Like all animal species in late gestation, ewes in late pregnancy must have access to enough high quality, high energy feed. Lush green pastures, which look good but often have poor nutritional value, frequently cannot satisfy these nutritional needs and the ewe is unable to consume enough to meet her energy needs.

This combination of inadequate nutrition and heavily pregnant ewes creates the perfect scenario for outbreaks of pregnancy toxaemia in ewes – a scenario that is increasingly possible in the Crookwell district over the next few months.

Pregnancy toxaemia or twin lamb disease is a direct result of energy deficiency in late pregnancy. Low levels of blood glucose lead to brain damage, dehydration, kidney failure and potentially death.

Initiating factors

• Ewes in late pregnancy, often bearing twins
• Low energy diet - green pastures high in water and low in dry matter and nutrients, often the result of autumn rains creating a late flush
• Severe weather impacting on the ewe’s capacity to feed.

Symptoms

• Affected ewes separate from the mob, become lethargic, dull and stop eating
• Nervous signs develop, including tremors, staggering and blindness
• The ewe goes down and lies on her side for 3 to 4 days, becoming comatose before death.

Treatment

It’s essential to increase the affected ewes’ energy intake as soon as possible. Drenching with 50mls of propylene glycol night and morning provides a rapidly available energy source and if administered early in the course of the disease, can reverse the condition.

The prognosis is far better if the ewe is still standing when treatment is initiated. If the ewe returns to eating and gives birth to her lambs, she will usually survive.

Prevention

If environmental and flock factors are creating conditions favourable to pregnancy toxemia, start the flock on a high energy ration – grain or sheep nuts are effective but must be introduced slowly.

Minimise stressful situations when managing ewes in late pregnancy. Avoid sudden changes in feed or periods of starvation from unnecessary yarding or transport. Be alert in periods of extreme weather, making sure ewes receive supplementary feed and shelter.

Hypocalcaemia

Be alert to similar symptoms caused by low blood calcium. Often the two diseases occur in similar circumstances, although hypocalcaemia usually occurs after the ewe has lambed and she goes down quickly, remains alert and responds much more quickly to treatment (IV or subcutaneous calcium) than ewes affected by pregnancy toxaemia.