Living up to our Dairy Tomorrow strategy’s commitment to ‘protect and nurture the environment for future generations’ will require some new thinking. That’s why DairyNZ is about to kick off on-farm work to investigate the potential to breed cows that do their part naturally.
This research is the first step in a seven-year partnership programme called Livestock genetics and management to reduce farm environmental impacts. It is being funded by DairyNZ and the Ministry for Business, Innovation and Employment (MBIE), with co-funding from partners CRV Ambreed and Fonterra. The aim is to figure out which cow-level characteristics are the best targets for selective breeding to reduce their contributions to farm-level nitrogen (N) leaching (‘nitrogen footprint’).
From theory to practice
Preliminary research has shown the amount of N in a cow’s milk and urine both respond to dietary N, and that milk urea N concentration is partially controlled by genetics. The initial theory is that selection to reduce milk urea N content (cheaply measured as part of herd testing) will also reduce urinary N. However, our theories must be tested against data, so we’re casting a wide net in the first phase of our on-farm work.
This is a highly collaborative project, with Massey University, Lincoln University, AbacusBio and AgResearch all playing a role. The first cab off the rank is using high-tech sensors, developed by AgResearch, to directly measure the timing, N content and volume of every urination event of individual cows over fourday trials. At the same time, researchers will genotype (DNA fingerprint) the cows and measure the N content of their milk and blood, how much pasture they consume, and the N content of that pasture.
The cows have been chosen to represent a wide range of sires for which breeding values for milk urea N content are available. This will help to maximise the statistical power available to DairyNZ and Massey University geneticists to identify genes that control these traits and the genetic relationships between them, particularly milk and urinary N adjusted for diet.
Data will be used to:
- find out if selection on milk urea N will impact urinary N
- investigate alternative cow-level traits that might do a better job
- look for genetic trade-offs with production and health traits
- determine (using models) which cow-level traits have the strongest connection to farm-level N losses.
The ideal trait for selective breeding would be easy to measure, under strong genetic control, a key driver of farm-level leaching, and have no trade-offs with economically important traits. Milk N is a promising candidate, but time, and data, will tell.
This programme will help farmers meet environmental targets in three key ways:
- Developing genetically low N-footprint animals.
- Offering breeding and management strategies to reduce N leaching.
- Reducing sector-wide N leaching by 20 percent.
This article was originally published in Inside Dairy February 2019