Considering greenhouse gas emissions from feed production in diet formulation for dairy cows as a means of reducing the carbon footprint

Dairy production often faces conflicting goals, such as reducing greenhouse gas emissions, increasing food production and achieving self-sufficiency without transgressing planetary boundaries. This study examined ways to decrease emissions intensity per kg of milk from high-producing cows by selecting feed ingredients with a low carbon footprint while also considering local alternatives. Diets comprising of grass-legume mixture silage and three concentrate mixtures (standard commercial, based on by-products, and domestic crops grown on-farm) were randomly allotted to three groups of high-producing Swedish Holstein cows (N = 48). Over 7 weeks, no differences were observed (mean ± SEM) in feed DM intake (commercial: 24.3, by-products: 24.7, domestic: 24.2 kg/day, ± 0.51 kg/day), energy-corrected milk (ECM) yield (commercial: 38.3, by-products: 38.5, domestic: 37.8, ± 0.98 kg/day) or enteric methane production (commercial: 387, by-products: 378, domestic: 402 g/day, ± 17.3 g/day) among the diets. However, an evaluation of the primary carbon footprint of feed production (excluding transportation emissions) showed that the by-products and domestic diets gave lower emissions than the commercial diet, 9.4, 10.2, and 11.9 Feed CO₂ equivalents (CO_2-eq) kg/day, respectively (SEM: ± 0.38 Feed CO_2-eq kg/day). The emission intensity, expressed as feed emissions per kilogram of ECM yield, showed that the by-product-based and domestic diets generated lower carbon footprints, with emissions of 254 and 284 g Feed CO_2-eq/kg ECM, respectively, in comparison to 320 g Feed CO_2-eq/kg ECM observed for the commercial diet (SEM: ± 10.7 g Feed CO_2-eq/kg ECM). Considering greenhouse gas emissions from feed production in diet formulation resulted in a lower overall feed carbon footprint and lower emission intensity per ECM. These findings can assist in formulating dairy rations for high-yielding dairy cows that balance conflicting goals while maintaining productivity.