News & Advice

Milk fever (low calcium) might be just the tip of the iceberg for transition cows!

Jun 7, 2023 | Calving, Dairy, Dairy Animal Health & Welfare, Farm systems, Minerals

Katrina Roberts, Herd Health Veterinarian, Anexa Vets

In most herds, the basic metabolic prevention strategies appear to work, but when you dig a bit deeper you may find that you are only just “getting by” with your current plan. When we experience an unusual or unique season, doing the same as previous years may NOT give you the same results! Feed type & quality, how feed is being utilised, how cows are holding condition are all so season dependent yet have a big impact on how well cows get through calving and into lactation. So much about this year is different to ‘usual’ that it is even more important than ever to review your Transition Management Plan well before calving, taking into account what’s happening on your farm, right now.

You can check your plan is working without waiting for down cows and wobbly cows that need treatment; talk to your vet to work out the best time to take some blood samples from freshly-calved early calvers to check your transition cow plan is hitting the mark.

Many of you have implemented changes in your transition management in recent years on the back of some really cool research carried out at Anexa looking at the prevalence of subclinical hypocalcaemia in our dairy herds.


Here are some of the key points from that research:

  • Between 1/3 and 1/2 of cows have low blood calcium in the colostrum period; with day one after calving having the highest prevalence of hypocalcaemic cows. Recent research suggests that day-4 calcium (end of what we call the colostrum period) is a better predictor of performance during that lactation.
  • Cows aged 6 and over are at the highest risk, but 10-15% of 3-year-olds also had low blood calcium.
  • Giving cows an oral Calpro Bolus within 12 hours of calving will boost calcium levels for up to 8 hours.


What can technology tell us?

With technology use on farm becoming more common, farmers are beginning to see differences in rumination rates in the post-calving recovery period. There is still much to learn to be able to fully interpret all the data. For example, we know that cows with low calcium have lower rumination rates (adequate calcium levels are crucial for muscle contraction) and we also know that cows with lower rumination rates will have lower calcium (due to rumination in some feeding systems being a proxy for lower dry matter intakes) but we can’t always tell which comes first! Watch this space for more research in the years to come as we try and untangle this.



Springing cows need about 40 g of elemental magnesium. They will get about 20 g from their diet and therefore need to be supplemented with a further 20 g. Ensure you allow for realistic, not optimistic, weather-dependent wastage! It is recommended to use more than one form of magnesium for the springers if you can (such as magnesium sulphate, magnesium oxide or magnesium chloride). Collect new calves from the springer mob twice a day and take the freshly calved cows to their fresh feed with their magnesium and calcium allocation as soon as possible after calving.

Magnesium dose rates: Ensure you allow for realistic, not optimistic, weather-dependent wastage! If in doubt, talk with your vet.


Avoid paddock stripes, aim to spread magnesium evenly. As cows will just avoid heavily dusted areas, not getting the magnesium they need.


Milk fever prevention

For milk fever prevention for those high-risk cows (6+ year olds, cows with BCS of >5, Jerseys and cows that go down every year), give a calcium supplement immediately after calving (our recommendation is a Calpro Bolus), and again 12 hours later. The treatment could actually be repeated every 12 hours until out of the danger period for these recurrent problem cows. IV calcium is not recommended as a preventative as it causes a rapid spike in blood calcium, which is followed by a rapid drop. If you do use IV calcium our recommendation is to give an oral Calpro Bolus too (as soon as the cow can swallow safely) to maintain more even blood calcium levels.


High BCS Cows & Late Calvers

If you have quite a few mature cows that have a Body Condition Score greater than 5 (BCS>5), this group may need to be managed separately pre-calving and offered 90% of maintenance requirements instead of 100%. Mineral supplementation of late calving cows is often haphazard as they become a smaller mob and more difficult to dust with causmag. You may consider using an alternative strategy to supplement their diet with magnesium such as a magnesium bolus; these are long acting, slow-release forms of magnesium and are quite effective for high-risk animals.


Colostrum Cows

Colostrum cows are the most important (and most annoying!) mob on the farm. Feed them ad lib high quality feed and do not skimp on calcium. How you choose to give them calcium is farm dependent (oral drenches, dusting their break or mixed in with the feed) but you need to be aware of the potential limitations of your method. Colostrum cows are more interested in looking for their calf than eating, so if the PK trailer with lime flour mixed in it is at the back of the paddock you can understand why the colostrum cows aren’t eating it. Milking the colostrum cows once-a-day may be a possibility, however this management change will need some proactive planning to ensure you get the best results from it.


How do you measure if your plans are working?

Recording clinical metabolic cases will enable you to track progress but this is only useful after a problem occurs. Instead consider getting your vet to collect blood samples from 10 freshly-calved cows to test for calcium, magnesium, phosphate and ketones (energy status) to give you an early indicator of how well your management plan is working. Recognising a change is needed before clinical disease occurs will save time and money while also improving both animal and human welfare during an already stressful time.


If you would like further information regarding the transition period or how to prevent milk fever in your dairy cows this season – please talk to your lead Anexa Vet, or contact one of our Herd Health Advisors.


Other resources you may find helpful:

It’s all about Calcium!


How did last season’s springer management work on your farm?





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