With the onset of lactation a cow’s calcium requirement increases by 400%. To meet this demand a cow will obtain calcium from their bones and diet – and if insufficient – draw from their muscles and nerves, leading to muscle weakness or ‘downer cows’.

A NZ study indicated that cows suffering from clinical milk fever produced 14% less milk and sub-clinical 7% less.

Cows with milk fever are also:

• 8x more likely to develop mastitis

• 3 – 6x more likely to endure calving difficulties

• 3x more likely to experience retained foetal membranes (RFM)

• 2 – 5x times more likely to develop displaced abomasum.

For every one clinical milk fever case as many as 10 cows could have sub clinical hypocalcaemia with key consequences for each being:

Clinical Case - impaired nerve and muscle function leads to the ‘downer cow’ situation.

Sub Clinical Case - the muscles of the digestive tract, uterus and teat end may be impaired.

Reduced rumen and gut motility lead to reduced dry matter (DM) intake. Decreased DM intake can lead to an increased risk of other metabolic disorders such as ketosis, fatty liver and displaced abomasum.

Milk fever or sub clinical hypocalcaemia can also:

• lead to decreased energy intake – negatively impacting the milk yield

• effect the uterus, resulting in calving difficulties or prolapse and ultimately lead to decreasing reproductive performance

• result in mastitis due to a reduced immune function.

SIGNS & STAGES OF MILK FEVER

The best way to mitigate problems associated with milk fever is prevention. This starts with maintaining low blood calcium level before calving through a sound ‘Close Up Dry Cow’ programme (ie. no supplementation 21 days pre-calving) and then adequate supplementation of calcium through the entire season, starting with 1.1% of dry matter intake per cow.

Typically, acute milk fever occurs within a few days after calving. If milk fever occurs within the first 48 hours after calving, it is an indication that the ‘Close Up Dry Cow’ programme was not adequate. If milk fevers occur within 10 days of calving, the colostrum group did not get enough calcium supplementation. If milk fevers occur at a later stage during the lactation (i.e. autumn milk fever) it is a strong indicator that calcium supplementation is inadequate.

Sub-acute milk fever cows experience muscle twitching and tremors; the cows are excitable. In these cases there is often a magnesium deficiency as well as magnesium supports the absorption of calcium. In all cases ensure adequate calcium and magnesium is supplied to the cow.

Refractory milk fever is an acute form with poor or no response to treatment. This cow may remain alert, eat and milk but cannot get up.

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FARM STUDY’S

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