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CONTRIBUTOR(S): XLVets, Vetstream Ltd,

Milk fever

Milk fever

Milk fever, also known as hypocalcemia, occurs when a cow’s blood calcium levels become dangerously low.  The highest risk period for this occurrence is around calving time.

A cow suffering from milk fever
©Peter Jackson


At calving, the cow may be unable to meet her rapidly increasing requirements for calcium. She may be unable to absorb sufficient calcium from her gut or mobilize enough calcium from her bones to meet the requirements that calving and lactation demands.

The average milk yield for the UK national herd has increased by 30% over the last 25 years, and so the demands of lactation now make it extremely difficult for the dairy cow to maintain blood calcium concentrations at calving. More often than not, milk fever is a consequence of production and management issues on farm.

The average annual incidence of milk fever in the UK is approximately 5%, but individual farms can have an incidence of 60-70% during certain periods of the year.

The incidence of milk fever can vary widely from farm to farm, between certain periods of the year, between different ages and between different breeds of cow, but it should be possible to maintain the incidence of hypocalcaemia to below 5 cases per 100 calvings.

The management and nutrition of the cow during the dry period has a strong influence on the susceptibility of individual cows to milk fever and as such transition cow management is crucial.

What are the costs to the farm?

The estimated cost of a single, simple case of milk fever, in the UK, has been calculated to be £51.92 from lost productivity, treatment and labor costs (correct 2018). However, milk fever may result in secondary problems such as, calving difficulties, uterine prolapse (calf bed out), retained fetal membranes (cleansings), mastitis and “downer cow” syndrome.

The average cost of a case of milk fever (UK 2018) has thus been calculated to be £420.63 (including re-treatments, veterinary costs etc). Fatal cases have been estimated to cost £3,618.97 in treatments, labor, veterinarian costs and replacement of the cow (UK 2018).

As ever, prevention is better than cure, both from a cow welfare and a financial point of view.

What are the signs of milk fever?

Initially the cow may be hypersensitive with head shaking, teeth grinding and muscle tremors. The cow will be dull and lethargic with a decreased appetite. She may have cold ears, could have a stiff gait and may “paddle” feet or be reluctant to move.

The cow may become recumbent, often with a noticeable “S-bend” kink in her neck, which may progress to her head turning to the side and resting on the shoulder – as shown in the image above.

Pupils may dilate.

The rumen stops turning over causing the cow to bloat. Feces may bulge in the rectum and the cow may be constipated.

If calving then the cow may be unable to calve herself and will require assistance. The uterus (womb/calf bed) may prolapse.

If treatment is left too late then the cow is more prone to secondary problems and may become a “downer cow”.

If untreated the cow will lie on her side unable to move and will eventually die.

Which cows are affected?

Milk fever can affect any cow, but high yielders, particularly those on their 3rd (or greater) lactation are most at risk. It’s most common in cows which have recently calved or are close to calving. Most commonly a condition of dairy cows but can affect suckler cows too.

Cows which have suffered previously with milk fever are at greater risk of suffering again in subsequent lactations.

Channel Island breeds are particularly at risk.

What is the treatment?

Mild symptoms

Provide calcium; inject subcutaneously – ask your veterinarian to show you how to do this in a safe and sterile way. Monitor response while checking for other problems:

  • Is she calving?
  • Is she bloating?
  • Does she have mastitis?

If the cow is improving then ensure that she has excellent nursing care. Propping her up to allow her to eructate (belch!). Providing a soft bed with plenty of grip on the floor. Spread sand around if surface is slippery. Food and water must be within the cows reach at all times. Encourage her to try standing. Rolling and lifting may be required – ensure that you are equipped to do this safely.

Any calf should be removed, and milking should be restricted for 24 hours and may need to be restricted for a few days further. Monitor carefully for signs of mastitis.

Once recovered, ensure that you take steps to prevent further cases – see below.

Severe symptoms/cases that don’t improve with initial treatment

Call your veterinarian and make it clear that this is an emergency and immediate assistance is required.

Your veterinarian may take a blood sample and can administer intravenous calcium and any other treatments that are required

These cows may require pain relief.

These cows will require excellent nursing (see above) and may require regular lifting and turning. Ensure that you are equipped with both the facilities and the knowledge to lift cows in a way that is safe to both the cow and the personnel involved.  Ask your veterinarian for advice.


Relapses can occur in approximately 25% of cases treated. However, it is also important not to over treat, as this can affect the ability of the cow to start regulating her own calcium levels again.

Check the cow regularly to ensure that symptoms are not recurring and that she is improving. Monitor regularly for mastitis and treat if necessary – ask your veterinarian for advice.

If the udder becomes engorged and painful then hand milk enough to relieve the discomfort.

If the cow is not improving then do not delay calling the veterinarian.

Cows that are treated promptly have a much better chance of recovery with minimal complication.

How can milk fever be prevented?

There are three main strategies used for the prevention of milk fever.

Calcium restriction during the “close up/late” transition dry period

This activates calcium maintenance mechanisms in the cow’s body. It is only effective if sufficiently low dietary calcium levels are fed (<20g/day). However, due to the fixed calcium concentrations of forages fed in the pre-calving diet, and even with the use of calcium antagonists, manipulation of the diet to low enough calcium levels is rarely possible.

Dietary Cation Anion Balance (DCAB)

It has been shown that prepartum dietary cation-anion balance (DCAB) is strongly correlated to the clinical incidence of milk fever. Reducing DCAB rather than the calcium content of the prepartum ration is now considered the method of choice for preventing milk fever. DCAB is defined as:

  • DCAB (mEq/Kg DM) = (sodium + potassium) – (chlorine + sulphur).

The DCAB ration can be easily calculated if the percentage concentrations (in Dry Matter terms) of sodium, potassium, chlorine and sulphur ions are known. For a DCAB ration to be successful, close work with your veterinarian and nutritionist is essential.

Note: although DCAB is a popular milk fever prevention strategy, in some areas full DCAB is very difficult to achieve. For example, farmers may be restricted by the types of forage that are available. Sometimes a partial DCAB may be used, alongside other control strategies such as restricted grazing paddocks, low calcium buffer feeds, a combination of calcium antagonists/binders fed, along with supplementation with magnesium products etc.  If using a partial DCAB system then close monitoring will be of increased importance to ensure that DCAB is achieved. 

Oral supplementation with calcium bolus at calving

This is labor-intensive, time consuming and may even have negative effects as a large depot of calcium can switch off homeostatic pathways. This should not be used as a first line prevention.

Work with your veterinarian and nutritionist to minimize milk fever problems on your farm.

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