Kelly S Swanson’s research while affiliated with University of Illinois, Urbana-Champaign and other places

Various pet food diet formats are available, but many are poorly studied. The objective of this study was to determine the apparent total tract macronutrient digestibility (ATTD) of frozen raw, freeze-dried raw, fresh, and extruded dog foods and assess their effects on serum metabolites, hematology, and fecal characteristics, metabolites, and microbiota of healthy adult dogs. Ten beagle dogs (4.10 ± 0.74 yr) were used in a replicated 5x5 Latin square study to test the following diets: Chicken and Barley Recipe [extruded; Hill’s Science Diet (EXT)], Chicken and White Rice Recipe [fresh; Just Food for Dogs (FRSH)], Chicken Formula [frozen raw; Primal (FRZN)], Chicken and Sorghum Hybrid Freeze-dried Formula [freeze-dried raw; Primal (HFD)], and Chicken Dinner Patties [freeze-dried raw; Stella & Chewy’s (FD)]. The experiment was composed of five 35-d periods, with each ending with fecal and blood collections. Data were analyzed using Mixed Models in SAS 9.4, with P<0.05 being significant. Treatment was a fixed effect and dog a random effect. Protein ATTD was higher for FRZN and FD than other diets and higher for HFD than FRSH and EXT. Fat ATTD was higher for HFD than FRZN and EXT and lower for EXT than other diets. Fecal output was higher for dogs fed EXT than those fed other diets and higher for dogs fed FRSH than those fed FRZN, HFD, or FD. Fecal pH was lower in dogs fed EXT and FRSH than those fed other diets. Fecal scores were higher (looser) in dogs fed EXT and FRSH than those fed FRZN and FD. Fecal dry matter was higher in dogs fed FD than those fed other diets and higher in those fed FRZN and HFD than those fed EXT and FRSH. In general, fecal short-chain fatty acids were highest in dogs fed EXT, intermediate in dogs fed FRSH and HFD, and lowest in dogs fed FRZN and FD. Fecal isobutyrate and isovalerate were highest in dogs fed HFD, lowest in dogs fed FRSH, and intermediate in dogs fed other diets. Fecal primary bile acids were higher, while secondary bile acids were lower in dogs fed FRSH than in dogs fed other diets. Fecal microbiota were greatly impacted by diet, with alpha diversity, beta diversity, and relative abundances of over 40 bacterial genera being different among treatments. This study shows that dietary format may lead to great differences in nutrient digestibility and fecal characteristics, metabolites, and microbiota. More research is needed to distinguish the effects of ingredient source, processing method, and nutrient composition.

A global rise in pet ownership and an increasing tendency towards the humanisation of pets have resulted in a greater focus on improving animal health and longevity. These developments coincide with the increased recognition of the role of the gut microbiome in animal health. The gut microbiome has been shown to play a prominent role in gastrointestinal health, and it is becoming increasingly clear that these health benefits extend beyond the gut and into different physiological systems, such as the immune system. Dietary supplementation with products known as ‘biotics’, which include probiotics, prebiotics, synbiotics and postbiotics, is a strategy used to modify the gut microbiome and promote host health. Although biotics have been successfully used in companion animals, questions remain regarding appropriate biotic selection, mechanisms of action, optimum inclusion levels and safety. This review aims to summarise the effects of biotics on the gut microbiome of dogs and cats and assess their potential role in supporting gastrointestinal health.

Feline obesity puts many cats at risk for comorbidities such as hepatic lipidosis, diabetes mellitus, urinary tract diseases, and others. Restricted feeding of specially formulated diets may improve feline health and safely support weight loss while maintaining lean mass. The objective of this study was to determine the effects of restricted intake of weight control diets on weight loss, body composition, voluntary physical activity, serum metabolic and inflammatory markers, and fecal metabolites and microbiota of obese cats. Twenty-four obese adult domestic shorthair cats [body weight (BW) = 5.51 ± 0.92 kg; body condition score (BCS) = 8.44 ± 0.53] were used. A leading grocery brand diet was fed during a 4-wk baseline to identify intake needed to maintain BW. After baseline (wk 0), cats were allotted to one of two weight control diets (DRY or CAN) and fed to lose 1.5% BW per wk for 18 wk. At baseline and 6, 12, 18 wk after weight loss, dual-energy x-ray absorptiometry scans were performed, blood and fecal samples were collected, and voluntary physical activity was measured. Change from baseline data were analyzed statistically using the Mixed Models procedure of SAS, with P<0.05 being significant and P<0.10 being trends. BW was reduced by 1.54 ± 0.51% per wk. Restricted feeding of both diets led to BW (P<0.01) and fat mass loss (P<0.01), reduced BCS (P<0.01), reduced leptin (P<0.01) and insulin (P<0.01) concentrations, and increased superoxide dismutase (P<0.01) and active ghrelin (P<0.01) concentrations. Change from baseline fecal scores were reduced (P<0.01) with restricted feeding and weight loss, while total short-chain fatty acid, acetate, and propionate concentration reductions were greater (P<0.05) in cats fed CAN than those fed DRY. Fecal bacterial alpha diversity measures increased (P<0.01) with restricted feeding and weight loss. Fecal bacterial beta diversity was altered by time in all cats, with wk 0 being different (P<0.05) than wk 6, 12, and 18. Change from baseline relative abundances of 3 fecal bacterial phyla and over 30 fecal bacterial genera were impacted (P<0.05) or tended to be impacted (P<0.10) by dietary treatment. Our data demonstrate that restricted feeding of both weight control diets was an effective means for weight loss in obese adult domestic cats. Some changes were also impacted by diet, highlighting the importance of diet formulation and format, and nutrient composition in weight control diets.

Premium” pet foods are often formulated with meat slurries. Meat slurries are believed to be of higher quality than rendered meals, but inadequate research has been performed to test how their inclusion affects palatability, digestibility, or indicators of gastrointestinal health. Therefore, the objectives of this study were to determine how chicken slurry inclusion affected the palatability and apparent total tract macronutrient digestibility (ATTD) of dog foods and to assess their effects on the fecal characteristics, metabolites, and microbiota of dogs. A replicated 3x3 Latin square design digestibility study was conducted using 9 healthy adult dogs (age = 5.44 ± 0.53 yr) to test diets containing 0% (control; CON), 8% (low inclusion; LOW), and 16% (high inclusion; HIGH) chicken slurry. The experiment comprised three 21-day experimental periods (14 days of adaptation, 5 days of total fecal collection (used for ATTD calculations), and 2 days of blood collection). On the first day of fecal collections, one fresh sample was collected for measurement of pH, dry matter (DM) content, fermentative metabolite concentrations, and microbiota populations. A 2-day palatability study (n=20 dogs) was also conducted to compare CON vs. HIGH. Data were analyzed statistically by Mixed Models using SAS 9.4, with P<0.05 being significant. In the palatability study, dogs were shown to prefer (P<0.05) the HIGH diet by a ratio of 2:1. In the digestibility study, fecal output, scores, pH, and DM percentage were not different among diets. The ATTD of protein was higher (P<0.05) for the HIGH diet (84.6%) than for the LOW (82.7%) or CON (82.6%) diets. The ATTD of other nutrients and energy were not different among diets (all over 80%). Fecal propionate, butyrate, and total short-chain fatty acid concentrations were higher (P<0.05) in dogs fed the LOW diet (122.0, 67.4, and 408.2 βmol/g, respectively) than those fed the HIGH diet (89.0, 46.9, and 338.2 βmol/g, respectively). The other fecal metabolites (acetate, branched-chain fatty acids, ammonia, phenol, and indole) were not different among treatments. Few changes to the fecal microbiota were noted. However, the relative abundance of fecal Fusobacterium was higher (P<0.05) in dogs fed the CON diet than those fed the HIGH diet (25.% vs. 20.0% relative abundance). In summary, chicken slurry inclusion improved palatability but had minimal effects on nutrient digestibility and fecal characteristics, metabolites, and microbiota.

Antibiotics are known to cause loose stools, disrupt the fecal microbiota, and alter fecal bile acid (BA) profiles of dogs. Recovery may be aided by diet, but little research has been conducted. The objective of this study was to determine how a veterinary low-fat diet affected the fecal characteristics, metabolites, BA, and microbiota of dogs receiving antibiotics. Twenty-four healthy adult dogs [7.38 ± 1.95 yr; 7.67 ± 0.76 kg body weight (BW)] were used in an 8-wk completely randomized design study. During a 2-wk baseline, all dogs were fed a leading grocery brand dry kibble diet (GBD). Over the next 2 wk, dogs were fed GBD and received metronidazole orally (20 mg/kg BW twice daily). At wk 4, dogs were randomly allotted to one of two treatments [GBD or Blue Buffalo Natural Veterinary Diet GI Gastrointestinal Support Low-Fat (BB)] and fed for 4 wk. Fecal scores were recorded daily and fresh fecal samples were collected at wk 2, 4, 5, 6, 7, and 8 for measurement of pH, dry matter content, and metabolite and BA concentrations. Fecal microbiota populations were analyzed by 16S rRNA gene amplicon sequencing and qPCR-based dysbiosis index (DI). All data were analyzed as repeated measures using the Mixed Models procedure of SAS 9.4, testing for effects of treatment, time, and treatment*time and significance set at P<0.05. Metronidazole increased (P<0.0001) fecal scores (looser stools), reduced fecal short-chain fatty acid, branched-chain fatty acid, phenol, and indole concentrations, increased primary BA concentrations, and decreased secondary BA concentrations. Metronidazole also reduced fecal bacterial alpha diversity, altered the abundance of 58 bacterial genera, and increased DI. During antibiotic recovery, change in fecal pH, dry matter percentage, and metabolite and immunoglobulin A concentrations were altered (P<0.05) by diet. Fecal BA concentrations recovered quickly for all dogs. Change in lithocholic acid was affected (P<0.0001) by diet, but other BA were not. Recovery of over 25 bacterial genera was impacted by diet (P<0.05). While many bacterial taxa returned to baseline levels after 4 wk, others did not fully recover. DI and bacterial alpha diversity measures recovered quickly for all dogs, but were not impacted by diet. In conclusion, metronidazole drastically altered the fecal microbiota and metabolites of dogs. While most variables returned to baseline by wk 8, diet may be used to aid in recovery.

Antibiotics are used to treat gastrointestinal diseases or infections, but are known to negatively affect stool quality and gut microbiota in cats and dogs. Therefore, identifying dietary strategies that may aid in antibiotic recovery is of interest. The objective of this study was to determine how a veterinary gastrointestinal diet affected the fecal characteristics, metabolite and bile acid (BA) concentrations, and microbiota of cats recovering from metronidazole administration. Twenty-four healthy adult cats were used in an 8-wk completely randomized design study. During a 2-wk baseline, all cats consumed a leading grocery brand diet (GBD). Over the next 2 wk, cats consumed GBD and received metronidazole (20 mg/kg BW twice daily). At wk 4, cats were randomly allotted to one of two treatments [GBD; BLUE Natural Veterinary Diet GI Gastrointestinal Support (BB)] and fed for 4 wk. Fecal scores were recorded daily and fresh fecal samples were collected at wk 2, 4, 5, 6, 7, and 8 for measurement of pH, dry matter (DM) %, metabolites, and microbiota. Microbiota were analyzed by 16S rRNA gene sequencing and qPCR, which was used to calculate dysbiosis index. Data were analyzed as repeated measures using the Mixed Models procedure of SAS 9.4, testing for effects of diet, time and diet*time. Metronidazole had dramatic effects on all outcomes, including increased fecal scores (looser stools), reduced fecal pH and DM%, reduced fecal short-chain fatty acid, branched-chain fatty acid, ammonia, phenol, and indole concentrations, and altered fecal BA concentrations (increased primary BA; reduced secondary BA). Metronidazole reduced fecal bacterial alpha diversity, increased dysbiosis index, and altered the relative abundance of 78 bacterial genera. Fecal outcomes partially recovered over the next 4 wk, with some being impacted by diet. Fecal acetate concentrations were higher after metronidazole in cats fed BB. Dysbiosis index and alpha diversity measures slowly recovered over 4 wk, without diet differences. Recovery of 16 bacterial genera were impacted by diet. Fecal BA profiles demonstrated a prolonged impairment of primary to secondary BA conversion, with cholic acid being lower after metronidazole in cats fed BB. In conclusion, our data demonstrate that metronidazole is a powerful antibiotic that has long-lasting effects on the fecal microbiota and metabolites of cats. Outcome variables slowly recovered over time, but a gastrointestinal diet may aid in recovery.

Probiotic use in dogs is increasing, with spore-forming Bacillus species gaining interest due to their viability during processing, storage, and in the gastrointestinal tract. B. subtilis is known for its adaptable metabolism that may be useful in pets subjected to abrupt dietary changes. The objective of this study was to determine dietary apparent total tract macronutrient digestibility (ATTD) and fecal characteristics, metabolites, and microbiota of healthy adult dogs supplemented with B. subtilis ATCC PTA-122264. All procedures were approved by the University of Illinois IACUC prior to experimentation. Dogs [n = 12; 6 ± 1 yr; 8.71 ± 0.91 kg body weight (BW)] were used in a replicated 3x3 Latin square design (n = 12/group) and fed to maintain BW. In each 42-d experimental period, dogs were allotted to one of three treatments: Control (kibble diet only), Low [kibble diet + 1×109 colony-forming units (CFU) of B. subtilis], and High (kibble diet + 5×109 CFU of B. subtilis). After a 22-d adaptation phase, a 5-d fecal collection phase was followed by a blood collection phase. On d 28, dogs were abruptly changed to a canned diet and fed for 14 d, with fecal samples collected on d 30 (2 d post change), 34 (6 d post change), 38 (10 d post change), and 42 (14 d post change). Fecal microbiota data were evaluated using QIIME2. All other data were analyzed using the Mixed Models procedure of SAS, with P < 0.05 being considered significant. B. subtilis supplementation of the kibble diet did not influence food or energy intake, fecal output, ATTD, most serum metabolites, hematology, fecal characteristics, fecal bacterial alpha and beta diversity indices, and dysbiosis index, demonstrating the safety of the strain in dogs. However, fecal Streptococcus and Blautia abundances were higher in High dogs than Low or Control dogs, while E. coli abundance was less in Low dogs than High and Control dogs. The abrupt change to a canned diet led to significant alterations in fecal characteristics, dysbiosis index, and bacterial abundances, which were not influenced by B. subtilis supplementation. Bacterial alpha diversity measures were affected, with observed ASV (amplicon sequence variants) and the Fisher Index reducing, and the Shannon Index increasing by dietary change. The abrupt dietary change caused a distinct shift in microbial communities, as evidenced by principal coordinates analysis plots. The relative abundances of various fecal bacterial taxa, including Bifidobacterium, Faecalibaculum, Turicibacter, and Lactobacillus were decreased, while Collinsella, Ruminococcus gnavus group, and Escherichia-Shigella were increased with the dietary change. Our data support the notion that daily supplementation of 1 – 5×109 CFU of B. subtilis ATCC PTA-122264 in healthy dogs is safe and does not affect markers of general health and fecal characteristics, warranting further exploration.

Probiotics are defined as live microorganisms that confer a health benefit on the host when administered in adequate amounts. Bacillus coagulans GBI-30, 6086 (BC30) is a commercially available, lactic acid-producing, spore-forming bacteria that exhibits diverse functions. Contrary to most lactic acid-producing bacteria, B. coagulans spores can withstand extreme conditions, lending resiliency through commercial pet food processing, storage, and chemical and enzymatic digestion through the gastrointestinal tract. Previous studies in humans and livestock suggest B. coagulans have probiotic potential, although research in dogs is limited. Therefore, the objectives were to determine the effects of B. coagulans on nutrient digestibility, hematology, immunoglobulin concentrations, and fecal characteristics, metabolites, and microbiota populations of healthy adult dogs before and after an abrupt diet change. Pointer dogs [n = 12; age = 5.9 ± 2.5 yr; body weight (BW) = 26.6 ± 6.1 kg] were used in a replicated 3 × 3 Latin square design and fed commercial diets containing no probiotics or prebiotics. Probiotic or placebo capsules were administered before each daily feeding, with the following treatments tested: 1) basal diet + placebo (control; 250 mg maltodextrin); 2) basal diet + B. coagulans (low dose; 5 x 108 CFU/d); and 3) basal diet + B. coagulans (high dose; 2.5 x 109 CFU/d). An extruded kibble diet was fed to all dogs during a 28-d diet transition phase, after which dogs were abruptly switched to a commercial canned diet with fecal samples collected 2-, 6-, 10-, and 14-d after diet change. All data were analyzed using the Mixed Models procedure of SAS 9.4, with P < 0.05 being significant. Prior to dietary change, nutrient digestibility, food intake, immunoglobulin concentrations, metabolites, and hematology were not affected by treatment. However, fecal scores were decreased (P < 0.05; firmer stools) in dogs fed B. coagulans than controls. Also, fecal Faecalibacterium abundance was greater (P < 0.05) in dogs fed the low B. coagulans dose than those fed the high dose or controls. There were no interaction effects observed due to B. coagulans supplementation throughout the diet transition, but the abrupt transition to canned food reduced (P < 0.0001) fecal DM content and increased (P < 0.0001) fecal scores (looser stools) and pH. The diet transition also increased (P < 0.01) fecal Clostridium hiranonis, Collinsella, Fusobacterium, and Ruminococcus gnavus abundances and decreased (P < 0.01) fecal Bifidobacterium, Blautia, Faecalibacterium, Prevotella copri, Streptococcus, and Turicibacter abundances. Abundances of E. coli, Faecalibacterium, and Prevotella copri were modulated (P < 0.05) by B. coagulans supplementation alone. Our results demonstrate that although B. coagulans did not appear to attenuate shifts in fecal consistency and microbiota populations during an abrupt dietary change, this species may aid in maintaining stool quality and does not negatively impact nutrient digestibility or canine health.

Black soldier fly larvae (BSFL) serve as an alternative protein source for pet food products. Even though BSFL are one of many insect species being added to dog foods and treats, knowledge of its effects in cats remains limited. Further investigations are imperative to delineate the effects of BSFL-based ingredients in cats. Therefore, the objective of this study was to determine the effects of BSFL on serum chemistry, hematology, fecal characteristics, and oral health measures of adult cats. All procedures were approved by the University of Illinois IACUC prior to experimentation. Adult cats [n = 25; 17 females, 8 males; 6.28 ± 0.27 yr of age; 4.50 ± 0.18 kg body weight (BW)] were used in a completely randomized design. The study was composed of a 21-d baseline phase and a 70-d experimental phase. During the baseline phase, all cats were fed a control diet based on chicken meal (35% of diet). After baseline, cats were randomly assigned to 1 of 2 experimental diets: control diet (n = 12) or BSFL-containing diet (20% whole BSFL meal and 24% chicken meal; n = 13). At baseline, teeth were cleaned by a veterinary dentist. Breath samples were analyzed for volatile sulfur compounds (VSC), salivary pH was measured, and blood samples were collected for serum chemistry and hematology at baseline and after 35 d and 70 d on treatment. At baseline and after 70 d on treatment, fecal samples were scored and collected for pH, dry matter, and metabolite measurement. Gingivitis, plaque, and calculus scores were performed by a veterinary dentist after 70 d on treatment. All data were analyzed using the Mixed Models procedure of SAS. Diet, time, and diet*time interaction effects were tested, with P < 0.05 being considered significant. Over time, VSC increased (P < 0.0001) in all cats, but was unaffected by diet. Diet*time interactions were observed for fecal pH, fecal scores, and blood cholesterol and triglyceride concentrations. Blood cholesterol concentrations increased (P < 0.05) over time in cats fed the control diet, but remained stable in cats fed the BSFL diet. The opposite effect was observed with blood triglycerides. Triglyceride concentrations increased (P < 0.05) in cats fed the BSFL diet over time, but were stable in cats fed the control diet. Cats consuming BSFL had reduced (P < 0.05) fecal pH, dry matter content, and protein catabolite concentrations, but increased (P < 0.05) fecal short-chain fatty acid concentrations and fecal scores. Overall, 20% BSFL dietary inclusion had comparable effects as chicken meal, suggesting that it will serve as a suitable replacement in cat foods.

Metronidazole is a potent antibiotic often prescribed to treat gastrointestinal enteropathies, but is known to induce loose stools, negatively alter the fecal microbiome, and affect fecal metabolite production. Dietary intervention may aid in post-antibiotic recovery, but little research has been conducted regarding the potential of fiber utilization for microbial recovery in canines. Using an in vitro fermentation assay, the objective was to investigate the fermentation characteristics of dietary fibers using fecal inocula from dogs treated with metronidazole. All procedures were approved by the University of Illinois IACUC prior to experimentation. Healthy male beagles (n = 4) were fed a commercial canned diet for 2 wk, then administered metronidazole [20 mg/kg body weight (BW) twice a day] for 2 wk. Fresh fecal samples were collected at wk 2 [diet only (CTL)] and 4 [antibiotic treatment (ANT)], stabilized in a 20% glycerol solution, and then frozen. On the in vitro fermentation day, feces from each time point were thawed and used to inoculate tubes. At baseline and after 6, 12, and 18 h of fermentation, pH, short-chain fatty acid (SCFA) concentrations, and microbiota populations were measured. SCFA were measured by gas chromatography and fecal microbiota populations were analyzed by 16S rRNA sequencing. All blank tube-corrected changes from baseline data were analyzed using repeated measures and the MIXED procedure of SAS 9.4, with significance set at P < 0.05. QIIME2 analysis was used for bacterial diversity measures. As expected, metronidazole administration heavily influenced microbiota populations and fiber fermentability characteristics. Pectin fermentation reduced (P < 0.001) pH and increased (P < 0.001) SCFA concentrations over time, but responses were less (P < 0.001) in ANT tubes than CTL tubes. Beet pulp fermentation also reduced (P < 0.001) pH and increased (P < 0.001) SCFA concentrations over time. Whereas the magnitude of pH change was small between inoculum sources, SCFA concentrations were different (P < 0.001) between ANT tubes and CTL tubes. Propionate and butyrate concentrations were greater (P < 0.001) in CTL tubes than ANT tubes at all time points, but acetate concentrations varied over time. Chicory pulp fermentation reduced (P < 0.001) pH over time, with greater (P < 0.01) reductions in ANT tubes than CTL tubes. Chicory pulp fermentation increased SCFA concentrations, but had different patterns based on inoculum source. Metronidazole altered microbiota populations by reducing (P < 0.001) bacterial alpha diversity. The analysis of bacterial beta diversity revealed separate clusters for dogs in the absence and presence of metronidazole. Beta diversity analysis also showed that tubes containing chicory pulp clustered separately from those containing the other fibers. Relative abundances of over 50 bacterial genera differed (P < 0.05) among inoculum sources. In summary, interesting fermentation patterns in response to varying fiber sources were observed, allowing for improved insight into their potential abilities when provided to antibiotic-treated dogs.