Silent killers – ovine pregnancy toxaemia

Pregnancy toxaemia is also known as twin lamb disease.  It is caused by the increased energy requirements in late pregnancy being greater than the energy provided by the animal’s diet.  Good nutrition is essential for its prevention – a challenge when feed prices are soaring.

During the first stages of pregnancy – days 1 to 45 – the supply of dietary energy is usually adequate because autumn grass is generally still available and there is little energy demand from the developing foetus.  During the next stage – days 45 to 90 – undernutrition can affect lamb birthweight but weather and/or grazing conditions need to be severe for at least 14 days to seriously impair placental development.

Adequate nutrition brings greater bearing on lamb birthweight, or even survival, during the last six weeks of pregnancy. Numerous studies have shown significantly higher mortality rates in twin or triple lambs from ewes that are underfed in the final stages of pregnancy, from 90 to 145 days. 

Ovine pregnancy toxaemia is most often found in the last month of gestation in lowground flocks, affecting older ewes carrying multiple lambs. However, it may affect any age or breed and ewes in over-fat or very poor condition are most at risk.  The condition follows from severe energy shortage, which might be caused by poor quality roughage, insufficient supply of concentrate or high foetal demand.  Clinical signs can be caused by sudden stressful events such as severe weather conditions, handling/vaccination or housing.

Clinical signs

The clinical signs, in the early stages, include disorientation – a sign to look for is a ewe not coming to the feed trough – leading to isolation from the flock.  Over the next 24 to 48 hours, affected ewes will become increasingly dull and depressed and they become blind.  A common finding is a ewe pressing her head into the corner of the pen and there may be muscle tremors around the muzzle and affecting the ears.

While there are ways of treating ovine pregnancy toxaemia, response levels are generally poor.  If the clinical signs are detected early, housed ewes can be separated and offered palatable feed and water to promote appetite. Approximately 30% of cases, caught when ewes are still able to walk, respond to treatment which includes drenching with propylene glycol, intravenous glucose and glucocorticoid injection.  Ewes with pregnancy toxaemia must be checked at least twice a day for signs of abortion/lambing as they may be too weak to expel the foetuses/lambs.


A pregnant ewe’s energy requirement is at its highest during the last six weeks of pregnancy, which is when 70% of the lamb’s birthweight is gained.  Body condition scoring provides the monitoring tool to ensure that ewes are maintained at optimal condition and this is based on feeling the amount of muscle and fat deposition over and around the vertebrae in the loin region.  Ideally, sheep should have a body condition score of 2.5 to 3 six weeks  before lambing and at least 2 to 2.5 at lambing.


If ewes are exclusively grass fed, special emphasis needs to be placed on feeding high quality roughage in late pregnancy.  Feedstuffs need to be analysed for energy and protein levels so that the diet can be properly calculated.  To ensure correct feeding levels for pregnant ewes after body scoring, ewes should be divided into groups of similar nutrient requirements, grouped according to body condition score, number of lambs and expected lambing date.  Measuring blood metabolites can help in the assessment of the adequacy of the diet and other health problems, such as foot rot, should be treated promptly.  And, in case of extreme weather conditions, emergency feed rations should be kept at hand.

Similar picture for goats

Pregnancy toxaemia can affect all ruminants, so although gestation periods differ, goats can also suffer pregnancy toxaemia.  Causes, clinical symptoms and treatments are broadly similar to those for sheep and monitoring the pregnant female’s diet and body condition scoring should be carried out in the later stages of pregnancy.

For guidance on body condition scoring for sheep, visit