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

Authors: LIEBE, DOUGLAS - Virginia Polytechnic Institution & State University; Hall, Mary Beth; WHITE, ROBIN - Virginia Polytechnic Institution & State University

Submitted to: Journal of Dairy Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/20/2020
Publication Date: 11/1/2020
Citation: Liebe, D.L., Hall, M.B., White, R.R. 2020. Contributions of dairy products to environmental impacts and nutritional supplies from United States agriculture. Journal of Dairy Science. 103(11):10867-10881. https://doi.org/10.3168/jds.2020-18570.
DOI: https://doi.org/10.3168/jds.2020-18570

Interpretive Summary: Recommendations to abandon animal agriculture or remove animal products from our diets typically assume that a plants-only diet will meet people’s nutritional needs and that greenhouse gas emissions (GHGE) will decline. At the same time, no mention is made of how elimination of livestock will occur, but this matters for animal welfare and public perception concerns. In a study to evaluate the impact of removing dairy cattle from U.S. agriculture and its impact on GHGE and the U.S.’s ability to meet the nutrient needs of its people, we modeled 3 scenarios for removing dairy cattle from U.S. agriculture: dairy cattle kept under current management and all products are exported, are immediately depopulated through slaughter, or were retired to pasture. Retirement to pasture was included, not so much as a practical option, but one that the public might find more acceptable than slaughter. Available pasture could support approximately 44% of the national dairy herd. We also explored 4 options for repurposing the cropland used to feed dairy cattle: allocation to crops in the proportions currently grown in the U. S., to fruits and vegetables, to nuts and legumes, or to nongrain, nonoilseed, nonsugar crops. We assumed that tillable land would not go out of production. Dairy cow removal scenarios reduced U.S. GHGE minimally (0% for current management, and 1.0% for retirement to pasture). Effect of dairy cattle depopulation depended upon how the cropland was repurposed. Food production would be increased, and, with reallocation only of land used for silage, all cropping scenarios reduced U.S. national GHGE by 0.6 to 0.7%, except for conversion to all vegetables and fruits which were neutral (~0%). However, when grain and silage land was repurposed to fruits and vegetables, GHGE increased by 0.8%. Elimination of dairy products from U.S. diets would show the greatest reduction in available sources of the essential nutrients calcium (-73%), vitamins D (-54%) and B12 (-57%), and choline, vitamin A, and alpha- linolenic acid. Although some reduction in GHGE would be achieved with elimination of dairy cattle farming in the U.S., food supplies of some limiting essential nutrients would decline under all scenarios which would affect the ability to meet the U.S. population’s nutrient requirements from foods.

Technical Abstract: Questions regarding the balance between contribution to human nutrition and environmental impact of livestock food products rarely evaluate specific species or how to accomplish the recommended depopulation. The objective of this study was to assess current contributions of the U.S. dairy industry to the supply of nutrients and environmental impact, characterize potential impacts of alternative land use for land previously used for crops for dairy cattle, and evaluate the approaches’ impacts on U.S. dairy herd depopulation. Data on U.S. dairy production were obtained from the analysis conducted by White and Hall (2017; https://doi.org/10.1073/pnas.1707322114). We modeled three scenarios to reflect different sets of assumptions for how and why to remove dairy cattle from the U.S. food production system coupled with 4 land use strategies for the potential newly available land previously cropped for dairy feed. Scenarios also differed in assumptions of how to repurpose land previously used to grow grain for dairy cows. The current system provides sufficient fluid milk to meet the annual energy, protein, and calcium requirements of 71.2, 169, and 254 million people, respectively. Vitamins supplied by dairy products also make up a high proportion of total domestic supplies from foods, with dairy providing 39% of the vitamin A, 54% of the vitamin D, 47% of the riboflavin, 57% of the vitamin B12, and 29% of the choline available for human consumption in the U.S. Retiring (maintaining animals without milk harvesting, dairy cattle under their current management resulted in no change in absolute greenhouse gas emissions (GHGE) relative to the current production system. Both depopulation and retirement to pasture resulted in modest reductions (6.8 to 12.0%) in GHGE relative to the current agricultural system. Most dairy cow removal scenarios reduced availability of essential micronutrients such as alpha-linolenic acid, Ca, and vitamins A, D, B12 and choline. Those removal scenarios that did not reduce micronutrient availability also did not improve GHGE relative to the current production system. These results suggest that removal of dairy cattle to reduce GHGE without reducing the supply of the most limiting nutrients to the population would be difficult.