Breeding low-methane sheep

Green rolling hills studded with fluffy white sheep is an image New Zealand has traded on for decades, both to promote our wool and meat and to entice visitors to the country. But like a number of primary industry sectors, sheep farming is increasingly under scrutiny due to the greenhouse gas emissions of the animals. Now, they may be part of the solution, with New Zealand researchers having selected and bred the world’s first low-methane-emitting sheep!

Reducing greenhouse gases on the farm

Sheep are ruminants, alongside cows, goats, deer, antelopes – and giraffes! Ruminants are hooved mammals with a specially adapted ruminant digestive system that uses fermentation to get nutrients from their plant-based diet. A byproduct of ruminant digestion is the emission – through burping – of methane, a powerful greenhouse gas.

Within New Zealand, the majority of methane is from cows. However, like all sectors, sheep farmers are looking for ways to reduce the impact of their industry on climate change.

Ruminant digestion

Cows are ruminants. They have especially adapted digestive systems that allow them to only eat plants.

Looking for ways to reduce emissions from sheep, AgResearch, the Pastoral Greenhouse Gas Research Consortium (PGgRc) and the New Zealand Agricultural Greenhouse Gas Research Centre came together in a collaborative project supported by the Ministry for Primary Industries and the Ministry of Business, Innovation and Employment.

Breed-able traits

One of the ways scientists are looking to reduce methane emissions from sheep is to breed sheep with reduced methane emissions.

The research programme began by establishing that some sheep naturally produced lower emissions and that this trait was passed on to successive generations.

How do you establish how much methane a sheep is burping out? Researchers have several tools they can use to measure the methane emissions of animals. These include respiration chambers and ‘portable accumulation chambers’ or PACs. Respiration chambers are enclosed containers with automated systems that continuously sample the air entering and leaving the container. Temperature, humidity and airflow are continuously controlled.

PACs are a cheaper more portable option. These are sheep-sized polycarbonate boxes that can be lowered over a sheep on a race in the sheep shed. The sheep is then held inside the PAC for 50 minutes during which time air samples are taken in order to be analysed for methane concentration.

Researchers also had to monitor the amount and types of feed the sheep were fed.

Scientists worked closely with an animal ethics committee to ensure the devices were safe and comfortable for the sheep. Sheep were also acclimatised to the devices to make sure they were not stressed by the enclosed chambers.

Rights: AgResearch

Sheep in PAC chambers

Sheep in portable accumulation chambers (PACs). The PAC uses a gas analyser measuring device to determine the methane emissions from the sheep.

By determining the methane emissions in an initial flock of 1,000 sheep, researchers then divided the sheep into two closed flocks of high-emitting and low-emitting animals. These flocks were used to establish that these traits were inheritable. AgResearch scientist Dr Suzanne Rowe said they were also able to establish a cumulative gain. In year 1, the reduction of methane was 1%, and after three generations, they had 11% less methane emissions per kilogram of feed eaten.

Another important consideration was whether the sheep with lower methane emissions were also healthy and still able to produce good meat and wool. The scientists were able to select for low-emission traits and still retain other desirable traits including lean growth (growth of valuable body parts with high protein content), good carcass yield and wool production and better parasite resistance.

This is a significant development for New Zealand’s agricultural sector, giving sheep farmers a practical tool to help lower greenhouse gases.

Dr Suzanne Rowe

“Until now, the only way farmers could lower on-farm emissions has been to constantly improve their overall farming efficiency,” says Dr Rowe. “What we have produced is an animal that is up there with elite flocks … so there are no negative trade-offs.” Farmers can rest assured that these low-methane sheep are sustainable both in terms of farm profit as well as being better for the environment.

Rights: AgResearch

Dr Suzanne Rowe

AgResearch scientist Dr Suzanne Rowe on a trailer of portable accumulation chambers (PACs). The PACs were developed so they could be easily transported for use on farms.

What now?

Beef + Lamb New Zealand Genetics has launched a new ‘methane research breeding value’ to help ram breeders select for important traits to bolster within their flock. Farmers will have access to low-methane rams from 2022 – the time it will take to breed and grow rams on a commercial scale.

Sheep stud breeders are being encouraged by PGgRc to have their rams measured in AgResearch’s portable chambers to measure the animals’ methane emissions, allowing their methane breeding value to be calculated. Each animal spends 50 minutes in the chamber twice within a 14-day period.