Sleepy sickness/pregnancy toxaemia/ketosis is seen in ewes in late gestation and can be very serious. Signs include lethargy, ataxia, recumbency and death.
Sheep with a low body condition score (2 or less), or high body condition score (4 or more) are more susceptible to this disease, as are those carrying more than one fetus.
In late gestation, the fetus and associated tissues (uterus, placenta etc) take up a large amount of space in the abdomen, limiting the amount of feed ewes can take in. Despite the liver increasing glucose production, each fetus requires 30–40g of glucose/day in late gestation, which represents a significant percentage of the ewe’s glucose production. Glucose is preferentially directed to supporting the fotuses rather than the ewe, so they compensate by using fat stores instead.
However, in a negative energy balance, this increased mobilization of fat may overwhelm the liver’s capacity and result in hepatic lipidosis, with subsequent impairment of function. Since heavier ewes have more fat stores they can mobilize fat more readily, explaining their increased chances of getting sleepy sickness. Additionally, twin-bearing ewes appear to have more difficulty producing glucose and clearing ketone bodies, thus increasing their susceptibility to pregnancy toxeamia.
Ewes have a much better chance of survival if they are treated earlier in the course of the disease. Treatment is oral propylene glycol – acetol or ketol, and chances of survival are increased by giving oral or injectable calcium.
Prevention however, is far better than cure, so careful attention to body condition throughout pregnancy is vital. In early pregnancy, to gain weight, ewes need post grazing covers of 900kgDM/Ha, in mid pregnancy this rises to 1000kgDM/Ha.
Multiple ewes in late pregnancy need post grazing covers of 1200kgDM/Ha, and no bulky feeds should be given. Attention to nutrition of ewes in pregnancy, will increase ewe and lamb survival and have a positive impact on lactation. Ewes can only gain weight in early and mid lactation so feed budgeting early on in pregnancy allows you to correct the situation.