Lactation failure in the sow


Milk from the lactating sow is crucial to supply neonatal piglets with nutrition and antibodies to help them grow and thrive. In the period surrounding farrowing and lactation, sows and gilts are going through many physiologic changes that must be critically managed to ensure high levels of milk production. When these lactation levels are inadequate, a condition called Postpartum Dysgalactia Syndrome (PDS) occurs. PDS is characterized by any of the following: low milk production, anorexia (off-feed), fever, mastitis, and uterine infections; however, some females may not show obvious clinical signs other than producing piglets with below average weaning weights. PDS can be caused by changes in sow/gilt body composition and metabolism, response to stress in the environment, and the presence of infectious agents



  • Describe normal teat function and lactation
  • Define postpartum dysgalactia syndrome (PDS) and associated clinical signs
  • Discuss treatment and prevention strategies for PDS


Normal Lactation

Lactation (milk production) is a very important process in pig production. The lactating sow/gilt is the major source of neonatal piglet nutrition and immunity. It’s critical to ensure milk production is functioning properly to provide baby piglets nutrients essential for growth and health. The remainder of this article will use the term “sow” to include all breeding females (unless otherwise specified), knowing that gilts are included in that group as well.

The lactating sow is the primary source of nutrition for her litter, and her unique mammary system allows for the successful feeding of that litter.  Female pigs have paired mammary gland located in two parallel lines on the underside of their body.  The total number can vary from 12-22 glands.

After a sow gives birth, milk ejection is highly controlled by the hormones oxytocin and prolactin. Both of these are released as a result of vigorous nuzzling and suckling from the piglets at the teats. The sow has a very high threshold for the release of oxytocin, meaning there must be extensive stimulation (in the form of piglet suckling/nuzzling) for its release. Piglets can be seen nuzzling and suckling at the mammary glands for minutes at a time, but the actual milk letdown itself lasts only about 15 seconds. Normal, healthy piglet litters generally suckle every 45-60 minutes or about 30 times per day. It takes the sow about 35 minutes to refill her mammary glands in preparation for the next lactation time (Hurley 2010).

Females will continue to produce milk in increasing amounts given proper suckling intensity. This depends on the frequency of nursing, litter size, and the age and weight of the piglets. Repeated milk removal is the major factor in maintaining lactation. In other words, the more often a mammary gland is emptied, the more opportunity it has to refill with an increasing amount of milk. Heavier piglets in general have a stronger suckle action, stimulating a stronger oxytocin release, and greater milk flow. Most sows reach peak lactation levels at 21 days post-farrowing (Hurley 2010).

Lactation is maintained only by those glands that are actively and continuously suckled.  If a mammary gland is not properly nursed or unused, involution occurs. The gland can still be suckled and productive after 24 hours with no activity, but by three days after non-use, the lactation shutdown is irreversible. After weaning, the involution process is nearly complete by 7 days.

Recent studies (Farmer 2012) have shown that glands suckled in first lactation will produce more milk and a have a better foundation for redevelopment and increased lactation for the second lactation.

Transition from Gestation to Lactation

The transition from gestation to lactation is a dynamic and complex process. It involves major changes in sow metabolism, hormone levels, and body composition. Most mammary gland development occurs in the last one-third, or after 75 days, of gestation under the influence of increasing estrogen levels from the placenta. There is a large shift in the makeup of the mammary glands, switching from depositing fat to depositing protein and developing the structures needed for lactation. If the mammary system is not properly developed and there are deficiencies in sow nutrition, health, or stresses in their environment, a poor transition from gestation to lactation will result, and the overall risk of PDS increases.


Postpartum Dysgalactia Syndrome (PDS): Signs and Contributing Factors

Clinical Signs

The term PDS has been adopted to encompass not only the clinical signs, but physiologic, metabolic, and environmental factors surrounding sow lactational failure. Previously, the term MMA (mastitis, metritis, and aglactia) has been used to describe the mammary gland infection, uterine infection, and milk production decrease often seen in this failure. Sow mammary glands appear swollen, firm, red, have a reduced and/or watery/bloody milk discharge. Sows may also have a vaginal discharge, fever, reduced appetite, and lethargy. Piglets may also be subsequently affected by a reduced milk intake and potential ingestion of pathogens. They may appear to be lethargic, have poor body condition and growth, and diarrhea. Although many of these clinical signs are fairly obvious, it is not uncommon to see sows with no clinical signs of PDS, other than noting a decreased weaning weight of piglets on weaning day.

Factors in the development of PDS

Three major factors can contribute individually or act together bring about PDS. They are: 1) body composition/metabolism or “body building syndrome” 2) response to stress and 3) infectious agents.

          Body Composition and Metabolism. Management of feeding in the late gestation and early farrowing periods are important to reduce the metabolic risk factors associated with PDS. First of all, the genetics of most modern sows lend themselves to being in a catabolic state, or a state of breaking down their stored body fat and muscle, immediately prior to farrowing. These body stores (fat and muscles) become the sow’s main source of energy during lactation (Papadopoulos 2010).

With this catabolic state in mind, two “body building” syndromes are associated with PDS (Zimmerman 2019). Fat Sow Syndrome (FSS), occurs when sows gain excessive weight in gestation and enter farrowing too heavy, causing a more prolonged birthing process, increased stress for dam and litter, and decreased appetite and thirst in early lactation. It’s important to have sows eat and drink well during lactation, as water is a major component of milk and milk production uses 65-70% of the lactating sow’s daily energy requirements (Zimmerman 2019).  Additionally, when sows eat less, their digestive system moves at overall slower rate, which can lead to constipation. Constipation, in turn, can cause a bacterial overgrowth, which makes the sow more susceptible to infections that are a factor in PDS (discussed below).

Overmuscled Sow Syndrome (OMSS) describes the effects of modern swine genetics that have increased the ability of sows to have more piglets. These sows are leaner, which increases the risk of an early catabolic phase before farrowing (Zimmerman 2019). During the last 5-10 days of gestation, these OMSS sows are using their own body stores to grow a large number of fetuses. By the time they farrow, they already have depleted body stores and now have less to use for producing milk for this large litter. Thus, a failure in lactation and PDS is more likely.

            Response to Environmental Stress. Sow environment can greatly affect a stress response, contributing to PDS. Despite numerous reports over the last 30 years, there is no clear conclusion regarding impact of housing, environment, or movement of sows prior to parturition, but a short period of adaptation of the sow to the new farrowing-lactation environment appears to be warranted (Papadopolos 2010). Although research opinions differ on lengths of time, some period of acclimatization to the new farrowing environment appears to be necessary to reduce stress at farrowing (Martineau 2013).

No matter what type of housing system, heat stress is a known risk factor for PDS. The farrowed sow and her litter provide a temperature regulation challenge, with sows and piglets having and almost 30 degree difference in ideal temperatures while being located in close proximity. Overheating of the mammary glands, often from heat lamps used for the litter, directly decreases milk production, along with the high temperatures suppressing sow appetite (Zimmerman 2019).

Additionally, any sort of pain in the sow suppresses oxytocin, leading to a decrease in milk letdown and piglet growth. Examples of painful circumstances include a chronic health condition, lameness, or injury.

            Infectious Agents.  Infectious agents also contribute to PDS. The most commonly isolated bacteria in PDS/mastitis cases are coliforms; E.coli being the primary culprit (Zimmerman 2019). Coliform bacteria contain endotoxins, which causes an enhanced inflammatory response, making sows have a fever, reddened, warm mammary glands, and overall lethargy. Endotoxins can come from bacteria in the sow’s farrowing environment, the mammary gland itself, and most importantly, her own intestines. As described above, sows near farrowing often experience constipation. When this happens, coliform bacteria can accumulate in the colon and release their endotoxins locally or into the farrowing environment (Martineau 2013).

Treatment and Prevention of PDS

Treatment efforts for PDS should focus on getting sows eating and drinking, reducing the effects of endotoxins, and preventing further bacterial spread. Non-steroidal anti-inflammatory drugs (NSAIDs), such as flunixin meglumine and meloxicam, are recommended to reduce fever and alleviate inflammation. Oxytocin, usually in repeated doses, is recommended to stimulate milk production and relieve signs of mastitis. Antimicrobials are justified when the sow has generalized signs of infection or obvious uterine and mammary discharge, with care taken to use those based on the appropriate spectrum of activity against confirmed causal bacteria. All treatment methods should be carried out under the guidance of the herd veterinarian.

Since many factors contribute to the development of PDS, a multi-faceted management approach is needed for its prevention. Basic husbandry and nutrition management are key not only to preventing PDS, but also managing it when clinical signs appear.

  • Clean, easily obtained water should be available to sows at all times. This will promote milk production and reduce constipation.
  • Proper nutritional management of periods surrounding farrowing will benefit sows for a successful lactation. Gestation feed amounts should balance fetus growth without excessive sow weight gain. Added fiber in late gestation diets is helpful to prevent constipation. All feed should be clean, free of molds and debris, to encourage sow appetite. Sow feeders in farrowing may need to be cleaned multiple times a day to ensure this.
  • Acclimatization to the farrowing area generally decreases the risk of PDS (Martineau 2013), but the actual number of days of acclimatization can vary depending on herd parameters.
  • Sows should enter into a farrowing area that has been fully cleaned and disinfected, practicing all-in, all-out pig flow. These areas should be in complete repair with no chance of injury to the piglets or sow, given that this provides opportunity for infection and pain, which are risk factors for PDS.
  • Farrowing room environment is a challenging but important component to managing pig comfort and the development of PDS. Make sure to keep the sow’s area at around 60-65°F, while piglets need to have supplemental heat in their living areas at 85-90°F. Since the sow and piglets live in such close proximity, frequent observations must be taken to ensure these temperatures are maintained.
  • After farrowing, careful observations of both sow and piglet health must be taken. If either develops diarrhea, cough, or other health issues, it is possible infectious agents in these can contribute to PDS.


Effective lactation is important to keep both sows and piglets healthy and thriving. This process, especially the transition from gestation to farrowing, must be intensely managed in order to prevent the development of PDS. Signs of PDS include low milk production, loss of appetite, fever, mastitis, and uterine infections, and piglets that are underweight. When these signs occur, management and treatment options should focus on three major areas that contribute to PDS: 1) sow nutrition and metabolism 2) stresses in the sow’s environment and 3) infectious agents. With knowledge and implementation of many basic husbandry and feeding techniques, the effects of PDS can be eliminated or minimized.


References and Citations

Farmer, C., Palin, M-F., Theil, P.K., Sorenson, M.T., Devillers, N. 2012. Milk production in sows from a teat in second parity is influenced by whether it as suckled in first parity. J. Anim, Sci. Nov;90(11):3743-51.

Hurley, W. Lactation biology of swine: The basics.  2010. Proceedings of 41st Annual Meeting of the American Association of Swine Veterinarians. Omaha, NE. 3-4.

Martineau, G.P., Y. Le Treut, D. Guillou, et al.  Postpartum dysgalactia syndrome: A simple change in homeorrhesis? J Swine Health Prod. 2013; 21(2): 85-93.

Papadopoulos, G.A., C. Vanderhaeghe, G. P. J. Janssens, J. Dewulf, D. G. D. Maes.  Risk factors associated with postpartum dysgalactia syndrome in sows. Vet J. 184(2):167-71.doi: 10.1016/j.tvjl.2009.01.010. Epub 2009 Feb 20.

Zimmerman, J.J., L.A. Karriker, A. Ramirez, K.J. Schwartz, G.W. Stevenson, and J. Zhang. Diseases of Swine, Eleventh Edition. 2019. John Wiley & Sons, Inc.  p. 313-338.


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