Evaluation of selected high-starch flours as ingredients in canine diets

Cereal grains represent 30 to 60% of the DM of many companion animal diets. Once incorporated into a diet, the starch component of these grains can provide an excellent source of ME. However, crystallinity and form of starch are variable and can cause incomplete digestion within the gastrointestinal tract. Diets fed in this experiment included one of six high-starch flours as the main source of carbohydrate. The flours originated from barley, corn, potato, rice, sorghum, and wheat. The diets were extruded and kibbled. Starch fraction concentrations of flours consisted of nearly 100% rapidly digestible starch (RDS) and slowly digestible starch (SDS) combined. Starch fraction concentrations of diets paralleled concentrations in flours. Flours varied widely in concentrations of CP, fat, starch, and total dietary fiber. Ileal OM and CP digestibilities were lowest for the potato flour treatment (74 and 64%, respectively). Ileal and total tract starch digestibilities were different (P<.05) among treatments; however, the starch component of all diets was nearly completely digested (>99%). Total tract digestibility of DM and OM was lowest for sorghum (80 and 84%, respectively) compared to all other diets. Crude protein digestibility was highest for corn (87%). Wet fecal weights tended (P<.08) to be greatest for dogs fed the barley treatment (175 g/d). However, dry fecal weights (dried at 55 degrees C) were greatest for dogs consuming the sorghum diet (51 g/d). Fecal scores were consistently greater (i.e., looser stools) for the barley treatment. Any of these flours could be used without negative effects on digestion at either the ileum or in the total tract. Fecal consistency data for dogs consuming the barley treatment indicate that diets containing large amounts (>50%) of barley may not be advantageous for dog owners who house their animals indoors for most of the day.