Prevent milk fever during transition period

Milk fever

Milk fever arises when cows are unable to mobilise sufficient calcium at calving. This page is intended to provide a better understanding of the challenge of controlling (sub)clinical milk fever for dairy farmers. Always consult your own veterinary surgeon for diagnosis and advice.

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What is milk fever?

Milk fever, or hypocalcemia, is a calcium deficiency. The disease has a clinical and a subclinical form and affects when cows they are at their most vulnerable – during the transition period. Cows need a large amount of calcium immediately after calving: initially they take the calcium from their blood and later from their diet and bones. If unable to mobilise sufficient calcium the affected animal won’t be able to stand properly and will have a reduced appetite resulting in poor health and performance. 


“Providing dry cows with enough clean water is very important if you want them to consume enough dry matter.”


Arnout Dekker, Veterinary surgeon, Phibro


Milk fever symptoms

There are two forms of hypocalcemia: clinical and subclinical.

Clinical milk fever symptoms

A cow that is struck by clinical milk fever will shows signs of severe calcium deficiency: she won’t be able to stand and will feel cold to the touch.

Subclinical milk fever symptoms

Despite having a much higher incidence than clinical hypocalcemia, the effects of subclinical hypocalcemia are often severely underestimated. While an affected cow will be able to stand and function largely as normal, she will perform much less efficiently as a result of the underlying calcium deficiency and will be much more susceptible to diseases. The incidence of problems such as mastitis, uterine infections, endometritis and placenta retention will increase. 

Henco Splinter about reducing cases of milk fever

“Research shows that approximately 60% of cows suffer from subclinical milk fever. By reducing these cases, dairy farmers can effectively boost their herd’s health and productivity.”


Henco Splinter, Dairy Technical Specialist, Phibro

Cause and effect

How to prevent milk fever?

A cow’s demand for calcium increases significantly as she gets closer to calving. A large amount of calcium is required for the increased bone growth in the unborn calf and the production of colostrum.

To meet this demand, the cow first takes calcium from its blood. Because this doesn’t suffice, the cow has to mobilise more calcium from its diet and its bones. Most of the time, cows can’t get enough available calcium, leading to (sub)clinical milk fever. In general, older cows are more susceptible to (sub)clinical milk fever than younger ones.


What are the consequences of milk fever?

While clinical milk fever can be fatal, subclinical cases can also have a serious impact as a result of lost milk production and the costs and time involved in bringing the cow back to full health. While obvious symptoms are absent, subclinical cases of milk fever can be the gateway to an increase in mastitis, retained placenta, endometritis, uterine infections and other diseases as a result of the immune system being weakened immune system. This will have an obvious detrimental effect on milk output and can incur significant time, energy and financial costs to return the cow to full health.


Reduce cases of milk fever

Start by testing the macromineral content of all the forages which will be fed to the dry cows. Select forages with low potassium content. Formulate the ration to minimize potassium content of the ration as much as possible and use palatable ingredients.

AniStart helps to reduce (sub)clinical milk fever. An optimised calcium metabolism around calving results in healthier, more productive dairy cows.
By adding AniStart to the dry cow ration, your cows can mobilise more calcium and can start their subsequent lactation with more milk and fewer health events.


How to treat milk fever

Downer cows are typically treated with intravenous calcium. Subcutaneous application, and oral calcium formulations, are available to address milder and suspected cases. Note these different forms of calcium are not equivalent to each other. There is more to calcium treatments than meets the eye; as any other treatment, they should only be administered under the guidance of a veterinarian.

Consultation dairy cows

Get a transition assessment for your herd

If you’d like to find out more about how we could help you to optimise your herd’s performance, please submit your telephone number to request a callback. We’ll call you within three working days to set a date for a telephone or face-to-face meeting to discuss the following:


Current situation analysis

We’ll work with you to understand your herd’s current status and to identify areas for improvement.


Designing a plan of action

We’ll recommend where improvements can be made and how our products can unlock your herd’s full potential.



We’ll carry out a detailed review to make sure the changes we’ve put in place are working effectively and, where necessary, provide additional support and advice to enable your herd to continue to improve.

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