Influence of dietary protein and fructooligosaccharides on fecal fermentative end-products, fecal bacterial populations and apparent total tract digestibility in dogs

Using meta-analysis to understand the impacts of dietary protein and fat content on the composition of fecal microbiota of domestic dogs (Canis lupus familiaris): A pilot study

The interplay between diet and fecal microbiota composition is garnering increased interest across various host species, including domestic dogs. While the influence of dietary macronutrients and their associated microbial communities have been extensively reviewed, these reviews are descriptive and do not account for differences in microbial community analysis, nor do they standardize macronutrient content across studies. To address this, a meta-analysis was performed to assess the impact of dietary crude protein ("protein") and dietary crude fat ("fat") on the fecal microbiota composition in healthy dogs. Sixteen publications met the eligibility criteria for the meta-analysis, yielding a final data set of 314 dogs. Diets were classed as low, moderate, high, or supra in terms of protein or fat content. Sequence data from each publication were retrieved from public databases and reanalyzed using consistent bioinformatic pipelines. Analysis of community diversity indices and unsupervised clustering of the data with principal coordinate analysis revealed a small effect size and complete overlap between protein and fat levels at the overall community level. Supervised clustering through random forest analysis and partial least squares-discriminant analysis indicated alterations in the fecal microbiota composition at a more individual taxonomic level, corresponding to the levels of protein or fat. The Prevotellaceae Ga6A1 group and Enterococcus were associated with increasing levels of protein, while Allobaculum and Clostridium sensu stricto 13 were associated with increasing levels of fat. Interestingly, the random forest analyses revealed that Sharpea, despite its low relative abundance in the dog's fecal microbiome, was primarily responsible for the separation of the microbiome for both protein and fat. Future research should focus on validating and understanding the functional roles of these relatively low-abundant genera.

Updating the Classification of Chronic Inflammatory Enteropathies in Dogs

Chronic inflammatory enteropathies (CIEs) in dogs are currently classified based on response to sequential treatment trials into food-responsive (FREs); antibiotic-responsive (AREs); immunosuppressant-responsive (IREs); and non-responsive enteropathies (NREs). Recent studies have reported that a proportion of NRE dogs ultimately respond to further dietary trials and are subsequently misclassified. The FRE subset among CIEs is therefore probably underestimated. Moreover, alterations in the gut microbiota composition and function (dysbiosis) have been shown to be involved in CIE pathogenesis in recent research on dogs. Metronidazole and other antibiotics that have been used for decades for dogs with AREs have been demonstrated to result in increased antimicrobial resistance and deleterious effects on the gut microbiota. As a consequence, the clinical approach to CIEs has evolved in recent years toward the gradual abandonment of the use of antibiotics and their replacement by other treatments with the aim of restoring a diverse and functional gut microbiota. We propose here to refine the classification of canine CIEs by replacing the AREs category with a microbiota-related modulation-responsive enteropathies (MrMREs) category.

Supplementation with Silybum marianum Extract, Synbiotics, Omega-3 Fatty Acids, Vitamins, and Minerals: Impact on Biochemical Markers and Fecal Microbiome in Overweight Dogs

Overweight and obese dogs can develop metabolic dysfunction, characterized by an inflammatory response and involvement of liver functions. If a modulation of the gut microbiome and its interaction with the gut-liver axis is implicated in the development of metabolic dysfunction, exploration becomes necessary. Over the past decade, diverse therapeutic approaches have emerged to target pathogenic factors involved in metabolic dysfunction. This study investigated the impact of a supplement with hepatoprotective activity, containing extracts of Silybum marianum, prebiotics, probiotics, n-3 polyunsaturated fatty acids, vitamins, and minerals on hematological markers of liver functions and inflammation, as well as on the intestinal microbiota of 10 overweight adult dogs over a 35-day time span. Animals underwent clinical and laboratory evaluations every 7 days, both before the administration of the supplement (T0) and after 7, 14, 21, 28, and 35 days (T1, T2, T3, T4, and T5). In comparison to T0, a significant (p < 0.05) decrease in ALP, glucose, direct bilirubin, and CRP was observed from T3 to T5. The alpha diversity of the fecal microbiota significantly decreased (p < 0.05) only at T1, with high variability observed between dogs. Total short-chain fatty acid and lactic acid were also lower at T1 (p < 0.05) compared to the other times of sampling. The beta diversity of the fecal microbiota failed to show a clear pattern in relation to the sampling times. These results of blood parameters in overweight dogs show a reduction of the inflammation and an improvement of metabolic status during the study period, but the effective contribution of the supplement in this clinical outcome deserves further investigation. Furthermore, the considerable individual variability observed in the microbiome hinders the confident detection of supplement effects.

Effects of Increasing Levels of Purified Beta-1,3/1,6-Glucans on the Fecal Microbiome, Digestibility, and Immunity Variables of Healthy Adult Dogs

Yeast-purified beta-1,3/1,6-glucans (BG) can modulate dogs' immune systems and microbiome, but the optimal inclusion dose remains unknown. The aim of the study was to evaluate the effects of 0.0, 0.07, 0.14, and 0.28% inclusion of BG in a dry extruded diet on the digestibility, immunity, and fecal microbiota of healthy adult dogs. Eight male and female border collies [n = 4; body condition score (BCS) = 5] and English cocker spaniels (n = 4; BCS = 5), aged 3.5 ± 0.5 years, were randomly distributed into two 4 × 4 balanced Latin squares. Fecal microbiota (using 16S rRNA sequencing, Illumina®), apparent digestibility coefficients (ADC) of nutrients, fecal concentrations of short-chain fatty acids (SCFA) and branched-chain fatty acids (BCFA), ammoniacal nitrogen, lactic acid, IgA and pH, lymphocyte immunophenotyping, intensity and percentage of phagocytosis and oxidative burst were determined. No differences were observed in Faith (p = 0.1414) and Pielou-evenness (p = 0.1151) between treatments, but beta diversity was different between 0.0% and 0.14% BG groups (p = 0.047). Moreover, the Firmicutes phylum was the most abundant in all groups and exhibited the highest relative abundance after the consumption of 0.14% BG, a finding considered beneficial for the canine microbiome. The Erysipelotrichaceae and Ruminococcaceae families, along with the Faecalibacterium and Prevotella genera, considered favorable for their involvement in butyrate production and other metabolites, showed increased abundance after the consumption of 0.14% BG. The potentially pathogenic Proteobacteria phylum displayed lower abundance after the consumption of 0.14% BG. Fecal concentrations of the evaluated compounds and pH did not differ after consumption of the BG at all percentages. Higher crude protein ADC was found after 0.14 and 0.28% BG consumption (p < 0.0001), but no differences were found for other nutrients. Phagocytosis, oxidative burst, and lymphocyte populations were not modulated by any of the treatments; however, 0.14% BG modulated the lymphocyte T CD4+:CD8+ ratio (p = 0.0368), an important marker of immune system efficiency. The inclusion of 0.14% BG resulted in the best responses and was the best dose evaluated.

The effects of hydrolyzed protein on macronutrient digestibility, fecal metabolites and microbiota, oxidative stress and inflammatory biomarkers, and skin and coat quality in adult dogs

Research on protein hydrolysates has observed various properties and functionalities on ingredients depending on the type of hydrolysate. The objective of this study was to evaluate the effects of hydrolyzed chicken protein that was incorporated into diets on digestibility, gut health, skin and coat health, oxidative stress, and intestinal inflammation markers in healthy adult dogs. Five complete and balanced diets were manufactured: (1) CONd: 25% chicken meal diet; (2) 5% CLHd: 5% chicken liver and heart hydrolysate plus 20% chicken meal diet; (3) CLHd: 25% chicken liver and heart hydrolysate diet; (4) 5% CHd: 5% chicken hydrolysate plus 20% chicken meal diet; (5) CHd: 25% chicken hydrolysate diet. A replicated 5 × 5 Latin square design was used which included 10 neutered adult Beagles. Each of the 5 periods consisted of a 7-d washout time and a 28-d treatment period. All diets were well accepted by the dogs. Fecal butyrate concentration was higher while fecal isovalerate and total phenol/indole were lower in dogs fed CLHd than CONd (P < 0.05). Dogs fed CHd had higher fecal immunoglobulin A concentration when compared with CLHd (P < 0.05); however, both groups were comparable to the CONd. There was no difference among groups in serum cytokine concentrations, serum oxidative stress biomarkers, or skin and coat health analyses (P > 0.05). Fecal microbiota was shifted by CLHd with higher abundance in Ruminococcus gauvreauii group as well as lower Clostridium sensu stricto 1, Sutterella, Fusobacterium, and Bacteroides when compared with CONd (P < 0.05). There was also a difference in beta diversity of fecal microbiota between CLHd and CHd (P < 0.05). In conclusion, chicken protein hydrolysate could be incorporated into canine extruded diets as a comparable source of protein to traditional chicken meal. The test chicken protein hydrolysates showed the potential to support gut health by modulating immune response and microbiota; however, functional properties of protein hydrolysates are dependent on inclusion level and source.

Faecal metabolome responses to an altered dietary protein:carbohydrate ratio in adult dogs

High-protein diets may aid weight loss and weight maintenance programs in both humans and dogs, although the effect of dietary protein levels on gut metabolism and functionality has not been studied in depth. The current study aimed to investigate the effect of an altered dietary protein:carbohydrate ratio on gut function in adult dogs by means of faecal metabolomic fingerprinting. More specifically, functional metabolic differences in dogs fed a high-protein/low-carbohydrate (HPLC) vs. low-protein/high-carbohydrate (LPHC) diet were studied by equally allocating twelve clinically healthy (6 lean and 6 obese) Beagles into two groups in a cross-over design, with each group receiving two isocaloric diets for four weeks. The faecal metabolome revealed that different protein:carbohydrate ratio can influence host and/or gut microbiome metabolism and function, while no effect was observed on the body condition. Targeted analysis demonstrated that the HPLC diet significantly increased the concentration of indole, spermidine, and pipecolinic acid and decreased the concentration of azelaic acid, D-fructose, mannose, and galactose (p < 0.05). Multivariate modelling (OPLS-DA) of the untargeted faecal metabolome revealed distinctly different metabolomic profiles following the HPLC vs. LPHC diet, with 18 altered pathways. The HPLC diet influenced amino acid and lipid metabolism, potentially promoting weight loss and immune function, whereas the LPHC diet affected carbohydrate fermentation and may promote anti-oxidative function.

A Novel Prebiotic Fibre Blend Supports the Gastrointestinal Health of Senior Dogs

Senior pets can suffer from a wide range of age-related diseases that can impact the quality of life for the pet and the relationship between a pet and their owner. Dietary fibre plays a key role in shaping the gastrointestinal health in mammalian species. The aim of this study was to investigate the impact of a novel prebiotic fibre blend containing sugar beet pulp, galacto-oligosaccharides, and cellulose on the health of senior dogs when fed on top of a background commercial dry diet. Thirty-two dogs aged >8 years received the prebiotic fibre blend as a dietary topper for 21 days on top of a nutritionally complete diet using a cross-over study design. The prebiotic fibre blend improved the gastrointestinal health of senior dogs as measured through improved faecal quality scores, a reduction in faecal pH, changes to the taxonomic composition of the gut, and a reduction in faecal branched-chain fatty acids, which are markers for proteolytic degradation. Broader systemic measures, such as changes to serum cytokines, were not impacted by the prebiotic fibre blend. In conclusion, a novel prebiotic fibre blend containing sugar beet pulp, galacto-oligosaccharides, and cellulose improved the gastrointestinal health of senior dogs and could have a range of potential future dietary applications.

The Effect of Dietary Protein Concentration on the Fecal Microbiome and Serum Concentrations of Gut-Derived Uremic Toxins in Healthy Adult Cats

The purpose of this study was to evaluate the effect of feeding healthy adult cats with foods containing variable protein concentrations on the fecal microbiome and serum concentrations of the gut-derived uremic toxins indoxyl sulfate, p-cresol sulfate (pCS), and trimethylamine-n-oxide. Twenty healthy young adult cats were randomized into two groups and fed either a low-protein diet (LPD; 7.4 g/100 kcal ME) or a high-protein diet (HPD; 11.0 g/100 kcal ME) for a 12-week period. Serum uremic toxin concentrations were measured via liquid chromatography tandem mass spectrometry, and the fecal microbiome was characterized using shallow sequence shotgun metagenomics. Cats that consumed the HPD had higher pCS concentrations at 8 weeks (p = 0.028) when compared to baseline. After 12 weeks, cats fed the HPD had higher fecal alpha diversity indices at both the taxonomic and functional levels and lower fecal Bifidobacterium relative abundance compared to those cats fed the LPD. In conclusion, a change in diet and dietary protein concentration shifted the fecal microbial community and microbial function. Feeding cats a high amount of protein increased serum concentrations of the uremic toxin pCS; however, the effect was short-lived.

Effects of Food Factors and Processing on Protein Digestibility and Gut Microbiota

Protein is an essential macronutrient. The nutritional needs of dietary proteins are met by digestion and absorption in the small intestine. Indigestible proteins are further metabolized in the gut and produce metabolites via protein fermentation. Thus, protein indigestibility exerts a wide range of effects on gut microbiota composition and function. This review aims to discuss protein digestibility, the effects of food factors, such as protein sources, intake level, and amino acid composition, and making meat analogues. Besides, it provides an inventory of antinutritional factors and processing techniques that influence protein digestibility and, consequently, the diversity and composition of intestinal microbiota. Future studies are warranted to understand the implication of plant-based analogues on protein digestibility and gut microbiota and to elucidate the mechanisms concerning protein digestibility to host gut microbiota using various omics techniques.

Adding a polyphenol-rich fiber bundle to food impacts the gastrointestinal microbiome and metabolome in dogs

Introduction

Pet foods fortified with fermentable fibers are often indicated for dogs with gastrointestinal conditions to improve gut health through the production of beneficial post-biotics by the pet's microbiome.

Methods

To evaluate the therapeutic underpinnings of pre-biotic fiber enrichment, we compared the fecal microbiome, the fecal metabolome, and the serum metabolome of 39 adult dogs with well-managed chronic gastroenteritis/enteritis (CGE) and healthy matched controls. The foods tested included a test food (TF1) containing a novel pre-biotic fiber bundle, a control food (CF) lacking the fiber bundle, and a commercially available therapeutic food (TF2) indicated for managing fiber-responsive conditions. In this crossover study, all dogs consumed CF for a 4-week wash-in period, were randomized to either TF1 or TF2 and fed for 4 weeks, were fed CF for a 4-week washout period, and then received the other test food for 4 weeks.

Results

Meaningful differences were not observed between the healthy and CGE dogs in response to the pre-biotic fiber bundle relative to CF. Both TF1 and TF2 improved stool scores compared to CF. TF1-fed dogs showed reduced body weight and fecal ash content compared to either CF or TF2, while stools of TF2-fed dogs showed higher pH and lower moisture content vs. TF1. TF1 consumption also resulted in unique fecal and systemic metabolic signatures compared to CF and TF2. TF1-fed dogs showed suppressed signals of fecal bacterial putrefactive metabolism compared to either CF or TF2 and increased saccharolytic signatures compared to TF2. A functional analysis of fecal tryptophan metabolism indicated reductions in fecal kynurenine and indole pathway metabolites with TF1. Among the three foods, TF1 uniquely increased fecal polyphenols and the resulting post-biotics. Compared to CF, consumption of TF1 largely reduced fecal levels of endocannabinoid-like metabolites and sphingolipids while increasing both fecal and circulating polyunsaturated fatty acid profiles, suggesting that TF1 may have modulated gastrointestinal inflammation and motility. Stools of TF1-fed dogs showed reductions in phospholipid profiles, suggesting fiber-dependent changes to colonic mucosal structure.

Discussion

These findings indicate that the use of a specific pre-biotic fiber bundle may be beneficial in healthy dogs and in dogs with CGE.

Evaluation of the Influence of Coprophagic Behavior on the Digestibility of Dietary Nutrients and Fecal Fermentation Products in Adult Dogs

Coprophagia is a common and undesirable behavior observed in dogs; however, little is known about its causes or possible consequences when analysis of the animal's feces is needed for experimental purposes. Therefore, this study evaluated the effect of coprophagy on digestibility, fecal pH, and fermentative metabolites. Twelve healthy dogs with a mean age of 3.50 ± 1.45 years were included and divided into two groups: coprophagic (COP) and non-coprophagic (NCOP). The study lasted 30 days, the last 6 days being used to collect feces for the analysis of the apparent digestibility of coefficients (ADC), fecal pH, and the concentration of short- and branched-chain fatty acids, ammonia, and fecal lactic acid. Statistical analysis was performed using the SAS software. No differences were observed for most variables, except for the ADC of nitrogen-free extract (NFE), which presented the highest average for the COP. This result should be interpreted with caution, as the NFE is estimated from calculations and was not determined in the laboratory; in addition, the results represent not only starch and sugars but also some parts referring to fibers. Therefore, coprophagy seemed not to influence the fecal variables analyzed.

The promotion mechanism of prebiotics for probiotics: A review

Prebiotics and probiotics play a positive role in promoting human nutrition and health. Prebiotics are compounds that cannot be digested by the host, but can be used and fermented by probiotics, so as to promote the reproduction and metabolism of intestinal probiotics for the health of body. It has been confirmed that probiotics have clinical or health care functions in preventing or controlling intestinal, respiratory, and urogenital infections, allergic reaction, inflammatory bowel disease, irritable bowel syndrome and other aspects. However, there are few systematic summaries of these types, mechanisms of action and the promotion relationship between prebiotics and probiotic. Therefore, we summarized the various types of prebiotics and probiotics, their individual action mechanisms, and the mechanism of prebiotics promoting probiotics in the intestinal tract. It is hoped this review can provide new ideas for the application of prebiotics and probiotics in the future.

From Chihuahua to Saint-Bernard: how did digestion and microbiota evolve with dog sizes

Health and well-being of dogs are of paramount importance to their owners. Digestion plays a key role in dog health, involving physicochemical, mechanical and microbial actors. However, decades of breeding selection led to various dog sizes associated with different digestive physiology and disease sensitivity. Developing new products requires the consideration of all the multi-faceted aspects of canine digestion, the evaluation of food digestibility, drug release and absorption in the gut. This review paper provides an exhaustive literature survey on canine digestive physiology, focusing on size effect on anatomy and digestive parameters, with graphical representation of data classified as "small", "medium" and "large" dogs. Despite the huge variability between protocols and animals, interesting size effects on gastrointestinal physiology were highlighted, mainly related to the colonic compartment. Colonic measurements, transit time permeability, fibre degradation, faecal short-chain fatty acid concentration and faecal water content increase while faecal bile acid concentration decreases with body size. A negative correlation between body weight and Proteobacteria relative abundance was observed suggesting an effect of dog body size on faecal microbiota. This paper gathers helpful in vivo data for academics and industrials and supports the development of new food and pharma products to move towards canine personalized nutrition and health.

Assessment of the Effects of Edible Microalgae in a Canine Gut Model

Microalgae are a source of bioactive compounds having recently been studied for their possible application as health-promoting ingredients. The aim of the study was to evaluate in an in vitro canine gut model the effects of four microalgae, Arthrospira platensis (AP), Haematococcus pluvialis (HP), Phaeodactylum tricornutum (PT) and Chlorella vulgaris (CV), on some fecal microbial populations and metabolites. The four microalgae were subjected to an in vitro digestion procedure, and subsequently, the digested biomass underwent colonic in vitro fermentation. After 6 h of incubation, PT increased propionate (+36%) and butyrate (+24%), and decreased total BCFA (−47%), isobutyrate (−52%) and isovalerate (−43%) and C. hiranonis (−0.46 log10 copies/75 ng DNA). After 24 h, PT increased propionate (+21%) and isovalerate (+10%), and decreased the abundance of Turicibacter spp. (7.18 vs. 6.69 and 6.56 log10 copies/75 ng DNA for CTRL vs. PT, respectively); moreover, after 24 h, CV decreased C. coccoides (−1.12 log10 copies/75 ng DNA) and Enterococcus spp. (−0.37 log10 copies/75 ng DNA). In conclusion, the microbial saccharolytic activities and the shift in fecal bacterial composition were less pronounced than expected, based on current literature. This study should be considered as a preliminary assessment, and future investigations are required to better understand the role of microalgae in canine nutrition.

The Use of Disinfectant in Barn Cleaning Alters Microbial Composition and Increases Carriage of Campylobacter jejuni in Broiler Chickens

To maintain food safety and flock health in broiler chicken production, biosecurity approaches to keep chicken barns free of pathogens are important. Canadian broiler chicken producers must deep clean their barns with chemical disinfectants at least once annually (full disinfection [FD]) and may wash with water (water wash [WW]) throughout the year. However, many producers use FD after each flock, assuming a greater efficacy of more stringent cleaning protocols, although little information is known regarding how these two cleaning practices affect pathogen population and gut microbiota. In the present study, a crossover experiment over four production cycles was conducted in seven commercial chicken barns to compare WW and FD. We evaluated the effects of barn cleaning methods on commercial broiler performance, cecal microbiota composition, Campylobacter and Salmonella occurrence, and Campylobacter jejuni and Clostridium perfringens abundance, as well as on short-chain fatty acid (SCFA) concentrations in the month-old broiler gut. The 30-day body weight and mortality rate were not affected by the barn cleaning methods. The WW resulted in a modest but significant effect on the structure of broiler cecal microbiota (weighted-UniFrac; adonis P = 0.05, and unweighted-UniFrac; adonis P = 0.01), with notable reductions in C. jejuni occurrence and abundance. In addition, the WW group had increased cecal acetate, butyrate, and total SCFA concentrations, which were negatively correlated with C. jejuni abundance. Our results suggest that WW may result in enhanced activity of the gut microbiota and reduced zoonotic transmission of C. jejuni in broiler production relative to FD in the absence of a disease challenge. IMPORTANCE We compared the effects of barn FD and WW methods on gut microbial community structures and pathogen prevalence of broiler chickens in a nonchallenging commercial production setting. The results revealed that barn cleaning methods had little impact on the 30-day body weight and mortality rate of broiler chickens. In addition, the FD treatment had a subtle but significant effect on the broiler cecal microbiota with increased abundances of Campylobacter and decreased SCFA concentrations, which would support the adoption of WW as a standard practice. Thus, compared to FD, WW can be beneficial to broiler chicken production by inhibiting zoonotic pathogen colonization in the chicken gut with reduced cost and labor of cleaning.

Assessment of the Effects of the Synbiotic Combination of Bifidobacterium longum subsp. infantis CECT 7210 and Oligofructose-Enriched Inulin Against Digestive Bacterial Infections in a Piglet Model

The use of bifidobacteria as probiotics has proven to be beneficial in gastroenteric infections. Furthermore, prebiotics such as inulin can enhance the survival and growth of these bacteria. Two trials were performed to evaluate the effects of the administration of Bifidobacterium longum subsp. infantis CECT 7210 and oligofructose-enriched inulin against Salmonella enterica serovar Typhimurium or enterotoxigenic Escherichia coli (ETEC) F4. A total of 72 (Salmonella trial) and 96 (ETEC F4 trial) weaned piglets were used in a 2 × 2 design (with or without synbiotic, inoculated or not with the pathogen). After adaptation, animals were orally inoculated. Performance and clinical signs were evaluated. On days 4 and 8 (Salmonella trial) and 3 and 7 (ETEC F4 trial) post-inoculation (PI), one animal per pen was euthanized. Blood, digestive content and tissue samples were collected and microbiological counts, fermentation products, serum inflammatory markers and ileum histomorphometry analysis were performed. Both challenges had an impact on faecal consistency (p < 0.001), including the faecal shedding of Salmonella and increased numbers of enterobacteria and coliforms. The synbiotic administration did not have any effect on pathogen loads but induced changes in the fermentation profile, such as increased valeric acid in both trials as well as decreased acetic acid, except for Salmonella-challenged animals. The effect on propionate varied among trials, increasing in challenged synbiotic-treated pigs and decreasing in non-challenged ones in the Salmonella trial (P interaction = 0.013), while the opposed occurred in the ETEC F4 trial (P interaction = 0.013). The administration of the synbiotic increased intraepithelial lymphocytes (IEL; p = 0.039) on day 8 PI in the Salmonella trial and a similar trend occurred in non-challenged pigs in the ETEC F4 trial (P interaction = 0.086). The results did not provide evidence of reduced pathogen load with the synbiotic, although a modulation in fermentative activity could be identified depending on the challenge. Consistent increases were found in IEL, suggesting that this synbiotic combination has some immunomodulatory properties.

Dogs' Microbiome From Tip to Toe

Microbiota and microbiome, which refers, respectively, to the microorganisms and conjoint of microorganisms and genes are known to live in symbiosis with hosts, being implicated in health and disease. The advancements and cost reduction associated with high-throughput sequencing techniques have allowed expanding the knowledge of microbial communities in several species, including dogs. Throughout their body, dogs harbor distinct microbial communities according to the location (e.g., skin, ear canal, conjunctiva, respiratory tract, genitourinary tract, gut), which have been a target of study mostly in the last couple of years. Although there might be a core microbiota for different body sites, shared by dogs, it is likely influenced by intrinsic factors such as age, breed, and sex, but also by extrinsic factors such as the environment (e.g., lifestyle, urban vs rural), and diet. It starts to become clear that some medical conditions are mediated by alterations in microbiota namely dysbiosis. Moreover, understanding microbial colonization and function can be used to prevent medical conditions, for instance, modulation of gut microbiota of puppies is more effective to ensure a healthy gut than interventions in adults. This paper gathers current knowledge of dogs' microbial communities, exploring their function, implications in the development of diseases, and potential interactions among communities while providing hints for further research.

A high-protein diet containing inulin/oligofructose supports body weight gain associated with lower energy expenditure and carbohydrate oxidation, and alters faecal microbiota in C57BL/6 mice

Prebiotic supplements and high-protein (HP) diets reduce body weight and modulate intestinal microbiota. Our aim was to elucidate the combined effect of an inulin/oligofructose (FOS) and HP diet on body weight gain, energy metabolism and faecal microbiota. Forty male C57BL/6NCrl mice were fed a control (C) diet for 2 weeks and allocated to a C or HP (40 % protein) diet including no or 10 % inulin/FOS (C + I and HP + I) for 4 weeks. Inulin/FOS was added in place of starch and cellulose. Body weight, food intake, faecal energy and nitrogen were determined. Indirect calorimetry and faecal microbiota analysis were performed after 3 weeks on diets. Body weight gain of HP-fed mice was 36 % lower than HP + I- and C-fed mice (P < 0⋅05). Diet digestibility and food conversion efficiency were higher in HP + I- than HP-fed mice (P < 0⋅01), while food intake was comparable between groups. Total energy expenditure (heat production) was 25 % lower in HP + I- than in C-, HP- and C + I-fed mice (P < 0⋅001). Carbohydrate oxidation tended to be 24 % higher in HP- than in HP + I-fed mice (P < 0⋅05). Faecal nitrogen excretion was 31-45 % lower in C-, C + I- and HP + I- than in HP-fed mice (P < 0⋅05). Faecal Bacteroides-Prevotella DNA was 2⋅3-fold higher in C + I- and HP + I- relative to C-fed mice (P < 0⋅05), but Clostridium leptum DNA abundances was 79 % lower in HP + I- than in HP-fed mice (P < 0⋅05). We suggest that the higher conversion efficiency of dietary energy of HP + I but not C + I-fed mice is caused by higher digestibility and lower heat production, resulting in increased body mass.

On the Variability of Microbial Populations and Bacterial Metabolites within the Canine Stool. An in-Depth Analysis

Simple Summary

The present study investigated for the first time the impact that different sampling points have on the abundance of microbial populations and metabolites within the canine stool. We found that inner stool subsamples resulted in higher concentrations of bacterial metabolites but not of microbial populations. These findings suggest that stool subsampling is unlikely to represent the canine microbiota and metabolome uniformly. We believe that complete homogenisation of the whole stool prior to analysis may improve the final outcome when investigating the canine gut microbiome.

Abstract

Canine faecal microbial populations and metabolome are being increasingly studied to understand the interplay between host and gut microbiome. However, the distribution of bacterial taxa and microbial metabolites throughout the canine stool is understudied and currently no guidelines for the collection, storage and preparation of canine faecal samples have been proposed. Here, we assessed the effects that different sampling points have on the abundance of selected microbial populations and bacterial metabolites within the canine stool. Whole fresh faecal samples were obtained from five healthy adult dogs. Stool subsamples were collected from the surface to the inner part and from three equally sized areas (cranial, central, caudal) along the length axis of the stool log. All samples were finally homogenised and compared before and after homogenisation. Firmicutes, Bacteroidetes, Clostridium cluster I, Lactobacillus spp., Bifidobacterium spp. and Enterococcus spp. populations were analysed, as well as pH, ammonia and short-chain fatty acids (SCFA) concentrations. Compared to the surface of the stool, inner subsamples resulted in greater concentrations of SCFA and ammonia, and lower pH values. qPCR assay of microbial taxa did not show any differences between subsamples. Homogenisation of faeces does not affect the variability of microbial and metabolome data. Although the distribution patterns of bacterial populations and metabolites are still unclear, we found that stool subsampling yielded contradictory result and biases that can affect the final outcome when investigating the canine microbiome. Complete homogenisation of the whole stool is therefore recommended.

Duration of Prebiotic Intake Is a Key-Factor for Diet-Induced Modulation of Immunity and Fecal Fermentation Products in Dogs

Prebiotics promote health benefits, however, there is no consensus on the minimal intake period required in order to obtain good results. This study evaluated the effect of the time of ingestion of prebiotics on fecal fermentation products and immunological features in dogs. Twenty-four adult dogs were randomly distributed in a block design with six groups and four treatments. Diet and intake period were variation factors. Diets were either a control diet without the addition of prebiotic (CO) or with the inclusion of 1% of a commercial product containing a minimum of 0.38% galactooligosaccharides (GOS), 0.5% (B1) or 1% (B2) of a prebiotic blend. Time variable was set at 30 and 60 days for evaluation of immunity and gut health. Results were analyzed in the Statistical Analysis System software (SAS), version 9.4, considering the repeated measures over time design, and means were compared by the Tukey test and p < 0.05 was significant. Propionic acid was the only variable that had an interaction effect, with reduction of this metabolite in treatment B2 in the period of 60 days. At T60, concentrations of immunoglobulin A, lactic acid, and pH in the feces increased (p < 0.05) in all treatments regardless of prebiotic inclusion or not. GOS increased fecal score and lactic acid concentrations. Therefore, a 60-day intake period of a prebiotic blend was not sufficient to modulate fecal and immune variables and higher concentrations of a single prebiotic would be more relevant for results.

Opportunities of prebiotics for the intestinal health of monogastric animals

The goal of prebiotic applications from different sources is to improve the gut ecosystem where the host and microbiota can benefit from prebiotics. It has already been recognized that prebiotics have potential roles in the gut ecosystem because gut microbiota ferment complex dietary macronutrients and carry out a broad range of functions in the host body, such as the production of nutrients and vitamins, protection against pathogens, and maintenance of immune system balance. The gut ecosystem is very crucial and can be affected by numerous factors consisting of dietary constituents and commensal bacteria. This review focuses on recent scientific evidence, confirming a beneficial effect of prebiotics on animal health, particularly in terms of protection against pathogenic bacteria and increasing the number of beneficial bacteria that may improve epithelial cell barrier functions. It has also been reviewed that modification of the gut ecosystem through the utilization of prebiotics significantly affects the intestinal health of animals. However, the identification and characterization of novel potential prebiotics remain a topical issue and elucidation of the metagenomics relationship between gut microbiota alteration and prebiotic substances is necessary for future prebiotic studies.

State-of-the-Art of the Nutritional Alternatives to the Use of Antibiotics in Humans and Monogastric Animals

Simple Summary

Antibiotic resistance represents a worldwide recognized issue affecting both human and veterinary medicine, with a particular focus being directed towards monogastric animals destined for human consumption. This scenario is the result of frequent utilization of the antibiotics either for therapeutic purposes (humans and animals) or as growth promoters (farmed animals). Therefore, the search for nutritional alternatives has progressively been the object of significant efforts by the scientific community. So far, probiotics, prebiotics and postbiotics are considered the most promising products, as they are capable of preventing or treating gastrointestinal diseases as well as restoring a eubiosis condition after antibiotic-induced dysbiosis development. This review provides an updated state-of-the-art of these nutritional alternatives in both humans and monogastric animals.

Abstract

In recent years, the indiscriminate use of antibiotics has been perpetrated across human medicine, animals destined for zootechnical productions and companion animals. Apart from increasing the resistance rate of numerous microorganisms and generating multi-drug resistance (MDR), the nonrational administration of antibiotics causes sudden changes in the structure of the intestinal microbiota such as dysbiotic phenomena that can have a great clinical significance for both humans and animals. The aim of this review is to describe the state-of-the-art of alternative therapies to the use of antibiotics and their effectiveness in humans and monogastric animals (poultry, pigs, fish, rabbits, dogs and cats). In particular, those molecules (probiotics, prebiotics and postbiotics) which have a direct function on the gastrointestinal health are herein critically analysed in the prevention or treatment of gastrointestinal diseases or dysbiosis induced by the consumption of antibiotics.

Effects of High-Fat Diet at Two Energetic Levels on Fecal Microbiota, Colonic Barrier, and Metabolic Parameters in Dogs

Increased consumption of energy-rich foods is a key factor in overweight, obesity, and associated metabolic disorders. This would be, at least in part, related to microbiota disturbance. In rodent models of obesity, microbiota disruption has been associated with alteration of the intestinal barrier, endotoxemia, inflammation grade, and insulin sensitivity. The aim of the present study was to assess the effects of a high-fat diet (HFD), fed at two energetic levels, on microbiota, intestinal barrier, and inflammatory and metabolic parameters in dogs. A HFD (33% fat as fed, 4,830 kcal/kg) was given to 24 healthy Beagle dogs at 100% (HF-100; n = 8) and at 150% (HF-150; n = 16) of their maintenance energy requirements for 8 weeks. Analysis of similarity revealed a significant difference in gut microbiota β-diversity following the diet compared to week 0 in both groups while α-diversity was lower only in the HF-150 group. Firmicutes/Bacteroidetes ratio was higher in the HF-150 group compared to the HF-100 group at weeks 2 and 8. A reduction in insulin sensitivity was observed over time in the HF150 group. Neither endotoxemia nor inflammation was observed in either group, did not find supporting data for the hypothesis that the microbiota is involved in the decline of insulin sensitivity through metabolic endotoxemia and low-grade inflammation. Colonic permeability was increased at week 4 in both groups and returned to initial levels at week 8, and was associated with modifications to the expression of genes involved in colonic barrier function. The increase in intestinal permeability may have been caused by the altered intestinal microbiota and increased expression of genes encoding tight junction proteins might indicate a compensatory mechanism to restore normal permeability. Although simultaneous changes to the microbiota, barrier permeability, inflammatory, and metabolic status have not been observed, such a causal link cannot be excluded in dogs overfed on a HFD. Further studies are necessary to better understand the link between HFD, intestinal microbiota and the host.

Varying Protein Levels Influence Metabolomics and the Gut Microbiome in Healthy Adult Dogs

The optimal ranges of protein for healthy adult dogs are not known. This study evaluated the impact of long-term consumption of foods containing low, medium, and high levels of protein on serum, urine, and fecal metabolites, and gut microbiome in beagles. Following maintenance on a prefeed food for 14 days, dogs (15 neutered males, 15 spayed females, aged 2–9 years, mean initial weight 11.3 kg) consumed the low (18.99%, dry matter basis), medium (25.34%), or high (45.77%) protein foods, each for 90 days, in a William’s Latin Square Design sequence. In serum and/or urine, metabolites associated with inflammation (9,10-dihydroxyoctadecanoic acid (DiHOME)), 12,13-DiHOME) and kidney dysfunction (urea, 5-hydroxyindole sulfate, 7-hydroxyindole sulfate, p-cresol sulfate) increased with higher protein levels in food, while one-carbon pathway metabolites (betaine, dimethylglycine, sarcosine) decreased. Fecal pH increased with protein consumed, and levels of beneficial indoles and short-chain fatty acids decreased while branched-chain fatty acids increased. Beta diversity of the fecal microbiome was significantly different, with increased abundances of proteolytic bacteria with higher protein food. Feeding dogs a high amount of protein leads to a shift to proteolytic gut bacteria, higher fecal pH, and is associated with increased levels of metabolites linked with inflammation and kidney dysfunction.

The Effects of Nutrition on the Gastrointestinal Microbiome of Cats and Dogs: Impact on Health and Disease

The gastrointestinal (GI) microbiome of cats and dogs is increasingly recognized as a metabolically active organ inextricably linked to pet health. Food serves as a substrate for the GI microbiome of cats and dogs and plays a significant role in defining the composition and metabolism of the GI microbiome. The microbiome, in turn, facilitates the host's nutrient digestion and the production of postbiotics, which are bacterially derived compounds that can influence pet health. Consequently, pet owners have a role in shaping the microbiome of cats and dogs through the food they choose to provide. Yet, a clear understanding of the impact these food choices have on the microbiome, and thus on the overall health of the pet, is lacking. Pet foods are formulated to contain the typical nutritional building blocks of carbohydrates, proteins, and fats, but increasingly include microbiome-targeted ingredients, such as prebiotics and probiotics. Each of these categories, as well as their relative proportions in food, can affect the composition and/or function of the microbiome. Accumulating evidence suggests that dietary components may impact not only GI disease, but also allergies, oral health, weight management, diabetes, and kidney disease through changes in the GI microbiome. Until recently, the focus of microbiome research was to characterize alterations in microbiome composition in disease states, while less research effort has been devoted to understanding how changes in nutrition can influence pet health by modifying the microbiome function. This review summarizes the impact of pet food nutritional components on the composition and function of the microbiome and examines evidence for the role of nutrition in impacting host health through the microbiome in a variety of disease states. Understanding how nutrition can modulate GI microbiome composition and function may reveal new avenues for enhancing the health and resilience of cats and dogs.

Interplay between Neuroendocrine Biomarkers and Gut Microbiota in Dogs Supplemented with Grape Proanthocyanidins: Results of Dietary Intervention Study

Simple Summary

The connection between animal health and gut microbiota has been studied during the past years through different diet modulation experiments; however, there is still a paucity of information about the prebiotic functions in the gastrointestinal tract of companion animals. Considering this, a population of dogs living in the same environment has been subjected to a nutritional study, with different doses of proanthocyanidins extracted from grapevine supplied to the diet. Characterization of the gut microbiota and data from endocrine analysis in saliva have been collected. Dogs responded differently to the dietary intervention, and results underlined the existence of a difference between subjects in terms of fecal microorganisms and neuroendocrine markers, leading us to think the balance of gut microbiota is going to play a strong role in diet formulation based on host health modulation.

Abstract

Several studies on the interaction between gut microbiota and diets, including prebiotics, have been reported in dogs, but no data are available about the effects of dietary administration of grape proanthocyanidins. In the study, 24 healthy adult dogs of different breeds were recruited and divided in 3 groups of 8 subjects each. A group was fed with a control diet (D0), whilst the others were supplemented with 1 (D1) or 3 (D3) mg/kg live weight of grape proanthocyanidins. Samples of feces were collected at the beginning and after 14 and 28 days for microbiota, short chain fatty acid, and lactic acid analysis. Serotonin and cortisol were measured in saliva, collected at the beginning of the study and after 28 days. A significantly higher abundance (p < 0.01) of Enterococcus and Adlercreutzia were observed in D0, whilst Escherichia and Eubacterium were higher in D1. Fusobacterium and Phascolarctobacterium were higher (p < 0.01) in D3. Salivary serotonin increased (p < 0.01) at T28 for D1 and D3 groups but cortisol did not vary. Proanthocyanidins administration influenced the fecal microbiota and neuroendocrine response of dogs, but a high variability of taxa was observed, suggesting a uniqueness and stability of fecal microbiota related to the individual.

Deciphering the Bifidobacterial Populations within the Canine and Feline Gut Microbiota

During the course of evolution, dogs and cats have been subjected to extensive domestication, becoming the principal companion animals for humans. For this reason, their health care, including their intestinal microbiota, is considered of considerable importance. However, the canine and feline gut microbiota still represent a largely unexplored research area. In the present work, we profiled the microbiota of 23 feline fecal samples by 16S rRNA gene and bifidobacterial internally transcribed spacer (ITS) approaches and compared this information with previously reported data from 138 canine fecal samples. The obtained data allowed the reconstruction of the core gut microbiota of the above-mentioned samples coupled with their classification into distinct community state types at both genus and species levels, identifying Bacteroides, Fusobacterium, and Prevotella 9 as the main bacterial components of the canine and feline gut microbiota. At the species level, the intestinal bifidobacterial gut communities of dogs and cats differed in terms of both species number and composition, as emphasized by a covariance analysis. Together, our findings show that the intestinal populations of cats and dogs are similar in terms of genus-level taxonomical composition, while at the bifidobacterial species level, clear differences were observed, indicative of host-specific colonization behavior by particular bifidobacterial taxa.IMPORTANCE Currently, domesticated dogs and cats are the most cherished companion animals for humans, and concerns about their health and well-being are therefore important. In this context, the gut microbiota plays a crucial role in maintaining and promoting host health. However, despite the social relevance of domesticated dogs and cats, their intestinal microbial communities are still far from being completely understood. In this study, the taxonomical composition of canine and feline gut microbiota was explored at genus and bifidobacterial species levels, allowing classification of these microbial populations into distinct gut community state types at either of the two investigated taxonomic levels. Furthermore, the reconstruction of core gut microbiota coupled with covariance network analysis based on bifidobacterial internally transcribed spacer (ITS) profiling revealed differences in the bifidobacterial compositions of canine and feline gut microbiota, suggesting that particular bifidobacterial species have developed a selective ability to colonize a specific host.

In Vitro Evaluation of the Effects of Tylosin on the Composition and Metabolism of Canine Fecal Microbiota

Simple Summary

The antibiotic-responsive enteropathy is a common canine chronic disorder for which tylosin represents an effective widely used therapeutic option, although its mechanism of action, beyond the well-known antibacterial activity, is still unclear. Given the beneficial role of prebiotic substrates for gut health, positive outcomes deriving from the association of tylosin with some prebiotic oligosaccharides might be supposed. The present study investigated in vitro the effects of tylosin, alone or supplemented with fructooligosaccharides, galactooligosaccharides, or xylooligosaccharides, on the composition and activity of the fecal microbiota of healthy dogs. It was partially confirmed that the antibacterial effect of tylosin, given the reduction of some microbial populations and metabolites, e.g., volatile fatty acids. Interestingly, the association of tylosin with prebiotics revealed counteracting effects on some undesirable changes exerted by tylosin, e.g., the reduction of bacteria generally considered beneficial such as lactobacilli and Clostridium cluster XIVa as well as volatile fatty acids, i.e., microbial fermentative end-products that are recognized as essential for enterocytes homeostasis.

Abstract

The present study investigated the in vitro effects of tylosin (TYL), alone or associated with prebiotics (PRE), on selected canine fecal parameters. Eight treatments were set up: control diet with no addition of substrates; TYL; Fructooligosaccharides (FOS); Galactooligosaccharides (GOS); Xylooligosaccharides (XOS); TYL + FOS; TYL + GOS; TYL + XOS. The flasks (five for treatment), containing a canine fecal suspension (prepared with the feces of healthy adult dogs) and the residue of an in vitro digested dry dog food, were incubated in an anaerobic chamber at 39 °C. TYL and PRE were added at a concentration of 0.2 and 1 g/L, respectively. Samples were collected after 6 and 24 h for analyses. PRE decreased pH values, iso-butyrate, and iso-valerate throughout the incubation; increased lactobacilli, cadaverine, and, tendentiously, total volatile fatty acids after 6 h; increased n-butyrate, putrescine, spermidine, and reduced spermine and E. coli after 24 h. TYL resulted in lower total volatile fatty acids and lactobacilli and higher Clostridium cluster I after 6 h and higher pH values, spermidine, and E. coli throughout the study. When associated with TYL, PRE counteracted some undesirable effects of the antibiotic such as the decrease of lactobacilli and Clostridium cluster XIVa at both 6 and 24 h. In the present study, TYL exhibited inhibitory effects on canine fecal microbiota partially counteracted by PRE supplementation.

Effects of Brewer's spent grain and carrot pomace on digestibility, fecal microbiota, and fecal and urinary metabolites in dogs fed low- or high-protein diets1

Brewer's spent grain (BSG) and carrot pomace (CAP) were used as fiber sources in low- or high-protein diets in dogs. Ten adult Beagles were involved in 5 feeding periods of 19 d in a cross-over design. Experimental diets contained 7.5% of total dietary fiber (TDF) from BSG or CAP and 20% or 40% of crude protein in dry matter. A diet with 3.5% TDF from both fiber sources and 20% crude protein was used as reference. Fecal dry matter was 27% higher for diets with BSG compared to CAP (P < 0.001). Apparent fecal digestibility of crude protein was 7% to 11% higher in diets with 40% protein concentration (P < 0.001), while apparent digestibility of crude fat was 2% to 3% higher for diets with CAP (P < 0.001). Carrot pomace increased the apparent fecal digestibility of TDF, phosphorus, and magnesium (P < 0.001), while 40% protein diets had a positive impact on TDF and sodium and a negative effect on magnesium apparent fecal digestibility (P < 0.001). Inclusion of CAP increased fecal short-chain fatty acids (P = 0.010), mainly acetate (P = 0.001). i-butyrate (P = 0.001), i-valerate (P = 0.002), biogenic amines (P < 0.001), and ammonium (P < 0.001) increased with higher dietary protein levels. Diet-induced changes in the fecal microbiome were moderate. Relative abundance of Bifidobacteriales was higher for the low-protein diets (P = 0.001). To conclude, BSG and CAP can be used as fiber sources in canine diets and are well tolerated even at higher inclusion rates, the effect on microbial protein fermentation seems to be limited compared to the dietary protein level.

Kestose supplementation exerts bifidogenic effect within fecal microbiota and increases fecal butyrate concentration in dogs

Kestose, a fructooligosaccharide (FOS) with one fructose monomer linked to sucrose, is a key component of the prebiotic activity of FOS. This study aimed to evaluate the prebiotic potential of Kestose in terms of the impact on population change in the intestinal microbiota and fecal short-chain fatty acid (SCFA) concentration in dogs. Kestose 2 g per dog was administered daily with conventional diet to 6 healthy, adult beagle dogs for 8 weeks followed by 4 weeks of follow-up period without Kestose supplementation. Fresh fecal samples were obtained before and every 4 weeks until the end of the follow-up period. Genomic DNA extracted from the fecal samples was subjected to 16S rRNA gene analysis using next generation sequencer and to quantitative polymerase chain reaction (qPCR). Fecal acetate, propionate, butyrate, lactate and ethanol concentrations were measured by high-performance liquid chromatography. 16S rRNA gene analysis and qPCR showed increasing trend of genus Bifidobacterium after Kestose supplementation while genera Bacteroides and Sutterella decreased. Clostridium perfringens decreased below the detection limit within first 4 weeks after starting Kestose supplementation. Fecal butyrate concentration was significantly increased at week 8 and returned to the base level after 4 weeks of the washing period. To the best of our knowledge, this is the first study to reveal effect of Kestose on the populational changes in fecal microbiota and fecal butyrate concentration in dogs.

Role of gut microbiota in dog and cat's health and diseases

Mammalian gastrointestinal tract is colonized by a large number of microorganisms, known as gut microbiota, that play a key role in the physiological and pathological states. In particular, the gastrointestinal tract of dogs and cats harbors a complex and highly biodiverse microbial ecosystem. Recent studies see it involved in a wide range of life processes, including energy needs, metabolism, immunological activity, and neuro-behavioral development. This review focuses on the role of the microbiota on the health of pets and will discuss changes that occur in the disease.

A Randomized Double Blinded Placebo-Controlled Clinical Trial of a Probiotic or Metronidazole for Acute Canine Diarrhea

Acute diarrhea is a common, often self-limiting, cause of presentation for veterinary care, yet there is a paucity of data on frequently-prescribed treatments. The purpose of this randomized, double blinded placebo-controlled clinical trial was to compare two anecdotally-recommended treatments: a probiotic combination and metronidazole. Sixty dogs without concurrent comorbidities were randomized into three treatment groups. The time to resolution of diarrheal signs was evaluated using owner surveys and fecal scoring charts. Dogs presenting with acute diarrhea achieved acceptable fecal consistency after 3.5 ± 2.2 days when receiving probiotic, 4.6 ± 2.4 days with oral metronidazole, and 4.8 ± 2.9 days with placebo; statistically significant differences were not identified between treatment groups (p = 0.17). These findings failed to provide evidence for the common use of metronidazole in this cohort of dogs with acute canine diarrhea, and a larger study population would be required to identify a statistically significant effect of probiotics.