Effects of graded dietary resistant starch concentrations on apparent total tract macronutrient digestibility, fecal characteristics, and fecal fermentative end-products in healthy adult dogs

Abstract Text: Resistant starch (RS) is fermentable by gut microbiota and effectively modulates fecal short-chain fatty acid (SCFA) concentrations in pigs, mice, and humans.  Resistant starch may have similar beneficial effects on the canine gut; however, the dose of a single source of RS that is effective in manipulating fecal fermentative end-products, but does not negatively affect stool quality, has yet to be determined.  Thus, the objective of this study was to evaluate the effects of 0, 1, 2, 3, and 4% dietary high-amylose maize cornstarch (HI-MAIZE® 260; RS) on apparent total tract macronutrient digestibility, fecal characteristics, and fecal fermentative end-product concentrations in healthy adult dogs.  An incomplete Latin square design was used, with each treatment period lasting 21 days (d0-17 adaptation; d18-21 fresh and total fecal collection) and each dog serving as its own control.  Seven dogs (mean age = 5.3 yr; mean BW = 20 kg) were randomly allotted to one of five treatments, which were formulated to be iso-energetic and consisted of graded amounts of 100% amylopectin cornstarch, RS, and cellulose, and fed as a top dressing on the food each day.  All dogs were fed the same amount of a basal diet throughout the study and fresh water was offered ad libitum.  Data were evaluated for linear and quadratic effects using SAS.  Because the RS used in this study is approximately 40% digestible and 60% indigestible starch, the dogs received the following amounts of indigestible starch daily:  0% = 0 g; 1% = 1.8 g; 2% = 3.6 g; 3% = 5.4 g; and 4% = 7.2 g.  Dry matter, organic matter, crude protein, fat, and gross energy digestibilities were linearly decreased (P < 0.05) in dogs with increased consumption of RS.  Fecal output was linearly increased (P < 0.05) in dogs with increased consumption of RS.  Fresh fecal pH was linearly decreased (P < 0.05) in dogs with increased consumption of RS.  Fecal scores and fecal fermentative end-product concentrations, including ammonia, SCFA, branched-chain fatty acids, phenols, and indoles, were not affected by the consumption of RS.  The results observed in this study compared to previous studies performed in other animal models and humans seem to indicate that RS is slowly fermentable in dogs and may not greatly impact large bowel health in this species.

Keywords: Resistant starch; Canine; Digestibility