At this time of year an outbreak of milk fever or hypocalcaemia could be expected and may only become apparent by the confronting sight of dead and dying sheep, especially after feeding grain for a prolonged period.
Hypocalcaemia, or milk fever, is a deficiency of calcium in the blood.
It usually occurs in mature, fat ewes during the last six weeks of pregnancy or the first 10 days after lambing, although other classes of sheep may also be affected.
It often follows a stressful event, such as shearing, crutching, transportation, driving, yarding, fasting or inclement weather.
Milk fever usually occurs on either rapidly growing pasture, lush pasture, green cereal crops, when feeding grain, or on pasture that has plants containing oxalate such as sorrel and soursob.
An affected sheep will initially stagger and have muscle tremors, after which it will become weak, slip into a coma and die quite rapidly within four to six hours.
During a post-mortem, there is little evidence to be seen in a sheep that has died from milk fever.
Cases of milk fever are often confused, or misdiagnosed, with pregnancy toxaemia or twin lamb disease.
Milk fever characteristics include: a rapid onset; affected sheep remain alert; death occurs quickly; a large number of cases may occur at the one time; cases occur on lush feed rather than lack of feed; and a good response to the appropriate treatment.
Sheep affected with milk fever should be treated as a matter of urgency with calcium/magnesium solution (often known as 4-in-1) given under the skin. Calcium/magnesium solution is readily available from a veterinary practice or rural merchandiser.
Cases may be prevented by adding a calcium supplement if feeding grain, or by giving dry roughage to sheep on lush feed.
■For more information, contact your local veterinarian or Agriculture Victoria animal health staff, or if you are in NSW, contact your Local Land Services.
— Dr Jeff Cave
district veterinary officer