Contributions of dairy products to environmental impacts and nutritional supplies from United States agriculture

摘要

Questions regarding the balance between the contributionto human nutrition and the environmentalimpact of livestock food products rarely evaluate specificspecies or how to accomplish the recommendeddepopulation. The objective of this study was to assesscurrent contributions of the US dairy industry to thesupply of nutrients and environmental impact, characterizepotential impacts of alternative land use for landpreviously used for crops for dairy cattle, and evaluatethe impacts of these approaches on US dairy herd depopulation.We modeled 3 scenarios to reflect differentsets of assumptions for how and why to remove dairycattle from the US food production system coupled with4 land-use strategies for the potential newly availableland previously cropped for dairy feed. Scenarios alsodiffered in assumptions of how to repurpose land previouslyused to grow grain for dairy cows. The currentsystem provides sufficient fluid milk to meet the annualenergy, protein, and calcium requirements of 71.2, 169,and 254 million people, respectively. Vitamins suppliedby dairy products also make up a high proportion oftotal domestic supplies from foods, with dairy providing39% of the vitamin A, 54% of the vitamin D, 47% ofthe riboflavin, 57% of the vitamin B_(12), and 29% of thecholine available for human consumption in the UnitedStates. Retiring (maintaining animals without milkharvesting) dairy cattle under their current managementresulted in no change in absolute greenhouse gasemissions (GHGE) relative to the current productionsystem. Both depopulation and retirement to pastureresulted in modest reductions (6.8–12.0%) in GHGErelative to the current agricultural system. Most dairycow removal scenarios reduced availability of essentialmicronutrients such as α-linolenic acid, Ca, and vitaminsA, D, B_(12), and choline. Those removal scenariosthat did not reduce micronutrient availability also didnot improve GHGE relative to the current productionsystem. These results suggest that removal of dairycattle to reduce GHGE without reducing the supply ofthe most limiting nutrients to the population would bedifficult.