Abstract Demand for grass-based dairy production, which relies heavily on grazing and use of forage crops, is growing in the United States, primarily due to reported human health benefits of the milk produced as well as perceived environmental and animal welfare benefits. We used a whole-farm model to evaluate environmental footprints of all-grass, grass supplemented with grain, and confinement dairy production systems in the temperate climate of the northeastern U.S. Model results were depicted per unit of farmland and per unit of milk produced to provide alternate perspectives from the viewpoint of land management and commodity production. For most environmental indicators, the grass-based systems had smaller environmental impacts per unit of farmland but larger impacts per unit of milk produced compared to confinement fed systems. To verify the simulation of grass-based operations, eight dairy farms - ranging from herds that were grazed and fed only forage to herds that received some grain supplementation - were surveyed and modeled. Due to variation in climate, soil characteristics and management practices, a comparison of the two grass-based farm types showed no significant differences in environmental impacts. Farms of the same size using each production strategy along with a more traditional confinement production system were then simulated using the same climate and soil conditions for a better comparison. Predicted nitrogen and phosphorus losses to the environment, fossil energy use, water use, and greenhouse gas emissions were less from the grass-based farms compared to the confinement operation. Due to lower milk production on the grass-based dairies, nutrient losses and greenhouse gas emissions expressed per unit of milk produced were generally greater than those of the confinement system. Within the grass-based dairy systems, the system that supplemented with grain had slightly lower nitrogen and phosphorus losses per unit of farmland compared to the grass-only system, and much lower losses and emissions when expressed per unit of milk produced. Total production cost was less for the all-grass dairy than the grass with grain dairy. With a greater milk price, the all-grass system provided greater profitability per unit of land used and per unit of milk produced compared to the confinement farm of similar size. These data indicate that grass-based dairy farms can provide environmental benefits to a local watershed, but due to a lower efficiency in milk production, they may increase the aggregate environmental impacts of regional and global supply chains.

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美国东北部草本乳制品生产的环境评估

摘要 美国对严重依赖放牧和使用饲料作物的草基乳制品的需求正在增长，这主要是由于所生产的牛奶对人类健康的益处以及感知到的环境和动物福利益处。我们使用全农场模型来评估美国东北部温带气候下全草、草辅谷物和月子奶生产系统的环境足迹 模型结果描述了每单位农田和生产的每单位牛奶，以提供土地管理和商品生产的不同观点。对于大多数环境指标，与月子喂养系统相比，基于草的系统对每单位农田的环境影响较小，但对每单位生产的牛奶产生的影响较大。为了验证基于草的操作的模拟，对八个奶牛场进行了调查和建模——从放牧和仅饲喂草料的牛群到接受一些谷物补充的牛群。由于气候、土壤特征和管理实践的差异，两种草本农场类型的比较显示在环境影响方面没有显着差异。然后使用相同的气候和土壤条件模拟使用每种生产策略以及更传统的圈养生产系统的相同规模的农场，以进行更好的比较。与封闭操作相比，基于草的农场对环境、化石能源使用、水使用和温室气体排放的预测氮和磷损失较少。由于草基奶牛场的牛奶产量较低，以每单位生产的牛奶表示的营养损失和温室气体排放量通常大于限制系统的营养损失和温室气体排放量。在以草为基础的乳品系统中，与纯草系统相比，补充谷物的系统每单位农田的氮和磷损失略低，每生产单位牛奶的损失和排放量要低得多。全草乳制品的总生产成本低于含谷物乳制品的草。由于牛奶价格更高，与类似规模的月子农场相比，全草系统每单位使用的土地和生产的每单位牛奶提供更高的盈利能力。这些数据表明，草基奶牛场可以为当地流域带来环境效益，但由于牛奶生产效率较低，