News & Advice

May is the perfect time to review minerals on your farm

May 2, 2022 | Dairy, Dairy Animal Health & Welfare, Minerals

Julia Baynes, Veterinarian, Anexa Vets Morrinsville

Autumn is here, and May is the perfect time to take stock of your mineral programme on farm.

There are numerous reasons for this: 

  • Minerals may make up a significant cost on farm  (up to $10 – $15 per cow per season) and it’s important to ensure that you are getting the best return on investment by not under-supplementing or over-supplementing your animals. 
  • Mineral intake differs significantly between milkers and dry cows  on most farms, and the availability of certain minerals and trace elements, particularly copper, is reduced in winter pasture. 
  • Heifers are coming home from grazing, and their mineral status can be very different to the herd. We know from analysis of thousands of previous seasons’ test results, they often have significantly lower selenium and copper levels; both important trace elements for healthy cows and a successful mating. 
  • Most herds will not have done any mineral testing since last spring, or perhaps even last autumn.  A lot has changed since then! The range of supplements fed due to the drought conditions could mean the mineral status of your herd has changed. 
  • Planning your transition feeding now, with a careful look at mineral supplementation, can help to reduce issues at calving and mating. 


“But my mineral plan is fine…” 

Every season, we hear from farmers that they don’t need to do any trace element testing in autumn, because they haven’t had any problems and they have done the same mineral supplementation as last season. However,  no two seasons are the same.

Often, during a more detailed discussion, some ‘red flags’ get raised that suggest that minerals may be playing a part in a bigger issue; for example:  ill-thrifty calves, heifers with broken shoulders after calving, a high number of assisted calvings, retained fetal membranes or down cows or perhaps a  poorer reproductive performance  than expected?

While mineral status in the mature cows might be ok, heifers coming home from grazing can be a very different story. They have been exposed to different pasture and soil composition at the grazing block as well as different supplementation methods. We cannot assume that treating them with the ‘herd trace element plan’ will be satisfactory.

The best way to start your mineral assessment is to have a  Mineral Check discussion  with your vet. They will ask you a series of questions to get a picture of your mineral supplementation on farm and may  identify potential issues  that could warrant testing or  further investigation. 


“To test, or not to test?” 

All vets will tell you that best practice mineral planning on your farm should involve testing. It is the only way to truly know the mineral status of your animals. If, when you get the results back, the levels are adequate, this is a good thing – it means your current plan is working and you don’t need to change anything or spend money on unnecessary extra supplements.

The best time to test R2 heifers and mature cows  for the key trace elements (copper, selenium)  is in autumn, magnesium in the pre-calving period (3 – 4 weeks prior to calving), and calcium and NEFAs (indicates energy balance) in the post-calving period (2 weeks post-calving).

And don’t forget about your yearlings  – they should be tested for copper and selenium +/- B12 heading into their first winter, which will mean that supplementation is done well before you get busy with calving.

We recommend liver biopsies for copper,  because this is where copper is stored in the body. The liver acts like a resevior: constantly supplying copper to the blood supply and keeping circulating levels within a normal range.  A blood test for copper is less informative – it will only become low in animals who are severely copper deficient and have exhausted their liver stores, meaning that it is rare to diagnose a mob as deficient based on a blood test.

Selenium isn’t stored in the body, so blood samples are the simplest way of checking this trace element status.

Anexa vets want to give you the best bang for your buck through appropriate testing, both in terms of the type of testing performed, and the number of animals tested. 


“But it’s cheaper just to jab them with something anyway” 

On the surface, this may be true. However, there is also the very real risk that: 

  • You are spending money on supplementation that isn’t required, 
  • You are creating  toxic levels  in the animals. We test herds every year that show toxic levels of copper in their livers, which can lead to sudden death. Animals with liver damage due to clinical or sub-clinical facial eczema are particularly at risk.
  • The type of supplement you are using is not appropriate for the stock you are treating (e.g. animals with liver disease should not receive injectable copper), 
  • You aren’t giving them enough to achieve the desired levels. 

A Mineral Check discussion  with your vet (+/- testing), will help you decide where to best spend your mineral budget dollars. 


“I’m keen to take a look at my minerals this year…” 

If you are interested in taking a good look at your mineral supplementation plans, and  ensure your animals’ mineral status is on track, please  speak to your Anexa Vet. They can have an initial Mineral Check discussion with you and make plans from there.

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