Understanding How Grazing Management Impacts Methane Emissions

Background

With increasing focus on reducing the environmental impacts of cattle production, there is a critical need for data on methane mitigation strategies in Canadian production systems. The Canadian Beef Industry has goals set of reducing methane emissions from the beef industry by 33% by 2030. Research so far has been focused around feed additive technologies to reduce methane emissions, which is more applicable to feedlot production. However, cattle on grass have the highest methane emissions, in which currently available methane mitigation strategies are not practical.

To understand how to reduce methane emissions on pasture, we need to understand current baseline levels of methane production as well as how common grazing management strategies affect methane emissions.

Objectives

• To increase the understanding of management factors which influence enteric methane emissions in grazing cattle

What they will do

These researchers want to collect baseline data around the effects of grazing management strategies and methane emissions. Also, since measuring methane is costly and takes a long time, they are wanting to test new techniques that may be able to capture methane emissions of cattle on pasture in cheaper and easier way.

In study 1 they will look at continuous vs. rotational grazing on methane emissions. This will be done at the University of Guelph with two groups of eight cow/calf pairs per treatment for 12 weeks. The cows on the rotational grazing paddocks will be moved every 2-3 days. They will use greenfeed feeders to estimate methane production. Cows and calves will be monitored for health and performance, as well as pasture sampled for forage quantity and quality.

In study 2 they will use 32 pregnant heifers at the University of Guelph to look at high or low legume pastures. The pasture will be divided into 12 strips for grazing with birdsfoot trefoil integrated into pastures at about 5% and 40%. Fields will be cut in early summer then stockpiled for grazing in August. Heifers will receive new forage every 2-3 days and greenfeed feeders will be used to estimate methane production. Heifers will be monitored for health and performance, as well as pasture sampled for forage quantity and quality.

In study 3, researchers will look at the relationship between classic laboratory scale predictions of methane production and animal level enteric methane emissions. They will use forage samples from the first two experiments in the Rusitec system (gold standard) and compare that to measures taken in the field study to determine accuracy of methane predictions.

In the fourth study the team will look at the relationship between NDF digestibility and enteric emissions (current gold standard) using NIR (the easier and cheaper method). They will compare NIR prediction to wet chemistry to determine if this can accurately predict NDF.

In the final study they will look at stocking density effects on methane emissions at the University of Alberta. Here they will evaluate methane emissions and rumen fermentation of either low (target of 40% grass harvested) or high (80%) over 3 years.

Implications

This project will provide some baseline information on the effects of common grazing management practices on GHG emissions.