Effects of a single-cell protein source from Paecilomyces variotii on diet digestibility and palatability and intestinal functionality of adult dogs

Introduction This study aimed to evaluate the effects of a single-cell protein (SCP) source from Paecilomyces variotii on the apparent total tract digestibility (ATTD) of macronutrients and energy, diet palatability, fecal fermentative metabolites, and microbiota in dogs. Materials and methods Five extruded diets containing 0, 4, 8, 12, and 16% of SCP were manufactured. To isolate the metabolizable energy (ME) and the ATTD of the SCP, an additional test diet was manufactured containing 80% of the 0% diet and 20% of SCP. In Experiment I, 15 adult Beagle dogs were distributed in a randomized block design with 5 diets (0 to 16% SCP) and two periods of 21 days each, totaling 6 repetitions/treatment. In Experiment II, for the palatability test, 16 adult dogs were used, comparing the diets: 0 vs. 4% SCP; 0% vs. 8% SCP; and 4% vs. 16% SCP. In Experiment III, the SCP digestibility was estimated by the substitution method with 12 adult Beagle dogs. Results The SCP presented ATTD of dry matter (DM) = 64.3%; ATTD of crude protein = 83.9%; ATTD of acid-hydrolyzed ether extract = 78.3%; and ME of 3843.3 kcal/kg. The ATTD of DM, organic matter, gross energy and the ME of the diets decreased linearly as the dietary inclusion of SCP increased (0 to 16% SCP; p < 0.05). There was a quadratic effect in fecal concentrations of propionate, butyrate, and total short-chain fatty acids, and a linear increase in isobutyrate and total branched-chain fatty acids, with the dietary inclusion of SCP ( p < 0.05). Animals fed the 8% SCP diet presented an increase in alpha-diversity indexes ( p < 0.05). Dogs fed the 4% SCP diet presented higher fecal abundance of Lactobacillus and Limosilactobacillus , when compared to the 0% group ( p < 0.05). Besides, a higher fecal abundance of Lactobacillus and Butyricicoccus and lower abundance of Enterococcus , and Enterocloster was observed in dogs fed the 8% SCP diet compared to the 0% group ( p < 0.05). Conclusion These results demonstrate that the dietary inclusion of 4 and 8% SCP promotes less impact on diet digestibility and may beneficially modulate the fecal microbiome and its metabolites in dogs, without affecting diet palatability.