The fermentation and drying process concentrates mycotoxins present in the original grain by roughly three times relative to the raw feedstock. Aflatoxin and deoxynivalenol (DON/vomitoxin) are the most common concerns; FDA has established action levels for both in animal feed. Importers should require a third-party mycotoxin certificate of analysis from each lot before acceptance.

Wet spent grain (high moisture) is typically a local or regional commodity due to rapid spoilage, while dried forms such as DDGS are shelf-stable and suitable for international trade. At the HTS level, wet versus dried presentation can affect the applicable tariff line, so the moisture specification in the commercial invoice should accurately reflect the product's condition at export.