5 Dairy cow – milk fever milk fever Development and causes Factors relevant to the development of milk fever include: • the 6–8 weeks prior to calving (dry period) • the 2 days following calving • the daily milk yield • the required amount of calcium • the quantity of calcium actually available Background information Milk fever is a disorder of calcium and phosphorus metabolism, which is observed primarily in dairy cows that have recently calved. It is caused by a drop in blood calcium levels, leading to a calcium deficiency (known as hypocalcaemia). In an increasing number of cows that have recently calved, a phosphorus deficiency is also being diagnosed alongside a calcium deficiency . Daily milk yield: The cow is dried off 6–8 weeks before the expected calving date. She is no longer milked and does not produce any milk during this period. After calving, lactation begins and milk yield rises rapidly. Calcium requirement: The amount of calcium required depends heavily on the daily milk yield, as milk contains a lot of calcium. During the dry period, the calcium requirement is very low, as the cow only needs to meet the needs of herself and her growing calf. As soon as lactation begins, the cow’s calcium requirement rises sharply. Quantity of available calcium: With calving and the onset of lactation, calcium requirements rise sharply. It takes the cow’s metabolism up to two days to adapt to this situation. Insufficient mobilisation of calcium from the bones, compared with the sudden surge in demand, can lead to a calcium deficit and trigger milk fever (= hypocalcaemia). 6–8 weeks before calving Calving 2 days after calving Daily milk intake Amount of calcium required Available calcium Risk phase Time
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