Pregnancy Toxaemia (Twin Lamb Disease)

Pregnancy toxaemia, commonly known as twin lamb disease, is a serious and potentially fatal metabolic condition affecting ewes in late pregnancy. It typically develops rapidly, so early recognition and prompt treatment make a significant difference to outcomes.

What causes it?

In the final weeks of pregnancy, the energy demands of rapidly growing lambs increase sharply — particularly in ewes carrying twins, triplets, or more. If the ewe's energy intake doesn't meet these demands, her body begins breaking down fat reserves for energy, producing ketones as a by-product. In excess, these ketones become toxic, leading to the clinical signs of the disease.

Risk factors

  • Carrying multiple lambs (twins, triplets or more)

  • Over-fat or under-fat ewes at the start of pregnancy

  • Inadequate nutrition in late pregnancy, including sudden feed changes or poor-quality forage

  • Concurrent stress, such as bad weather, transport, or another illness reducing appetite

  • Older ewes, or those with dental problems limiting feed intake

Signs to look out for

Signs typically appear in the final 3–4 weeks of pregnancy and can progress quickly:

  • Separation from the flock, dullness or lethargy

  • Reduced appetite

  • Apparent blindness or star-gazing (holding the head high)

  • Uncoordinated movement or circling

  • Muscle tremors

  • Teeth grinding

  • Recumbency (unable to rise), progressing to coma if untreated

Because signs can escalate quickly, any ewe showing these symptoms in late pregnancy should be treated as an emergency.

Diagnosis

  • Clinical signs in a ewe in late pregnancy, particularly if known or suspected to be carrying multiples

  • Blood or urine testing for ketones, which supports diagnosis and helps guide treatment

  • Scanning records, where available, to identify high-risk ewes carrying multiple lambs in advance

Treatment

  • Oral or intravenous glucose/energy supplementation, depending on severity

  • Supportive care, including appetite stimulation and correcting any concurrent issues such as calcium or magnesium imbalance

  • In advanced cases, or where the ewe fails to respond, early induction of lambing or caesarean section may be necessary to save the ewe

  • Prognosis worsens the longer treatment is delayed, so early veterinary involvement is important

Prevention

  • Pregnancy scanning to identify ewes carrying multiples, so feeding can be tailored accordingly

  • Body condition scoring ewes at key points through pregnancy, adjusting nutrition to avoid ewes becoming too fat or too thin

  • Appropriate late-pregnancy nutrition, increasing energy intake to match the demands of the final weeks, particularly for ewes carrying multiples

  • Minimising stress in late pregnancy, including careful handling and avoiding sudden feed or routine changes

  • Grouping ewes by scanning result (singles, twins, triplets+) to allow targeted feeding

Still have questions?

If you have a ewe showing any of the signs above, please treat it as urgent and contact us on 01797 252321. We're also happy to help plan late-pregnancy nutrition and body condition scoring to reduce your flock's risk.