Cyanide poisoning
Sorghum and its by-products may contain cyanogenic glucosides. Inconsistent results have been reported for brewer's grains in Nigeria, from total absence in spent grains from red and white varieties (Adewusi et al., 1994) to levels higher than safe limits (128 mg/kg DM vs. 50-100 mg/kg) (Okafor et al., 2003).
Tannins
Many sorghum varieties contain tannins, which have detrimental effects on the nutritive value of the grain and its by-products, particularly for monogastric species. By-products that contain large amounts of testa tend to concentrate tannins and should, therefore, be cautiously used for poultry and pig feeding. It should be noted that tannins may or may not be considered beneficial for food production. In some traditional foods and beverages, the phenolics of red sorghum give a desired flavour and colour. In sorghum liquor manufacture, tannins inhibit harmful micro-organisms and increase productivity, while producing aromatic compounds that give sorghum liquors their special flavour. However, low-tannin sorghums without testa are preferred in the starch extraction process, as sorghum pigments can discolour the end product (NRI, 1999). White sorghums are also being promoted in West Africa for the brewing of lager beer due to their low levels of phenolics (INTSORMIL, 2008).
Mycotoxins
Fresh sorghum by-products such as sorghum beer residues are prone to moulding, which may cause severe toxicity. In South Africa, 76 cows (from a herd of 100) developed a neurological syndrome (weakness of the hindquarters, ataxia and eventually paralysis) after consuming sorghum beer residues contaminated with Aspergillus clavatus over a period of 8 months (Lugt et al., 1994).