Sheep genetics reduce methane
It would cost less to reduce methane emissions by breeding better sheep, than by offsetting greenhouse gases through carbon forestry, new research shows.
AgResearch’s Invermay Agriculture Centre had already been using portable chambers that could measure the methane sheep belched out for a number of years. This research showed that some sheep emitted less methane than others.
For a recent study by the centre’s researcher Suzanne Rowe rams that emitted lower levels of methane were bred to low methane-emitting ewes.
The study compared the emissions from low-emitting sheep to flocks bred from rams and ewes that emitted high levels of methane. The study showed low-methane sheep emitted 10% to 12% less methane than the high-methane animals.
Calculations from these studies found it would be cheaper to reduce methane through sheep genetics than through carbon schemes that relied on forestry for offsetting.
John McEwan, animal genomics researcher at AgResearch, said initial calculations showed that the cost to reduce a tonne of methane equivalent through breeding lowemitting sheep was $1.72. The calculations were done using conversion factors as used in the emissions trading scheme.
‘‘This is markedly less than the $85 per tonne CO2 [equivalent] being paid by the emissions trading scheme currently.
‘‘It is this $85 per tonne CO2 [equivalent] value in the emission trading scheme that underpins New Zealand’s forestry conversions and is expected to rise higher in future,’’ McEwan said.
Reduction through better genetics would only mitigate part of the Government’s proposed methane emission reductions of 10% by 2030 and 24% to 47% by 2050. Other methods would also be needed and would cost more per tonne of methane emitted, McEwan said.
However, forestry also had defined limitations. Forests could not continuously absorb the extra methane emitted from fossil fuels for many decades.
Forests were a limited shortterm fix as the country transitioned to low carbon energy sources, McEwan said.
‘‘New Zealand had to find a manageable path to being net carbon zero by 2050, or more correctly restricting temperature change to a given agreed value.
‘‘It had to do this at minimal cost to the economy, and avoid rapid swings in prices, especially for leveraged asset values like land,’’ McEwan said.
There was untapped potential to make faster genetic gains in the sheep industry and there was a compelling case that this method should be aggressively pursued, McEwan said.
According to the study, lowemitting sheep would not find their way into the national flock immediately and there would be no significant reduction of emissions for the first five years as there would be genetic lag effects, and because of low adoption rates of new genetic technologies.
In 2007 Southland sheep breeder Leon Black was one of the first to ask if there were differences between the levels of methane that sheep produced.
Black said there were always many variations in any animal population. Some sheep produce more milk than others, or converted feed into meat more efficiently, he said.
The theory needed to answer a number of questions. Firstly, was there variation in how much methane different sheep produced? If there was, was it repeatable? If it was repeatable, was that variation consistent? And importantly, would the variation be passed on to the offspring?
To all these questions the answer was yes, Black said.
Farmers who grow wool and meat needed to consider if animals bred for lower methane produced better wool or meat, or less wool or meat.
Lower methane-producing sheep were found to convert feed into wool and meat much more efficiently, Black said.
Black had measured his flock since 2008. Low methane-emitting rams were already finding their way into the flocks of wool and meat farmers and would produce daughters who inherited lower methane-emitting genetics, Black said.