Milk Fever
Milk fever, or hypocalcaemia, is when the dairy cow has lowered levels of blood calcium. Milk fever generally occurs within the first 24 hours post-calving, but can still occur two to three days post-calving. It can be either clinical or subclinical.
- Clinical milk fever includes both “downer” and “non-downer” cows with less than 1.4mM blood calcium.
- Sub-clinical milk fever includes cows with less than 2.0mM but more than 1.4mM blood calcium.
Milk fever increases the risk of other metabolic diseases and infections, such as ketosis and metritis, and approximately 5 percent of downer cows do not recover.
The dairy cow obtains calcium from her diet or from stores in her bones. Although there are substantial amounts of calcium available from these sources, the absorption from the intestines, or resorption from bone, is under tight hormonal control and is affected by other minerals (e.g. phosphorus and magnesium) and vitamins (e.g. vitamin D).
With the onset of lactation, and production of colostrum, the cow’s requirement for calcium increases substantially (400 percent increase in a day). To meet these calcium requirements, the cow must increase both the absorption and resorption processes. Any factors that interfere with these processes mean the cow cannot meet the increased demand for calcium, and this results in lowered blood calcium concentration and milk fever.
