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.

In recent dog and cat experiments, a novel milk oligosaccharide biosimilar (GNU100) positively modulated fecal microbiota and metabolite profiles, suggesting benefits to gastrointestinal health. The objective of this study was to investigate the effects of GNU100 on the fecal characteristics, microbiota, and bile acid (BA) concentrations of healthy adult dogs treated with antibiotics. Twelve healthy adult female dogs (mean age: 3.74±2.4 y) were used in an 8-week crossover design study (dogs underwent both treatments). All dogs were fed a control diet during a 2-week baseline, then randomly allotted to 1 of 2 treatments (diet only or diet + 1% GNU100) for another 6 weeks. From weeks 2-4, dogs were orally administered metronidazole (20 mg/kg BW) twice daily. Fecal scores were recorded daily and fresh fecal samples were collected at weeks 2, 4, 5, 6, and 8 for measurement of pH, dry matter, microbiota populations, and BA, immunoglobulin A, and calprotectin concentrations. On weeks 0, 4, and 8, blood samples were collected for serum chemistry and hematology analysis. All data were analyzed as repeated measures using the Mixed Models procedure of SAS version 9.4, with significance considered P<0.05. Metronidazole increased (P<0.0001) fecal scores (looser stools) and modified (P<0.05) fecal microbiota and BA profiles. Using qPCR, metronidazole reduced fecal Blautia, Fusobacterium, Turicibacter, Clostridium hiranonis, and Faecalibacterium abundances, and increased fecal Streptococcus and Escherichia coli abundances. DNA sequencing analysis demonstrated that metronidazole reduced microbial alpha diversity and influenced the relative abundance of 20 bacterial genera and families. Metronidazole also increased primary BA and reduced secondary BA concentrations. Most antibiotic-induced changes returned to baseline by week 8. Fecal scores were more stable (P=0.01) in GNU100-fed dogs than controls after antibiotic administration. GNU100 also influenced fecal microbiota and BA profiles, reducing (P<0.05) the influence of metronidazole on microbial alpha diversity and returning some fecal microbiota and secondary BA to baseline levels at a quicker (P<0.05) rate than controls. In conclusion, our results suggest that GNU100 supplementation provides benefits to dogs treated with antibiotics, providing more stable fecal scores, maintaining microbial diversity, and allowing for quicker recovery of microbiota and secondary BA profiles which play an essential role in gut health.

A variety of functional ingredients, including fibers, prebiotics, probiotics, and postbiotics may be added to pet foods to support gastrointestinal and immune health. While many of these ingredients have been tested individually, commercial foods often include blends that also require testing. This study was conducted to evaluate the effects of diets containing blends of fibers, ‘biotics’, and/or spray-dried plasma on apparent total tract digestibility (ATTD), stool quality, fecal microbiota and metabolites, and immune health outcomes of adult dogs. Twelve healthy adult intact English pointer dogs (6 M; 6 F; age = 6.4 ± 2.0 yr; BW = 25.8 ± 2.6 kg) were used in a replicated 3x3 Latin square design to test diets formulated to: 1) contain a low concentration of fermentative substances (control diet; CT); 2) be enriched with a fiber-prebiotic-probiotic blend (FPPB); and 3) be enriched with a fiber-prebiotic-probiotic blend + immune-modulating ingredients (iFFPB). In each 28-d period, 22 d of diet adaptation was followed by a 5-d fecal collection phase and 1 d for blood sample collection. All data were analyzed using SAS 9.4, with significance being P<0.05 and trends being P<0.10. FPPB and iFPPB diets led to shifts in numerous outcome measures. Dry matter (DM), organic matter, fat, fiber, and energy ATTD were lower (P<0.01), fecal scores were lower (P<0.01; firmer stools), and fecal DM% was higher (P<0.0001) in dogs fed FPPB or iFPPB than those fed CT. Serum triglycerides and cholesterol were lower (P<0.01) in dogs fed FPPB or iFPPB than those fed CT. Fecal protein catabolites (isobutyrate, isovalerate, indole, ammonia) and butyrate were lower (P<0.05), while fecal immunoglobulin A (IgA) was higher (P<0.01) in dogs fed FPPB and iFPPB than those fed CT. Fecal microbiota populations were affected by diet, with alpha diversity being lower (P<0.05) in dogs fed iFPPB and the relative abundance of 20 bacterial genera being altered in dogs fed FPPB or iFPPB compared to CT. The circulating helper T cell:cytotoxic T cell ratio was higher (P<0.05) in dogs fed iFPPB than those fed CT. Circulating B cells were lower (P<0.05) in dogs fed FPPB than those fed iFPPB, and lower (P<0.05) in dogs fed iFPPB than those fed CT. Our results demonstrate that feeding a fiber-prebiotic-probiotic blend may provide many benefits to canine health, including improved stool quality, beneficial shifts to fecal microbiota and metabolite profiles, reduced blood lipids, and increased fecal IgA.

Most canine microbiome trials are conducted in a controlled environment, with an unverified assumption that identical findings can be extrapolated to household dogs. In this study, the fecal microbiome of healthy beagles living in household or controlled environments was characterized with shotgun metagenomic sequencing and compared. Beagles were recruited from U.S. households (Pet, n = 54), a private kennel (Kennel, n = 39), and the University of Illinois at Urbana-Champaign (UIUC, n = 34). Dogs were fed an identical diet (fresh chicken, non-extruded and cooked) or diet type (kibble, various brands) for ≥ 7 days. Shannon diversity index was significantly higher in Kennel than Pet when fed both fresh and kibble, and significantly higher than UIUC when fed fresh only. β-Diversity was significantly different among the three cohorts on both diets. Mainly, species belonging to Actinobacteriota, Bacteroidota, Firmicutes_A, Firmicutes, and Proteobacteria were differentially abundant among the cohorts. Likewise, significant discriminant features in the functional data were observed among the cohorts after controlling for diet type. The findings demonstrate the living environment as an important factor in microbial composition, and further draw attention to possible limitations in the translation of findings between dogs in controlled versus free-living environments.

Canine obesity can be managed by dietary energy restriction using a specifically formulated weight loss diet. The objective of this study was to determine the effects of weight loss on body composition, voluntary physical activity, and blood metabolites of overweight dogs while being fed a high-protein, high-fiber diet. All procedures were approved by the University of Illinois Institutional Animal Care and Use Committee prior to experimentation. Twelve overweight adult spayed female dogs (BW: 15.3±2.1 kg, BCS: 8.1±0.6) were fed a high-protein (CP: 42.0% DMB), high-fiber (TDF: 22.0% DMB) diet during a 5-wk baseline phase (wk 0) to identify food intake needed to maintain BW. A 24-wk weight loss phase followed. After wk 0, food was initially provided at 80% the amount needed to maintain BW and then adjusted weekly with a goal of 1.5–2% weight loss per wk. Data were analyzed statistically overtime using SAS 9.4. After 24 wk, dogs lost 31.2% of initial BW (P < 0.0001), with 1.4±0.7% weight loss per wk. BCS decreased by 2.8 units (P < 0.0001). During weight loss, dogs consumed an average of 457.5±61.4 kcal/d, with energy intake being reduced by a total of 43.8% by wk 24 compared to baseline. Lean muscle mass, fat mass, and fat percentage were reduced (P < 0.0001) by 1.3 kg, 3.1 kg, and 11.7% respectively. Serum triglycerides, alkaline phosphatase, white blood cell counts, and neutrophils were decreased (P < 0.0001), but serum bilirubin, creatinine, and blood urea nitrogen were increased (P < 0.01) over time. Average daily physical activity changed over time, but was not greatly different due to weight loss. Our results suggest that a high-protein, high-fiber diet promotes fat mass loss, minimizes lean muscle mass loss, and reduces inflammatory marker and triglyceride concentrations in overweight dogs. Therefore, it is a suitable nutritional solution for weight loss programs in dogs.