BackgroundGut microbes influence their hosts in many ways, in particular by modulating the impact of diet. These effects have been studied most extensively in humans and mice. In this work, we used whole genome metagenomics to investigate the relationship between the gut metagenomes of dogs, humans, mice, and pigs.ResultsWe present a dog gut microbiome gene catalog containing 1,247,405 genes (based on 129 metagenomes and a total of 1.9 terabasepairs of sequencing data). Based on this catalog and taxonomic abundance profiling, we show that the dog microbiome is closer to the human microbiome than the microbiome of either pigs or mice. To investigate this similarity in terms of response to dietary changes, we report on a randomized intervention with two diets (high-protein/low-carbohydrate vs. lower protein/higher carbohydrate). We show that diet has a large and reproducible effect on the dog microbiome, independent of breed or sex. Moreover, the responses were in agreement with those observed in previous human studies.ConclusionsWe conclude that findings in dogs may be predictive of human microbiome results. In particular, a novel finding is that overweight or obese dogs experience larger compositional shifts than lean dogs in response to a high-protein diet.Electronic supplementary materialThe online version of this article (10.1186/s40168-018-0450-3) contains supplementary material, which is available to authorized users.

Obesity has become a health epidemic in both humans and pets. A dysbiotic gut microbiota has been associated with obesity and other metabolic disorders. High-protein, low-carbohydrate (HPLC) diets have been recommended for body weight loss, but little is known about their effects on the canine gut microbiome. Sixty-three obese and lean Labrador retrievers and Beagles (mean age, 5.72 years) were fed a common baseline diet for 4 weeks in phase 1, followed by 4 weeks of a treatment diet, specifically, the HPLC diet (49.4% protein, 10.9% carbohydrate) or a low-protein, high-carbohydrate (LPHC) diet (25.5% protein, 38.8% carbohydrate) in phase 2. 16S rRNA gene profiling revealed that dietary protein and carbohydrate ratios have significant impacts on gut microbial compositions. This effect appeared to be more evident in obese dogs than in lean dogs but was independent of breed. Consumption of either diet increased the bacterial evenness, but not the richness, of the gut compared to that after consumption of the baseline diet. Macronutrient composition affected taxon abundances, mainly within the predominant phyla, Firmicutes and Bacteroidetes. The LPHC diet appeared to favor the growth of Bacteroides uniformis and Clostridium butyricum, while the HPLC diet increased the abundances of Clostridium hiranonis, Clostridium perfringens, and Ruminococcus gnavus and enriched microbial gene networks associated with weight maintenance. In addition, we observed a decrease in the Bacteroidetes to Firmicutes ratio and an increase in the Bacteroides to Prevotella ratio in the HPLC diet-fed dogs compared to these ratios in dogs fed other diets. Finally, analysis of the effect of diet on the predicted microbial gene network was performed using phylogenetic investigation of communities by reconstruction of unobserved states (PICRUSt).

The gut microflora play a crucial role in several physiologic functions of the host, including maturation of the gut-associated lymphoid tissues during the first months of life. Oral administration of probiotic lactic acid bacteria (LAB) modulates the immune system of humans and some laboratory animals. This effect has never been examined in dogs; therefore, our aim was to study the capacity of a probiotic LAB to stimulate immune functions in young dogs. Puppies were allotted to two groups receiving either a control diet or a diet supplemented with 5 x 10(8) colony forming units (cfu)/d of probiotic Enterococcus faecium (SF68) from weaning to 1 y of age. Fecal and blood samples were collected from the dogs at different time points for the measurement of fecal immunoglobulin (Ig)A, circulating IgG and IgA, and the proportions of lymphoid cell subsets. Fecal IgA and canine distemper virus (CDV) vaccine-specific circulating IgG and IgA were higher in the group receiving the probiotic than in controls. There were no differences in the percentages of CD4(+) and CD8(+) T cells between the groups, but the proportion of mature B cells [CD21(+)/major histocompatibility complex (MHC) class II(+)] was greater in those fed the probiotic. These data show for the first time that a dietary probiotic LAB enhance specific immune functions in young dogs, thus offering new opportunities for the utilization of probiotics in canine nutrition.

Thirty-four senior dogs (pointers 8-11 years, beagles 9-11 years) were used to evaluate the effects of oligosaccharides on nutritional and immunological characteristics. Dogs were randomly allotted to treatments [1% chicory (CH), 1% mannan-oligosaccharide (MOS), 1% chicory + 1% MOS (CM), or no supplementation (control, CON)] in a parallel design with a 4 week baseline period followed by a 4 week treatment period. Dietary supplementation with MOS or CM tended (P = 0.07) to increase food intake due, in part, to an increase in fermentable fibre and a decrease in energy content of the diet. Although wet faecal output increased (P < 0.05) for dogs supplemented with MOS or CM, when corrected for food intake, no differences were noted. The CM treatment increased (P < 0.05) faecal score (1 = hard and dry, 5 = watery liquid), although these scores remained in a desirable range (3 to 3.5). Chicory supplementation increased (P = 0.07) fat digestibility. Chicory or MOS increased (P < or = 0.05) faecal bifidobacteria concentrations 0.4 and 0.5 log10 cfu/g DM, respectively, compared to the CON, while MOS decreased (P < 0.05) faecal E. coli concentrations. Oligosaccharides did not affect white blood cell (WBC) concentrations, but CH and CM tended to increase (P = 0.10) neutrophil concentrations compared to control dogs. Peripheral lymphocyte concentrations were decreased in dogs supplemented with MOS (P = 0.06) and CM (P < 0.05). Chicory and MOS alter faecal microbial populations and certain indices of the immune system of senior dogs.

Cysteine, via chelation reactions, ameliorates biochemical lesions caused by excessive ingestion of several trace elements. Because oral cysteine per se is considerably more protective than the in vivo metabolic cysteine precursors, methionine or cystine, chelation of cysteine with trace elements likely occurs primarily in the gut, thereby decreasing absorption of both cysteine and the trace element in question. Hence, using copper as an example, orally administered cysteine markedly improves growth and reduces liver copper deposition in chicks or rats fed a high level of inorganic copper. Likewise, excessive copper ingestion impairs sulfur amino acid (SAA) utilization and increases the dietary requirement for SAA. Cobalt and selenium toxicities are also ameliorated by oral cysteine ingestion, with the responses being even more striking than those occurring with copper toxicity. While inorganic arsenic poisonings are generally ameliorated by administering cysteine or a cysteine derivative (e.g., dimercaptopropanol), organic pentavalent arsenic toxicity is exacerbated by cysteine administration. Cysteine in this instance acts as a reducing agent, facilitating conversion of organic pentavalent arsenicals such as roxarsone and arsanilic acid to the more toxic trivalent state.

Background: Giardiasis is a common, potentially zoonotic disease, and dogs often harbor and shed cysts without showing clinical signs. Treatment with the probiotic Enterococcus faecium SF68 has been shown to stimulate mucosal and systemic immunity in a variety of animal models and in young dogs, and to reduce giardial cyst and antigen shedding in rodents.Hypothesis: Adult dogs with chronic naturally acquired giardiasis will have decreased giardial fecal cyst and antigen shedding and increased innate and adaptive immunity after 6 weeks probiotic treatment with E. faecium SF68.Animals: Twenty adult dogs.Methods: After a 6-week dietary equilibration period, dogs were randomized to receive E. faecium SF68 or placebo for 6 weeks, and then crossed over to the alternate treatment. We measured cyst shedding, fecal giardial antigen, fecal immunoglobulin A (IgA) concentration, and circulating leukocyte phagocytic activity at multiple timepoints to determine the effect of E. faecium SF68 on giardiasis and immune responses in these dogs.Results: No differences were observed between placebo or E. faecium SF68 treatment for giardial cyst shedding, fecal antigen shedding, fecal IgA concentration, or leukocyte phagocytic activity.Conclusions: Short-term treatment with E. faecium SF68 of dogs with chronic naturally acquired subclinical giardiasis fails to affect giardial cyst shedding or antigen content and does not alter innate or adaptive immune responses.

Background: The gastrointestinal (GI) microbiota has a strong impact on the health of cats and these populations can be altered in GI disease. Little research has been done to associate improvement in diarrhea with changes in GI microbiota.Objective: To evaluate GI microbiota changes associated with diet change and related improvement in diarrhea in cats with chronic naturally occurring diarrhea.Animals: Fifteen adult Domestic Shorthair cats with naturally occurring chronic diarrhea. Methods: Controlled crossover dietary trial for management of diarrhea. Fecal microbiome was assessed using 454-pyrosequencing. Relationships among fecal score (FS), diet, and microbiome were explored using partial least square method, partial least square method -discriminant analysis, and orthogonal partial least square method with discriminant analysis (OPLS-DA).Results: Dominant bacterial phyla included the Firmicutes and Bacteroidetes, followed by Fusobacteria, Proteobacteria, Tenericutes, and Actinobacteria. Orthogonal partial least squares (OPLS-DA) clustering showed significant microbial differences within cats when fed Diet X versus Diet Y, and with Diet Y versus baseline. Significant correlations were found between the microbiome and FSs. Those bacteria with the strongest correlation with FS included Coriobacteriaceae Slackia spp., Campylobacter upsaliensis, Enterobacteriaceae Raoultella spp., Coriobacteriaceae Collinsella spp., and bacteria of unidentified genera within the families of Clostridiales Lachnospiracea and Aeromonadales Succinivibrionacease, suggesting that increased numbers of these organisms may be important to gut health.Conclusions and Clinical Importance: Alterations in intestinal microbiota were associated with improvement in diarrhea, but, from our data we cannot conclude if changes in the microbiome caused the improvement in diarrhea, or vice versa.

This study tested the hypothesis that sedentary cats have the ability to adapt to high-fat carnivore diets by increasing fat oxidation. Twenty-four hour indirect calorimetry was used to determine total energy expenditure (TEE) and macronutrient oxidation in six vasectomized male (VAS) and six ovariectomized female (OVX) cats isocalorically fed lower-fat (53% fat, 45% protein) and higher-fat (71% fat, 26% protein) meat-based diets at maintenance for 8 days. Fat oxidation increased linearly with fat intake with a mean slope of 0.91 g fat oxidized/g fat intake ( P < 0.001), with no change in TEE. However, VAS male cats were able to more precisely match fat oxidation with fat intake than OVX female cats ( P < 0.02). Body fat content did not significantly influence fat oxidation. These results demonstrate that cats maintain body weight during short-term isocaloric feeding of a high-fat carnivore-type diet in part by increasing fat oxidation commensurate with increases in fat intake. This ability may be an important mechanism underlying the resistance of cats to obesity, despite habitual consumption of high-fat diets.