The dry period is one of the most important times during a dairy cow’s annual cycle and is the ultimate point in the cow’s cycle of producing a calf and producing milk. During the final 3 weeks before calving, a cow’s energy requirements start to increase towards foetal development and colostrum production. It’s harder for them to meet these demands in the face of reduced dry matter intakes due to reduced rumen capacity.

As a result, focus needs to be on getting the dry period right, to realise peak yields in the fresh cow period and optimise cow health and performance throughout lactation. Blood testing or metabolic profiling of dry cows can be a useful tool in monitoring dry cow health and identifying any underlying issues.

There are multiple reasons to carry out blood testing in dry cows, including investigating fresh cow diseases after calving such as milk fever, held cleansings, metritis, mastitis, ketosis and LDAs, or just testing to routinely monitor the health of dry cows.

Even the best managed systems should be doing these tests, ideally at least on a quarterly basis, as it is a good way to monitor how well the system is working. Or see what is happening after you have opened a new silage clamp or moved the dry cows into an alternative shed with differing feed access for example.

Monitoring is always a good way to assess where you are at, and by doing it in the dry period it is the perfect time to make ration or environmental changes in response to the results, to help maximise performance next lactation.

Farmers can either test for everything or pick out a couple of points tailored to your own issues on farm. Most farms should speak with their farm vet on what to test for initially and then look at whether it is a one-off screening or something that is done more regularly.

You can do as little or as much as you want. If you are calving all year round, you might want to look at sampling at quarterly intervals and use it as a monitoring tool. Or if you are block calving, you could do a selection of cows all in one go.

That generally standard blood tests will look at indicators of metabolism and energy balance, including non-esterified fatty acids (NEFAs), and Beta-hydroxybutyrate (BHB)(The later can be monitored in the fresh cow period too).

These are indicators of energy balance, including whether cows are eating enough energy; does the ration supply enough and is there access to that ration. Blood urea is an indicator of dietary protein supply and can highlight when diets are low.

They are your indicators of whether cows are meeting that energy demand of the calf and the future colostrum and milk production, or whether they are going to be ‘milking off their back’ and losing their body condition once they calve. Additionally, problems with dry period nutrition could also impact colostrum quality and quantity.

Blood tests can also look at minerals such as calcium, magnesium and phosphorus, which are all closely interlinked and critical for a smooth calving and health of cow’s post-partum. If these minerals are out of balance, farmers might see more cases of milk fever and held cleansings which are a ‘downwards spiral’ to loss of production and issues with fertility in later lactation.

Blood tests in dry cows can also identify issues in trace element levels, in particular selenium, vitamin E and iodine. If you are getting a lot of slow calves born or still births you should look at your iodine levels in the dry cow ration.

As well as specific problems, trace elements can have an impact on poor immune function. So, if your cows are getting more mastitis in early lactation or metritis, you could have a trace element issue that you are not really aware of, which is making the cows more prone to picking up an infection.
Poor performing calves could also be an indicator that something is not quite right in the dry period. Calves could have a weakened immune system as a direct result of low trace elements in the dry cow.

When looking at how many cows to test, While it depends on group size and why farmers are testing, a sample of 10 cows is generally recommended. You want a good representative sample, not just thin or fat cows, then hopefully results will be applicable to the group as a whole.
Ultimately, testing dry cows is an additional cost if farmers are not already doing it. However, it is an investment into dry cow health and performance in the next lactation.

If you can deal with a problem before it becomes a real problem and rectify it through nutrition or space management, you are actually going to save money in the long run, because all of the diseases in the fresh cow are very costly and will affect your milk production.