Recent cattle feeding economics in the upper Midwest have encouraged increasing inclusion of distillers grains in feedlot rations. There have been suggestions that changes in grain processing may be beneficial as starch content of the diet decreases. Recently methods have been developed to estimate fecal starch digestibility in field studies using fecal protein as a marker. An estimate of fecal starch digestibility across a wide range of distillers grain inclusion and starch levels would be useful information to evaluate the utility of more extensive grain processing. This study was an evaluation of field estimates of fecal starch digestion as part of a larger study evaluating dietary cation-anion exchange in very high levels of distillers grains with solubles. Estimated starch digestibility tended to decrease as the level of modified distillers grains with solubles increased from 0 to 75% of the diet, suggesting that additional research evaluating further processing of corn for high distillers grains diets may be warranted.