Causes of lambing sickness and milk fever

Lambing sickness (pregnancy toxaemia) and milk fever are metabolic diseases often caused by poor nutrition.

Lambing sickness caused by poor nutrition

Lambing sickness is caused by an imbalance between energy supply and demand due to poor nutrition. It occurs in the last 2 months of pregnancy when 70% of lamb growth is happening. It more commonly affects ewes pregnant with twins, even if they haven't had nutritional problems earlier in their pregnancy.

Ewes suffering from lambing sickness might look like they're in good condition, but their nutritional levels will have fallen due to a variety of reasons, such as pastures lacking nutrients.

Milk fever caused by calcium deficiency

Milk fever is caused by a calcium deficiency in the bloodstream, usually occurring in the last 6 weeks of pregnancy and the first 3 months of lactation when calcium needs are the highest. Ewes could already be prone to a calcium deficiency due to a lack of calcium in the diet.

For example, ewes feeding on poor quality pastures or grain diets without added calcium, or grazing oxalate-containing plants that bind calcium in the intestines, preventing absorption, are susceptible. Older ewes are more susceptible to milk fever.

Dietary and environmental triggers of lamb sickness and milk fever

Certain dietary and environmental factors can place extra stress on ewes and trigger the onset of lambing sickness and milk fever. These factors in late-pregnant ewes include:

  • mustering for shearing or crutching
  • holding off feed for long periods such as in the yards for shearing or crutching, or while trucking
  • severe cold, rain or wind that cause ewes to seek shelter rather than graze, and the extra muscular contractions required for shivering and maintenance of body heat that exhaust low energy reserves
  • sudden change of diet, for example onto lush pastures, resulting in dietary upsets or being held in eaten-out holding paddocks.

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