Rebalancing stocking rate and individual animal performance

Methane and nitrous oxide emissions are strongly related to the quantity of feed eaten. However, it's possible to produce the same amount of milk or meat from a farm with different amounts of feed being eaten.

For example, if three ewes produce three lambs, more feed is needed than if two ewes produce three lambs because an additional ewe must be fed. Similarly, less feed is needed if two cows produce 1,000kg of milk solids than if three cows produce 1,000kg of milk solids. If beef cattle reach their target slaughter weight earlier, less total feed is needed.

Quite simply, if less feed is eaten, less methane is belched into the atmosphere. Less nitrogen is consumed and returned to the soil in urine and dung, meaning less nitrogen is lost to leaching and emitted as nitrous oxide.

This isn't a new idea. New Zealand farmers have been improving individual animal performance for decades. 

There’s no one-size fits all route, but it starts by examining your current system and testing whether this approach could work for you.

Can you look to further increase individual animal performance but drop stocking rate such that output and profit are maintained? This may be via the use of better genetics, re-examining supplementary feeding and re-visiting fertiliser practices.

Feed quality also plays a role (although might not be picked up by all the different greenhouse gas calculators just yet). By feeding animals better quality feed, they need less to produce the same amount of product. 

For dairy farmers, a good place to start is to consider - is every cow producing enough to cover her cost of living? If not, there is potential to reduce cow numbers? 

For sheep, beef and deer farmers, a good place to start is to break your farm down into land management units - different topography, soil types, drainage properties, etc. You can then assess the profitability of different land management units and this can help to identify where there may be opportunities to change how you manage those units. This could mean retiring poor performing areas and increasing stocking rate in other areas, while still reducing overall stock numbers and improving performance. 

Using feed budgets at a block or management unit level is also useful to help inform this process and help you ensure you are driving the desired outcomes. 

Modelling by the Biological Emissions Reference Group and for the NZAGRC shows that a combination of lower stocking rates and improved individual animal performance can, in some circumstances, reduce emissions by up to 10%, maintain product output and maintain, if not improve, profits.

The scope to make gains via this route varies widely. Many farmers have already done what they can to get the best balance between stocking rate and individual animal performance for their unique circumstances. For some, reductions in stocking rate can be achieved alongside increases in individual animal performance, but for others this might not be possible; modelling suggests that dropping stocking rate alone will reduce profitability in most situations.

As with any approach to reducing emissions, it's critical to start by finding out what your greenhouse gas emissions are and how any changes to your current system will affect these numbers.

This approach relies on balancing reductions in stocking rate with increases in individual animal performance, to maintain product output.

The biggest risk is that stocking rates are reduced but there's no increase in individual animal performance, resulting in a drop in emissions and profits. Pasture and feed management is particularly important as high stocking rates help maintain pasture quality. If pasture quality reduces as a result of lower stocking rates, it will be very difficult to increase animal performance. If supplementary feeds are used, care will need to be taken to ensure feeding practices are adjusted to meet the needs of higher-performing stock.

Some farmers who have reduced stocking rates and increased individual animal performance some time ago observed an initial reduction in total methane. However, they've since found that their methane emissions have increased due to the total feed intake now being greater than before they made the changes. This is due to improved genetics and management. 

It is important to understand how emissions change over time, particularly in relation to total feed eaten and overall stocking rate. Tracking your greenhouse gas numbers, year on year, using the same calculator, can help with this. 

For more on improving reproductive performance and removing non-productive animals in the dairy sector, please see the DairyNZ website.

For more on the impact of modelling stock reductions with improved performance, check out these reports: 

• Farm systems modelling for GHG reduction on Māori-owned farms: achieving the Zero Carbon targets | New Zealand Agricultural Greenhouse Gas Research Centre (nzagrc.org.nz)
• Takahuri Whenua: Approaches to Systems and Land Use Change to Reduce GHG Emissions | New Zealand Agricultural Greenhouse Gas Research Centre (nzagrc.org.nz)
• Mitigating GHG on Māori Farms in New Zealand (agfirst.co.nz)

For more information on the impact of feed eaten on methane production, see this Ag Matters page.