New tool to slash nitrate leaching from dairy cows and the quest to reduce methane through genetics

 Two news items on research to reduce the environmental impacts of dairy cattle have been released today, one dealing with the search for tools to reduce nitrate leaching to the waterways, the other looking for a link between methane and cow genetics.

Lincoln University reports:

The latest research from Lincoln University’s Pastoral Livestock Production Lab offers new hope to dairy farmers in the search for tools to reduce nitrate leaching to the waterways, with the genetic disposition of the cows themselves delivering a big part of the solution.

The Pastoral Livestock Production Lab is a key constituent of the University’s Faculty of Agricultural and Life Sciences Department and the Centre of Excellence for Designing Future Productive Landscapes, where students, postgraduate researchers and academics are dedicated to creating and implementing more productive, resilient and sustainable agroecosystems for the future.

The latest findings show that grazing dairy cows with low milk urea nitrogen breeding values (MUNBV) have a 28% reduction in the urinary urea nitrogen loading rate per urine patch than cows with higher MUNBVs.

The lowest MUNBV animals in the study excreted 165.3 g less urinary urea nitrogen per day than the highest MUNBV animals. As an example, at four cows per hectare, this difference equates to 241kg urinary urea less deposited onto pasture, resulting in 41kg less nitrate leached per hectare per year.

The research, completed by PhD student Cameron Marshall (recipient of the Lincoln University Doctoral Scholarship), also showed that the low MUNBV cows also yielded an increase in milk protein percentage.

Lincoln’s Professor of Livestock Production Pablo Gregorini says the findings are very significant for farmers and the entire agriculture sector.

“Cameron’s work shows that the cows themselves are an important tool in helping to cut nitrate leaching and nitrous oxide emissions, and in helping farmers meet their regulatory reductions. To be able to do this and increase milk protein at the same time is a huge win:win for the sector.

“Most farmers’ herds will naturally comprise a mixture of low MUNBV cows and higher MUNBV cows, with the trait being identified through testing the milk. Simply identifying the animals with low MUNBVs will enable famers to breed from their existing stock and change the makeup of their herd over time.”

Research into the differences between low MUNBV and higher MUNBV animals will continue, with Cameron Marshall studying the data to identify where further benefit-yielding research should be directed.

 The Livestock Improvement Corporation reports:

A pilot trial seeking to identify a possible link between the methane cows produce and their genetics has got under way in the Waikato.

The trial involving dairy breeding bulls is believed to be a world-first and is being run by Livestock Improvement Corporation (LIC) and CRV which together sire 90% of the New Zealand dairy herd through their artificial breeding bulls. The project has received funding from the New Zealand Agricultural Greenhouse Gas Research Centre (NZAGGRC).

Stage one of the trial involves measuring the amount of methane that a small number of bulls produce with specialised equipment imported from North America. Once the systems have been fully tested, a full trial will get underway in February 2021 to identify individual bulls that produce less methane and potentially breed a lower methane emitting cow.

Chief scientist at LIC, Richard Spelman says,

“Research in other ruminating animals such as sheep has identified genetic variation for methane production so we’re undertaking research to see if there are similar results in New Zealand dairy cattle.

“If we’re successful and establish that the variability of methane emissions between New Zealand dairy bulls can be linked back to their genetics, the opportunity is to utilise this variability to breed cows from lower methane-emitting bulls. This type of science doesn’t happen overnight but we have real potential to help farmers meet the 2050 methane target under the Climate Change Response Act.”

As part of the first stage of the trial, the daily feed intake and methane output of 12 young bulls, is being closely monitored at LIC’s Chudleigh Farm with another seven being assessed under similar conditions by CRV using the same methodology. The two separate group of bulls will be monitored using the same equipment but due to biosecurity protocols it is not possible to move bulls to a single measurement facility.

LIC’s bulls are being housed in a purpose-built barn and fed Lucerne hay cubes imported from Australia in feed bins that measure how much each bull eats. The bulls visit a Greenfeed – a special methane measuring device – and are enticed to do so by a small feed of pellets to keep them in the machine for three to five minutes. Methane is measured each time the bulls visit the Greenfeed machine giving around three readings per animal per day.

The welfare of the bulls taking part in the trial is being constantly monitored by LIC, with oversight from the Ruakura Ethics Committee which has approved the project. The bulls have the freedom to move around in their pens; eat, drink and sleep when they wish.

Data captured during the trial will be shared between LIC and CRV as well as the Al Rae Centre at Massey University which will undertake independent analysis of the findings. If the trial is successful, the same method will be used on around 300 bulls in a full trial scheduled for February, Spelman continues.

“By 2023 we also hope to validate the methane measurements we captured in young bulls during the initial trial stages were representative of the methane output in lactating cows. This work has the potential to deliver real benefits to farmers in the future by providing another tool to reduce their farm emissions and consequently improve agriculture’s environmental footprint by enabling farmers to utilise these results in their breeding decisions.”

R&D manager at CRV, Phil Beatson says, “This project is important for several reasons. Firstly, because New Zealand must reduce its methane emissions per unit of feed eaten by cattle, and second because there is real potential for a genetic tool to be developed from this project.

“It’s exciting that this issue has brought together some of the best brains in New Zealand with the collaborating parties including both CRV and LIC but also AgResearch, DairyNZ, MPI, NZAGRC, PGGRC, AbacusBio and Massey University. It’s also a world-leading initiative – to our knowledge no other group has looked at measuring methane in young breeding bulls as a potential pathway to identifying superior genetics for low methane.”

Harry Clark, director of the New Zealand Agricultural Greenhouse Gas Research Centre says,

“We’re pleased to be supporting this project and drawing on LIC and CRV’s genetic expertise. We know there’s currently no silver bullet for reducing emissions but if farmers have insights into genetics that result in low methane-emitting cows, we’ll be one step closer.”

Sources:  Lincoln University; Livestock Improvement Corporation

Author: Bob Edlin

Editor of AgScience Magazine and Editor of the AgScience Blog

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