Cattle are criticized as climate killers - and wrongly so, as scientists make clear. They contribute only 5 percent of total emissions.
Cattle have come under criticism as climate killers due to methane emissions. Both feeding and genetics offer approaches to minimize methane losses. It all depends on a clever combination. That was the conclusion of an expert workshop held at the 75th annual meeting of the Society for Nutritional Physiology (GfE).
Ruminants should not be considered general "climate killers" due to their quantitative contribution to global greenhouse gas emissions with less than 5 percent of total emissions, explained private lecturer Dr. Björn Kuhla from the Institute of Nutritional Physiology at the Leibniz Institute for Farm Animal Biology in Dummerstorf. Nevertheless, ruminants have a share in emissions that could be reduced by more than 30 percent through various approaches. For Kuhla, however, a combination of measures aimed at optimized feeding to maintain animal health while simultaneously aiming to reduce methane emissions and increase carbon sequestration in the soil seems more effective and desirable. The latter, he said, can be supported by intelligent pasture management concepts.
Tracking methane levels with infrared and laser technology
To estimate methane emissions, the use of mid-infrared spectra (MIR) of milk proved promising, explained Prof. Dr. Nicolas Gengler of Gembloux Agro-Bio Tech at the University of Liège in Belgium. MIR spectra are already routinely used on a large scale to estimate milk composition, he said, but also to estimate methane emissions. With reliable information on animal-specific methane emissions, management and breeding could benefit significantly in the long term, Gengler said. Prerequisites, he said, include standardizing the evaluation of MIR spectra and ensuring the applicability of the equations for estimating methane levels when using feed additives that influence methane formation in the forestomach.
In addition, genetics can also contribute to methane emission reduction. The variation in methane emissions with the same feed and performance is partly genetically determined, but measuring methane emissions in individual animals is very complex, said Prof. Dr. Hermann H. Swalve of the Institute of Agricultural and Nutritional Sciences at Martin Luther University Halle-Wittenberg in Halle/Saale. One approach that has been successfully pursued is "laser methane measurement" in the cow's breath. The definition of concrete characteristics is currently being discussed. Economic aspects and correlations with other traits should also be taken into account. In principle, according to Swalve, it should be questioned whether the microbiome itself should also be dealt with more intensively by breeding and which breeding strategy promises the greatest success.
Consider interactions with other emissions
Another option is to control methane emissions through feeding. The list of measures to be included in the methane reduction "toolbox" is quite extensive, and efficiency, price and side effects, especially on performance, vary widely. This was pointed out by Prof. Dr. Michael Kreuzer of the Institute of Agricultural Sciences at the Swiss Federal Institute of Technology in Zurich. Individual mitigation measures would also have to be examined for their effects on other emissions such as nitrogen (for example, nitrous oxide, ammonia or nitrate). Some products showed effects against more than one type of emission, such as tannin, while others did not, such as lipids. Overall, it is advisable to consider the rapid feasibility of measures for animal production systems in light of the much shorter half-life of methane in the atmosphere compared to carbon dioxide, in order to achieve correspondingly rapid effects on or against global warming, Kreuzer said.
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