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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.
Loza et al. (Fri,) studied this question.