Factors affecting digestibility of starches and their implications on adult dog health

Abstract

Pet food represents a large share of the U.S. economy, and the majority of it is produced through extrusion. Starches comprise between 30% and 60% of extruded dog foods and sources include cereals, tubers, legumes, and co-products from the human food chain. Starches are well digested and metabolized by dogs, with variations according to food processing parameters, starch source, and dog breed. Dogs have a higher expression of enzymes related to starch digestion, glucose absorption and metabolism compared to the wolf. Several studies have reported that starch total tract apparent digestibility (ATTD) by dogs is well above 95%. Although starches are not required by dogs, they are an important source of energy and provide structure and binding of kibbles. The degree of starch digestion depends on factors like granular structure, amylose: amylopectin ratio, degree of gelatinization, and other nutrients present in the food matrix such as fibers, lipids and proteins. Tubers and legumes are well utilized by dogs, but most times require heat treatment to deactivate anti-nutritional factors and improve digestibility, while cereal starches seem to be well digested even in their raw form. Slowly digestible or resistant starches may contribute to satiety, lower glucose and insulin responses and improved colonic microbiota. In conclusion, there is enough evidence supporting that properly processed cereals and tubers included in dog foods are digestible, palatable and do not present health concerns, but the scientific literature lacks information on pulses, ancient grains, and food processes beyond extrusion.