Challenging the thinking around Milk Urea Nitrogen

Beneath the surface
with David Law
Forward Farming

Since the 1970s, New Zealand farmers have been heavily reliant on synthetic nitrogen to grow their pasture.

They’ve been led to believe that heavy use of synthetic nitrogen is the only way to boost pasture growth and, as a result, milk production and profitability.

Therefore, there is a widely-held belief among farmers that if they reduce synthetic nitrogen, they will lose milk production, grass growth and money.

But we are proving that we can help farmers reduce their use of synthetic nitrogen without a reduction in milk production or grass growth, by sliding them into a biological transformation.

A high Milk Urea Nitrogen reading has long been an indicator that the herd has potential to produce large volumes of milk.

However, there is a bit of a problem with this theory. When you put synthetic nitrogen on your pasture you may be making the grass grow, but you are also essentially putting poison into your cows.

Cows excrete excess N

To remain healthy the cow must excrete the excess nitrogen through urine, which leaches straight into the soil, then waterways.

Not only that, but the cow uses so much energy to process the nitrogen via the liver that she simply does not have enough energy to produce high volumes of milk; she may only be producing 300kgMS.

High Milk Urea Nitrogen is also often linked to high Somatic Cell Count, sore feet and high empty rates.

The issue of high Milk Urea Nitrogen can also be found on farms where farmers buy in high-protein feed. High protein feed is good, if it is needed, but many farmers only do half the job; without balancing correctly with carbohydrates and starch, cows’ systems are put under unnecessary stress.

Farmers with feed pads are able to remedy the problem of excess nitrogen by feeding supplements with high amounts of carbohydrates – such as maize silage – to ‘soak up’ the excess nitrogen and balance the levels in the cows’ bodies.

But to balance the system and decrease the levels of nitrogen in the cow via feed is a costly exercise.

Balance the soil

The alternative to this whole system is to balance the soil, so the microbiology thrives and encourages the natural production of nitrogen through photosynthesis.

Balanced soil grows grass that is naturally higher in carbohydrates, so a more balanced feed is going into the cow. Also, a balanced soil plus microbe enhancement will deliver nitrogen naturally to the pasture.

Not only that, but the less synthetic nitrogen applied to the grass, the less nitrogen entering the cow in the first place – and the lower the Milk Urea Nitrogen reading.

When this balancing is performed correctly, milk production will not be negatively affected.

Without the stress of processing excess nitrogen, the cow now has the energy to produce larger volumes of milk; this would suggest milk quality is also better.

On the Total Replacement Therapy demonstration farm, Alan Law’s Milk Urea Nitrogen reading has fallen from an average of 26 MUN two seasons ago to an average of 19.8 MUN last season, an average reduction of 24 per cent. It is tracking at another 10 per cent less for this season, at around 16-18 MUN, while milk production has increased.

Alan’s cows are producing well, and his grass is growing better than ever – despite the fact that his Milk Urea Nitrogen reading is half of what it was last season. This MUN reduction is following the same trend as the 60 per cent reduction last season in synthetic nitrogen application.

This challenges the general thinking that a high Milk Urea Nitrogen reading is critical for milk production, and it is now our task to continue proving this point on other farms.

By having a balanced soil and enhanced biology, and pasture species delivering nitrogen naturally, there is a more efficient production of carbohydrates and less excess nitrogen to get rid of.

Balancing the feed naturally through photosynthesis means most excess nitrogen is removed from feed; feed is better quality and will require minimal balancing to get it right.


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