Pasture intensification in beef cattle production can affect methane emission intensity

Area of Science:

• Agricultural Science
• Environmental Science
• Animal Science

Background:

• Greenhouse gas (GHG) emissions, particularly methane from cattle, contribute significantly to climate change.
• The agricultural sector is a major source of GHG emissions due to the intensification of food production.
• Ruminal fermentation in cattle is a primary source of methane emissions in the livestock industry.

Purpose of the Study:

• To evaluate enteric methane emissions and emission intensities in Nellore cattle.
• To assess the impact of different grazing system intensification levels on methane output.
• To determine the effect of animal age on methane emission intensity.

Main Methods:

• Utilized the sulfur hexafluoride (SF6) tracer technique to measure methane emission.
• Compared four grazing systems: irrigated high stocking rate (IHS), dryland high stocking rate (DHS), moderate stocking rate (DMS), and degraded low stocking rate (DP).
• Evaluated Nellore cattle at different ages (13.1 and 21.8 months) across seasons and grazing cycles.

Main Results:

• Intensive systems (IHS, DHS) yielded higher forage quality, animal performance, and carcass production per hectare.
• Methane yields varied significantly between seasons and age cycles.
• While intensive systems had higher total methane emissions per hectare, emission intensities (per weight gain or carcass) were not significantly different between production systems, but were lower in younger animals.

Conclusions:

• More intensive grazing systems increase carcass production per hectare but do not necessarily reduce methane emission intensity.
• Raising Nellore cattle to approximately 19 months in moderately intensified systems (DMS) or irrigated high stocking rate systems (IHS) can lower GHG emission intensity per kilogram of carcass.
• Moderate intensification strategies, combined with optimal animal age, show promise for mitigating GHG emissions from Brazilian tropical pastures.