REPRODUCTION PIH-96
PURDUE UNIVERSITY. COOPERATIVE EXTENSION SERVICE.
WEST LAFAYETTE, INDIANA
Troubleshooting Swine Reproductive Failure
Authors
Lawrence Evans, Iowa State University
Jack Britt, North Carolina State University
Clyde Kirkbride, South Dakota State University
Don Levis, University of Nebraska
Reviewers
John P. Hurtgen, New Freedom, Pennsylvania
John J. Parrish, University of Wisconsin
Wayne L. Singleton, Purdue University
Some reproductive failure occurs in all swine breeding
operations, but for practical purposes reproductive failure is
regarded significant only when production levels fall below the
expected norm. These norms may vary from operation to operation
and are based on such things as percentage of animals cycling,
conception and farrowing rates, average litter size and number of
pigs produced per sow per year (Table 1). The detection of
moderate rates of subfertility depends upon the observational
ability of the caretaker, regular recording of reproductive
events and analysis of reproductive records.
There is a tendency to equate reproductive failure with
infectious disease, but most problems are not infectious. This
tendency probably springs from the need to assign the problem to
a tangible factor such as an infectious agent and from public
awareness of infectious reproductive diseases. Most reproductive
problems have causes that involve management practices, nutri-
tion, environmental effects, toxicoses, genetics and disease con-
ditions. Solving reproductive problems requires a thorough
knowledge of the breeding herd management and the collection and
analysis of pertinent objective data (Table 2). This may be
followed by submission of appropriate samples to a diagnostic
laboratory. Many problems defy an exact laboratory diagnosis
because the causative agent may no longer be present or the prob-
lem may have been related to prior management or environmental
factors.
It is often practical to categorize the reproductive problem
into one or more areas so that specific investigations or tests
can be applied. Table 3 shows the more common reproductive signs
or complaints concerning swine reproduction. Bars indicate the
relative importance of the female or the male to each of these
reproductive problems. Each category will be discussed in this
fact sheet with reference to some known causes and diagnostic
procedures.
Anestrus
Gilts. Common complaints with gilts are delayed puberty,
silent estrus and anestrus after a few heats. These problems
often are related to modern housing and are influenced by breed
and age of the gilts, the season, whether a boar is present and
to some extent the duration of daylight or artificial lighting.
Landrace and Large White breeds tend to cycle better in
enclosed facilities and at an earlier age than most other breeds.
It is stock from herds that have been shown to reproduce well
under management conditions similar to those intended for the
animals purchased. About 80% to 85% of the gilts should be show-
ing regular cycles by 7 to 8 months of age, but this percentage
may be much lower in the summer and fall months. This percentage
will not increase significantly for gilts kept beyond 9 months of
age. Thus, it is not genetically or economically sound to keep
noncyclic gilts beyond 9 months of age.
Gilts that are kept in an enclosed facility, isolated or
tethered are older when reaching puberty than are gilts kept out-
side. When gilts are housed in enclosed facilities, smaller
numbers per pen (8 to 12) are better than larger numbers. It is
best to provide 8 to 10 hours of daylight or artificial light per
day and 20 sq ft floor space per animal. Longer day lengths will
decrease the proportion of gilts cycling. Moving gilts to new
pens or to outside housing and exposure to adult boars often will
stimulate heat in a number of the noncycling gilts (See PIH-89,
Managing the Gilt Pool).
Table 1. Expected norms for reproductive performance.
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Gilts cycling by 7 months 75% to 80%
Weaned sows cycling by 1 week-1st litter 70% to 75%
-older 80% to 85%
First service farrowing rate-gilts 80% to 85%
-weaned sows 85% to 90%
Litter size-total 10 to 13
-born alive 9 to 12
Boar, rested for 1 week:
-ejaculate volume 150 to 300 ml
-sperm concentration 200 to 300 x 106/ml
Boar fertility-sows that farrow from
matings to that boar 80% to 90%
Sows diagnosed pregnant that
subsequently farrow 95%
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Since undetected heats often are mistaken for anestrus, heat
detection methods should be evaluated. Tests for estrus should be
conducted at least once daily with the aid of a mature boar. Each
female must have sufficient time for behavioral interaction with
the boar either by moving the boar from female to female or by
moving females past the boar's pen. With the latter method, immo-
bilization is usually seen in sows or gilts in estrus. The care-
taker may assist in detecting estrus by applying back pressure to
the females as they interact with the boar. Continuous exposure
of the gilt to boar stimuli decreases the efficiency of this
method because the interaction between the animals becomes less
intense over time. Electronic devices which have vaginal probes
have been used successfully for detecting estrus but require
additional labor.
Gilts should be examined closely for underdeveloped external
genitalia. These often are heavily muscled, lean animals which
have delayed puberty and, because this is a heritable condition,
replacement gilts should not be selected from these animals.
Table 2. Data useful in identifying reproductive problems.
_________________________________________________________________
Number of times each boar is used weekly.
Conception and (or) farrowing rates for each group of sows.
Percentage of gilts bred by 8 months of age.
Percentage of sows rebred by 1 week after weaning.
Percentage of sows diagnosed pregnant that subsequently farrow.
Average litter size, born alive, mummies, and stillborns
for each group of sows.
Culling rate after weaning:
% 1st litter
% 2nd litter
% Older
Estimates of feed intake during gestation and lactation.
_________________________________________________________________
Table 3. Signs of reproductive failure.
_________________________________________________________________
Female suspect Male suspect
Anestrus
Failure to mate
Bleeding at mating
Repeat breedings
Abortions
Mummies
Stillbirths
Fewer pigs per litter
Pregnant sows that
fail to farrow
_________________________________________________________________
Importance: Primary Shared Little
_____________________________________________________________
Weaned Sows. A common cause of anestrus in weaned sows is
insufficient energy or protein intake during lactation. This is
particularly important in sows weaning their first litters. The
frequency of feeding, the design of the feeders (large enough for
sows) and waterers, and the nutrients in the feed should be
evaluated. There may be a need to add energy or increase the pro-
tein in the lactation diet when feed intake is low. Improper
feeding which leads to excessive weight loss during lactation or
insufficient weight gain during pregnancy are the primary con-
siderations when anestrus occurs following weaning. Conversely,
excessive feed intake during gestation (overweight sows) will
lead to decreased feed intake during lactation resulting in
severe weight loss and sometimes anestrus after weaning.
The length of lactation also influences return of heat. Sows
with short lactations, particularly if less than 21 days, may
require more time to cycle after weaning. There is evidence to
suggest that weaning the heaviest pigs in the litter at least 48
hours early will improve cycling performance, especially in
first-litter sows.
The stress of grouping sows and withholding feed after wean-
ing will lengthen the average interval to estrus. Thin sows
should be fed 6 to 8 lb of the gestation diet for at least the
first week after weaning. Housing sows in crates or small groups
may increase the percentage of sows that cycle early. Exposure
to a mature boar, either in adjacent pens or by daily movement of
the boar among the sows, also will stimulate early cycling in
postweaned sows. Mixing 3 or 4 sows with the boar for the first
48 hours after weaning reduces fighting among sows and provides
boar stimulus to initiate cycles.
The summer and fall months are periods of reduced cycling in
sows. The effect of this is minimal if the previously mentioned
practices are utilized and good heat detection methods are fol-
lowed.
The diagnosis of anestrous problems should be based upon
heat detection and breeding records. Eighty percent of the gilts
should be cycling regularly by 8 months of age, or an average of
4% of the gilts of that age should be in heat each day. Between
85% to 90% of the sows should have cycled within the first 10
days following weaning. Estrous detection methods and frequencies
should be checked closely to assure proper procedures are fol-
lowed. Other diagnostic procedures might include slaughter exami-
nations or obtaining serum progesterone levels to determine if
estrus has been missed.
Failure To Mate
Male refusal. Boars or sows may refuse to mate even though
the female is showing signs of estrus. Usually this is a boar-
oriented problem. Insufficient sexual behavior by the boar may
be caused by immaturity, lack of proper sexual experience, genet-
ics, overuse, over-conditioning or pain associated with breeding.
Normally young boars begin aggressive mating behavior by 5
to 6 months of age. Those that are not sexually active by 7.5
months are problem boars. Rarely is this problem related to a
deficiency of male hormone; consequently, hormone therapy gives
poor results. More often, the problem can be traced to a lack of
breeding experience or to the boar's ancestry. Providing young
boars with sexual experience through observation and interaction
with compatible males and females is the preferred therapy. Boars
that are unresponsive to this experience should be culled.
Experienced boars may have periods of reduced libido.
Overuse, heat stress, over-conditioning and old age are possible
causes for reduced libido, but pain associated with breeding is
the most common cause of abated libido. Pain from feet, leg or
back lesions caused by injury or disease is accentuated by mount-
ing and may inhibit sexual desire in the male. Lesions of the
penis or prepuce also may cause sufficient pain to inhibit sexual
activity.
Some boars may mount sows but be unable or unwilling to
enter the female. This may be due to pain from skeletal disease
or to abated libido occurring as the boar passes his prime age of
sexual drive. Other boars may develop the habit of diverting the
penis into their preputial diverticulum. This condition can be
corrected by surgery, but large diverticula are heritable and
predispose the boar to this problem.
Virgin boars that fail to mate should be examined for abnor-
malities of the penis, including fibrous tags (persistent frenu-
lum), incomplete erection or short penis syndrome. Usually these
boars can expose only the spiral tip of the penis while attempt-
ing to mate. These are heritable conditions, and affected boars
should not be used for breeding stock production. Boars with
fibrous tags often can be salvaged for commercial use with surgi-
cal correction.
The diagnosis of these boar problems is based on good obser-
vations, radiographs to detect bone disease, and, occasionally,
examination of a boar under anesthesia for penis or preputial
problems.
Female refusal. Sows or gilts in estrus may occasionally
refuse a boar, particularly a young boar. For this reason mature
boars are better teasers. Gilts that aggressively refuse the
male should be culled as undesirable genetic stock. Shy gilts
that simply avoid the boar when in estrus may breed normally with
additional boar experience. However, it is more desirable to
select replacement gilts that readily express estrous behavior at
an early age. Sows or gilts that object to entry of the boar may
have cervical, vaginal or urethral damage from prior breeding or
farrowing.
Bleeding at Mating
Hemospermia (blood in the semen) has been clinically associ-
ated with reduced conception rates. Bleeding boars should be
examined for trauma of the shaft and spiral part of the penis.
This occurs commonly from homosexual activity and with pen mat-
ing, when boars have difficulty entering sows. Sexual rest for
two weeks and elimination of the cause are necessary for return
to normal function. Bite wounds to the penis usually are
inflicted by an intruding sow or boar during breeding. One or
more boars in the pen may be injured. Affected boars should be
given antibiotics for 10 days and sexual rest for 3 weeks. After
this time, the boar should be test-mated and examined under
anesthesia if bleeding still occurs.
After breeding, virgin gilts and some sows may bleed from
cervical, vaginal or urethral injury. Most recover by the next
estrous period.
The diagnosis of a bleeding problem is made by observation
at mating, vaginal examination of the female and, occasionally,
examination of the boar under anesthesia.
Repeat Breedings
When repeat breeding is a herd problem, it is helpful to
determine the percentage of repeat breeding sows, the percentage
of sows with return intervals of 24 days or more, and the service
records of individual boars.
Repeat breedings, regular intervals. When more than 15% of
the bred sows return to estrus within 18 to 23 days, both male
and female infertility must be investigated. Primary considera-
tions are boar infertility and poor timing of matings that result
in lower conception rates. Very low conception rates often indi-
cate male infertility. Diagnostic efforts should include semen
quality examination, observation of boar behavior and mating
ability and a review of boar management and use.
Boars used excessively (more than 7 matings per week) on a
continual basis may have reduced fertility. Therefore, boars
should be rotated every 24 hours during heavy pen mating usage (2
boars for every 4 to 6 sows weaned per week). When hand-mating
or artificial insemination (AI) is employed, heat detection and
breeding times are important. Best fertility occurs when females
are bred 10 to 12 hours before ovulation. However, the interval
from the start of heat to ovulation is variable. That interval is
estimated to be 30 to 36 hours in gilts and 38 to 44 hours in
sows, but the detection of first signs of heat may be difficult
or delayed. For this reason, two services per heat period are
recommended. Table 4 gives a suggested breeding schedule based
upon the frequency of heat detection checks.
Table 4. Breeding schedule for hand-mating (hours after detecting
heat).
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Frequency of heat detection
_____________________________________________
Type of female once daily twice daily
_________________________________________________________________
Gilt 0 & 24 12 & 24
Sow 12 & 36 24 & 36
_________________________________________________________________
Double-mating increases conception rates by 10% to 30%
because it increases the chance of breeding near ovulation.
Nearly all the sows and at least 70% of the gilts should have
double services if adequate heat detection methods are used.
Boars exposed to high environmental temperatures (greater
than 90o F) for several days may suffer reduced fertility for
several weeks. Providing shade and water sprinklers for the boar
during hot weather reduces heat stress and semen damage (see
PIH-87, Cooling Swine). Likewise, acute systemic diseases that
cause a high fever in the boar can cause semen damage. Con-
versely, boars exposed to cold stress for several days during the
winter can be rendered infertile or subfertile for several
months.
Evaluation of semen samples will detect the infertile and
some subfertile boars. Other subfertile boars can be detected
only by evaluating the breeding record (farrowing rate and litter
size) of individual boars.
When an individual sow or gilt returns to estrus repeatedly
at regular intervals after breeding, lesions of the oviducts or
uterus should be suspected. The reproductive tract can be exam-
ined at slaughter or by surgery.
Another cause of reduced fertility in the female is uterine
infection. Bacteria may be introduced into the uterus at farrow-
ing or at breeding. Most of the affected sows return to normal
fertility by the next estrus unless a chronic urinary tract
infection exists. The sow with a urinary tract infection may have
bloody urine. A few animals may have a noticeable vaginal
discharge at approximately 16 to 17 days after breeding as they
abort the pregnancy. The boar with preputial infection often is
responsible for spreading infection among females.
Parvovirus is the most prevalent viral agent involved with
infertility. It rarely causes repeat breeding alone but often
results in mummification of fetuses. It occurs much more fre-
quently in gilts than in sows.
Eperthrozoonosis (Epy) has been suggested but not proven to
be a cause of infertility in the sow and gilt. This is most often
diagnosed as a problem in the fall. It is theorized that the
decrease in fertility during late summer is analogous to a sea-
sonal anestrus in other species rather than the effect of
eperthrozoonosis.
Repeat breeding with a delayed return to estrus. Normally,
the incidence of delayed (24 days or more) return to estrus fol-
lowing breeding is rarely higher than 3% to 4%. This percentage
may increase by 3 to 4 times for females mated in July, August,
September and October and when bred females are moved and mixed
during early pregnancy (up to 4 weeks postbreeding).
Delayed return to estrus suggests a loss of early pregnancy.
Uterine infections caused by viral or bacterial agents may be the
cause. Pseudorabies and parvovirus are viral agents that may
cause this problem. Bacterial agents associated with lower con-
ception rates and delayed return to heat include a wide variety
of organisms. Staphylococcus species (spp.), alpha- and beta-
hemolytic Streptococcus spp., Escherichia coli, Pasteurella mul-
tocida, Actinobacillus spp. and Eubacterium suis are commonly
present in the vagina and occasionally are introduced into the
uterus. A chronic leptospirosis infection may cause repeat breed-
ing in sows, but abortions are usually seen in other sows in the
herd. The involvement of Mycoplasma spp. and Ureaplasma spp. in
swine infertility is questionable.
Bacterial infections may be prevalent in the uterus or
vagina due to contamination from the farrowing barn, bladder
infections or breeding. Sanitation in the farrowing and breeding
facilities is extremely important when attempting to curtail this
problem. Removal of manure from behind sows in individual stalls,
on a daily basis, may be helpful.
Diagnostic efforts in repeat breeding problems should be
directed to:
1. Boar fertility and use.
2. Bacterial culturing of vaginal discharge.
3. Serological (blood) tests for pseudorabies and parvovirus.
Interpretation of the test results is difficult unless
results of a prebreeding test also are available.
4. Diagnostic procedures for early pregnancy detection, includ-
ing blood tests for progesterone or estrone sulfate, and
ultrasonic tests.
5. Examination of reproductive tracts collected at slaughter.
Bacterial culturing of these tracts may not be satisfactory
because of contamination of the organs with scalding water
and urine during slaughter procedures.
Abortions
An abortion rate of 1% to 2% is regarded as normal in the
swine breeding herd. The number increases slightly during the
fall months.
When many abortions occur, specimens should be submitted to
a diagnostic laboratory. An exact diagnosis is achieved only 20%
to 30% of the time. Abortions are caused by infectious, toxic,
genetic, metabolic, and other factors.
Infectious agents such as pseudorabies virus, Streptococcus
spp., E. coli, Erysipelothrix rhusiopathia, Salmonella spp.,
Pasteurella spp., and Actinobacillus pleuropneumonia cause sys-
temic disease, fever, and abortion in 2 to 14 days. They fre-
quently cause abortion storms. The disease condition currently
called Swine Infertility and Respiratory Syndrome (SIRS) or Mys-
tery Swine Disease normally follows a similar pattern. Sick sows
are observed first, followed by abortions and later by stillborn,
weak pigs and mummies. Nursing and weaned pigs often will have
pneumonia. A viral agent is the most likely cause. In Europe a
similar syndrome known as Porcine Reproductive and Respiratory
Syndrome (PRRS) has been associated with a new viral isolate
named the Lelystad virus. Researchers in the United States have
isolated a viral agent (BIAH-001) responsible for causing SIRS
which seems to differ antigenically from the Lelystad isolate.
Leptospirosis and brucellosis usually cause abortions
without prior evidence of systemic disease. Leptospira bratislava
is a recently investigated serotype which appears to be
widespread in swine herds and has been isolated from aborted
fetuses. Its incidence in abortion storms and swine reproductive
failure syndrome is very low. Toxoplasmosis and mycotic infection
cause sporadic abortions of a similar nature.
Toxic agents also cause abortions. Carbon monoxide poisoning
produced by poorly adjusted or unvented heaters in the farrowing
house causes late-term abortions without much evidence of sys-
temic disease in the sow. These aborted pigs have cherry red tis-
sues. Zearalenone is a mycotoxin produced in moldy feeds which
has been associated with causing abortions (See PIH-129, Mycotox-
ins and Swine Performance). Aflatoxin, ergot and vomitoxin are
agents produced by moldy feed, but they do not generally cause
abortion. Likewise, nitrates or nitrites in feed or water have
not been shown to cause abortion or fetal loss in swine.
Cold stress also can cause abortion in late-term sows. Usu-
ally this is caused by inadequate energy intake and acute heat
loss when bedding is scant or absent. These abortions may occur
during the winter when sows are on limited feed and lie on cold
concrete floors.
Diagnostic procedures for determining causes of abortion
include submission of aborted fetuses and placentae to a diagnos-
tic laboratory for culture and histologic examination; submission
of blood samples to be tested for pseudorabies, brucellosis and
leptospirosis; testing feeds for mycotoxins, and monitoring the
environment for carbon monoxide or cold stress.
Mummified Fetuses
Mummified fetuses occur in normal farrowings at a rate of 4%
to 5%. These represent fetuses that died in the uterus at 35 to
90 days gestation without causing sufficient uterine reaction
to result in abortion. Noninfectious causes of mummies include
placental insufficiency and lethal developmental abnormalities.
Parvovirus is the most common infectious agent known to
cause mummification; however, other viruses such as EMC, Entero-
viruses and the Swine Reproductive Respiratory Syndrome may cause
mummies in the litter. Parvovirus has been diagnosed most com-
monly with mummies and hence, has received a great deal of atten-
tion.
Infection of the litter with parvovirus must occur in the
first 70 days of gestation to cause fetal death. Fetuses usually
vary in age and size at death because the virus spreads slowly
from one fetus to another in the uterus. It occurs in both sows
and gilts, but most sows have immunity prior to breeding. Gilts
raised in isolation may not have prebreeding exposure to parvo-
virus, and they are much more likely to become infected during
pregnancy. Gilts can be tested for immunity (seroconversion) to
parvovirus prior to the breeding period, and immune animals can
be used for breeding. Exposing the gilts and animals being intro-
duced to the breeding herd to boars and older sows or their
manure generally improve seroconversion rates. Additionally, the
gilts should develop immunity to other viral agents in the herd.
Gilt herds which have been maintained in isolation for disease
control may rely on prebreeding vaccination for parvovirus pro-
tection.
Parvovirus can be readily identified in mummified fetuses by
laboratory examination. This is the most reliable method of diag-
nosis. Elevated serologic titers are not significant evidence
that parvo caused fetal loss unless blood samples also have been
taken before breeding and a rise in parvovirus antibodies can be
demonstrated in the second sample.
Stillbirths
A stillbirth rate of 6% to 8% is common in farrowing units.
This represents death of the fetus just before or during farrow-
ing. These rates increase rather dramatically as the sow ages,
particularly after 6 litters.
There are several factors that contribute to increased
stillbirths. Infections such as leptospirosis or pseudorabies and
carbon monoxide toxicity may increase stillbirths, but abortion
will be present in other sows if these agents are present.
Overweight sows and gilts or those subjected to heat stress
have higher stillbirth rates. Likewise, sows or gilts that are
uneasy in the farrowing facilities or are disturbed during far-
rowing are likely to have slower farrowings with more still-
births. Low blood glucose, hemoglobin or calcium may reduce the
responsiveness of the uterine muscles and cause delayed or pro-
longed labor resulting in stillbirths.
Sows with large litters and prolonged parturition and sows
with small litters, but large pigs, have a higher incidence of
stillborn. Gilts with small pelvic size also have higher
stillborn rates. Stillbirths can be significantly reduced if far-
rowings are supervised and sows with prolonged labor are treated
with oxytocin. Supervision of farrowings has been facilitated by
synchronized farrowings with prostaglandin and oxytocin.
Diagnosis of the cause of stillbirth involves testing for
infectious agents, carbon monoxide toxicity, altered blood chem-
istry, observing the farrowing process to determine if still-
births are related to prolonged labor and determining the age and
parity of problem sows.
Small Litters
Small litters are considered significant when more than 15%
of sows farrow fewer than 7 pigs. Major factors affecting litter
size are breed and heterosis of the dam, number of previous
litters (parity of the sow), duration of prior lactation, and
adequacy of male services.
It is obvious that breed and heterosis of the dam will
influence the number of pigs farrowed. Selecting gilts from prol-
ific dam and sire breed lines will generally increase litter
size.
Litter size generally increases with each parity beyond the
second litter, but litter size weaned is generally reduced after
6 litters. To maintain maximum litter size and replacement effi-
ciency, a herd should be approximately 25% to 30% first and
second litter sows.
Breeding sows at less than 21 days after farrowing will gen-
erally reduce litter size. Litter size tends to increase as the
interval from previous farrowing is increased, up to about 35
days. However, total pigs per sow per year are significantly
higher with the shorter lactation period. The appropriate weaning
age for a given production unit will depend upon nursery manage-
ment and the reproductive response of the weaned sows.
Inadequate boar coverage also will decrease average litter
size. Subfertile or overused boars can cause small litters.
Improper timing at mating, breeding too early or too late, will
cause individual sows to recycle or have small litters. Poor con-
ception rates in pen or pasture breeding will accentuate the boar
usage leading to overusage, small litters, and increased recy-
cling. With handmating, the boar/sow ratio recommended is 1 boar
per 2 sows weaned weekly. This results in approximately 4 matings
per week for each boar. Pasture and pen mating ratios should be
about 1 boar to each 2 to 3 sows weaned per week with the boars
working in groups of 2 in a pen of 8 to 12 sows and another 2
boars rotated in their place at 24 hour intervals. This maximizes
boar usage through less competition but minimizes overuse of
individual boars.
Diagnostic procedures for determining the cause of reduced
litter size in the herd include assessing boar fertility and use,
genetic factors, breeding practices and average parity of the sow
herd. A secondary approach is determining the possible presence
in the herd of infectious agents that interfere with reproduc-
tion.
Pregnant Sows That Fail to Farrow
Occasionally, sows or gilts that were presumed or diagnosed
pregnant fail to farrow. Viral infections that cause death of the
entire litter during early gestation can result in sows that look
pregnant but never farrow. Parvovirus introduced at 30 to 60 days
of gestation is a likely cause.
Misdiagnosis of pregnancy occurs with variable frequency
depending upon the method used and the skill of the diagnosti-
cian. Generally, sows that are incorrectly called pregnant (false
positive) can be identified by good heat detection methods but
anestrus during the late summer and fall months may mask the mis-
diagnosis.
Pseudopregnancy in the sow occurs when noncycling sows or
gilts are exposed to estrogenic agents such as zearalenone (some-
times produced in moldy feed). Concentrations of 4 to 10 ppm
zearalenone will cause anestrus. These sows fail to return to
estrus, react questionably to pregnancy testing dev-
ices that detect fluid in the uterus and have some mammary
development. Pseudopregnancy also may occur more frequently in
sows bred in early fall.
Procedures for diagnosis of failure to farrow are directed
to assessments of pregnancy detection procedures, the possibility
of moldy feed and infectious agents. Examination of reproductive
tracts at slaughter may reveal uteri full of mummified fetuses.
These should be tested for parvovirus. Sows with empty tracts,
which have large pale, mature corpora lutea but no old corpora
lutea or new large follicles, and a thickened congested uterine
lining suggest pseudopregnancy. If available, feed from previous
periods should be tested for zearalenone.
Summary
The first step in investigating swine reproductive failure
is recognition of the problem with a thorough review of produc-
tion records. Many times several problems exist simultaneously,
but the attention directed toward these problems often improves
the reproductive management and productivity even when a diag-
nosis has not been confirmed.
Other recommended PIH fact sheets:
PIH-1 Management of the Boar
PIH-8 Managing Sows and Gilts for Efficient Reproduction
PIH-59 Infectious Swine Reproductive Diseases
PIH-74 Management of Developing Gilts and Boars
PIH-87 Cooling Swine
PIH-89 Managing the Gilt Pool
PIH-129 Mycotoxins and Swine Performance
REV 12/92 (7M)
______________________________________________
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