According to the Renewable Fuels Association as of 2018 there was >40 MMT of distillers grains coproducts produced in the U.S. Over 75% of those coproducts are fed to beef and dairy cattle. There are numerous reviews of the nutrient and chemical composition of distillers grains co-products, including the analysis of low molecular weight organic compounds . To our knowledge there have been no reports of ethyl carbamate as a component of distillers grains co-products, despite the known occurrence as a fermentation by-product whose levels are regulated for human consumption. This lack of scientific literature prompted two questions, 1) is EC present in the co-products derived from the production of ethanol from corn or milo (sorghum)? 2) if so, does EC accumulate in animals fed fermentation co-products? Methods for EC quantification published in the past decade were mostly adapted from the AOAC method 994.07 , the majority of which focused on alcoholic beverages and fermented foods . Reports on EC quantification in biological samples were very limited . Thus, analytical methods specific for distillers grains co-products and bovine blood/plasma are needed to assess how incorporating fermentation co-products into feeds have impacted animal nutrition with respect to the potential toxicity of EC. This report describes a GC-MS assay for sensitive and selective quantification of EC. This assay was then applied for analysis of EC from samples of distillers grains coproducts and bovine plasma samples.