Canine obesity is associated with reduced lifespan and metabolic dysfunction, but can be managed by dietary intervention. This study aimed to determine the effects of restricted feeding of a high-protein, high-fiber (HPHF) diet and weight loss on body composition, physical activity, blood metabolites, and fecal microbiota and metabolites of overweight dogs. Twelve spayed female dogs [age: 5.5±1.1 yr; body weight (BW): 14.8±2.0 kg, body condition score (BCS): 7.9±0.8] were fed a HPHF diet during a 4-wk baseline phase to maintain BW. After baseline (wk 0), dogs were first fed 80% of baseline intake and then adjusted to target 1.5% weekly weight loss for 24 wk. Body composition using dual-energy x-ray absorptiometry and blood samples (wk 0, 6, 12, 18, 24), voluntary physical activity (wk 0, 7, 15, 23), and fresh fecal samples for microbiota and metabolite analysis (wk 0, 4, 8, 12, 16, 20, 24) were measured over time. Microbiota data were analyzed using QIIME 2. All data were analyzed statistically over time using SAS 9.4. After 24 wk, dogs lost 31.2% of initial BW and had 1.43±0.73% weight loss per wk. BCS decreased (P<0.0001) by 2.7 units, fat mass decreased (P<0.0001) by 3.1 kg, and fat percentage decreased (P<0.0001) by 3.1 kg and 11.7% with weight loss. Many serum metabolites and hormones were altered, with triglycerides, leptin, insulin, C-reactive protein, and interleukin-6 decreasing (P<0.05) with weight loss. Relative abundances of fecal Bifidobacterium, Coriobacteriaceae UCG-002, undefined Muribaculaceae, Allobaculum, Eubacterium, Lachnospira, Negativivibacillus, Ruminococcus gauvreauii group, uncultured Erysipelotrichaceae, and Parasutterella increased (P<0.05), whereas Prevotellaceae Ga6A1 group, Catenibacterium, Erysipelatoclostridium, Fusobacterium, Holdemanella, Lachnoclostridium, Lactobacillus, Megamonas, Peptoclostridium, Ruminococcus gnavus group, and Streptococcus decreased (P<0.01) with weight loss. Despite the number of significant changes, a state of dysbiosis was not observed in overweight dogs. Fecal ammonia and secondary bile acids decreased, while fecal valerate increased with weight loss. Several correlations between gut microbial taxa and biological parameters were observed. Our results suggest that restricted feeding of a HPHF diet and weight loss promotes fat mass loss, minimizes lean mass loss, reduces inflammatory marker and triglyceride concentrations, and modulates fecal microbiota phylogeny and activity in overweight dogs.

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.

Obesity and estrogen reduction are known to impact the gut microbiota and gut microbial-derived metabolites in some species, but limited information is available in dogs. The aim of this study was to determine the effects of dietary macronutrient profile on apparent total tract macronutrient digestibility, fecal microbiota, and fecal metabolites of adult female dogs after spay surgery. Twenty-eight adult intact female beagles (age: 3.02 ± 0.71 yr, BW: 10.28 ± 0.77 kg; BCS: 4.98 ± 0.57) were used. After a 5-wk baseline phase (wk 0), 24 dogs were spayed and randomly allotted to one of three experimental diets (n=8/group): 1) control (CO) containing moderate protein and fiber (COSP), 2) high-protein, high-fiber (HPHF), or 3) high-protein, high-fiber plus omega-3 and medium-chain fatty acids (HPHFO). Four dogs were sham-operated and fed CO (COSH). All dogs were fed to maintain BW for 12 wk after spay, then allowed to consume twice that amount for 12 wk. Fecal samples were collected at wk 0, 12, and 24 for digestibility, microbiota, and metabolite analysis. All data were analyzed using repeated measures and linear Mixed Models procedure of SAS 9.4, with results reported as change from baseline. Apparent organic matter and energy digestibilities had greater decreases in HPHF and HPHFO than COSH and COSP. Increases in fecal acetate, total short-chain fatty acids, and secondary bile acids were greater and decreases in primary bile acids were greater in HPHF and HPHFO. Principal coordinates analysis of weighted UniFrac distances revealed that HPHF and HPHFO clustered together and separately from COSH and COSP at wk 12 and 24, with relative abundances of Faecalibacterium, Romboutsia, and Fusobacterium increasing to a greater extent and Catenibacterium, Bifidobacterium, Prevotella 9, Eubacterium, and Megamonas decreasing to a greater extent in HPHF or HPHFO. Our results suggest that high-protein, high-fiber diets alter nutrient and energy digestibilities, fecal metabolite concentrations, and fecal gut microbiota, but spay surgery had minor effects. Future research is needed to investigate how food intake, nutrient profile, and changes in hormone production influence gut microbiota and metabolites of dogs individually and how this knowledge may be used to manage spayed pets.

Canine microbiome studies are often limited in the geographic and temporal scope of samples studied. This results in a paucity of data on the canine microbiome around the world, especially in contexts where dogs may not be pets or human associated. Here, we present the shotgun sequences of fecal microbiomes of pet dogs from South Africa, shelter and stray dogs from India, and stray village dogs in Laos. We additionally performed a dietary experiment with dogs housed in a veterinary medical school, attempting to replicate the diet of the sampled dogs from Laos. We analyse the taxonomic diversity in these populations and identify the underlying functional redundancy of these microbiomes. Our results show that diet alone is not sufficient to recapitulate the higher diversity seen in the microbiome of dogs from Laos. Comparisons to previous studies and ancient dog fecal microbiomes highlight the need for greater population diversity in studies of canine microbiomes, as modern analogues can provide better comparisons to ancient microbiomes. We identify trends in microbial diversity and industrialization in dogs that mirror results of human studies, suggesting future research can make use of these companion animals as substitutes for humans in studying the effects of industrialization on the microbiome.