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Methods for Improving Pre-Weaning Survival Rates of Piglets:
II. Farrowing and Dystocia
Jeffrey Wiegert1
and Mark Estienne2
1Department of Animal and Poultry Sciences and
2Tidewater Agricultural Research and
Extension Center, Virginia Tech
INTRODUCTION
Knauer and Hostetler (2013) concluded that increased sow productivity in the U.S. between
2005 and 2010 occurred primarily as a consequence of improved management and genetics. The
researchers examined data representing annual production by approximately 1.8 million sows,
and reported increases in total litter size and pigs born live. Although the number of pigs weaned
increased as well, the percentage of pigs that died before weaning was relatively constant
between 2005 and 2009, and actually increased from 2009 to 2010. Those data do not represent
all pig farms in the U.S. and may or may not be applicable to many small-scale and niche market
operations. They do suggest, however, that there is potential for further increasing sow
productivity by decreasing pre-weaning mortality.
Pre-weaning mortality in piglets may be interpreted as a welfare concern, and certainly
represents a large economic loss for the producer. In fact, some estimates place the average value
of each newborn piglet at just under $25 (Lay et al., 2002), although this may vary greatly
according to breed, season, input costs, and current market prices. Producers with high pre-
weaning mortality wean fewer pigs per sow per year and miss the opportunity to capitalize on
good breeding herd performance (e.g., high farrowing rates, large litter sizes, etc.). Maximizing
pre-weaning survivability, which is the percentage of piglets born alive that survive to weaning,
then becomes one of the most important production goals of the sow farm.
This paper is the second in a three part series addressing methods for improving pre-weaning
survivability in pigs and focuses on techniques to be employed during and immediately
following farrowing. Emphasis will be placed on how to properly assist sows during difficult
farrowings.
Persons who wish to be added to, or deleted from, the Small-Scale and Niche Market Pork
Producers electronic mailing list should notify Mark Estienne at [email protected].
Small-Scale and Niche Market Pork Production Bulletin No. 5; February 6, 2015 Virginia Tech- Tidewater Agricultural Research and Extension Center, Suffolk, VA
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METHODS FOR IMPROVING PIGLET SURVIVAL
Indications that farrowing is imminent
Recognizing signs that farrowing is imminent is necessary to prepare for pig arrival. Physical
and behavioral changes associated with farrowing, as well as approximate times from expression
of behavior to commencement of farrowing, are presented in Table 1. Streaming milk from the
teats is the most reliable indicator that farrowing will soon occur. Sows with good milk letdown
will begin farrowing within 12 to 24 hours, and often sooner.
Table 1: Indications of impending farrowing and approximate time until farrowing
Physical / Behavioral Indicators Approximate Time Until Farrowing
Nest Building Behavior1
48 to 72 hours
Restlessness and Agitation 48 hours
Milk Drops (i.e., udders fill with milk) 24 to 36 hours
Vulva Swelling 12 to 24 hours
Streaming Lactation (i.e., milk dripping from teats) 12 to 24 hours
Increased Respiration Rate2
24 hours
Uterine Contractions less than 2 hours
Expulsion of Fluids and Meconium (feces from
fetuses)
less than 1 hour
1If provided with suitable substrate, such as straw, sows will attempt to use the substrate to build a nest.
In “barren” environments (e.g., farrowing crate situated on a concrete floor) the nest building behavior is
manifested in such activities as pawing at the floor. 2Range of respiration rates (breaths per minute) for sows at 24, 12, and 6 hours pre-farrowing are 35 to
45, 75 to 85, and 95 to 105 (Straw and Meuten, 1992).
Dystocia
Occurrences of dystocia (difficult, impeded, or abnormal birth) are relatively uncommon and
occur at a rate of approximately 3% in properly managed sows (Runnels and Clark, 1992).
However, when dystocia does occur high piglet death loss may result. Dystocia will extend the
duration of farrowing and piglets may die in the reproductive tract due to suffocation, or after
delivery due to the combined effects of oxygen deprivation and physical injuries and/or delayed
colostrum intake.
The birthing interval is the amount of time that passes from the birth of one piglet until the
birth of the next piglet or presentation of placentae (tissues that surround fetuses in the uterus).
Normal birthing interval is approximately 20 to 30 minutes. Some variation in the birthing
interval, particularly at the beginning and end of farrowing, should be expected. A birthing
interval exceeding one hour is abnormal, and may indicate dystocia.
The leading causes of dystocia in swine, as well as symptoms and appropriate methods of
treatment, are presented in Table 2. Correctly diagnosing the cause of dystocia is necessary to
determine the proper treatment. Treatment methods may be hormonal or physical depending on
the cause of dystocia.
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Table 2. Causes of dystocia, symptoms and recommended treatment for sows (Sherrie Clark-
Deener, D.V.M.; Virginia-Maryland Regional College of Veterinary Medicine, Blacksburg;
personal communications)
Cause Percentage of Cases Symptom Treatment
Uterine Inactivity 37 Weak or Absent
Contractions
Treatment with
Oxytocin
Incorrectly Positioned
Fetus
33 Strained Contractions Physical Intervention
Obstruction of Birth
Canal
13 Strained Contractions Physical Intervention
Abnormal Uterus 10 Normal Contractions
but No Piglet Birth
Physical Intervention
Size of Fetus too Large
for Size of Sow Pelvis
4 Strained Contractions Physical Intervention
Maternal Excitement 3 Restlessness and
Irritability
Stimulate Lactation /
Remove Distractions
Hypocalcemia (low
blood levels of calcium;
also called “milk fever”)
Less than 1 Instability or
Inability to Stand
Injectable Calcium
(under guidance by
veterinarian)
Hormonal Treatment. Oxytocin is a protein hormone that is secreted from the pituitary gland, a
garden pea-sized organ lying just below the brain. Among its functions is the excitation of
smooth muscle fibers in the uterus and mammary glands. In this way, it is responsible for both
uterine contractions during farrowing and later, for lactation.
Blood concentrations of oxytocin increase immediately prior to farrowing. Massaging the
sow’s underline, hand-milking individual nipples, and encouraging piglet suckling will increase
oxytocin demand in the mammary and stimulate secretion from the pituitary gland. The
resulting secretion of oxytocin into the bloodstream makes the hormone available for use by the
uterus, and may expedite a slow farrowing. However, sows with weak contractions, no
contractions, or long birthing intervals during the latter-half of farrowing may benefit from
oxytocin treatment.
Indeed, if uterine contractions do not resume following mammary stimulation as described
above, administration of exogenous (i.e., injectable) oxytocin may be appropriate. Always check
the birth canal for signs of obstruction before giving oxytocin. Do not administer oxytocin if a
piglet is stuck in the birth canal. The increased pressure from strengthened uterine contractions
may rupture the umbilical cord of the trapped piglet. Without oxygen from the blood carried in
the umbilical cord, the pig will die of suffocation and be farrowed stillborn.
Following are some notes regarding the proper use of oxytocin:
The dose of oxytocin typically recommended is 0.5 cc (10 I.U.), given intramuscularly
or injected into the vulva.
Oxytocin should not be administered until after the sixth piglet is born.
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No more than two injections of oxytocin should be given during a single farrowing
event. The second injection should be given approximately 30 minutes after the first,
and only if contractions do not resume following the first injection.
Overdosing of oxytocin will induce a refractory period of up to three hours during
which hormone receptors become desensitized to both internally produced and
externally injected oxytocin. Uterine contractions and milk letdown may cease during
this time.
Oxytocin requires a veterinary prescription.
Physical Intervention (Sleeving). Better known as sleeving, physical intervention is the act of
palpating the uterus to manually remove a blocked or incorrectly positioned fetus. Dams with
stuck piglets will appear distressed and may vocalize and change positions often. Some fluid and
meconium (feces from fetuses) discharge will likely be present as well.
Palpating the uterus is an invasive process and carries the risk of irritating the reproductive
tract, disrupting normal contractile rhythms, and introducing foreign contaminants. Any injuries
or infections associated with sleeving may decrease subsequent feed intake and milk production
and if left untreated, may cause long-lasting disease, decrease future reproductive performance,
or, in extreme cases cause death of the sow. Adherence to proper sleeving technique should be
followed on every occasion.
A step-by-step procedure for sleeving is provided below:
1. Remove all jewelry (rings, watches, etc.) from the arm to be sleeved. Persons with long
fingernails should not sleeve a sow.
2. Sleeve the arm corresponding to the side on which the sow is lying. For example, if the
sow is lying on her right side, the producer should sleeve with their right arm.
3. Wear a clean shoulder-length obstetrical glove and lubricate the glove generously. Take
care not to contaminate the glove before entering the sow.
4. Lubricate the vulva and vagina before entering the sow.
5. Enter the vagina with fingers together and pointed forward. Keep the thumb tucked into
the palm when entering and while inside the reproductive tract.
6. Grasp the piglet gently, but firmly, using an appropriate grip. Pictures representing
appropriate grips for front-facing and back-facing pigs are presented in Figure 1.
7. Pull pig out at a slight ventral angle (towards the sow’s feet) to minimize pelvic
resistance.
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8. Immediately re-enter the sow to remove other piglets whose birth may have been
blocked.
9. Continue sleeving every 25 minutes or until normal farrowing resumes.
Closely monitor assisted sows for a minimum of three days following farrowing, as they may
suffer lameness, pelvic inflammation, vaginal/uterine infection, loss of appetite, and/or decreased
milk production. Contact a veterinarian if any of the following symptoms appear: feed and water
refusal, inconsistency in urination and defecation, off-color urine, greater than normal pus and
mucus discharge, or black and bloody discharge from the vulva. A veterinarian may prescribe
antibiotics, drugs for pain mitigation and/or drugs to decrease swelling.
Savaging. During and immediately following farrowing, gilts and sows will occasionally attack
and kill their newborn piglets. Maternal infanticide, better known as savaging, is relatively
uncommon and often overlooked in pig production, but in extreme cases can be responsible for
10 to 25% of total pre-weaning mortality (Spicer et al., 1986; Ahlstrom et al., 2001; Harris and
Gonyou, 2003). Survey data collected and submitted by employees of commercial farrowing
farms in central Canada indicated that 5.3% of first-parity gilts show some degree of aggressive
behavior towards their offspring, with 2.9% of gilts fatally attacking one or more piglets (Harris
and Gonyou, 2003). It is likely, however, that these values underestimate the true occurrences of
piglet-directed aggression, as gilts in the study were observed only sporadically throughout the
workday and no observations were made in the evening and nighttime hours. Other reports have
suggested piglet-directed aggressive behaviors in up to 15% of dams (Turner, 2011).
The exact reason why gilts and sows savage their piglets is unknown. One could speculate
that gilts associate their unfamiliar birthing pain with their newborn piglets and attack them out
of fear or anger. In reality, the true cause of savaging is likely not that simple, and may in fact be
the result of many factors. For example, even though confinement farrowings (i.e., in farrowing
crates) statistically yield the highest total pre-weaning survivability (Blackshaw et al., 1994),
incidences of savaging are typically increased in farrowing crates when compared to loose-
housing farrowing systems (Cronin et al., 1996). Other factors, such as social stress (pen-mixing
stress) during mid-gestation and discomfort or unfamiliarity with the farmer or farrowing
technicians may increase the expression of savaging behaviors. Providing environmental
enrichment (e.g., straw bedding) and continuous lighting during farrowing has been shown to
decrease both the incidences of savaging and the number of piglets killed by savaging (Harris
and Gonyou, 2003; Ringgenberg et al., 2012).
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Figure 1: Appropriate grips for sleeving piglets (National Hog Farmer, 2012)
Over-the-Head Technique
Thumb-in-Jaw Technique
Hock Technique
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Gilts that attack their piglets should be culled from the breeding herd. Harris et al. (2003)
reported that 14% of sows that showed savaging behavior in their first litter expressed similar
behaviors in subsequent farrowings, while less than 1% of sows that did not savage their first
litter showed savaging behavior in later farrowings. Studies reviewed by Turner (2011) showed
some success in decreasing savaging events after placing selection pressure against the trait (i.e.,
culling savage gilts and selecting replacement gilts from females with docile temperaments).
When gilts or sows are displaying aggressive behaviors towards their newborn offspring,
pigs should be removed from the farrowing area and kept in a warm and dry holding area until
the risk subsides and it is safe to reintroduce them with the dam. Usually, savaging behavior
stops once farrowing has concluded and consistent nursing begins.
24/7 Farrowing Supervision
Supervised farrowings may be the most beneficial management strategy for improving
piglet survivability. Producers who provide continuous farrowing care are better prepared to
assist with dystocia, respond to the cries of injured piglets, remove placenta from the heads of
suffocating pigs, dry off newborns, encourage suckling and colostrum consumption, and adjust
fans and heat sources to better regulate the environment. Indeed, large increases in pre-weaning
survivability are achieved when farrowings are attended by a trained and competent individual
(Britt, 1986). Large decreases in the number of stillborn pigs is often seen as well, suggesting
that many dead pigs classified as “stillborn” by the producer were in fact live-born animals that
could have lived to weaning had they received timely assistance (White et al., 1996).
In one study, the simple act of towel-drying and placing neonatal piglets under a heat source
improved piglet survivability, decreased the number of stillborn pigs, and decreased the number
of pigs crushed by maternal overlay (Andersen et al., 2009). Litter size at weaning and
individual pig weaning weight may also be improved by providing individual pig attention
during farrowing (White et al., 1996).
Attending all farrowings is time and labor intensive, and may not be feasible for many small-
scale producers. To some extent, the timing of farrowing can be controlled by use of
commercially available prostaglandin-F2α (PGF2α) products such as Lutalyse1 (Zoetis, Inc.;
Kalamazoo, MI). Intramuscular injection of 2 mL (10 mg) of Lutalyse causes farrowing in sows
approximately 30 hours later, and is a potentially useful strategy to coordinate timing of
farrowing with labor availability. For example, pregnant sows could be injected with Lutalyse at
say 9:00 a.m. on Monday, resulting in most sows farrowing Tuesday afternoon. Producers
desiring to use this technology must know exact breeding dates and the average length of
gestation for their herd, and only inject Lutalyse within three days of normal farrowing.
For example, if average length of gestation in your herd is 115 days, then Lutalyse should
not be administered before day 112 of gestation. Otherwise, piglets may be born immature and
with low viability. Research has shown that litters from sows that were induced to farrow with
1 Mention of a trade name or proprietary product does not constitute a guarantee or warranty by
Virginia Tech and does not imply its approval to the exclusion of other products which may be
suitable.
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PGF2α and attended by a trained individual showed decreased mortality rate and number of
stillborn pigs when compared to non-induced and unattended litters. Further, average litter
weight was greater in induced and attended farrowings on both three days and twenty-one days
post-farrowing (Nguyen et al., 2010).
CONCLUSION
Focusing on pig health and well-being during and immediately following the process of
farrowing will decrease pig mortality rates and stillbirth percentages while increasing the number
of pigs weaned per sow per year. These strategies, though, are time and labor intensive,
particularly on small-scale farms, and producers will need to assess the costs and benefits of their
application. Increased animal welfare resulting from improved piglet survival should be
considered, as well. A few points to bear in mind throughout farrowing that may improve piglet
pre-weaning survivability are:
Be able to recognize the physical and behavioral indicators of impending farrowing.
Know how and when to intervene and assist with difficult farrowings.
Have any necessary equipment, drugs, and medicines ready to be used in the event of
dystocia.
Cull gilts that savage piglets or that show piglet-directed aggression.
During farrowing by savaging gilts or sows, be prepared to move at-risk pig to safety.
If possible, attend every farrowing and provide maximum individual piglet attention.
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