Simulação de sistemas de produção de leite orgânico nos Estados Unidos

Abstract

Organic milk production is one of the fastest growing segments of US agriculture. There is an increasing number of US organic farmers who are transitioning to no grain supplementation due to additional premiums paid by some milk processors. However, there is limited information about the economic and environmental performance to support farmers decision to make the transition from grain to no grain feeding. Our objective was to compare the economic and environmental performance of traditional (ORG-T) vs. grass-fed (ORG-GF) organic dairy farms using the Integrated Farm System Model over 25 years of daily weather conditions. An average farm with 90 ha of land base, 52 Holstein cows, and 186 d of grazing was constructed using data from 84 organic dairies across 6 states (WI, PA, NY, NH, VT, and ME). The ORG-T diet was characterized by pasture, conserved feed including grass-legume and corn silages, and grain during the grazing season, and conserved feed and grain during the winter season. The ORG-GF was characterized by an all pasture diet during the grazing season, and all conserved feed diet except corn silage during the winter season. Milk price and annual milk production used in the simulations averaged 71.5 vs. 81.7$/100 L and 6,590 vs. 4,879 kg/cow for ORG-T vs. ORG-GF, respectively. The net return/cow was 35% greater in the ORG-GF ($2,766) than ORG-T ($2,051). Additional premiums paid by milk processors to the ORG-GF farm system appear to compensate for its lesser milk when production compared with the ORG-T farm system. Average greenhouse gas (GHG) emission, including biogenic CO2, was 87% greater in ORG-GF (0.56 kg of CO2 eq/kg of ECM) than ORG-T (0.30 kg of CO2 eq/kg of ECM), which is not surprising due to increased fiber intake and lesser milk production in ORG-GF cows. Overall, the ORG-GF farm system seems to be more profitable that its ORG-T counterpart, but at expense of more GHG emissions per unit of ECM. Farmers adopting the ORG-GF management should develop strategies to improve forage quality and milk production to reduce their farm carbon footprint.