Nutrient digestibility and fecal characteristics, microbiota, and metabolites in dogs fed human-grade foods

Abstract

Human-grade (HG) pet foods are commercially available, but they have not been well studied. Our objective was to determine the apparent total tract digestibility (ATTD) of HG pet foods and evaluate their effects on fecal characteristics, microbiota, and metabolites, serum metabolites, and hematology of dogs. Twelve dogs (mean age=5.5±1.0; BW=11.6±1.6 kg) were used in a replicated 4×4 Latin square design (n=12/treatment). The diets included: 1) Chicken and Brown Rice Recipe (extruded; Blue Buffalo); 2) Roasted Meals Tender Chicken Recipe (fresh; Freshpet); 3) Beef & Russet Potato Recipe (HG beef; JustFoodForDogs); and 4) Chicken & White Rice Recipe (HG chicken; JustFoodForDogs). Each period consisted of 28 d, with a 6-d diet transition phase, 16 d of consuming 100% of the diet, a 5-d phase for fecal collection, and 1 d for blood collection. All data were analyzed using the Mixed Models procedure of SAS 9.4. Dogs fed the extruded diet required a higher (P<0.05) daily food intake (dry matter basis; DMB) to maintain BW. The ATTD of dry matter (DM), organic matter (OM), energy, and acid-hydrolyzed fat (AHF) were greater (P<0.05) in dogs fed the HG diets than those fed the fresh diet, and greater (P<0.05) in dogs fed the fresh diet than those fed the extruded diet. Crude protein ATTD was lower (P<0.05) for dogs fed the extruded diet than those fed all other diets. Dogs fed the extruded diet had greater (P<0.05) fecal output (as-is; DMB) than dogs fed fresh (1.5-1.7 times greater) or HG foods (2.0-2.9 times greater). There were no differences in fecal pH, scores, and metabolites, but microbiota were affected by diet. Dogs fed HG beef had higher (P<0.05) relative abundance of Bacteroidetes and lower (P<0.05) relative abundance of Firmicutes than dogs fed the fresh or HG chicken diets. The Actinobacteria, Fusobacteria, Proteobacteria, and Spirochaetes phyla were unchanged (P>0.05), but diet modified the relative abundance of nearly 20 bacterial genera. Similar to previous reports, these data demonstrate that the fecal microbiota of dogs fed HG or fresh diets is markedly different than those consuming extruded diets, likely due to ingredient, nutrient, and processing differences. Serum metabolites and hematology was not greatly impacted by diet. In conclusion, the HG pet foods tested resulted in significantly reduced fecal output, were highly digestible, maintained fecal characteristics, serum chemistry, and hematology, and modified the fecal microbiota of dogs.

Heterogeneity of gut microbial responses in healthy household dogs transitioning from an extruded to a mildly cooked diet

“…However the association between a MC diet and positive health perception has been previously reported using a survey administered to a group of dog owners after a veterinarian formulated MC diets for the dogs ( Johnson et al, 2016 ). Dogs accepted MC diets well and remained healthy in two additional feeding trials ( Algya et al, 2018 ; Do et al, 2021 ).…”

“…As a result of this diverse and free-living study population these findings may be more generalizable to the dog population than other studies that focus on a single breed or a single diet. Two previously published studies using a similar diet comparison were conducted, however they consisted of eight and 12 Beagles in a laboratory setting ( Algya et al, 2018 ; Do et al, 2021 ). Dogs in the present study maintained their body weight throughout the study period, therefore changes in health and GM were independent of weight change.…”

“…Dogs in the present study maintained their body weight throughout the study period, therefore changes in health and GM were independent of weight change. Finally, the characterization of gut bacteria in this study was performed with metagenomic sequencing, a powerful technique enabling enhanced taxonomic resolution and accuracy, as well as increased detection of diversity and functional genes, a technique that has not yet been widely used in canine research ( Ranjan et al, 2016 ; Salas-Mani et al, 2018 ; Xu et al, 2019 ; Alessandri et al, 2019 ; Connelly et al, 2019 ; Do et al, 2021 ).…”

“…The nutritional profile of a MC diet may or may not differ significantly from dried and extruded pet food. Compared to dried and extruded food, MC diets have higher moisture content, higher digestibility of fats and protein, and dogs fed a MC diet for 28 days had lower levels of triglycerides ( Algya et al, 2018 ; Oba et al, 2020 ; Do et al, 2021 ). Additionally, positive health perception was reported by dog owners after feeding their dogs a veterinarian-formulated MC diet ( Johnson et al, 2016 ).…”

“…These studies have shown that raw food diets lead to increased levels of certain Fusobacteria and Proteobacteria ( Sandri et al, 2017 ; Algya et al, 2018 ; Schmidt et al, 2018 ). Similarly, MC diets have been associated with higher levels of certain Bacteroidetes, Fusobacteria and Proteobacteria, and lower levels of certain Actinobacteria and Firmicutes as compared to an extruded kibble diet ( Algya et al, 2018 ; Do et al, 2021 ). However, these studies were conducted in only a small group of dogs under a laboratory setting.…”