Methane emissions and growth performance of beef cattle grazing multi-species swards in different pesticide-free integrated crop-livestock systems in southern Brazil.

The aim of this study was to assess the growth performance, forage intake and methane (CH 4) emissions by beef cattle grazing under different spatiotemporal integrated crop-livestock systems (ICLSs). The experiment was conducted for two years (2017–2018 and 2018–2019) in warm season perennial pastures and cool season annual pastures grazed by beef steers. Three pesticide-free ICLS treatments – livestock-forestry (LF); crop-livestock (CL), and crop-livestock-forestry (CLF) – plus, a livestock control pesticide-free system (L) were conducted in randomized complete block design, with three replicates per treatment. Maize crop rotation was done with cool season cover crop under no-tillage. Eucalyptus trees (Eucalyptus benthamii) were planted in 2013 and intercropped with tree alleys. The animal performance, organic matter (OM) intake and enteric CH 4 emission, yield, and intensity were assessed. We found no significant difference (P > 0.05) for average daily gain (ADG), stocking rate (SR), and daily live weight gain (LWG) per area for the different ICLS arrangements and seasons. The ICLS arrangements did not affect (P > 0.05) CH 4 emission, yield, and intensity, with averages of 186 g steer−1 day−1, 26 g kg−1 OM intake and 210 g kg−1 of ADG, respectively. The average CH 4 emissions per steer per day, per OM intake, per ADG and LWG per area were greater (P < 0.05) for steers when grazing warm season compared to cool season pastures. The integration or not of beef cattle with crops and/or forestry does not influence CH 4 emissions, yield, and intensity by beef steers grazing pastures under moderate grazing intensity. Our results reinforce that well-managed integrated systems are a reliable climate-smart agriculture alternative for increasing production, e.g., grain, wood, meat, and mitigating or without increasing greenhouse gas emissions, such as CH 4 from enteric fermentation in beef cattle. • Different ICLSs do not affect the beef cattle's performance in moderate grazing management. • Intake and forage quality of pastures are not affected by ICLS arrangements. • ICLS arrangements do not affect enteric CH 4 emission. • CH 4 emissions were higher in warm season than cool season pastures. • A well-managed ICLS is an important diver of sustainability. [ABSTRACT FROM AUTHOR]