Sulphate toxicity
Due to the use of sulphuric acid in the 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).
Mycotoxins
Maize is susceptible to fungal infections producing mycotoxins, including aflatoxin, fumonisins, deoxynivalenol (vomitoxin), ochratoxin, T2 toxin and zearalenone. Due to the concentration that non-starch components undergo during the distillery process, mycotoxin concentrations are about three-fold in corn distillers grain compared to the original grain. It is thus of utmost importance that maize intended for bio-ethanol production be free of mycotoxins before processing. There are also ways to alleviate mycotoxin problems, such as removing damaged grains before they enter the process (Keshun Liu, 2011). Chemical treatments (NaOH, NH4OH, H2O2, NaClO, CH2OH) have been investigated to detoxify mycotoxins in stillage (Bennett et al., 1981; Lillehoj et al., 1979).
Copper
Certain traditional whisky distilleries use copper rather than stainless steel, for stills and pipework, 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. While 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.