Sulphate toxicity
Due to the use of sulphuric acid in the manufacturing process, ethanol by-products may be high in sulphate (0.5-1.7% DM) (McAloon et al., 2000), which increases the risk of sulphur toxicity in livestock fed large amounts of distillers grain. A high concentration of H2S inhibits the oxidative processes in nervous tissue and results in a central nervous system disorder called polioencephalomalacia, which may affect up to 6% of cattle fed diets containing more than 0.56% sulphur (Gould, 1998; Vanness et al., 2009).
Aflatoxins
Wheat intended for ethanol production should be free of ergot, fusarium and vomitoxin. These impurities do not break down in ethanol production and can be concentrated approximately threefold in the DDGS (Newkirk, 2011).
Copper
Some traditional whisky distilleries use copper stills and pipework (rather than stainless steel), and their by-products tend to contain high levels of copper, which is toxic to sheep. Maize distillers dark grain, for instance, may contain between 15 and 120 mg/kg of copper. Since copper content and biological copper availability are highly variable in whisky by-products, it is essential to check copper levels before buying such products if they are to be fed to sheep (Lewis, 2002). Copper is not an issue in industrial ethanol production.