Low‐Shear Extrusion of Grains Retains Resistant Starch to Increase Microbiome Saccharolysis and Fecal Hydroxy/Keto Redox Ratios of the Feline Gut

Abstract

ObjectivesFood extrusion processes mixed ingredients to cook food through application of mechanical shear force and heat. This degrades higher‐order starch structure to improve carbohydrate digestibility in the upper gastrointestinal tract. However, evidence indicates the role that digestion resistant starch (RS) plays in promoting health through activity of the gut microbiome. We examined the impact of reducing temperature and shear force in extrusion‐based processing of feline foods to impact gut microbiome metabolites (postbiotics) related to cat gastrointestinal health.MethodsCats were housed in environments promoting social interaction, had access to natural light that varied with season, daily opportunity to exercise and interact with Caretakers and were fed to maintain healthy body weight. Health was confirmed through clinical indices. Collections were under IACUC approved protocols. Identically formulated diets (poultry meal, rice, corn gluten, corn, cellulose and micronutrients) were produced with either HIGH or LOW shear force. Specific Mechanical Energy (SME) for the HIGH shear was 52 W.h/kg, and the Specific Thermal Energy (STE) was 41 W.h/kg, for a Total Energy (TE) of 94 W.h/kg. The SME for the LOW shear parameters was 22 W.h/kg, and the STE was calculated to be 38 W.h/kg, for a TE of 61 W.h/kg. Dietary intakes of RS were 0.3 g/(kg BW^0.75) and 5.1 g/(kg BW^0.75) for the HIGH shear and LOW shear groups, respectively. Randomized design, 2 groups; High Shear extrusion (HIGH, n = 18) and Low Shear (LOW, n = 19). Cats fed for 8 weeks; fecal collections in week 4 and 8. Fecal analyses: metabolomics by multiplatform LC‐MS, short chain fatty acids (SCFA) by GC‐FID and ammonia by indophenol colorimetry. Data were analyzed by independent t‐test for group‐wise differences at the 4 and 8 week timepoints.ResultsThe primary finding was of heightened gut microbiome saccharolysis and fermentation in the cats fed the LOW shear food, indicated by increased RS‐derived fecal saccharides maltotriose, maltose and glucose as well as increased fecal butyrate and lactate. By 8 week there was also a reduction in gut microbial putrefaction as indicated by decreased fecal ammonia and branched SCFA derived from valine, leucine and isoleucine. Also notable was the global shift in NADH/NAD+ redox couples (hydroxy/oxo couples) toward a more reduced state, such that 5 observed couples all had ratios significantly favoring the hydroxy form over the oxo form in the LOW‐ vs HIGH‐shear foods.ConclusionsOptimizing food extrusion for cats can enable more robust saccharolysis and resultant fermentation by the gut microbiome to promote production of postbiotics known to provide health benefits. Additionally, processing of the food resulted in decreased putrefaction by the feline gut microbiome. Finally, we document evidence that providing RS to a gut microbiome shifts the microbiome NADH/NAD+ redox milieu to favor the hydroxy (vs oxo) form of common two‐electron couples. This work is expected to increase the awareness of the benefits that resistant starch can have for an animal typically considered an obligate carnivore.Support or Funding InformationHill's Pet Nutrition, Inc. Topeka, Kansas, USAThis abstract is from the Experimental Biology 2019 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.