To investigate and compare commercial and farm-level milling operations in respect of the monitoring and control of Salmonella contamination.

Four commercial feedmills and four on-farm poultry feed mixers were intensively sampled. Samples included dust and spillages and were cultured for Salmonella. Serovars in ingredients on farms were associated with wildlife and/or livestock, whereas those in commercial mill ingredients were associated with domestically-produced cereals and imported vegetable protein. Endemic contamination of two commercial feedmills was reflected in isolates obtained from finished products and destination flocks. Renovation of equipment and chemical treatment of equipment and feed had not removed endemic strains, and previous routine monitoring in the commercial mills had not revealed the degree of contamination found in the present investigations.

Ingredient contamination was diverse and reflected the sources and storage environments used by mills and farms, respectively. The use of dust and spillage samples showed a clear sensitivity advantage over the previously-used monitoring methods in the feedmills.

Monitoring for Salmonella contamination of commercial feedmills requires sensitive methods, such as those employed in the present study. This is particularly important for endemic contamination.