Unground feedstuffs like cereals and roughage which are conspicuous by high proportions of finer particles and dust have to be estimated as risky environmental factors due to the accumulation of microorganisms (moulds, bacteria and lipopolysaccharides) and mites in the fines frequently. The dusty fraction in feed samples should be separated by sensorial inspection of feedstuffs (for example by sieves) and has to be looked at (using pocket lens) critically to find out lacks in the hygienic quality of feedstuffs. Dusty qualities of roughage contain high counts of moulds frequently, therefore a mycological investigation is to be recommended for these samples. The feedstuffs may influence the quantity and quality of air dust within the stable as the starch content (similar to the fed diet) indicates. Likewise corresponding LPS contents were measured in feeds and airborne dust of pig stables. Due to the high counts of microorganisms in the dusty fraction of cereals an intensive cleaning procedure for cereals has to be recommended for minimizing the load of germs; a reduced risk for deterioration can be expected. The residues of cleaning processes (combined mechanic/pneumatic procedures) of cereals should not be reutilized in the production of compound feeds by feed manufacturers, the nutritive value is relatively low anyway due to the high ash- and fiber-contents. Potential risks of dusty feedstuffs to animals' health and the influences of mites, moulds and lipopolysaccharides on the development of gastrointestinal and respiratoric disturbances are discussed. Experimental investigations are needed to elucidate the role of inhaled dust--and its content of lipopolysaccharides especially--in the development of respiratory diseases in veterinary medicine.