Animal board invited review: genetic possibilities to reduce enteric methane emissions from ruminants

Abstract

Measuring and mitigating methane (CH 4 ) emissions from livestock is of increasing importance for the environment and for policy making. Potentially, the most sustainable way of reducing enteric CH 4 emission from ruminants is through the estimation of genomic breeding values to facilitate genetic selection. There is potential for adopting genetic selection and in the future genomic selection, for reduced CH 4 emissions from ruminants. From this review it has been observed that both CH 4 emissions and production (g/day) are a heritable and repeatable trait. CH 4 emissions are strongly related to feed intake both in the short term (minutes to several hours) and over the medium term (days). When measured over the medium term, CH 4 yield (MY, g CH 4 /kg dry matter intake) is a heritable and repeatable trait albeit with less genetic variation than for CH 4 emissions. CH 4 emissions of individual animals are moderately repeatable across diets, and across feeding levels, when measured in respiration chambers. Repeatability is lower when short term measurements are used, possibly due to variation in time and amount of feed ingested prior to the measurement. However, while repeated measurements add value; it is preferable the measures be separated by at least 3 to 14 days. This temporal separation of measurements needs to be investigated further. Given the above issue can be resolved, short term (over minutes to hours) measurements of CH 4 emissions show promise, especially on systems where animals are fed ad libitum and frequency of meals is high. However, we believe that for short-term measurements to be useful for genetic evaluation, a number (between 3 and 20) of measurements will be required over an extended period of time (weeks to months). There are opportunities for using short-term measurements in standardised feeding situations such as breath 'sniffers' attached to milking parlours or total mixed ration feeding bins, to measure CH 4 . Genomic selection has the potential to reduce both CH 4 emissions and MY, but measurements on thousands of individuals will be required. This includes the need for combined resources across countries in an international effort, emphasising the need to acknowledge the impact of animal and production systems on measurement of the CH 4 trait during design of experiments.Keywords: genetics, greenhouse gases, enteric methane, ruminants ImplicationMeasuring and mitigating methane (CH 4 ) emissions from livestock is of increasing importance for the environment and for policy making. Potentially, the most sustainable way of reducing enteric CH 4 emission from ruminants is through the estimation of genomic breeding values to facilitate genetic selection. Enteric CH 4 emissions are difficult and expensive to measure, thus genomic prediction could provide significant, † E-mail: Yvette IntroductionClimate change is of growing international concern and it is well established that the release of greenhouse gases (GHG) is the driving factor (IPCC, 2006). Globally, livestock farming contributes...

Invited review: Large-scale indirect measurements for enteric methane emissions in dairy cattle: A review of proxies and their potential for use in management and breeding decisions

“…To address this one plausible strategy could be to increase animal productive efficiency while reducing CH 4 emissions per animal. This could be achieved by reducing MeY or decreasing DMI, or both, provided that there is no concomitant reduction in productivity or increase in feed consumption (Pickering et al, 2015).…”

“…Apart from management and nutrition, animal breeding could play a significant role in reducing the carbon footprint of dairy production systems (Hristov et al, 2013a;Knapp et al, 2014;Pickering et al, 2015). It is now possible to use genomic information to estimate genomic EBV for CH 4 in the context of modern breeding schemes (Meuwissen et al, 2013;Hayes et al, 2013).…”

“…Several techniques have been developed for the measurement of CH 4 emissions from ruminants, with varying degrees of accuracy (see review by Hammond et al, 2016), but routine individual measurements on a large scale (a requisite for genetic selection) have proven difficult to obtain and expensive (Pickering et al, 2015;Negussie et al, 2016). Therefore, identifying proxies (i.e., indicators or indirect traits) that are correlated with CH 4 emission but that are easy and relatively low cost to record on a large scale is a much-needed alternative.…”

Use of short-term breath measures to estimate daily methane production by cattle

“…There is a strong need to develop fast, simple and low-cost methods to measure enteric methane emissions on-farm (Pickering et al, 2015). For many years, most DMP measurements have been made over one or more 22 to 24 h period in respiration chambers (RC), or in the field using the sulfur hexafluoride (SF 6 ) tracer method (Johnson et al, 1994;Deighton et al, 2014).…”

National contributions to climate change mitigation from agriculture: allocating a global target

“…Meeting the 2°C goal will require widespread uptake of such existing options. In countries where GHG intensity per unit of production is already low, further mitigation will depend on new technologies such as breeding ruminants for lower emissions (Pickering et al, 2015). The Technology Mechanism under the UNFCCC -which will also serve the Paris Agreementcan support the transfer of more advanced technologies to developing countries, including those that may provide adaptation benefits as well.…”