sperm. There are tremendous differences between the fertility of two boars who inseminate a
single female with equal numbers of sperm at the same time (Dziuk, 1996). The higher fertility
boar will always produce a greater proportion of the offspring in this scenario.
        Waberski et al. (1994) have reported that more than 50% of gilts ovulate within 32 h after
onset of estrus, and 35% ovulate between 32 and 44 hours and 15% ovulate later than this time.
Because of the limitations to sperm and egg fertility, and the reported variability of ovulation
times in the gilt, it is perhaps not surprising that Flowers and Esbenshade (1993) reported that
single inseminations occurring either 12 or 24 h after estrus have lower farrowing rates compared
to protocols employing double matings. Triple matings do not improve farrowing rate but do
tend to improve litter size.
        In gilts Soede et al. (1995) has shown the importance of timing inseminations relative to
ovulation by using a single AI. The researchers evaluated the number of females that conceived
and the percent of normal embryos in each female. Inseminations occurring less than 24 hours
before ovulation and up to 8 hours after ovulation produced the highest conception rates and the
greatest number of normal embryos. However, single inseminations occurring after the time of
ovulation were detrimental to reproductive performance.

Effect of gonadotropins
        The ability to synchronize estrus in gilts would be of great importance for scheduling
replacement females. Although boar exposure can induce estrus, synchrony is not optimal.
PG600® has been shown to effectively induce estrus in ~50-60% of gilts within 5 days. This
occurs provided the gilts were prepubertal and were close to the natural age of puberty at the
time of treatment. In addition, many of the treated animals expressed a second estrus 21 days
after the first one, which allows for breeding at later ages. In studies using intramuscular PG600
injections and breeding at the induced estrus, at a fixed time without estrous detection on days 4
and 5 after PG600 treatment or at the 2nd estrus, ~65 of gilts farrow to fixed time AI, while 70%
farrow to AI at the induced estrus. Delaying breeding to 2nd estrus does improve farrowing rate
to 89%. Litter size was reduced when mated by fixed time AI but not when mated at estrus and
sow longevity was not decreased by mating at pubertal estrus (Holtz et al., 1999; Kirkwood et
al., 2000). Perhaps one way to improve overall reproductive rates from induced estrus will be
through administering the dose by subcutaneous injection instead of intramuscular, since it has
been shown to be more effective at inducing estrus and ovulation in 24% more gilts compared to
intramuscular injection (Knox et al., 2000a).

AI of Weaned Sows
Synchrony of Post-Weaning Estrus

        Most sows return to estrus within a fairly short period of time if temperatures are
moderate, feed intake has been adequate during lactation, body condition is good at weaning, and
sows have lactated for longer than 17 days. From the majority of data that exists, more than 80%
of weaned sows return to estrus and are bred by 7 days. Since most sows express estrus within
four to six days from weaning, this level of synchrony allows breeding groups to be established,
and determination of boar or semen needs, and labor requirements to be planned in advance.
Recent evidence suggests that a relationship exists between wean to estrus interval and time of
ovulation after onset of estrus. The relationship indicates that sows that return to estrus early
after weaning, ovulate late, and that sows that return late, ovulate early. Although in some cases
the relationship does exist, the relationship varies from a low of 29% to a high of 75%. What this
means is that in some herds, breeding based on the interval from weaning to estrus can be a very
poor estimator for over 70% of sows, and in some herds may be an excellent predictor in about
75% of sows but fail in the remaining 25% of sows. Therefore breeding on this schedule may fail
in 25% or more of the sows (Knox et al., 1999).
        As an example of this, Flowers (2000) adjusted breeding of sows based on their intervals
from wean estrus. Compared to standard breeding practices following onset of estrus (once on
each day of estrus), the researchers delayed breeding to 24 and 48 h for sows retuning in 5 or less
days, to 8 and 24 h for sows retuning in 6 to 7 days, or to 0 and 8 h after onset of estrus in sows
returning after 8 or more days. In one farm the procedure had no effect at all on farrowing rate
and on another farm it slightly improved the farrowing rate for early retuning sows but greatly
reduced performance in later returning sows. These data illustrate some important
considerations. The first is it is likely that estrus and ovulation time differences exist between
farms and that these relationships may be altered by season, genetics, weaning age, and parity.
        The time of ovulation after onset of estrus is variable for sows. Nearly 20% of sows
ovulate within 24 hours, 22% ovulate between 24 and 36 hours, 35% ovulate between 36 to 48
hours, and 18% ovulate between 48 to 60 hours, after onset of estrus. The remaining 5 to 6% of
sows that eventually will eventually ovulate, tend to do this between 3-5 days after first
expressing estrus (Knox et al., 1999).

Length of Estrus
        It appears that determining both the start and end of estrus may be of practical use since
the length of estrus is related to the time of ovulation after detection of estrus (Weitze, 1994).
Most sows ovulate about 75% of the way through estrus. This has been shown to be variable
though and ovulation may occur anywhere 50% of the way through estrus to 80%. Therefore it
appears that the relationship of length of estrus and the occurrence of ovulation is not fixed. Data
indicates that interval from ovulation to the end of estrus may be influenced by season. This
interval was shortest in fall and longest in spring (Knox et al., 2000b) The interval from
ovulation to the end of estrus averaged 25 h. It seems likely in light of this, that many animals
that mate on the symptoms of estrus for the duration of symptoms would have mated females
well after ovulation.

Mating Times in Sows
        A review of published research on the reproductive performance of sows under different
breeding protocols does not lend itself to making easy comparisons. Part of the reason for this is
the fact that different genetics, management, and seasons could all have influenced the outcomes
in addition to the breeding protocol. However, certain trends do appear to be interpretable from

these data. Examination of the pooled trials for the breeding methods that produced the greatest
farrowing rates and litter sizes indicated a slight improvement in farrowing rates and litter size
from methods employing at least a twice daily (2-3x) estrous detection regimens compared to
once daily. However, within experiment, research indicates that estrous detection frequency in
sows whether once, twice, or three times daily, had little impact on farrowing rate and litter size,
despite an increased percentage of first and second inseminations occurring within 24 h before
ovulation (Knox et al., 2000b). In general, most data indicates that reproductive rates remain
high when at least two inseminations occur during estrus. A third insemination may be beneficial
when animals show estrus for a longer period than expected such as a third day. No improvement
in reproductive rates have been observed for alternative insemination times when compared to
insemination at 0 and 24 h after onset of estrus (Flowers).

AI Fertility Enhancers
         Recent attention has been given to factors that might be used to improve the reproductive
efficiencies when using artificial insemination. There is controversy over using any additional
fertility enhancers since high reproductive rates are reported to be obtainable on farms without
using these supplemental procedures. However, the need to use new procedures and semen
additives should be evaluated individually and their implementation balanced against costs and
         The interest in seminal plasma as a fertility supplement when using AI stems from the
discovery that seminal plasma when added to AI doses improved fertility compared to standard
extended semen. This suggests that complexes contained within the boar ejaculate can impact
sperm fertility or reproductive processes in the female. Administration of seminal plasma prior to
insemination (60 cc) or at levels of 10% within an AI dose, can improve fertility. Seminal plasma
contains proteins, hormones (including estrogen), prostaglandin, and anti-inflammatory agents,
which may be involved in reducing the interval from AI to ovulation, and also improving the
fertility of low sperm inseminations. The mechanism by which its use accomplishes
improvement in fertility is not clear but may involve earlier ovulation, reduced sperm clearance
by the immune system, or improved sperm transport (Rozeboom, 2000).
         One new product is Predil® from Kubus International. This product is similar to AI
liquid extender but in addition is reported to contain substances that may be similar in nature to
those found in seminal plasma. Although a limited number of studies are available and the
contents are proprietary, some evidence suggests that when used at the estrus prior to breeding or
just prior to mating, when using AI, it improves reproductive rates. It is not clear how this pre-
insemination protocol may be influencing fertility, if at all, but from available ingredient lists,
may be reducing incidences of microbe contamination prior to or following breeding.
         The addition of oxytocin and prostaglandin to semen has gained the most attention over
the last several years. In many studies, although not all, farrowing rates have been improved but
not in all parity groups or in all seasons. Generally, the addition of 4 to 5 IU of oxytocin to
semen, immediately prior to use, or the addition of 0.5 cc of Lutalyse® to semen, improves
farrowing rates in warm seasons but not during cool or moderate months. The very nature of
activity these hormones suggests that sperm movement to the site of fertilization may be
somehow be involved, but this is not clear (Levis, 2000; Reicks, 2000).

Risks of Failure from Breeding Mistakes
Troubleshooting Fertility
         Singleton (1999) has reported the effects of the influence of semen quality, technician
ability and female fertility at the same moment on overall herd fertility. The important
information from this is that optimizing all three of the important criteria is essential for high
reproductive performance. Inefficiency in any one of these components can have dramatic
impacts on herd reproduction. Therefore it is important to maintain high levels of technical
proficiency when mating swine to minimize the effects of lowered semen quality.
         AI is a technique with a long track record for success in swine production operations and
has provided producers of all sizes with great flexibility and numerous advantages when properly
implemented. However, it is important to mention that there are certain phases in the AI
procedure that can be potential areas for AI failure. Whether purchasing semen from an outside
semen supplier or on farm collecting, improper semen handling which does not maintain high
quality of the extended semen can result in failure to settle females. It is important to maintain a
constant cool temperature (62-64 F), avoid excessive changes in semen temperature, rotate
semen daily in storage, use semen quickly after removing from cool storage, protect from
temperature change (warm and cold), protect from excessive pressure, and use semen as soon as
possible after collection and extension. Even the highest quality semen cannot compensate for
poor estrous detection and improperly timed inseminations. Detect for estrous once or twice
daily by providing adequate boar exposure with face to face contact, and inseminate females
twice during estrus.
         Do not attempt to breed too many females in a given time period as inseminator fatigue
can reduce fertility rates (multiple breeding technicians may be needed). Do not allow poor
hygiene with AI techniques, as this can introduce infectious organisms into the uterus and cause
infertility or abortion. Reduce animal stress before, during, and after mating that result from poor
equipment and facilities, undesirable or unhealthy environment, and untrained or improper
animal handling personnel.

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