Metritis on swine: what is it, causes, symptoms, prevention

Metritis, an inflammation of the uterus in sows, stands as a significant challenge in swine production, often leading to considerable economic losses. While frequently discussed as part of the Mastitis-Metritis-Agalactia (MMA) syndrome, metritis can also occur independently, characterized by uterine infection within 21 days postpartum, most commonly in the first 10 days after farrowing. Understanding its multifactorial etiology, recognizing clinical signs, and implementing robust prevention and treatment strategies are crucial for maintaining herd health and optimizing reproductive performance.

The complexities of metritis: causes and risk factors

Metritis in sows is not a standalone disease with a single cause, but rather a complex condition influenced by various interacting factors. The underlying issue is typically a bacterial infection of the urogenital tract. While specific bacterial species can vary, Gram-negative bacteria, particularly Escherichia coli, are often implicated.

Several factors can predispose a sow to developing metritis:

• Hygiene and sanitation: poor hygiene in farrowing pens and around the sow’s perineal area is a primary risk factor. Contaminated environments facilitate the entry of bacteria into the birth canal and uterus, especially during and after farrowing when the cervix is open and the uterus is vulnerable.
• Farrowing complications: prolonged farrowing, manual intervention during parturition, and a high number of stillborn piglets significantly increase the risk. These events can cause trauma to the uterine lining, making it more susceptible to bacterial colonization and subsequent infection. Retained fetal membranes also provide an excellent substrate for bacterial growth.
• Sow body condition and nutrition: both overly fat (body condition score 4+) and excessively thin sows are more prone to metritis. Inadequate nutrition, particularly a lack of crude fiber in the diet, can lead to constipation, which in turn increases the risk of bacterial translocation from the urinary tract to the birth canal and uterus. Sufficient water intake is also paramount, as dehydration can exacerbate issues.
• Stress and management practices: stress around the farrowing period, such as frequent changes in groups or inadequate resting space, can compromise the sow’s immune system, making her more vulnerable to infections. Slippery floors that discourage exercise also contribute to reduced activity and potentially increased risk.
• Immune status: a sow’s overall immune health plays a critical role. Factors leading to a negative energy balance around farrowing can impair immune function, leaving the sow more susceptible to uterine infections.

Clinical manifestations and diagnosis

The primary clinical sign of metritis in sows is a vaginal discharge that can range in color from white to brown, often appearing necrotic and malodorous. This discharge typically occurs within 48 hours after farrowing and may contain remnants of fetal membranes. Beyond the visible discharge, affected sows may exhibit systemic signs, including:

• Fever: rectal temperatures above 39.4°C (103°F) are a common indicator.
• Decreased appetite/anorexia: sows may show a reduced desire to eat or drink.
• Listlessness and depression: affected sows may appear lethargic and unwilling to move.
• Restlessness and reluctance to nurse: due to discomfort or pain, sows might avoid lying down or prevent piglets from suckling, often leading to reduced milk production (agalactia) and poor piglet growth.
• Mastitis: inflammation of the mammary glands is a frequent co-occurrence, further exacerbating the agalactia.

Diagnosis primarily relies on the visual observation of the characteristic vaginal discharge and its malodorous nature. Palpation of the udder to check for mastitis and monitoring of sow temperature are also important diagnostic steps.

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Impact on productivity and welfare

The consequences of metritis extend far beyond the immediate discomfort of the sow, significantly impacting herd productivity and economic viability:

• Increased piglet mortality: reduced milk production due to metritis and associated agalactia leads to starvation and increased susceptibility to other diseases in piglets, resulting in higher pre-weaning mortality rates. This directly translates to fewer weaned piglets per sow, a key performance indicator (KPI) in swine production.
• Reduced sow productivity: metritis can delay subsequent breeding cycles and reduce conception rates in affected sows, impacting the overall farrowing index and the number of piglets produced annually.
• Increased treatment costs: treatment of metritis often involves the use of systemic antimicrobials and supportive therapies, incurring direct costs for medication and veterinary intervention.
• Compromised animal welfare: the pain and discomfort associated with metritis, along with systemic illness, represent a significant welfare concern for the affected sow.

Prevention and management strategies

Effective management of metritis requires a multi-pronged approach focusing on stringent hygiene, proper nutrition, and timely intervention.

Strict biosecurity and hygiene

• Farrowing environment: thorough cleaning and disinfection of farrowing crates between farrowing cycles are paramount. Hot water (>95°C) followed by appropriate disinfectants helps to minimize bacterial load. Ensuring pens are dry before sows enter is also critical.
• Sow hygiene: washing sows with soap and water, paying particular attention to the mammary area, before moving them into farrowing facilities can reduce the introduction of pathogens. keeping the sow’s perineal area clean and dry during farrowing and lactation is essential.
• Intervention protocols: when manual assistance is necessary during farrowing, strict hygiene protocols must be followed. This includes thoroughly washing hands and arms, wearing well-lubricated disposable gloves, and washing the sow’s perineal region before any manual entry into the birth canal.

Nutritional management

• Fiber inclusion: ensuring adequate crude fiber in the gestation and lactation diets can help prevent constipation, a known risk factor.
• Water availability: provide constant access to fresh, clean water, especially for lactating sows who require significant amounts (15-30 liters per day). Low flow rates in drinking nipples should be avoided.
• Body condition scoring: maintain sows at an optimal body condition score throughout gestation, avoiding both obesity and excessive leanness.
• Targeted supplementation: nutritional strategies can support uterine health and overall immunity. Specialized feed additives that promote gut health and modulate the immune response can be beneficial. For example, supplements containing antioxidants, probiotics, or specific fatty acids could contribute to a more robust uterine environment. Vetagro offers innovative swine feed additives, including those with microencapsulated active ingredients designed for targeted release in the intestine, optimizing nutrient utilization and supporting overall health and resilience.

Proactive health monitoring and early intervention

• Daily monitoring: daily monitoring of sow rectal temperatures and appetite, especially in the first few days postpartum, allows for early detection of metritis.
• Prompt treatment: when metritis is diagnosed, prompt veterinary consultation and treatment are essential. This typically involves systemic antimicrobials selected based on susceptibility. In some cases, oxytocin may be used to aid uterine involution and expulsion of uterine contents, though regular suckling by piglets often provides sufficient natural stimulation. Anti-inflammatory drugs can also be used to improve sow comfort and recovery.
• Identification of at-risk sows: sows that required manual assistance during farrowing should be identified and may benefit from prophylactic antimicrobial treatment to prevent infection.