High-protein dried distillers grains in dog diets: diet digestibility and palatability, intestinal fermentation products, and fecal microbiota

This study aimed to evaluate the effects of high-protein dried distillers grains (HPDDG) on palatability and metabolizable energy (ME) of the diet, apparent total tract digestibility (ATTD) of nutrients and energy, intestinal fermentation products, and fecal microbiota in dogs. Four diets containing 0, 70, 140, and 210 g/kg of HPDDG were manufactured. To evaluate the ME and the ATTD of macronutrients of HPDDG itself, an additional test diet was manufactured containing 70% of the control diet formula (0 g/kg) and 300 g/kg of HPDDG. Fifteen adult Beagle dogs were distributed in a randomized block design, with two periods of 15 d each (n = 6). The HPDDG digestibility was obtained using the Matterson substitution method. For the palatability test, 16 adult dogs were used, comparing the diets: 0 vs. 70 g/kg of HPDDG and 0 vs. 210 g/kg of HPDDG. The ATTD of HPDDG were: dry matter = 85.5%, crude protein = 91.2%, and acid-hydrolyzed ether extract = 84.6% and the ME content was 5,041.8 kcal/kg. The ATTD of macronutrients and ME of the diets and the fecal dry matter, score, pH, and ammonia of the dogs did not differ among treatments (P > 0.05). There was a linear increase in the fecal concentrations of valeric acid with the inclusion of HPDDG in the diet (P < 0.05). Streptococcus and Megamonas genera reduced linearly (P < 0.05), and Blautia, Lachnospira, Clostridiales, and Prevotella genera showed a quadratic response to the inclusion of HPDDG in the diet (P < 0.05). Alpha-diversity results showed an increase (P < 0.05) in the number of operational taxonomic units and Shannon index and a trend (P = 0.065) for a linear increase in the Chao-1 index with the dietary inclusion of HPDDG. Dogs preferred the 210 g/kg diet over the 0 g/kg HPDDG diet (P < 0.05). These results demonstrate that the HPDDG evaluated does not affect the utilization of nutrients in the diet, but it may modulate the fecal microbiome of dogs. In addition, HPDDG may contribute to diet palatability for dogs.