Farrowing Management and Piglet Losses
When do losses of piglets occur and why?
The loss of embryos and fetuses during pregnancy, and loss of piglets
at birth, has been well documented in swine and in swine production
systems. Approximately 40% of potential piglets are lost as embryos
and fetuses before day 40 of gestation.
The reasons for these high rates of litter reduction may be a natural
mechanism to ensure pregnancy can be maintained or some piglets are
born to sustain the species, or may result due to defective embryos,
unfavorable uterine environments, and fetal competition for space. At
a much lower frequency, some fetuses die in the uterus before farrowing.
These undergo degeneration and depending upon when they are lost during
gestation, may appear as mummified very small or almost normal sized
fetuses at birth. Pigs that are fully formed, but fail to survive the
birth process are classified as stillborns.
How common are stillborns?
Stillborns average 6 to 7 % and but range anywhere from 5 to 10% across
farms. 1999 PigCHAMP summary data indicates the US average is 0.2 mummified
fetuses and 0.8 stillborn pigs per litter. It is reported that the USA
has a higher stillborn and preweaning mortality rate than other parts
of the world. This is thought to be due to the lower number of farrowing
personnel to sows, which can often exceed 1:250. It is suggested that
a 1:30 ratio could reduce the incidence of stillborn pigs. In herds
where stillbirths are higher than 10%, it is suggested that infectious
causes should be investigated.
Stillbirths are related to dystocia or difficult birth during farrowing.
Stillborn pigs are not identified as the runts in a litter and are observed
to occur more frequently in litters with less than 5 pigs and when more
than 14 are born in a litter. Stillborns are observed to be low when
8 pigs are born (.04) but this number increases as litter size increases.
Stillborns may occur due to premature rupture of the umbilical cord,
early detachment of the placenta from the uterus, or restricted blood
flow to the piglet during intense uterine muscle contractions, or during
passage through the pelvic canal.
It is also observed that the umbilical cord can get wrapped around
the piglet's body and get pinched or closed off in the pelvis. Stillborns
are also observed to increase when farrowing is induced earlier than
day 112 of gestation or if gestation is prolonged past day 116.
What is the ultimate cause of piglet loss?
The fetal lungs acquire the ability for gas exchange at birth. Major
changes in lung development occur at days 95-100. During the birth process
and soon after liquid is removed from the lung. It has been estimated
that the physiologic half-life of oxygen is less than 5 minutes and
irreversible brain damage occurs within 5 minutes of umbilical rupture
or even impeded blood flow through the umbilicus. It is thought that
93% of all intrapartum deaths are due to umbilical rupture since most
stillborn pigs have broken umbilical cords. Fetal hypoxia (lack of oxygen)
is most related to piglet survival at farrowing and even temporary hypoxia
during birth may cause permanent brain damage and reduce liveborn pig
survival. Pig fetuses are very susceptible to intrauterine asphyxia.
A period of prolonged intrauterine hypoxia caused by uterine hypertension
(high pressure due to contractions) could deplete energy stores (glycogen)
needed by the piglet after birth to survive. Most of the pig's glycogen
is found in skeletal muscle and this is essential both for movement
and temperature regulation. In cases of intrauterine asphyxia, inhalation
of fetal meconium (feces) is very common, and 87% of stillborn pigs
that die by asphyxiation, have meconium in the oral cavity.
The duration of parturition is highly related to stillbirths and therefore
short deliveries are considered highly desirable. As duration of farrowing
increases from 1 to 8 hours, stillbirths increase from 2.5 to 10.5%.
Interestingly, more than 2/3 of all stillbirths occur in farrowings
lasting less than 4 hours. Over 80% of stillborn losses occur in the
last 1/3 of the litter in sows. Stillbirths in gilts can occur more
frequently in the first two pigs born. The stillbirth rate increase
as the interval between pigs exceeds 20 minutes.
The average birth interval between successive live pigs is 13 to 18
minutes but between a live pig and stillborn pig is 45 to 55 minutes.
However, the intervals are longer between the first two and the last
two pigs born in a litter.
Generally speaking the last pig born has less than a 50% chance of survival
in any litter. Most piglets must leave the space they occupied during
pregnancy and enter empty space previously occupied by a delivered pig.
From there, they move through the uterine body, the cervix, and the
vagina, and finally exit though the vulva.
The umbilical cord is 60 to 75 cm long and if the 120-180 cm of the
uterus does not shorten sufficiently after emptying, then rupture of
the cord is inevitable. Therefore delivery must subsequently occur within
5 minutes of rupture. Umbilical rupture or premature placental detachment
is thought to occur in 20% of stillborn pigs from the first third of
the litter and involve up to 50% of stillborn pigs in the last 1/3rd
of the litter.
It is not known whether prostaglandin administered during farrowing
at this stage, could improve the process.
Stresses on the sow and stillbirths.
Temperatures above 30 °C in late gestation from days 102 to 110
increase rate of stillbirths and reduce piglet birth weight. The mechanism
for this remains unknown however. Lack of feed and absence of nesting
material is also suspected of increasing sow stress levels. Stress has
been shown to reduce oxytocin levels during parturition, which would
tend to prolong delivery. Therefore it is important to provide conditions
that will allow the sow to remain calm and comfortable.
How can you tell if pigs were stillborn?
Stillborn pigs appear normal but they can be distinguished from other
pigs that were born alive and died later after birth by the lung flotation
test. This test requires the lungs to be dissected and placed in water.
If the lungs float, the pig had air trapped in its lungs and was born
alive and breathed. If the lungs sink, they contained no air and the
animal never breathed. Stillborns can also be classified into type I,
which are prepartum deaths due to infection, and type II, which are
stillborns that occur during parturition, which are usually non-infectious.
Is lack of uterine contractions involved in stillbirths?
Uterine inertia is rare even during prolonged delivery. However, in
cases where this was identified, administration 10 I.U. of oxytocin
returned the pattern of contractions to normal for ~10 to 15 minutes.
However, this induction of massive contractions could potentially disrupt
blood flow to the placenta.
Can any treatments reduce stillbirths?
- Assisted births
An assistant present at farrowing can reduce the incidence of stillbirths.
Obstetrical assistance will minimize stillbirth rates, and inducing
farrowing during the normal working hours will improve the frequency
of observed farrowings. It has been reported that ~25% all stillborn
pigs can be revived by artificial respiration using a small funnel over
the snout. In addition, during assisted farrowing, an attendant can
successfully remove fluid and mucus that obstructs the pig's airway
and facilitate normal breathing. It was observed that 18 hour farrowing
supervision through the night and continuing into the daytime, increased
the number of pigs saved.
ACTH (25 to 60 I.U.) administered to sows i.m. on day 110 has been shown
to reduce duration of parturition and reduce stillbirths by 40-50% (0.2
pigs/litter saved). This thought to be related to increased corticosteroid
levels reaching the fetal lungs and gut and facilitating precocious
maturation. Estradiol benzoate given to sows also was reported to reduces
stillborn rates. It was suspected that estrogen increased muscle gap
junctions, increased oxytocin receptors, and relaxin receptors in both
myometrium and cervix. This collectively improved the ability to deliver
What are the factors involved in live piglet loss?
Mortality of pigs born alive results from a variety of causes. The industry
has set a 10% death loss as acceptable and USDA and PigCHAMP figures
indicate a 10 to 14% range for pre weaning mortality. Producers in the
top 90th percentile in production records have a preweaning mortality
of 8.3%. Of pigs that are liveborn and subsequently die, >50% die
within 4 d of farrowing. These typically involve weak pigs that are
crushed and die of starvation. Mortality in liveborn pigs is also associated
with sows that farrow early, especially those that are induced to farrow
on d 110 compared to 112. At day 109 of gestation, piglets can be delivered
but many pigs do not survive past one day post-partum. Even pigs from
days 110-111 have reduced survival.
Colostral Immunity and Milk
Immunity for the piglet is not obtained through placental transfer of
antibodies during gestation and therefore it is born with very limited
immune protection. Further, the piglet has finite reserves of body energy
and may even be energy deficient after a long and stressful delivery
process. It then becomes even more critical for the piglet to obtain
both antibodies and energy through the colostrum soon after birth. The
piglets should begin to suck within 10 to 35 minutes of birth. If they
fail to do so, they can be helped to nurse or even given colostrum.
Colostrum will serve to protect the piglet against a host of microbes
and also allow it to cope and survive in its new environment through
the energy expending activities of nursing, seeking warmth, and moving
to prevent being crushed by the mother. Nursing soon after birth and
nursing as frequently as possible are highly advantageous for piglet
survival since the newborn obtains antibodies only through colostrum
ingested within the first 24 h after birth.
Antibodies in the mother's milk are very high at this time and when
ingested, are readily absorbed.
The antibodies in the gut also serve to provide protection within the
gut of the piglet. After 24 h, gut acids in the piglet begin forming
and stomach pH lowers. After this time period, immunoglobulins from
the mother's milk cannot pass through the gut wall and are destroyed.
Thus, only the antibodies that are obtained in this manner during this
short period will serve to protect the piglet over the next few weeks.
What other factors can help reduce preweaning mortality?
Use of heat lamps. Three lamps used strategically have been shown to
be beneficial immediately near the time of birth. Lamps placed behind,
and on the sides of sows, but which do not place excessive heat on the
sows, can improve piglet survival. Keep all three on during farrowing,
and then remove the one behind when farrowing is completed.
This will keep pigs from getting or staying behind the sow where they
are prone to be crushed when the sow sits down. Then remove the second
side lamp at 48 h, which will keep the pigs located to only one side
for warmth. If open flooring is used in the farrowing crate a floor
mat should be used to reduce drafts on the pigs.
What about crushing?
Crushing has been linked to sow behavior, crate style, size of the sow,
and weak pigs. Piglets that suffered hypoxia or dystocia will deplete
their body stores of oxygen and even energy more quickly. These pigs
will be born weak and may therefore be the ones that are too weak to
move and are more susceptible to crushing, chilling and starvation.
Crates have been shown to reduce crushing by 3% compared to outdoor
Crushing remains a serious problem and crate design may be an important
aspect. Reports have indicated that free stall crates may crush more
pigs than more restrictive crates. Further, more sophisticated crates,
that utilize hydraulic cylinders or other mechanisms to slow the sow's
when lying down, can reduce pig loss by 0.8/litter.
Other methods to reduce crushing have involved the use of raised flooring
in the center of the crate to prevent the frequency and ease of pigs
being there when the sow lies down.