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.

Meta-Analysis and Ranking of the Most Effective Methane Reduction Strategies for Australia’s Beef and Dairy Sector

“…The researchers determined a 53.85% decrease in CH 4 emission generated from manure after turning or windrow composting manure. Almeida et al [17] argue for increased efficiency and production by triggering early puberty in breeding cows and reducing the post-weaning phase and associated feeding and emissions generated during non-productive times. Lean and Moate [20] found that providing ozonated water to cattle could reduce CH 4 by 20%.…”

“…A 5% increase in fertility by reducing age at joining reduced NSW emissions by 1.56%, 1.87%, 2.18%, and 2.5% for adoption rates of 50%, 60%, 70%, and 80%, respectively [17]. A 10% improvement in fertility reduced state emissions by 2.97%, 3.56%, 4.16%, and 4.75% subject to 50%, 60%, 70%, or 80% adoption rate [17].…”

“…A 5% increase in fertility by reducing age at joining reduced NSW emissions by 1.56%, 1.87%, 2.18%, and 2.5% for adoption rates of 50%, 60%, 70%, and 80%, respectively [17]. A 10% improvement in fertility reduced state emissions by 2.97%, 3.56%, 4.16%, and 4.75% subject to 50%, 60%, 70%, or 80% adoption rate [17]. With changes in feeding triggering early puberty, costs were considered to be low due to feed requirement, and can be implemented in any system or climate without need for policy or legislation.…”

“…To address the CH 4 emissions associated with ruminants and to boost production, animal nutrition models have evolved over the past six decades. The majority of research has focused on total mixed-ration diets typical of feedlot cattle, despite 96% of cattle in Australia grazing on pastures, and grazing breeding females constituting the largest source of CH 4 emissions in Australian agriculture [14][15][16][17].…”

Net greenhouse-gas emissions and reduction opportunities in the Western Australian beef industry

“…However, the breeding and productivity performance were already high for cattle in the Agricultural region, and this will not extend indefinitely. Strategies to mitigate enteric-methane emissions from livestock have been comprehensively discussed in the literature (Beauchemin et al 2022;Almeida et al 2023;FAO 2023) and include, but are not limited to, nutritional management of breeding animals, improving quality of available forage, genetic improvements and the introduction of enteric-methane supressing forages and pastures and enteric-methane supressing feed supplements.…”