A regional-scale assessment of nutritional-system strategies for abatement of enteric methane from grazing livestock

Abstract

Progress towards methane (CH4) mitigation for the red meat, milk and wool sectors in Australia and reduced CH4 emissions intensity (g CH4/kg animal product, typically milk or liveweight gain) involves not only reduced net emissions but also improved productive efficiency. Although nutritional additives have potential to reduce CH4 production rate of livestock (g CH4/head.day), systemic improvement of the nutrition of grazing breeding females, the largest source of CH4 emissions in Australian agriculture, will also be required to reduce emissions intensity. Systemic changes that increase productive efficiency for producers are part of the economic and environmental ‘win–win’ of reducing emissions intensity, and so offer good potential for adoption by industry. For sheep and cattle breeding enterprises, improved nutrition to achieve a younger age at first joining and increased reproductive rate will reduce the proportion of CH4-emitting, but unproductive, animals in a herd. However, if breeding stock are managed to be more productive (e.g. by superior nutrition leading to greater product/breeder) and more efficient (e.g. greater product per kilogram DMI) the producer is faced with the following management challenge. Should the enterprise increase stock numbers to utilise surplus feed and gain extra product, or reduce stock numbers to maintain previous product output with smaller enterprise net emissions (and emissions intensity), and so make land available for other uses (e.g. tree plantings, conservation zones). The right balance of incentives and price on carbon is necessary to achieve a result whereby total emissions from Australian agriculture are reduced, and so a positive impact on climate change is achieved.