Impacts of a fresh-frozen dog food on fecal consistency and microbiome in colony dogs

Fresh-frozen dog diets are becoming increasingly popular among pet owners, but little is known regarding the impact of this diet on canine gut health and the microbiome. This study evaluated the impacts of a fresh-frozen versus an extruded kibble diet on the fecal consistency, metabolites, and microbiome in 16 adult Labrador Retrievers (average age 4.2 ± 0.26 yr; average weight: 25.7 ± 3.18 kg) over the course of 6 months. Dogs were randomly assigned to one of the two diets in a parallel design. Feces were collected at baseline, 3 months, and 6 months for short-chain fatty acid, ammonia, and microbiome analyses. An additional sample was collected at 1 mo for microbiome analysis. Fecal microbiome was analyzed via 16S rRNA gene sequencing. Fecal consistency scores were recorded daily, and body weights and body condition scores were recorded weekly. Data were analyzed across time and treatments using a repeated measures analysis of variance. Results showed that fecal consistency was improved in the dogs fed the fresh diet, with differential changes detected shortly after the transition phase onto the test diets (P < 0.01). Fecal butyrate concentrations were greater in the fresh group (P < 0.01), and fecal valerate concentrations fluctuated more in the kibble group while the fresh group remained more consistent over time (P = 0.05). No differences were observed in fecal moisture, pH, ammonia, or other fecal short-chain or branched-chain fatty acids. General dog health was not negatively impacted by either diet, as observed through weight maintenance and veterinary wellness exams. Diet type impacted fecal microbiome composition, as shown by differences in beta diversity between the fresh and kibble groups (P < 0.01). In addition, microbiomes of dogs fed a fresh diet were enriched in short-chain fatty acid producers such as Turicibacter sanguinis, Ruminococcus, and Clostridium compared to dogs fed kibble. Overall, the fresh diet increased fecal consistency and fecal butyrate, although other fecal parameters were not different.