When a milking cow in spring runs short on magnesium, the cost incurred isn’t difficult to calculate.  In a worst case situation she dies, and the cost is the value of the animal, and her production during the coming season.  Should she die prior to calving, there’s also the value of the calf.

Because the problem becomes increasingly prevalent and severe as cows age, it is often the more valuable animals affected, and there is a dollar value on their lost breeding potential.

Two other things are worth bearing in mind.  Animals exhibiting clinical signs are only the tip of the iceberg.  For every animal requiring treatment there will be a number of others producing at lower than their potential.  Even when treated animals recover, their season’s production will be adversely affected.

But the issue most talked about is the cost in human time when an animal requires assistance.  Time and frustration and as one farmer recently stated, “it’s a complete waste – in all ways.”

Milking cows are remarkably robust animals, able to survive and produce well on a wide range of diets. So if you are treating cows suffering calcium/magnesium imbalance and deficiencies in spring as a regular activity, their diet is obviously a long way from that necessary for best performance.

The worst of the problem can be corrected simply, easily, and at low cost with an annual application of dolomite to pasture.  The transformation that takes place after an application of 200 – 230kg/ha of dolomite means that dolomite clients are a very loyal group.

Because grazing ruminants are unable to adequately store magnesium, adequate intake is required every day, and the most effective way is ensuring there is enough of it in every mouthful of pasture eaten.  The level of magnesium in dolomite treated pasture regularly lies between 0.22 – 0.25%, sufficient to meet the requirements of fully-fed high producing animals.

And it’s not at the expense of other essential elements.  When cows are unwell in spring it is seldom due to just a lack of magnesium. It’s nearly always a calcium and magnesium imbalance. Too much of one, and too little of the other, with each animal’s requirements being different.

Dolomite contains both magnesium and calcium at the ratio required for plant uptake, and the two are released at the same rate, with the speed being dictated by plant demand – the reason for a little going a long way.  There’s another aspect often overlooked and that is the cow’s requirement for extra energy in spring, particularly when it’s cold, wet, and windy.

Whether it’s because magnesium helps with the availability of phosphorus (an essential element in the formation of plant sugars), or the fact that it’s an ancient seabed deposit carrying a wide range of trace elements, is not clear. However, a single application of bulk dolomite in autumn is remarkably effective in reducing the number and severity of animals requiring treatment in spring.

No system is ever completely foolproof, but dolomite applied annually at 200 – 230kg/ha, providing 23 – 25kg/Mg/ha is sufficient to meet the annual magnesium requirements of high producing farms. As astute farmers have known for decades, it provides a well proven and reliable base for robust good health and high production in spring.

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