Baa Baa Green Sheep…

Having wool makes for great rhymes and a farm’s balance-sheets, but there’s another question that has, of late, started mattering more in the definition of a good sheep.

How much methane and environmental impact does that wool come with? It may sound bizarre, and even preposterous, to think of these animals – cute, fuzzy and busy-grazing-their-grass – in context of carbon emissions.

But these unaware creatures have been parking up a lot of unwanted gas for quite some time. That too, methane – yes that potent, short-lived greenhouse gas that is more than 100 times strong at trapping energy than carbon dioxide (CO2) as per some contentions. And that is, needless to say, also a sign of digestive inefficiency in livestock.

EPA (Environmental Protection Agency) descriptions have maintained that methane emissions, among other causes, also result from livestock and other agricultural practices. Emission estimates from the Inventory of U.S. Greenhouse Gas Emissions and Sinks: 1990–2016 had well underlined the dire need of attention here. Apart from electricity, transportation and industrial means agriculture and forestry made up a major slice (as much as 24 per cent in 2010) of Global Greenhouse Gas -GHG- emissions) and cultivation of crops and livestock was a hard to miss reason here.

Not much changed ahead, when in 2017 (Trends in Global Emissions) Boden, T.A., Marland, G., and Andres, R.J. at Carbon Dioxide Information Analysis Center, Oak Ridge National Laboratory, U.S. Department of Energy, spotted Agriculture, deforestation etc. as the second-largest contributors in global emissions.

The challenge is not limited to these bleating beauties but has been noted in other areas too – like rice paddies, cow farms, termites – and man’s mad rush to produce more with intensive-rearing methods may have only worsened the gurks until the stink became too huge to ignore.

To put it simply in the case of this particular livestock, a feed is about the resource, time, labour and money that both the sheep and the men put behind it. If a significant part of it is simply belched into the atmosphere, that can’t be good, even though, hard to believe.

In fact, when a sheep farts this much gas it is not just a carbon problem, but also a problem of wasted energy (as University of Western Australia (UWA) animal science professor, Philip Vercoe has reminded earlier too). Reducing these burps and farts is carbon-wise but can be linked to more productivity as well.

Methane gas from ruminant livestock (sheep and cattle) amounts to almost 1/3 of New Zealand’s greenhouse gas emissions: Landcare research

So work, of course, begun in academic and research circles to address this problem, and is going on at full tilt in various labs and pastures. If someone is trying methanogen-curbing vaccination, someone else is fiddling with mixing microbes from the low-methane-producing kangaroo forestomach and, along side, there is someone else in another corner trying to make sense of salting ruminant feed with 3-nitrooxypropanol. Did we mention that someone has already tried to woo cows in the UK to eat curry? Well.

Experiments have to get that offbeat and gutsy when it is about an issue that lies in the guts of a creature more grass-wandering and ruminant than an average human.

In studies such as ‘Heritability estimates of methane emissions from sheep’ researchers C. S. Pinares-Patiño, S. M. Hickey and others have already surmised that there is genetic variation between animals for CH4 emission traits even after adjustment for feed intake and that these traits are repeatable.

In this study, supported by Pastoral Greenhouse Gas Research Consortium, Sustainable Land Management and Climate Change and the New Zealand Agricultural Greenhouse Gas Research Centre, it was also suggested that it may be feasible to breed ruminants with lower methane emissions.

In a comparison of methane emissions from different sheep-keeping systems in semiarid regions, Syria, it came up that sheep with the same body mass produced higher CH4 emissions in extensive SKS (Sheep-Keeping Systems) than in semi-intensive and intensive SKSs, insinuating at the use of more digestible feed as a mitigation strategy.

The latest in this string of works is a University of California Davis study that is trying out seaweed additives and focuses on a digestive process called enteric fermentation for its potential to reduce [enteric] methane by about 30 per cent.

So what if one gets a new lower-emitting trait can also be 20 percent heritable and without sacrificing on higher wool growth? Specially when methane happens to make 40 per cent of all emissions in terms of global warming potential.

A single dairy cow generates about 3 tonnes of carbon dioxide equivalent every year in the form of methane

Something is afoot at Invermay Agricultural Centre and Agricultural research company AgResearch in Mosgiel, New Zealand.

With methane being the largest single contributor to greenhouse gases produced in New Zealand, state-owned New Zealand research institute AgResearch has been busy with some innovative ways to reduce emissions of it.

Trying to breed climate-friendly sheep –one that lets out 10 per cent less methane than others is an endeavour that subsumes all the more importance in a place like New Zealand where livestock emissions have been surfacing as huge contributors to greenhouse gas emissions (if it is 10 per cent of Australia’s total greenhouse emissions, it is serious Mate).

All that should matter more when Australia’s red meat industry has a goal of becoming carbon neutral by 2030. That should explain many projects and programs, also nudged strongly by the government, such as the National Livestock Methane Program and the Reducing Emissions from Livestock Research Program.

In the latest milestone, Scientists at AgResearch have radically tapped genetics to breed sheep that produce less methane from their grass diets. It is both an intriguing and an exciting phase of work. We try to graze for some answers and insights here in this interview with AgResearch’s Dr Suzanne Rowe where she shepherds us around both some salient and adjacent furrows like fermentation, practicability, chemical vs. biological methods, measurement frequency and ways, heritability focus, quality of feed and rumen, carbon maths etc. Chew on.

What got you excited in this direction? What traction or gaps had previous research attempts or interventions left before your team started on this trail?

Methane is a significant contributor to greenhouse gas emissions in New Zealand, and we felt genetics could help in this area. Ruminant digestion studies have shown that methane production from the fermentation of cellulose in the forestomach (rumen) accounts for approximately 8 per cent energy loss in digestion.

What is the significance of methane in overall GHG pie? How serious are sheep-related methane emissions vs. other sources like transport, fracking or termites? Do these approaches align with other agriculture or livestock categories – rice agriculture, cows?

In New Zealand, one-third of total greenhouse gas production comes from methane emitted from ruminant digestion and almost 50 per cent of GHG are generated from agriculture, so this is by far the most important source. Transport only accounts for 19 per cent.

What are the practical and actionable implications of this research? Also, any highlights for labs and future research apart from farms and carbon-credit opportunities here?

Practical implications are the breeding of livestock to reduce the emissions from ruminants. A breeding ewe (adult female sheep) produces about 18kg methane per year if we also account for her offspring. Methane has 25 times the global warming potential of carbon dioxide so this is 0.45 tonnes or carbon dioxide equivalent. Reducing the methane emissions in the NZ breeding flock by 1 per cent would save around 3,300 tonnes of methane being emitted or the equivalent of 85,000 tonnes of carbon dioxide equivalent. Our work has shown that this is possible and that there are no harmful effects to the animal or to production.

Reducing the methane emissions in the NZ breeding flock by 1 per cent would save 85,000 tonnes of carbon dioxide equivalent

How much do adjacent factors like body mass, chewing time/way, breeding, milk and wool yield, farm locations, feed rations, digestibility (soya/wheat/barley/eremophila), periods of grazing or keeping-type have any influence on this issue?

We can only comment on our breeding programme. Certainly other feeding and management regimes alter absolute methane emissions. What we have shown though is that whatever system is chosen, the sheep that have been bred to emit less methane will emit less than other sheep. In our selection lines we see an increase in wool production and a slight increase in lean meat production in low-emitting sheep.

This is likely to be due to different fatty acid profiles and energy sources for the animal from the rumen. Methane is produced by microbial fermentation of cellulose. We think that we are altering the proportions of the microbes and the fermentation pathways in the rumen. This is lowering the amount of methane produced as a by-product.

Do emissions and their seriousness change with types of land/geography/temperature/precipitation aspects or agriculture approaches?

It is likely that the more cellulose that needs to be digested; the more methane will be emitted. So low quality C4 grasses produce more methane per kilogram of dry matter ingested.

Do measurement methods and formulae have any impact on possible variations?

We have taken care to calibrate the measures that we use carefully so that all measures are comparable. We have found that the best approach for the animal and for the farmer is to measure animals for a very short period twice. Once and then two weeks later. This is the equivalent of measuring once for a longer period. We have developed portable accumulation chambers to do this easily in the animals’ natural pastoral habitat.

Feed intake, methane emissions and feed efficiency – have they been adequately measured in a common context by studies done so far?

Gaps in research are primarily around measuring these parameters whilst animals are grazing pasture. This is where we have focussed our work. This is particularly important in a country like NZ where animals are in a pastoral grazing system.

Can changing rearing methods from intensive to otherwise or revisiting livestock-density have any substantial effects?

Possibly. Methane emissions are likely to be lower per animal in an intensive system with high quality feed. Methane will also be higher per unit of product, but higher per hectare unless stocking rates are adjusted.

Biological vs. chemical mitigation of methanogenic microorganisms – what’s the verdict so far?
There is substantial work being carried out in all of these areas. Breeding is a successful method and cumulative over time so an attractive way of mitigating methane for a long term strategy. It is only likely to improve things by around one per cent per year though so there is room for other methods such as inoculants and vaccines that could have a much greater effect in the short term.

How crucial are areas like repeatability and genetic or hereditary-consistency for such efforts?

For breeding purposes, selection only works if what you are selecting for is heritable – i.e. passed on to the next generation. Methane emitted per unit of feed eaten has a heritability of 0.18 which is moderate and means that we can successfully make genetic progress.

We felt genetics could help: Suzanne Rowe

Can methane-mitigation be complementary to productivity/milk yield goals as well? Or is it orthogonal? Or contradictory?

Anytime that you put selection pressure in a single direction you lower the pressure in another area. For most production traits we don’t see a relationship between methane and production which means that if methane is selected within an index or a combination of traits simultaneously then we can still make progress in production whilst lowering methane.

What’s the possibility of emission sources turning into offsets or sinks?

There is currently talk of agriculture being included in New Zealand’s Emissions Trading Scheme, but this is a Government policy matter beyond the scope of AgResearch.

What will be a leap worth aiming for in future research endeavours or agriculture-innovations?

We are also studying the actual microbes in the cow’s rumen. By sequencing these microbes and looking at their proportional contribution, we are gaining a greater understanding of the effects of changing the gut microflora and the effect that this might have on the host animal and emissions.

Pratima H



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