This study aimed at investigating factors that contribute to changes in the quality of corn used in compound poultry feeds. Samples were collected from 6488 bulk cargos received at a feed mill located close to Brasília, Brazil. The parameters studied were divided into two groups: those related to corn chemical composition, including crude protein (% CP), ether extract (% EE), crude fiber (% CF), nitrogen-free extract (% NFE), and estimated metabolizable energy (ME), and corn physical characteristics, including density, moisture, and grain physical damage. High coefficients of determination (R²) and low coefficients of variation (CV) were determined for the chemical and physical parameters. The analysis of variance showed low to medium R². Month, year, supplier, and their interactions influenced (p <0.05) all chemical properties, as well as density, moisture, and ME. Physical characteristics were less affected by those factors, except for quantity of damaged grains. The principal component analysis separated the physical and chemical factors. The coefficients of the first component explained 54% of the total variation between variables. The first principal component showed that NFE and ME increased as humidity decreased. The second component also showed a decrease of physical problems due to reduction in humidity. Results indicate that the feed mills should take preventive measures when selecting suppliers, and diets should be formulated according to the differences in chemical and physical composition of corn supplied in different months and years.