Pregnancy toxaemia (twin lamb disease, ketosis) is a metabolic crisis affecting ewes in late pregnancy, typically caused by inadequate energy intake relative to the demands of rapidly growing multiple foetuses. It is a preventable condition that causes significant suffering and mortality in affected ewes and often results in the loss of their lambs.
In late pregnancy, ewes carrying multiple foetuses have greatly elevated energy requirements while rumen capacity is physically restricted by uterine expansion. If dietary energy is insufficient, the ewe mobilises body fat. In susceptible animals, this fat mobilisation leads to ketone body production exceeding the liver's capacity to process them, resulting in ketosis/pregnancy toxaemia. Very fat ewes (BCS 4-5) or very thin ewes (BCS <2) are at greatest risk—fat ewes have reduced appetite and greater fat mobilisation tendency; thin ewes have depleted body reserves.
Pregnancy toxaemia causes profound neurological and systemic signs: depression, separation from the flock, star-gazing and head pressing, blindness, recumbency, grinding teeth (indicating abdominal pain), and coma. Affected ewes are clearly severely ill and in distress. Without treatment, death occurs within a few days. Even with treatment, prognosis for advanced cases is poor, and survivors may have lost their lambs. The condition represents extreme welfare compromise that appropriate management should prevent.
Prevention centres on body condition scoring ewes at tupping (target BCS 3-3.5), managing to maintain appropriate condition throughout pregnancy, and providing adequate energy in late pregnancy (last 6-8 weeks). Scanning for litter size at 75-80 days allows ewes to be separated and fed according to litter size—singles, twins, and triplets have very different energy requirements. Physical access to feed is critical; competition at the feed barrier disadvantages older, lower-ranking ewes.
Energy supplementation in the last 6-8 weeks of pregnancy is essential for ewes carrying multiples. Concentrate supplementation alongside good quality forage provides the additional energy needed. Gradual introduction of concentrates prevents digestive upsets. Propylene glycol (a glucose precursor) can be provided as a preventive drench to at-risk ewes. Monitoring of flock body condition through pregnancy enables targeted intervention.
Treatment of clinical cases requires prompt action: intravenous glucose for comatose ewes, propylene glycol drenching (50ml twice daily) for ambulatory cases, assisted feeding, and supportive care. Caesarean section or induction of parturition may be considered for advanced pregnancy cases where foetal survival is prioritised. Pain relief should be provided. Treatment outcomes are much better in early-stage cases, emphasising the value of close flock observation during late pregnancy.
Regular body condition scoring throughout the flock's production cycle, active monitoring of ewes in late pregnancy (including separation of those showing early signs of depression or reduced appetite), and appropriate nutritional management are the pillars of pregnancy toxaemia prevention. The condition is largely avoidable through good management—its occurrence represents a welfare failure that careful attention to nutrition and monitoring can prevent.