Latest study confirms an animal-free food system is not holistically sustainable

By: Sara Place, Ph.D

Let’s be clear, a healthy and sustainable food system depends on having both plants and animals. Researchers at USDA’s Agricultural Research Service and Virginia Tech just published a study in the Proceedings of National Academies of Sciences confirming this socially debated fact. The study examined what our world would look like without animal agriculture in the U.S. The bottom line? We’d reduce greenhouse gas emissions in the U.S. by 2.6 percent, and 0.36 percent globally[1] — but we’d also upset our balanced food ecosystem and lack essential dietary nutrients to feed all Americans.

One important role livestock — such as cattle — play in our sustainable food system is taking human inedible food and ultimately making it nutritious. Specifically, cattle act as upcyclers — meaning they eat grasses and plant matter leftover from human food production and upgrade them into nutritional, high-quality protein. In fact, they produce 19 percent more edible protein than they consume[2].

Utesch Family Ranch

It’s worth noting, too, that human-inedible plants and leftovers make up a vast majority of livestock diets. According to a study from scientists at the United Nations Food and Agriculture Organization, 86 percent of what livestock eat globally is human-inedible plants and leftovers[3]. Research from the National Academies of Sciences, Engineering, and Medicine concluded that human-inedible plants and leftovers make up nearly 90 percent of a U.S. grain-finished beef animal’s lifetime feed consumption, while less than 10 percent of what they eat is grain[4]. Cattle graze the residues of grain harvest (the stalks and leaves left in the field after corn harvest), eat the byproducts from milling grains for flour production (wheat midds), cottonseed that is a leftover of cotton production, and distillers grains leftover from soy biodiesel and corn ethanol production.

Another benefit of livestock that is often overlooked is its use of otherwise unusable land for agriculture. More than 85 percent of the land where we graze cattle is not suitable for growing crops because it is too rocky, steep and/or arid to support cultivated agriculture[5][6].

If you eat a USDA-certified organic diet, what’s one of the major fertilizer sources for your vegetables, grains, and other plant foods? Animal manure. What consumes 1.9 billion pounds a year of plant-based leftovers produced by the U.S. human food, fiber, and biofuel industries? Livestock. Without livestock, how would we dispose of these plant-derived leftovers without creating an environmental problem?

Rather than continuing to debate what needs to come off our dinner plate all together, let’s start focusing our attention on making the whole plate better. The social battle underway about what type of agriculture is best (local vs. non-local, vegan vs. omnivore, organic vs. conventional, grass-fed vs. grain-fed) is getting us nowhere. We need it all for a resilient food system that provides choice and affordable, nutritional options. Our greater opportunity is in improving the food system’s sustainability, such as better soil health, economic viability of farmers, animal welfare, and lower greenhouse gas emissions, regardless of the production system.

Sara Place, Ph.D., is senior director, sustainable beef production research, at NCBA, a contractor to the Beef Checkoff Program. She was previously assistant professor in the Department of Animal Science at Oklahoma State University. Raised on a dairy farm in Chenango County, N.Y., she received her Ph.D. in Animal Biology from the University of California, Davis, and her B.S. in Animal Science from Cornell University

[1] White, R.R. and M.B. Hall. 2017. Nutritional and greenhouse gas impacts of removing animals from US agriculture. Proceedings of the National Academies of Sciences. 114(48) E10301-E10308. DOI: 10.1073/pnas.1707322114 (Note: 0.36% of global emissions calculated from estimate of 49 gigatons (Gt) of anthropogenic carbon dioxide equivalents emitted in the year 2010 from the Intergovernmental Panel on Climate Change Fifth Assessment Report. Summary of the report can be found at this link:

[2] Council for Agricultural Science and Technology (CAST). 1999. Animal Agriculture and Global Food Supply. Task force report N. 135 July 1999, Department of Animal Science, University of California, Davis, CA, USA. Available at:

[3] Mottet et al., 2017. Livestock: On our plates or eating at our table? A new analysis of the feed/food debate. Global Food Security. 14: 1–8.

[4] National Academies of Sciences, Engineering, and Medicine. 2016. Nutrient Requirements of Beef Cattle: Eighth Revised Edition. Washington, DC: The National Academies Press.

[5] 2011 Cattlemen’s Stewardship Review. Available at:

[6] USDA, Economic Research Service using data from the Major Land Use data series. Available at: