What causes ewes to prolapse

What Causes Ewes to Prolapse?

Ewe prolapse is a serious condition where internal organs, most commonly the vagina or uterus, protrude from the ewe's body. While it can occur at various times, it is most frequently observed in the final stages of pregnancy and during lambing. Understanding the underlying causes is crucial for prevention and effective management in sheep farming.

Understanding Prolapse in Ewes

Prolapse refers to the displacement of an organ from its normal position. In ewes, two main types are commonly seen:

• Vaginal Prolapse: This is the most frequent type, where the vaginal lining protrudes through the vulva. It can be intermittent, appearing when the ewe strains, or persistent.
• Uterine Prolapse: Less common than vaginal prolapse, this involves the uterus turning inside out and protruding from the vulva, often after lambing.

Primary Contributing Factors

Increased Abdominal Pressure

The most significant factor contributing to prolapse is increased pressure within the abdominal cavity. During late pregnancy, the growing fetus and enlarged uterus put considerable strain on the pelvic structures. Any additional pressure from straining due to constipation, difficult labor (dystocia), or even excessive coughing can push the vaginal or uterine tissues outwards. Straining is a direct physical force that overcomes the natural support structures of the reproductive tract.

Weakened Pelvic Diaphragm and Supporting Tissues

The pelvic diaphragm, a muscular structure that supports the pelvic organs, can become weakened. This weakening can be due to several factors:

• Genetics: Some ewes may have a genetic predisposition to weaker connective tissues and a less robust pelvic diaphragm, making them more susceptible.
• Age and Parity: Older ewes or those who have had multiple lambings might experience some natural weakening of supporting tissues over time.

Dietary Imbalances

Nutrition plays a pivotal role in maintaining tissue strength and hormonal balance, which are critical for preventing prolapse. Key dietary deficiencies include:

• Low Calcium (Hypocalcemia): Calcium is essential for muscle function and tone. A deficiency can lead to reduced muscle strength in the pelvic area and the vaginal walls, making them more prone to prolapse. This is particularly relevant as ewes approach lambing and their calcium requirements increase significantly.
• Low Magnesium (Hypomagnesemia): Magnesium is also vital for muscle and nerve function. Its deficiency can impair muscle tone and increase excitability, potentially leading to straining and contributing to prolapse.
• Other Nutritional Factors: While less common, deficiencies in other minerals or vitamins, as well as imbalances in the diet (e.g., high levels of certain legumes that can have estrogenic effects), have been anecdotally linked to prolapse in some flocks. High-energy diets fed to pregnant ewes without adequate fiber can also contribute to constipation and straining.

Obesity

Overly fat ewes, particularly those in late pregnancy, carry excess abdominal fat. This fat can put additional pressure on the pelvic organs and the reproductive tract, increasing the risk of prolapse. Obesity can also be associated with dietary imbalances and reduced physical activity, further exacerbating the problem.

Hormonal Influences

Hormonal changes during late pregnancy, particularly the increase in estrogen, can relax pelvic ligaments and connective tissues to prepare for lambing. While this is a natural process, it can, in some susceptible ewes, contribute to a relaxation of the supporting structures, making them more prone to prolapse when combined with other risk factors.

Environmental and Management Factors

Certain management practices can indirectly contribute to prolapse:

• Sudden Diet Changes: Rapid changes in feed, especially increasing concentrates without adequate fiber, can lead to digestive upset and constipation, resulting in straining.
• Stress and Rough Handling: Stressful events or rough handling of ewes, particularly during late pregnancy, can cause them to strain excessively.
• Poorly Designed Ramps or Steep Inclines: Forcing ewes to navigate steep inclines or poorly designed ramps can cause them to strain unnecessarily.

Prevention Strategies

Preventing prolapse involves addressing the key risk factors:

• Balanced Nutrition: Ensure ewes receive a well-balanced diet throughout pregnancy, paying close attention to calcium and magnesium levels, especially in the final weeks. Monitor body condition scores to avoid obesity.
• Manage Diet Carefully: Avoid abrupt changes in feed. Ensure adequate fiber intake to prevent constipation.
• Genetic Selection: If prolapse is a recurring issue in a flock, consider culling highly susceptible individuals and selecting breeding stock with no history of the condition.
• Minimize Stress: Handle ewes gently and avoid stressful situations during late pregnancy and lambing.
• Environmental Management: Ensure safe and easy access to feed and water, and avoid steep inclines or other hazards.

By understanding and mitigating these causes, sheep farmers can significantly reduce the incidence of prolapse in their flocks, improving animal welfare and productivity.