Feeding and fertilization practices and greenhouse gas emissions in specialized dairy farms of Dos Pinos in Costa Rica

Emissions of methane (CH4) and nitrous oxide (N2O) based on the feeding systems of 104 dairy farms in Costa Rica were estimated using IPCC procedures. This study indicated that farmers' decisions, which determine the feeding strategies for lactating cows, have a substantial impact on CH4 emissions per kg of milk. Lower CH4 emissions per kg milk were estimated on farms with high-producing cows consuming rations with lower neutral detergent fiber concentrations and higher amounts of concentrates. Hours spent in pasture did not influence estimated grass intake or CH4 emissions. However, higher feed efficiency appeared to be a key factor in reducing CH4 emissions per kg of milk. The study also showed that higher N2O emissions were associated with higher amounts of commercial nitrogen fertilizer application; however, the main source of N2O emissions was from the manure deposited during the grazing period. Future approaches to reduce farm gate emissions of CH4 per kg of milk in specialized dairy farms could include incorporating dietary fats in rations, feeding adequate amounts of concentrates and feeding forage at a more digestible stage. These findings are strongly influenced by the assumptions made in calculating CH4 and N2O emissions but do highlight the critical areas which affect greenhouse gas emissions.