Reducing dairy cattle emissions with diet

Better soils
with Brett Petersen
Kiwi Fertiliser & Golden Bay Dolomite

 Evidence points to the conclusion that too much nitrogen in pasture leads to increased greenhouse gas emissions GHG and nitrogen pollution of groundwater and streams.

Urination, belching, flatulating and defecation of ruminants on a natural diet are not so much of a problem but the problem can increase when nitrogen applications are added to the mix.

What we feed the stock has a major effect on what the stock excretes. Changing the input, changes the output. In short, the more nitrogen applied, the more pollutants occur to affect water and atmosphere, and ultimately, the climate.

Better control of feedstuffs results in more milk, improved animal health, higher conception rates, lower somatic cell counts, better weight gain, better body condition score, and more lactations per cow.

Problems occur in the rumen when low-fibre, high nitrate pasture passes through the rumen too quickly, causing low pH to develop in the rumen. This can be caused by high sugar grasses that are low in fibre, and low microbial diversity within the farm and the animals.

The fast rotations encouraged by Dairy NZ are part of this problem.

A 21-day rotation is based on the fallacy that ryegrass tillers produce three leaves before the first leaf starts to senesce. Ryegrass can produce up to five green leaves when properly fertilised. The pasture is too immature and lacks fibre. This increases GHG emissions.

Other faults can include feeding PKE which is poorly digested. The NZ Dairy Goat Co-op banned it in 2008 and their milk formula was deemed by an international study as being the best in the world.

Introducing bio-active additives to improve rumen function has not been encouraged and there are problems within the system getting them registered for use.

Balancing feed needs to be an individual choice, one that suits the property and the situation. There will be many different approaches. A global approach may not work.

It starts with balanced soil fertility and must be developed from there.

The protein levels in pasture are often too high. Protein is not measured, but pasture N x 6.25 is labeled as crude protein.

One way to reduce CP is by adding energy via maize silage at the appropriate times. The results improve digestion, reduce methane production, increase milk production, and increase profit.

Here is an example from a Waikato dairy farm 2018/19 season:

When 18.4 per cent of the diet is concentrates, with no imported forages. methane emissions reduced by 21.4 per cent (CNCPS) and 17 per cent (Overseer).

Methane emissions - calculated as kg methane/kg fat corrected milk - reduced by 21.3 per cent. This was due to the combined effects of increased per-cow milk production and decreased fibre in the diet. Fibre quality was improved.

There was an 8.5 per cent reduction in land required to maintain production.

The stocking rate of 2.94 cows per hectare reduced to 1.98 – a 33 per cent decrease.

There was a reduced requirement for replacement stock.

When it came to whole farm systems modelling, moving to a PMR diet kept milk production stable, GHG (including youngstock) and N losses decreased by 16 per cent. Profitability increased by 32 per cent. (Tacoma et al., 2021)

Kiwi Fertiliser has the expertise and the tools to improve your profitability while reducing the GHG footprint.

Thanks to Dr Lucy Waldon PhD, R Nutr (NZ, UK), AAS, R Fellow (Massey), MRSNZ, MNZARN.


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