Low‐Shear Extrusion of Grains Retains Resistant Starch to Increase Saccharolytic Activity of the Canine Gut Microbiome
Authors: Jackson Matthew Irick , Jewell Dennis E. , Waldy Christopher 
Published: June 2021

Processing of foods can increase digestibility and bioavailability of nutrients to improve the quality of diets. However retaining a low level of uncooked starchy carbohydrate can provide health benefits through action of the gut microbiome on digestion‐resistant starch (RS). We examined the impact of extrusion‐based processing of canine diets on fecal metabolites related to microbiome activity and host health. Identically formulated diets composed of corn, rice, egg, poultry meal, corn gluten, lard were produced with either HIGH or LOW shear force. Specific Mechanical Energy (SME) for the HIGH shear was calculated to be 48 W.h/kg, and the Specific Thermal Energy (STE) was 41 W.h/kg, for a Total Energy (TE) of 89 W.h/kg. The SME for the LOW shear parameters was calculated to be 10 W.h/kg, and the STE was calculated to be 42 W.h/kg, for a TE of 51 W.h/kg; a ~4‐fold reduction in MSE under the LOW shear parameters. Values provided are means ± SD. Based on extrusion and viscosity analysis, diets provided 0.8 ± 0.2 (HIGH) and 14.2 ± 3 (LOW) g resistant starch/100 g diet. Dogs were housed in pairs, provided daily group exercise in outdoor grassy runs and had access to natural light that varied with season. Health was monitored through clinical and physical indices. Collections were carried out under IACUC approved protocols. Dogs were fed to main healthy body weight. Dogs were calculated to consume 1.9 ± 0.8 (HIGH) and 34.8 ± 13.0 (LOW) g RS/day for dogs weighing 12.7 ± 2.3 kg. Fecal composition, quality and short chain fatty acids (SCFA) were assessed along with the fecal metabolome and microbiome. Analysis of feces from dogs consuming HIGH and LOW RS diets indicated that extrusion energy didn't impact fecal moisture, ash, organic dry matter or dry matter digestibility. Protein digestibility was slightly decreased on the LOW diet (HIGH = 92.4 ± 3.0, LOW = 89.4 ± 3.4; p < 0.05). Stool quality was not impacted by extrusion (5 point scale, 5 is best; HIGH = 4.34 ± 0.48, LOW = 4.17 ± 0.39). Dogs consuming the LOW diet produced feces with higher levels of the SCFA propionate (p = 0.056) and butyrate (p = 0.057). When fecal metabolomics were assessed, cholate and lithocholate bile acids increased on the LOW diet, but tauro and glycol‐conjugates of these decreased. Fecal long chain endocannabinoid ethanolamides were decreased by the LOW diet, while 2‐lipoylglycerols were increased. Although fecal amino acids did not differ by extrusion, levels of putrefactive methylbutyryl, valeryl and isovaleryl amino acid conjugates were significantly increased in feces from HIGH‐fed dogs. Conversely, fecal levels of maltotetrose, maltotriose and glucose were higher in LOW‐fed dogs, indicating that starch polymer reached the colon intact. At the genus level, HIGH diet increased relative abundances of Allobaculum, Blautia, Ruminococcus (Lachno), Megamonas, Dorea and Actinomyces, while LOW diet increased abundances of Adlercreutzia, Lactococcus, Dialister, Ruminococcus (Rumino), Prevotella, Pectinatus and Enterococcus with a trend toward increased Lactobacillus (p < 0.1). In summary, canines fed identically formulated diets produced with LOW or HIGH shear force had minimal changes in fecal composition or stool score despite consuming resistant starch levels that different by ~15 fold. In contrast, the fecal SCFA profile reflected increased production of saccharolytic SCFA, while the fecal metabolomics and microbiome data supported the conclusion of increased saccharolysis in the LOW extrusion condition.Support or Funding InformationHill's Pet Nutrition, Inc. Science and Technology Center, Topeka, KS 66617This abstract is from the Experimental Biology 2018 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.