Dr Jeff Cave, Senior Veterinary Officer
As we move further into winter, sheep producers may begin to see cases of pregnancy toxaemia or twin lamb disease in their ewes.
Twin lamb disease occurs because of an inadequate energy intake during the last 4 to 6 weeks of pregnancy.
During this final period of pregnancy, a ewe's energy needs increase substantially, as she has to provide energy for both herself and her rapidly growing lamb.
Ewes that are carrying twins are particularly susceptible, hence the name.
An outbreak of twin lamb disease is often triggered by stress and environmental conditions that lead to low food intake, such as during yarding, holding off feed or severe weather.
Affected ewes usually appear dopey, blind and unresponsive. The condition may progress over several days.
The presence of affected ewes is an indication that all is not well in the remainder of the flock.
Many other ewes may also be sub-clinically affected and may progress to become further cases of twin lamb disease.
Twin lamb disease occurs because of a breakdown of body fat at a rate with which the ewe's liver is unable to cope.
As a result, on autopsy, an affected ewe's liver will appear swollen, yellow, crumbly and greasy.
Affected ewes can occasionally be successfully treated with an energy-rich drench, such as glycerine, provided the drench is given in the early stages of the disease.
More importantly, good-quality supplementary feeding should be provided to the ewes most at risk.
Increasing the ewe's energy intake through appropriate ration formulation during the last 8 weeks of pregnancy can prevent twin lamb disease.
