Retained placenta on swine: what is it, causes, symptoms, prevention

While often overshadowed by more acute diseases, retained placenta in swine, though less common than in other livestock, represents a subtle yet significant impediment to optimal reproductive performance and overall herd health. This condition, characterized by the failure of the fetal membranes to be expelled within a normal timeframe after farrowing, can trigger a cascade of complications, leading to substantial economic losses for producers. Understanding its underlying causes, recognizing the clinical signs, and implementing effective management strategies are paramount to mitigating its impact.

Defining retained placenta: beyond the visual

In swine, the placenta is typically expelled within minutes to a few hours (up to 12 hours) after the last piglet is born. A diagnosis of retained placenta is generally made when the fetal membranes are not passed within 12 to 24 hours post-farrowing. Unlike ruminants, where a single, large placenta is expelled, sows have a diffuse placenta, meaning that multiple placental parts are associated with each piglet. Therefore, “retained placenta” in sows can refer to either the complete failure to expel any placental material or the retention of portions of the placenta.

The multifaceted etiology: why does it happen?

The causes of retained placenta in sows are often intertwined, reflecting a complex interplay of physiological, environmental, and management factors.

Prolonged farrowing (dystocia)

This is a primary culprit. Extended farrowing, whether due to uterine inertia (weak contractions), oversized piglets, malpresentations, or obstruction in the birth canal, can exhaust the uterus and hinder its ability to expel the placenta efficiently. The uterus, having worked tirelessly to deliver piglets, may lack the contractile force needed for placental detachment.

Uterine inertia

This refers to the uterus’s inability to contract effectively. It can be a consequence of prolonged farrowing, but also linked to factors such as older sows, sows in extreme body condition (too fat or too thin), large litter sizes, or even certain illnesses during farrowing.

Hormonal imbalances

Proper hormonal regulation, particularly involving oxytocin, is crucial for uterine contractions and placental expulsion. Any disruption in this delicate balance can predispose a sow to retained placenta.

Nutritional deficiencies

Inadequate nutrition, especially deficiencies in critical vitamins and minerals like Vitamin A, Vitamin E, and Selenium, can compromise uterine health and immune function, thereby increasing the risk of placental retention. These nutrients play a role in maintaining the integrity of the uterine lining and supporting the physiological processes of parturition.

Infectious agents

While not always the primary cause, certain uterine infections (e.g., bacterial infections like E. coli or Streptococcus species) can lead to inflammation and impair uterine function, making placental expulsion more difficult. These infections can also arise as a secondary complication of retained placenta.

Environmental stress

High ambient temperatures, particularly during summer months, can lead to heat stress in sows, potentially impacting farrowing duration and increasing the incidence of complications like retained placenta.

Management practices

Suboptimal farrowing management, such as excessive intervention during farrowing or unsanitary conditions, can also contribute to the problem.
 

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Recognizing the signs

The most evident sign is the absence of placental material after the expected timeframe. However, producers should be vigilant for more subtle indicators that may point to a retained placenta or subsequent complications:

• Foul-smelling vaginal discharge: this is a strong indicator of metritis (uterine infection), a common sequela to retained placenta. The discharge may be reddish-brown, dark, or purulent.
• Reduced appetite or anorexia: sows with retained placenta and subsequent infection often show a noticeable decrease in feed intake.
• Elevated rectal temperature (fever): systemic infection stemming from the retained placenta can manifest as a fever.
• Lethargy and depression: the sow may appear dull, listless, and unwilling to move.
• Decreased milk production (agalactia): infection and discomfort can lead to a reduction or complete cessation of milk flow, impacting piglet growth and survival.
• Swelling or discharge from the vulva: localized inflammation may be visible.
• Failure to lie quietly and contentedly: after farrowing, a healthy sow should appear calm and attentive to her piglets. Restlessness or continued straining could indicate an issue.

Treatment and prevention strategies

Treatment of retained placenta primarily focuses on preventing and managing secondary infections and supporting the sow’s recovery. Manual removal is generally not recommended in sows due to the diffuse nature of the placenta and the risk of uterine damage, which can further predispose the sow to infection and impair future fertility.

• Antibiotic therapy: systemic broad-spectrum antibiotics are often crucial to combat or prevent uterine infections (metritis) that commonly follow retained placenta.
• Supportive care: ensuring the sow has access to fresh water, good quality feed, and a clean, comfortable environment is vital for her recovery. Anti-inflammatory drugs may be considered to reduce pain and inflammation.
• Hormonal therapy (cautious use): in some cases, low doses of oxytocin may be administered to stimulate uterine contractions and aid expulsion, but only after ensuring there is no physical obstruction in the birth canal. Higher doses can be counterproductive.

Prevention is undoubtedly more effective than treatment. A proactive approach to sow management is key:

• Optimal nutrition: providing a balanced diet throughout gestation, ensuring adequate levels of vitamins (especially A and E) and selenium, is critical for supporting uterine health and immune function.
• Body condition management: avoiding over- or under-conditioning of sows helps prevent farrowing difficulties and promotes stronger uterine contractions.
• Farrowing assistance: prompt and appropriate assistance during prolonged or difficult farrowings can prevent uterine exhaustion and reduce the incidence of retained placenta.
• Hygiene: maintaining strict hygiene in farrowing facilities minimizes the risk of bacterial contamination and subsequent uterine infections.
• Stress reduction: creating a calm and stable farrowing environment can positively impact the sow’s physiological response during parturition.

Economic repercussions: the hidden costs

While an individual case of retained placenta might seem minor, its cumulative economic impact on a swine operation can be substantial. The consequences extend beyond direct veterinary costs and medication:

• Reduced fertility and increased culling: sows experiencing retained placenta are at a higher risk of metritis, delayed return to estrus, and subsequent infertility. This can lead to increased days open, reduced farrowing rates, and ultimately, premature culling of affected sows.
• Decreased milk production: the stress and infection associated with retained placenta can severely impact the sow’s milk production, leading to compromised piglet growth rates, increased pre-weaning mortality, and reduced weaning weights.
• Increased veterinary and treatment costs: diagnostic efforts, medications, and potential re-breeding expenses all add to the financial burden.
• Labor costs: time spent monitoring affected sows, administering treatments, and managing compromised litters diverts valuable labor resources.

Although specific KPI data for retained placenta in swine is less widely published than for dairy cattle, it’s understood that each incidence can contribute to:

• Increased farrowing-to-conception interval: a prolonged period between farrowing and successful re-breeding.
• Higher non-productive sow days: days when a sow is in the herd but not contributing to piglet production.
• Reduced lifetime piglets born; due to impaired reproductive performance and potential early culling.