Winter grazing research

With the practice of wintering animals on forage crops common place New Zealand, AgResearch has been investigating different methods of grazing animals over winter to maintain farm returns and improve environmental performance.

And results from a winter trial on a Te Anau station show that with the right planning and preparation it is possible to replace forage crops like brassicas with a mainly all-grass diet and net a raft of benefits.

How was the experiment run?

The work, initiated by Pamu Manager Matt Canton, and analysed by Dr David Stevens, took place on Mararoa Station and involved 60% of the station’s 13,900 breeding ewes.The station team worked for 8 months to provide the correct conditions for stock to thrive in a one-year trial. The long preparation period was necessary to make gradual adjustments to farm management and stock management and required changes to whole-farm practices which were then implemented throughout the one-year trial.

This was critical to the studies success and the changes included:

  • Involving the full farm team in planning, and upskilling for monitoring and allocation over the 18 months lead-up
  • Altering stock policies such as controlling ewe feed intake over the summer using larger flocks than normal practice
  • Feeding supplements early to release pasture to grow in autumn
  • Using nitrogen fertiliser in autumn to fill potential feed deficits
  • Reduced feed allocation residual targets throughout year – ranging from 1000 – 1200 kg DM/ha down from 1500 kg DM/ha
  • Using a hands-on body condition scoring as opposed to a visual screening
  • Altering the grazing plan to match feed growth rates and farm operations (such as winter shearing).

What lessons were learnt?

Planning and early engagement was the key.

Dr David Stevens

Several lessons were learnt from the trial. 

"It resulted in the changes becoming less time consuming overall, less arduous and provided clarity around the processes that needed to be put in place. The ability of management to be able to use good data also helped with trust in the process and enabled good decision making.

The Mararoa Station team could see deficits and surpluses early can can actively manage their resources."

Dr Stevens also said the farm used evidence from other scientific studies that instilled confidence that the changes would result in less soil damage, less nutrient run-off and improved nutrient distribution across the farm. The demand for feed was matched with supply in the spring flush meaning animal condition was maintained in late pregnancy resulting in higher body condition and increased ewe and lamb survival rates. A major benefit was the removal of the cost of a winter crop on the farm’s balance sheet.

It also reduced associated costs in animal health. This was offset by an increased need for nitrogen fertiliser to stimulate grass growth and some supplement stockpiling. But the farm returned six percent higher earnings before interest, taxes, depreciation and amortisation (or $29/ha).

Benefits of all-grass wintering

Other benefits of all-grass wintering compared to winter crop feeding were:

  • Lambing percentage 4.5% higher
  • Ewe deaths 1.2% lower
  • Feed utilisation higher
  • Stock health higher (improved foot health noted)
  • More consistent body condition
  • Greater staff satisfaction and improved workload
  • Ewes weighed 45 to 55 kg in the 1960s to 1980s
  • Ewes now weigh 60 to 70 kg.

Wintering farm stock on forage crops is now commonplace in New Zealand. However, it wasn’t always the case. This experiment showed that modern breeding stock, which are heavier than only a few decades ago, can thrive on a grass diet in the winter, a method of farming which was once the norm. The experiment concluded that changes to farm practices and planning lead to high performing stock and a reduction in the environmental impact of intensive grazing.


Further information about this trial and the SLMACC fund can be found in the links below

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