The impact of diseases in dairy cows on greenhouse gas emissions of milk production

Combining life cycle assessment with a dynamic stochastic simulation model allows to simulate the dynamics and consequences of diseases in livestock, and to reduce the environmental impact of our food production systems. This study aims to estimate the impact of diseases in dairy cows on greenhouse gas (GHG) emissions of milk production, using the Dutch situation as a case study, and contributes to reaching the sustainability development goals by providing information about climate change mitigation. Three diseases with a high incidence in intensive milk production systems were included: foot lesions, clinical mastitis, and subclinical ketosis. First, a dynamic stochastic Monte Carlo simulation model was used to simulate the impact of diseases on dairy cow productivity. Cows received a parity (1-5+), a potential milk production, and a risk of a disease. Based on type of disease, cows had a reduced daily milk yield, discarded milk if treated with antibiotics, a prolonged calving interval, and an increased risk of removal. Second, an LCA was performed to quantify the impact of diseases on GHG emissions from cradle-to-farm gate. Emissions of carbon dioxide, methane and nitrous oxide were estimated for processes along the dairy production chain that were affected by the consequences of diseases, including feed production, manure management and enteric fermentation. System expansion was applied to account for the production of meat from culled animals. Emissions of GHGs were estimated for a cow and herd with and without one of the diseases and were expressed as the sum of kg CO2 equivalents (100 years’ time horizon) per ton of fat-and-protein-corrected milk (kg CO2e/t FPCM). On average, GHG emissions increased by 1.5% per case of foot lesions, 6.2% per case of clinical mastitis, and 2.3% per case of subclinical ketosis. The increase in GHG emissions showed a high variation between parity and type of disease. Removal of cows was an important contributor for all diseases, and can increase GHG emissions by >50%. At the national level, the increase in GHG emissions resulting from these three diseases was estimated to be 0.4 Mton CO2e per year in total, which equals 15% of the total emission reduction target for the agricultural sector that is set by the Dutch government. In conclusion, reducing diseases in dairy cows is an effective strategy to mitigate GHG emissions of milk production and can contribute to sustainable development of the dairy sector.