Full steam ahead for cows!

Like all ruminants, cows play a significant role in the production of greenhouse gases, particularly methane. Genetic selection and foodstuffs can, of course, reduce this negative impact. But what is needed is a reliable method which is financially accessible both to farmers and the dairy industry, as well as which can be rolled out on a very large scale. A decisive step towards this has just been accomplished by researchers at Gembloux Agro-Bio Tech in partnership with the CRA-W. They have used information provided from the infra-red analysis of cows' milk to precisely and reliably estimate methane emissions. This step, which is even more crucial than European legislation on carbon labelling of foodstuffs, is making great progress.

In rural areas all over the world, it is stating the obvious to say that cows fart and burp.  Something which gives rise to a panoply of schoolboy jokes however, becomes a much more serious reality if we look at the bigger picture. This daily activity of our cows, which are fundamentally and necessarily ruminants, represents a significant contribution to the concentration of greenhouse gases in the atmosphere. Among these gases is methane, which, as is now universally known, has increased substantially over the past 150 years. Methane (CH₄) is produced in a cow's rumen, a complex 'pocket' which is situated upstream of the stomach, and results from the decomposition of cellulose from the plants upon which the animal is grazing. Ruminants therefore emit methane through their mouths during periods of rumination, rather than with their excrement as is often imagined.

The contribution of methane from cows to global warming is not negligible. Initially because, even although it remains in the atmosphere 8-10 times less than carbon dioxide (CO₂), CH₄ develops a warming potential which is some 23-25 times higher than CO₂. And our planet is home to nearly 1.3 billion cows. Although cows are far from being the only domestic animal which contribute to the emission of methane, their number is likely to rise in the coming decades under the effect of demographic growth. Currently, according to the Food and Agriculture Organisation (FAO), cattle rearing alone contributes to 4.5% of global warming. Even although the Western world will soon have to revert to less meat consumption, cows are unlikely to be rendered obsolete at any time in the near future: as sources of milk, leather and gelatine, etc. without overlooking their pulling power in some countries and their sacredness in India.

500 grams of methane per day

In our regions, enteric fermentation (i.e. the microbial decomposition of food in the rumen) leads to the emission of 400 to 500 grams of methane per cow per day. Much as transport and domestic heating, there is no reason why cattle rearing should not also contribute towards the global drive to reducing greenhouse gas emissions. This new mission involves work both on genetics and foodstuffs, seeking to identify stem cells from cows emitting the least methane and adapting foodstuffs to try to reduce this (the ideal is obviously to combine these two avenues wherever possible).

It is in this context that the recent work from the Department of Agronomical Sciences at Gembloux Agro-Bio Tech - University of Liège (Animal Production Science Unit: Hélène Soyeurt and Nicolas Gengler) and the 'Valorisation of Agricultural Products' Department (Agricultural Product Technology Unit: Frédéric Dehareng and Amélie Vanlierde) and 'Production and Sectors' (Animal Nutrition and Sustainability Unit: Eric Froidmont) at the Walloon Agricultural Research Centre (CRA-W) can be found. Globally, no one is able today to precisely identify the races of cows which emit the most methane, because individual variability between the animals is significant, depending on a number of criteria, such as the type of pasture. It is also known that Animal A and Animal B from the same race and subject to the same diet, may emit different quantities of methane. And this is not insignificant: it can be up to 60%! Evaluating the methane emitted by a cow does not, in itself, pose a problem. Experts currently use two proven methods. The first involves confining the animal in a breathing chamber (all incoming and outgoing flows - including methane - are thus quantified), the other uses a trace gas - sulphur hexafluoride (SF₆) - via a little capsule placed in the rumen. However, these techniques are complex and onerous to conduct if they have to be carried out on a large number of animals.

What the Gembloux teams have done is to use a new infra-red tool - an equation - which can be used on living lactating animals in normal conditions (alternating between field/barn), on a regional scale, or even on a farm scale (animal by animal) and using significant databases. The methodological basis of this new tool is mid-infra-red spectrometry (MID). In practical terms: when coming into contact with an infra-red ray, milk reveals a basic spectrum of biomolecules which make it up: fat, protein, minerals, urea, etc. 'Earlier studies have shown that the more short-chain fatty acids contained in the milk, the more methane the animal emits' explain the Gembloux researchers. 'We already knew from our earlier work, that MIR enabled fatty acids to be measured (Read The Mysteries Contained in a Drop of Milk). Since 2007, this measurement has been routinely practised in nearly one farm in three in Wallonia, in the context of milk control. This amounts to more than 100,000 animals, which in quantitative terms is significant. We therefore thought - and it has now been proven - that it would be possible to use the huge database provided by this spectral analysis being carried out for milk control, to predict the methane emissions of a large number of dairy cows in our region.' The major advance, recommended only recently by the researchers, consists of using all milk spectral information and not only that relating to fatty acids, to more accurately and reliably measure methane emissions.

The spectrum database includes, in the Walloon region, nearly 2.5 million pieces of information and has the advantage of being updated every month. This is the added bonus of this method! Moreover, it is more interesting than information relating to animals who are no longer productive. In the future we may, therefore, be able to check what characteristics of the milk of an animal are transmitted - or not - to her offspring. At a time when cattle rearing is being globalised (reproductive bulls in our regions may come from anywhere in the world), traditional methods could never have resulted in this level of precision. 'Technically, infra-red spectrometry is less reliable than the breathing chamber or using a trace gas', add the Gembloux researchers. 'But this weakness is largely compensated by the scale of the database available. This enables us, among other things, to use our methane equation to evaluate the effect of food and genetics, with a view to eventually helping farmers to implement the best practices possible in their farms.'

Carbon labelling of foods

The discovery of this method comes at a strategic moment in time. European authorities are currently trying to define a harmonised methodology of quantifying methane emissions. In this context, it is interesting for the Gembloux researchers to upscale their equation, i.e. to be able to apply it to as big a reference population as possible. 'Although the reliability of our method has been established, and at an acceptable cost in practice (20 euro cents per analysis), it remains to be shown that it is robust and that it can be used throughout Europe, or beyond, and that it can be applied to all types of races of cows. Fruitful relationships have been built in this regard with Irish research centres and through international networks such as the Animal Selection, Genetics and Genomics Network. This step, which is more crucial than European legislation on carbon labelling of foodstuffs, is making great progress. In the context of carbon labelling, it may appear inequitable for some farmers to see their dairy production fail to receive a positive label because they have failed to be identified as low emitters using a sufficiently refined and individual method. '

However, indiscriminate application of the equation as a means of wiping the environmental slate clean is not necessarily a step which the Gembloux researchers wish to take. 'If we look the problem through the microscope, i.e. reduction of methane at all costs, we risk embarking on a wild goose chase'. While some interest groups, for example, extol the use of cow foodstuffs based on concentrated feeds, to the detriment of pasture, this would significantly reduce the production of methane per kilo of milk, by, effectively intensifying production. But this would undoubtedly lead to increased emissions of nitrogen from the waste products of farming which, through the action of bacterial populations on the ground, contribute to the release of nitrogen protoxide, a gas which is ten times more warming than methane! Above all, it is important to take into account the life-cycles of various different elements and their respective balances. While grass encourages fermentation in the rumen (and hence the production of methane), grassy fields themselves are primarily non-negligible carbon sinks and use those areas which would otherwise provide only very limited cash crops, in particularly in Ardennes. A ruminant's role is to eat grass and ... to ruminate. Feeding them with corn, on the pretext that this plant causes less methane production, would be nothing more than an ecological absurdity, from the point of view of the impact such farming methods would have on the environment. Moreover, this would be unsustainable in a world which is rapidly approaching 10 billion people. A useful point to bear in mind, in this context of multiple crises (climate, energy, price of foodstuffs, etc.) ...