Sheep Pregnancy Toxaemia (Twin Lamb Disease): Prevention and Welfare in Ewes

Pregnancy toxaemia is one of the most significant welfare and economic challenges in sheep farming, causing metabolic collapse in late-pregnant ewes. Good nutritional management prevents most cases and dramatically improves welfare outcomes for ewes and their lambs.

Key Facts

Pregnancy toxaemia (twin lamb disease, ketosis) occurs in the final 4-6 weeks of pregnancy when ewes carrying two or more lambs cannot meet energy demands through diet alone, causing mobilisation of fat reserves and accumulation of ketone bodies
Energy deficit triggers a cascade of metabolic deterioration: ewes become progressively weaker, separate from the flock, develop neurological signs (star-gazing, apparent blindness, seizures), and without treatment die within days
The condition is most common in ewes carrying triplets or twins, particularly when body condition score (BCS) is below 2.5 at mating, when late-pregnancy nutrition is inadequate, or when feed access is disrupted by poor trough space, adverse weather, or bullying
Mortality in affected ewes without prompt treatment is very high (>80% in severe cases); even with treatment, prognosis is guarded once neurological signs appear
Subclinical ketosis — ewes producing insufficient milk for their lambs without obvious clinical disease — causes significant welfare harm to neonatal lambs through malnutrition
Prevention is straightforward and effective: body condition scoring ewes at mating and tupping, pregnancy scanning to identify twin/triplet bearers, and targeted supplementary feeding of at-risk ewes in late pregnancy
Glucogenic precursor supplements (propylene glycol, glycerol) administered orally twice daily are effective treatment in early cases; injectable dextrose and supportive care are required in more advanced cases
The condition disproportionately affects small and hill farming operations where nutritional planning may be less systematic and late-pregnancy weather creates additional feeding challenges

Welfare Considerations

Pregnancy toxaemia causes progressive, escalating suffering in affected ewes. The early stages — weakness, separation from the flock, reduced appetite — already represent welfare compromise, but the neurological deterioration of advanced cases is particularly distressing: ewes become effectively blind, may circle or press their heads against solid surfaces, develop seizures, and ultimately become recumbent and unable to rise. Lambs carried by affected ewes may die in utero or be born weak and hypothermic, unable to stand and suck, compounding the welfare harm across two generations. The tragedy of pregnancy toxaemia is its near-total preventability: the metabolic pathway is well understood, risk factors are identifiable weeks in advance, and targeted nutritional supplementation of at-risk ewes prevents the vast majority of cases. Operations that lose ewes to pregnancy toxaemia have generally failed in their nutritional management — either through inadequate BCS monitoring, failure to scan pregnancies, or insufficient feeding trough space that allows dominant ewes to exclude subordinates from feed. Systematic prevention is both economically rational and a basic welfare obligation.

What You Can Do

Body condition score all ewes at mating and target a BCS of 3-3.5 going into winter to provide adequate energy reserves for late pregnancy
Pregnancy scan all ewes to identify twin and triplet bearers, then provide targeted supplementary concentrate feeding to these animals in the final 6 weeks before lambing
Ensure adequate trough space (45cm per ewe minimum) and feed access for all ewes, paying particular attention to subordinate animals who may be displaced by dominant ewes
Monitor ewes daily in late pregnancy, particularly during adverse weather or periods when feed access may be disrupted, and act immediately on any ewe showing separation or reduced appetite
Keep propylene glycol or glycerol on hand and begin treatment immediately if a ewe shows early signs of pregnancy toxaemia — delay significantly worsens prognosis
Support agricultural extension services and farmer welfare networks that disseminate best practice in pregnancy nutrition management, particularly for small and hill farming operations with less systematic management