Mitigation of enteric methane emissions through pasture management in integrated crop-livestock systems: Trade-offs between animal performance and environmental impacts

Abstract

We evaluated the effect of different grazing intensities by steers on animal performance, herbage intake and CH4 emissions in the stocking period of a soybean-beef cattle integrated system in southern Brazil. Treatments consisted of different grazing intensities, defined by target sward heights (10, 20, 30 and 40 cm) of mixed black-oat (Avena strigosa Schreb.) and Italian ryegrass (Lolium multiflorum Lam.) pastures under continuous stocking. Grazing management affected herbage utilization and, consequently, animal performance and CH4 emission. At the individual level, CH4 emission and animal performance had optimal values when pasture height was managed within a range of 23–30 cm. At the farm level, we found a positive linear effect of grazing intensity on animal live weight gain per hectare and the associated environmental costs of land use. Liveweight gain increased by 90 g ha−1 day−1 and CH4 emissions increased by 500 g CO2eq ha−1 day−1 for each cm of target sward height reduction. Given that most producers graze pastures to very short heights, large-scale adoption of target heights within 23–30 cm in southern Brazil has the potential to achieve 13–14% of the mitigation target for GHG emissions from the whole agricultural sector and 22–25% of the target for enteric fermentation from the livestock sector pledged by the Brazilian Government in the Paris Agreement. We conclude that adequate grazing management is the key strategy to improve animal production and reduce the environmental impact from livestock in ICLS.