Is Manganese Your Farm's Hidden Handbrake

World class performance on farm requires world class attention to nutrition which means leaving no stone unturned. So when did you last consider manganese?

Never? Then let’s put it another way…

• Are your lambs finishing as early as possible? or

• How can you decrease your empty rate? or

• Can your farm produce more tonnes of dry matter per hectare?

Plentiful (even toxic) Manganese

Many local scientists advise that manganese is present in abundance in New Zealand and some go as far as to state there are “No known deficiencies of manganese in NZ”, Dr Edmeades (Superior Minerals vs Watt – initial ruling against Superior overturned on appeal).

Indeed I’ve found several clients with excessive pasture manganese levels (levels close to and over 400 mg/kgDM) that will prevent getting optimal lamb growth rates. These high manganese pastures are implicated in reduced lamb growth by as much as 25% (Grace) and some suggest even lower levels may negatively impact lamb finishing.

High pasture manganese levels usually appear in summer, when conditions are drier, soil is warmer and more acidic. Right when you want your lambs to be gaining the most weight.

The solution is economical and effective. Simply lime your paddocks to ensure pH between 6.0 to 6.5, with a range of 6.2-6.3 being ideal.

So Is Manganese Insufficiency In Animals Possible?

What counts is dietary manganese levels and the answer is definitely yes. On some farms under certain circumstances in New Zealand, it is likely to be a totally undiagnosed insufficiency.

A couple of months ago I was in Auckland visiting my nephew’s small citrus farm – many of the trees were showing signs of distinct ill thrift, stunted growth, severe yellowing of leaves, low fruit yield and poor fruit shape. I suggested we sample the leaves which we did from four different zones (limes, lemons, oranges and mandarins) and what we found surprised and delighted me.

Lemon leaves showing marked yellowing between the veins in more mature leaves. When trace minerals are involved as in this case, the old leaves are unlikely to recover quickly if at all due to reduced mobility of zinc and manganese, so the focus is on supporting new growth with the full spectrum of required minerals.

My first thoughts of magnesium and nitrogen deficiency proved correct but were not universal (magnesium adequacy did exist). However the added finding of significant and universal manganese and zinc deficiencies gave clear direction for intervention.

But What’s A Citrus Grove Got To Do With Production Animal Farming?

The principles of investigation are exactly the same.

• We look at the problem (either what we see or often – what we don’t) and relate it back to the causes.

• The animal output will always be limited by any shortfall of input, so diagnose the shortfall

• While we must consider the soil – just because a nutrient is in the soil, it does not mean it will be in the plant.

• Understand the difference between species, media (soil, plant or animal) and locations.

Why Is Manganese So Important?

This trace element is crucial in animals to enable use of carbohydrates and fats, for bone and cartilage development and importantly for efficient reproduction. Insufficiency will slow growth rates and lower reproductive performance. Deficiency will show as shortened and even deformed legs in young stock, disturbed oestrus and abnormalities in the newborn – typically staggering due to inner ear development failure.

In plants, manganese is an essential co-factor in the photosynthetic process. It is generally required in higher levels in plants than animals and because of this is generally overlooked when considering animal performance in New Zealand. Fair enough, in general, but if any of the following apply to your farm then further consideration is warranted.

Why Knowing Your Soil Type Is Essential

If your farm has significant areas where top soil is of these types:

• podzols,

• podzolised yellow-brown earths,

• gley podzols, or

• organic soils,

then consider manganese insufficiency as a potential contributor to lower than desired or expected animal performance.

What Is The Impact of Liming?

Manganese availability to plants is driven significantly by pH as shown on the chart to the right. The blue line indicates a reasonable target for soil pH.

So if you lime regularly or over zealously in any one application (rates in excess of 1T/ha) consider the impact on other nutrients such as manganese, as a period of induced deficiency may follow.

Is Animal Supplementation Required?

There are distinct differences between feed types and the levels of manganese they typically contain and with more farmers adding grain as a supplement the total dietary manganese intake should be considered.

While it would be rare to require additional manganese as direct animal supplementation under New Zealand farming systems, what is important is to consider the potential requirement for manganese fertiliser in some areas to ensure manganese is not limiting pasture yield.

Diagnosis of fertiliser requirement is done by considering both soil and pasture testing in context with the fertiliser history, the season, pasture yield history, the budget and the improvement being sought.

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