Mitigation of enteric methane emissions: cattle finished on pasture in an extensive system, fertilized or intercropped between grass and legumes

Abstract

Beef cattle production plays a key role in global food security. In this context, mitigation and intensification strategies (such as legume-grass intercropping and pasture fertilization) can reduce environmental impacts and support sustainable meat production, contributing to lower enteric methane (CH₄) emissions and enhance productivity in pasture-based finishing systems. This study was conducted from August 2021 to August 2022 at Embrapa Southeast Livestock (São Carlos, SP, Brazil). A total of 27 animals (27 ± 1 months old and 355.2 ± 6.8 kg) were used and weighed monthly. CH₄ emissions were measured using the sulfur hexafluoride (SF₆) tracer gas technique. Three treatments were evaluated with three replications each: 1) degraded pasture of Urochloa decumbens cv. Basilisk (DEG); 2) dryland pasture with a mixture of U. decumbens cv. Basilisk and U. brizantha cv. Marandu, recovered with 200 kg.N-urea.ha^-1.year^-1 (REC); 3) dryland pasture with a mixture of U. decumbens cv. Basilisk and U. brizantha cv. Marandu intercropped with Cajanus cajan cv. BRS Mandarim (MIX). Each treatment was assigned to three paddocks (1.25 ha), with stocking rates adjusted by the "put-and-take" technique. Performance and CH₄ emissions data were submitted to ANOVA, and means were compared by the Fisher test (5%) in SAS^® (PROC MIXED). Average daily CH₄ emissions (g/day) were not affected by treatment. However, annual CH₄ emissions per hectare were significantly lower in MIX and REC (158.8ᵇ and 170.2ᵇ kg/ha.year⁻¹, respectively) compared to DEG (436.3ᵃ kg/ha.year⁻¹). Similarly, CH₄ emissions per animal unit (AU = 450 kg body weight) were lower in MIX and REC (166.0ᵇ and 120.6ᵇ kg/AU.year⁻¹, respectively) than in DEG (179.4ᵃ kg/AU.year⁻¹). DEG had the highest CH₄ emissions, likely due to poor forage quality. MIX and REC, with intensification strategies, reduced CH₄ emissions and improve the productive efficiency of beef cattle, highlighting the importance of pasture management for sustainable production.