Mag is the killer

Dr Joe McGrath, Sollus head nutritionist

The headline might sound a little extreme, but it could be happening on your farm and there are several ways in which it can occur.

Salmonella can be the most dramatic disease caused by magnesium oxide supplementation. This assumption, that salmonella arrives in the feed / minerals, has experienced nutritionists shuddering in their boots.

The ACVM has recently issued a warning about magnesium oxide prills and granules increasing the risk of salmonellosis by a factor of 10.

But not all MgO is dangerous, so what attributes make a MgO product unfit for use?

There are two main points.

One is too large a particle size and the other is too much calcination (or cook length in the manufacturing process). Either of these attributes can have the same effect -they result in poor solubility in the rumen and the abomasum, so a portion remains unreacted by the time it reaches the small intestine.

Once into the small intestine trouble begins to brew.

While a larger chip may be dust free it can, under some circumstances remain partially undissolved as it passes from the abomasum into the small intestine. The same risk applies to MgO that is over-cooked.

But even fine MgO may be poorly soluble in the rumen if produced with poor practices.

To make things worse when as a farmer you think your cows are mag deficient you keep pouring more poor-quality mag in too fix the issue. All you are doing is overloading the small intestine.

MgO will react in a solution and drive the pH up, thus reducing the risk of acidosis and potentially improving milk fat percentage.  In the rumen this is a great attribute 99.9% of the time.

However, if it reaches the small intestine, this lift in pH causes the environment to favor some less than ideal bacteria that may already be present in the gut at small levels, especially Salmonella.

There are many cases of salmonella a year in NZ dairy herds, often with the cause unknown. However, from time to time there are major spikes. There was one back in 2014 and another at the start of 2021, with smaller ones in between, that were probably linked to MgO.

This is a risk that the Sollus team has always been aware of. So, we developed a magnesium to be included in all our product forms, that is fine enough to dissolve fully before it leaves the abomasum but at the same time is dust free.

Our proprietary manufactory process makes sure that our products remain largely dust free, safe and effective and to back it up we regularly test against various MgO sources for their safety by evaluating their rates of degradation. We can do this in our own lab and it is part of our quality and safety culture.

You need magnesium, just not bad magnesium.

A high quality MgO is simply put just about the best Mg source for dairy cows. It is cost effective, has multiple effective attributes and should be safe.

According to the ACVM, suppliers must be able to guarantee the solubility of their Mg products, if not they must put on their label that their feed product may cause salmonellosis.

So as a farmer, question your feed suppliers, make them show you their solubility data.

And maybe, cheapest is not always best.

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