310 Apparent total tract nutrient digestibility of raw, minimally processed, and retorted dog foods and their effects on fecal characteristics, metabolites, and microbiota of healthy adult dogs.

Abstract Previous research has demonstrated that pet food formats differ in their digestibility and impact on gastrointestinal health measures. However, these diets often vary in macronutrient concentrations and ingredient compositions, making it challenging to attribute differences. Therefore, the objectives of this study were to determine how diets of different formats formulated to similar nutrient targets using similar ingredients may affect the apparent total tract macronutrient digestibility (ATTD) and the gastrointestinal transit time (GTT) and fecal characteristics, metabolites, and microbiota of healthy dogs. Ten spayed female adult beagles (age = 6.10±1.20 yr) were used in a replicated 5x5 Latin square design to test the following diet formats: retorted (RT), minimally processed [sous vide (SV), steamed (ST)], and raw [high-pressure processed (HPP), freeze-dried (FD)]. The study comprised five 26-d periods, including a 7-d diet transition phase, 14-d treatment phase, and 5-d fecal collection. All feces excreted during the collection phase were pooled, dried, ground, and analyzed for dry matter (DM), organic matter (OM), crude protein, total lipid content, and gross energy. On the first day of fecal collections, one fresh fecal sample was collected to measure pH, DM content, fermentative metabolite concentrations, and microbiota composition. The following day, dogs were given a dye with their meal, feces were evaluated, and GTT was calculated. Data were analyzed by Mixed Models using SAS 9.4, with P < 0.05 being statistically significant. Fecal scores, pH, DM%, and GTT were not different among treatment groups. Dogs consuming the RT and FD diets had a higher (P < 0.05) as-is fecal output to DM intake ratio than dogs consuming the ST and HPP diets. The HPP and ST diets had higher (P < 0.05) DM and OM ATTD than the RT, FD, and SV (ST not different) diets. All diets had greater (P < 0.05) crude protein ATTD than the RT diet and higher (P < 0.05) fat ATTD than the FD diet. Energy ATTD was higher (P < 0.05) in the ST, HPP, and SV diets than in the FD and RT (SV not different) diets. Fecal acetate and butyrate were higher (P < 0.05) in dogs consuming the RT diet than the ST and SV (butyrate only) diets. Fecal isobutyrate, isovalerate, total BCFA, indole, and ammonia were higher (P < 0.05) in dogs consuming the RT diet than all other diets (ST not different for indole and ammonia). Alpha and beta diversity measures were not impacted, but diet altered the relative abundances of 3 bacterial phyla and 18 bacterial genera (P < 0.05). In summary, processing method influenced nutrient digestibility and the fecal metabolites and microbiota of healthy adult dogs. Further research is needed to evaluate additional factors such as packaging size, ingredient and macronutrient inclusion levels, different processing parameters, and other pet food formats.