290 Effects of chicken-based protein source on apparent total tract macronutrient digestibility, palatability, and fecal characteristics, microbiota, and metabolites of healthy adult dogs

Abstract Commercial pet foods categorized as “premium” or “super-premium” are often formulated with frozen meat sources, such as chicken slurry, while “grocery brand” extruded diets commonly contain rendered meats, such as chicken meal. However, inadequate research has been performed on the digestibility or health implications of these ingredient differences. Therefore, the objectives of this study were to determine how varying inclusion levels of chicken meal and chicken slurry 1) affect the apparent total tract macronutrient digestibility (ATTD) of dog foods, and 2) to assess their effects on palatability and the fecal characteristics, metabolites, and microbiota of healthy adult dogs. Nine healthy adult spayed female dogs (age = 5.44 ± 0.53 yr old) were used in a replicated 3x3 Latin square design to test the following diets: Control [no chicken slurry (CON)], low inclusion [8% chicken slurry (LOW)], and high inclusion [16% chicken slurry (HIGH)]. The experiment comprised three 21-d periods, including a 16-d adaptation phase and a 5-d fecal collection phase. All feces excreted during the total fecal collection phase were frozen until analyses and ATTD calculations. Fecal samples were pooled and dried at 55°C before being ground through a 2-mm screen. Fecal samples were then 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 for measurement of pH, DM content, fermentative metabolite concentrations, and microbiota composition. A palatability experiment with 20 dogs was conducted to evaluate CON vs. HIGH. Data were analyzed statistically by Mixed Models using SAS 9.4, with P < 0.05 being significant. There were minimal differences among diets. Fecal output (as-is and DM), scores, pH, and DM percentage were not different among treatment diets. Protein ATTD was greater (P < 0.05) in dogs fed HIGH than those fed LOW or CON, but ATTD of DM, OM, fat, and energy were not different among treatment diets. Fecal propionate, butyrate, and total short-chain fatty acid concentrations were greater (P < 0.05) in dogs fed LOW than those fed HIGH, with dogs fed CON being intermediate. Fecal acetate, branched-chain fatty acid, ammonia, phenol, and indole concentrations were not different among diets. Few changes to the fecal microbiota were noted. However, the relative abundance of fecal Fusobacterium was greater (P < 0.05) in dogs fed CON than those fed HIGH, with dogs fed LOW being intermediate. Dogs had a preference (P < 0.05) for HIGH over CON by a 2:1 ratio. In summary, chicken slurry inclusion had minimal effects on nutrient digestibility and the fecal characteristics, metabolites, and microbiota of healthy adult dogs. More research should be conducted with greater inclusion levels of chicken slurry and other animal proteins to identify if and where differences occur.