Know your trace element status

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topics:trace elements, evidence based veterinary service, deficiencies, copper

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summary know your trace elements

Knowing a herd’s trace element status can avoid associated health problems and save money, writes Jeremy Hunt

Several vitamins and minerals register as highly important to dairy farmers. But at the other end of the spectrum there are some trace elements whose impact aren’t always fully acknowledged, but are particularly critical.

That’s the view of Cumbria vet Richard Vecqueray of the Evidence Based Vet Consultancy (EBVC). He says plenty of dairy farmers will cite copper levels as being crucial when assessing their herd’s trace element profiles, when in fact copper is now infrequently diagnosed as a cause of suboptimal performance.

“As cow diets have become more dependent on conserved forage as part of an intensive feed regime – compared with a diet that was heavily dependent on grazed grass – copper problems have become less of an issue.

“They are usually caused by copper antagonists like sulphur, iron and molybdenum that bind up the copper but, because cow diets now contain a much higher proportion of whole crop and maize silage, copper problems are becoming less widespread.”

Mr Vecqueray says cows being managed for higher yields has presented milk producers with an ongoing challenge to meet their nutritional needs consistently throughout the lactation – including their trace element requirements

“A cow’s immune status and her liver function are important, as they are put under greater pressure when stressed – either nutritionally or environmentally. Also their anti-oxidant status is constantly being challenged and that brings into discussion the need to supplement with vitamin E, iodine and selenium.

“Missing any one of these three key elements means the other two aren’t functioning properly. They have to be considered together even though they are widely discussed individually. Milk producers often fall down by failing to recognise the close association of these trace elements and Vitamin E. They have a combined function and each must not be looked at independently,” he says.

But Mr Vecqueray says the herd’s trace element status is often the last area he looks at in problem cows.

“If cows fail to respond to a tried and tested change in management or diet, which has previously resolved a problem, that’s the point I start to look at trace elements.

“Farmers often assume there’s a simple deficiency causing a problem, when in fact it’s more likely to be something macro rather than micro. That’s why it’s important to remember that, while trace element and vitamin deficiencies may be causing a problem, that problem should be thoroughly investigated to find out the real cause.”

However, he does recommend a comprehensive annual review of a herd’s trace element status. A blood profile of the herd’s maiden heifer generation can provide an important window on the trace element and vitamin status.

“These are animals that have been reared at grass and probably had little feed supplementation, so are a good barometer. Taking blood profiles of cows just before they are dried off can also provide another important insight into the status of the herd as a whole. These two groups will expose a herd’s trace element weaknesses.”

While many milk producers rely on a regular supplier for their mineral requirements, this approach can often fail to meet the specific trace element and vitamin needs of high yielding cows.

“It’s the metabolic athletes that can often suffer from this approach – and it can even be because they are getting too much rather than too little of what they specifically need,” says Mr Vecqueray.

He advises a once-a-year trace element “check-up” to give herd owners a clear profile of their cows’ requirements – something that can lead to significant savings by avoiding offering mineral buckets as a fail-safe.

“As we head towards planning autumn and winter diets it’s timely for dairy farmers to assess their forage crops. Whole-crop and maize silage are mature forages and have lower mineral contents, but are more consistent in the minerals they deliver. A mineral profile costing £25-£30 will identify the magnesium, phosphorous, calcium, potassium, selenium, iodine and copper in forages.

“This profile will also show the macro-minerals in the forage – calcium, magnesium and phosphorous – and will allow herd owners to assess how much is going into the diet. It may mean cost savings can be made on phosphorous supplementation – one of the high cost minerals.

“In addition it also provides more information on the forage to help formulate an appropriate dry cow diet in terms of the sodium, potassium and chloride balance – vital for clinical and subclinical milk fever prevention.”

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