A study was carried out using thirty-six dogs to assess the impact of six extruded diets with different starch sources, on dog total GI tract apparent digestibility and glycemic and insulinemic response. Six dogs were randomly allocated to each diet. While starch digestibility was greater than 98% across all diets, differences were observed in digestibility of dry matter, immediate post-prandial glucose and insulin responses and later meal responses. These variations can be explained by the differing chemistry of each starch source. Further investigation is required of the nutritional characteristics of each starch ingredient using diet formulations designed to modulate glycemic response.