Methane emissions in pasture-based systems with contrasting intensification strategies in Uruguay in two periods: operational simplicity vs maximised productivity

Meeting the growing demand for high-quality animal protein while minimising environmental impact is a major challenge for dairy systems. In Uruguay, where livestock production accounts for roughly 73% of national greenhouse gas ( GHG ) emissions, mainly from enteric methane ( CH 4 ), pasture-based dairy systems must adapt to align with sustainability goals. This study evaluated whether two pasture-based dairy systems with contrasting intensification strategies could maintain low CH 4 emissions while sustaining productive efficiency. A low-input, operationally simple system ( OS ) with a stocking rate of 1.8 livestock units per hectare ( LU/ha ) was compared with a higher-input, productivity-oriented system ( HP ) at 3.0 LU/ha. Both systems were based on perennial pastures of similar botanical composition and managed under structured rotational grazing. Enteric CH 4 emissions were measured during winter and spring 2023 in 24 Holstein and Holstein × Jersey cows (12 per system), using the sulphur hexafluoride ( SF 6 ) gas-tracer technique. Milk yield and diet composition were also evaluated. Despite the higher stocking rate ( SR ) and greater annual milk yield in the HP system (10 106 vs 7 262 kg of milk per hectare), daily methane emissions per cow (280 g CH 4 /cow per day) and CH 4 emission intensity corrected per kg of fat and protein corrected milk ( FPCM ) were similar between systems (11 g CH 4 /kg FPCM, on average). However, CH 4 emissions per hectare were higher in the HP system (9.1 vs 6.8 kg CH 4 /ha per day), reflecting the impact of the higher SR on total emissions. When compared with values commonly reported for pasture-based dairy systems (10 – 21 g CH 4 /kg FPCM), both systems were at the lower end of this range for CH 4 intensity. These findings suggest that well-managed pasture-based dairy systems can sustain different intensification strategies without compromising environmental performance. However, continued efforts are needed to improve resource use efficiency and further reduce total greenhouse gas emissions.