Changes in feeding habits promoted the differentiation of the composition and function of gut microbiotas between domestic dogs (Canis lupus familiaris) and gray wolves (Canis lupus)

Fecal microbiota of the synanthropic golden jackal (Canis aureus)

The golden jackal (Canis aureus), is a medium canid carnivore widespread throughout the Mediterranean region and expanding into Europe. This species thrives near human settlements and is implicated in zoonoses such as rabies. This study explores for the first time, the golden jackal fecal microbiota. We analyzed 111 fecal samples of wild golden jackals using 16S rRNA amplicon sequencing the connection of the microbiome to animal characteristics, burden of pathogens and geographic and climate characteristics. We further compared the fecal microbiota of the golden jackal to the black-backed jackal and domestic dog. We found that the golden jackal fecal microbiota is dominated by the phyla Bacteroidota, Fusobacteriota and Firmicutes. The golden jackal fecal microbiota was associated with different variables, including geographic region, age-class, exposure to rabies oral vaccine, fecal parasites and toxoplasmosis. A remarkable variation in the relative abundance of different taxa was also found associated with different variables, such as age-class. Linear discriminant analysis effect size (LEfSe) analysis found abundance of specific taxons in each region, Megasphaera genus in group 1, Megamonas genus in group 2 and Bacteroides coprocola species in group 3. We also found a different composition between the fecal microbiota of the golden jackal, blacked-backed jackal and the domestic dog. Furthermore, LEfSe analysis found abundance of Fusobacterium and Bacteroides genera in the golden jackal, Clostridia class in blacked-backed jackal and Megamonas genus in domestic dog. The golden jackal fecal microbiota is influenced by multiple factors including host traits and pathogen burden. The characterization of the microbiota of this thriving species may aid in mapping its spread and proximity to human settlements. Moreover, understanding the jackal microbiota could inform the study of potential animal and human health risks and inform control measures.

Growth Stages and Inter-Species Gut Microbiota Composition and Function in Captive Red Deer (Cervus elaphus alxaicus) and Blue Sheep (Pseudois nayaur)

Blue sheep and red deer, second-class key protected animals in China, are sympatric species with a high degree of overlap of food resources in the Helan Mountains, China. Previous studies with blue sheep and red deer in nature have shown that their physiology is closely related to their gut microbiota. However, growth stages and changes occurring in these species in captivity are still unknown. Thus, 16S rRNA gene sequencing was used to explore diversity, composition and function of the gut microbiota in these two animal species. The diversity and structure of the gut microbiota in captive blue sheep and red deer changed at different growth stages, but the dominant microbiota phyla in the gut microbiota remained stable, which was composed of the phyla Firmicutes, Bacteroidetes and Verrucomicrobia. Moreover, gut microbiota diversity in juvenile blue sheep and red deer was low, with the potential for further colonization. Functional predictions showed differences such as red deer transcription being enriched in adults, and blue sheep adults having a higher cell wall/membrane/envelope biogenesis than juveniles. Microbial changes between blue sheep and red deer at different growth stages and between species mainly depend on the abundance of the microbiota, rather than the increase and absence of the bacterial taxa.

Gut microbiome of captive wolves is more similar to domestic dogs than wild wolves indicated by metagenomics study

Adaptation during the domestication from wolves (Canis lupus) to dogs (Canis lupus familiaris) is a debated ecological topic. Changes in food and environment are major divergences in the domestication of dogs. Gut microbes play an important role in animal adaptation to the food and environmental changes. In this study, shotgun sequencing was performed to compare the species diversity and functional diversity of gut microbes in wild wolves (group CLW, n = 3), captive wolves (group CLC, n = 4), and domestic dogs (group CLF, n = 4). The results found that Bacteroidetes, Firmicutes, Fusobacteria, Proteobacteria and Actinobacteria were the most abundant phyla and Bacteroides, Fusobacterium, Prevotella, Megamonas, Paraprevotella, Faecalibacterium, Clostridium were the most abundant genera in the gut of wolves and dogs. Groups CLW, CLC and CLF have shown significant difference in gut microbial species diversity and functional diversity. Bacteroides, Fusobacterium and Faecalibacterium were most abundant genera in groups CLW, CLC and CLF, respectively. Their abundance varied significantly among groups. Compared to the wild wolves, the intestinal microbiol genes of domestic dogs were significantly enriched in the carbohydrate metabolism pathway of KEGG database. One hundred and seventy-seven enzymes were detected with significantly higher abundance in group CLF than that in group CLW, and 49 enzymes showed extremely significant higher abundance in group CLF than that in group CLW (q < 0.01) base on the function abundance annotated in CAZy database. It is noteworthy that there were also significant differences in the abundance of 140 enzymes between groups CLC and CLW (q < 0.05). Clustering analysis based on both the species and the function abundance of intestinal microbiota all found that groups CLC and CLF clustered into one branch, while samples from group CLW clustered into the other branch. This result suggests that captive wolves are more similar to domestic dogs than wild wolves in both species composition and function composition of intestinal microbiota.

The Role of Feeding Characteristics in Shaping Gut Microbiota Composition and Function of Ensifera (Orthoptera)

Feeding habits were the primary factor affecting the gut bacterial communities in Ensifera. However, the interaction mechanism between the gut microbiota and feeding characteristics is not precisely understood. Here, the gut microbiota of Ensifera with diverse feeding habits was analyzed by shotgun metagenomic sequencing to further clarify the composition and function of the gut microbiota and its relationship with feeding characteristics. Our results indicate that under the influence of feeding habits, the gut microbial communities of Ensifera showed specific characteristics. Firstly, the gut microbial communities of the Ensifera with different feeding habits differed significantly, among which the gut microbial diversity of the herbivorous Mecopoda niponensis was the highest. Secondly, the functional genes related to feeding habits were in high abundance. Thirdly, the specific function of the gut microbial species in the omnivorous Gryllotalpa orientalis showed that the more diverse the feeding behavior of Ensifera, the worse the functional specificity related to the feeding characteristics of its gut microbiota. However, feeding habits were not the only factors affecting the gut microbiota of Ensifera. Some microorganisms' genes, whose functions were unrelated to feeding characteristics but were relevant to energy acquisition and nutrient absorption, were detected in high abundance. Our results were the first to report on the composition and function of the gut microbiota of Ensifera based on shotgun metagenomic sequencing and to explore the potential mechanism of the gut microbiota's association with diverse feeding habits.

Geographically diverse canid sampling provides novel insights into pre-industrial microbiomes

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

Fecal Shedding of Multidrug Resistant Escherichia coli Isolates in Dogs Fed with Raw Meat-Based Diets in Brazil

The practice of feeding dogs raw meat-based diets (RMBDs) is growing in several countries, and the risks associated with the ingestion of pathogenic and antimicrobial-resistant Escherichia coli in dogs fed these diets are largely unknown. We characterized E. coli strains isolated from dogs fed either an RMBD or a conventional dry feed, according to the phylogroup, virulence genes, and antimicrobial susceptibility profiles of the bacteria. Two hundred and sixteen E. coli strains were isolated. Dogs fed RMBDs shed E. coli strains from the phylogroup E more frequently and were positive for the E. coli heat-stable enterotoxin 1-encoding gene. Isolates from RMBD-fed dogs were also frequently positive for multidrug-resistant E. coli isolates including extended-spectrum beta-lactamase (ESBL) producers. Whole-genome sequencing of seven ESBL-producing E. coli strains revealed that they predominantly harbored blaCTX-M-55, and two strains were also positive for the colistin-resistant gene mcr-1. These results suggest that feeding an RMBD can affect the dog’s microbiota, change the frequency of certain phylogroups, and increase the shedding of diarrheagenic E. coli. Also, feeding an RMBD seemed to be linked with the fecal shedding of multidrug-resistant E. coli, including the spread of strains harboring mobilizable colistin resistance and ESBL genes. This finding is of concern for both animal and human health.

Harnessing the Biology of Canine Intestinal Organoids to Heighten Understanding of Inflammatory Bowel Disease Pathogenesis and Accelerate Drug Discovery: A One Health Approach

In a recent issue of the Lancet, the prevalence of Inflammatory Bowel Disease (IBD) was estimated at 7 million worldwide. Overall, the burden of IBD is rising globally, with direct and indirect healthcare costs ranging between $14.6 and $31.6 billion in the U.S. alone in 2014. There is currently no cure for IBD, and up to 40% of patients do not respond to medical therapy. Although the exact determinants of the disease pathophysiology remain unknown, the prevailing hypothesis involves complex interplay among host genetics, the intestinal microenvironment (primarily bacteria and dietary constituents), and the mucosal immune system. Importantly, multiple chronic diseases leading to high morbidity and mortality in modern western societies, including type II diabetes, IBD and colorectal cancer, have epidemiologically been linked to the consumption of high-calorie, low-fiber, high monosaccharide, and high-fat diets (HFD). More specifically, data from our laboratory and others have shown that repeated consumption of HFD triggers dysbiotic changes of the gut microbiome concomitant with a state of chronic intestinal inflammation and increased intestinal permeability. However, progress in our understanding of the effect of dietary interventions on IBD pathogenesis has been hampered by a lack of relevant animal models. Additionally, current in vitro cell culture systems are unable to emulate the in vivo interplay between the gut microbiome and the intestinal epithelium in a realistic and translatable way. There remains, therefore, a critical need to develop translatable in vitro and in vivo models that faithfully recapitulate human gut-specific physiological functions to facilitate detailed mechanistic studies on the impact of dietary interventions on gut homeostasis. While the study of murine models has been pivotal in advancing genetic and cellular discoveries, these animal systems often lack key clinical signs and temporal pathological changes representative of IBD. Specifically, some limitations of the mouse model are associated with the use of genetic knockouts to induce immune deficiency and disease. This is vastly different from the natural course of IBD developing in immunologically competent hosts, as is the case in humans and dogs. Noteworthily, abundant literature suggests that canine and human IBD share common clinical and molecular features, such that preclinical studies in dogs with naturally occurring IBD present an opportunity to further our understanding on disease pathogenesis and streamline the development of new therapeutic strategies. Using a stepwise approach, in vitro mechanistic studies investigating the contribution of dietary interventions to chronic intestinal inflammation and "gut leakiness" could be performed in intestinal organoids and organoid derived monolayers. The biologic potential of organoids stems from the method's ability to harness hard-wired cellular programming such that the complexity of the disease background can be reflected more accurately. Likewise, the effect of therapeutic drug candidates could be evaluated in organoids prior to longitudinal studies in dog and human patients with IBD. In this review, we will discuss the value (and limitations) of intestinal organoids derived from a spontaneous animal disease model of IBD (i.e., the dog), and how it can heighten understanding of the interplay between dietary interventions, the gut microbiota and intestinal inflammation. We will also review how intestinal organoids could be used to streamline the preclinical development of therapeutic drug candidates for IBD patients and their best four-legged friends.

Novel canine high-quality metagenome-assembled genomes, prophages and host-associated plasmids provided by long-read metagenomics together with Hi-C proximity ligation

The human gut microbiome has been extensively studied, yet the canine gut microbiome is still largely unknown. The availability of high-quality genomes is essential in the fields of veterinary medicine and nutrition to unravel the biological role of key microbial members in the canine gut environment. Our aim was to evaluate nanopore long-read metagenomics and Hi-C (high-throughput chromosome conformation capture) proximity ligation to provide high-quality metagenome-assembled genomes (HQ MAGs) of the canine gut environment. By combining nanopore long-read metagenomics and Hi-C proximity ligation, we retrieved 27 HQ MAGs and 7 medium-quality MAGs of a faecal sample of a healthy dog. Canine MAGs (CanMAGs) improved genome contiguity of representatives from the animal and human MAG catalogues – short-read MAGs from public datasets – for the species they represented: they were more contiguous with complete ribosomal operons and at least 18 canonical tRNAs. Both canine-specific bacterial species and gut generalists inhabit the dog’s gastrointestinal environment. Most of them belonged to Firmicutes, followed by Bacteroidota and Proteobacteria. We also assembled one Actinobacteriota and one Fusobacteriota MAG. CanMAGs harboured antimicrobial-resistance genes (ARGs) and prophages and were linked to plasmids. ARGs conferring resistance to tetracycline were most predominant within CanMAGs, followed by lincosamide and macrolide ones. At the functional level, carbohydrate transport and metabolism was the most variable within the CanMAGs, and mobilome function was abundant in some MAGs. Specifically, we assigned the mobilome functions and the associated mobile genetic elements to the bacterial host. The CanMAGs harboured 50 bacteriophages, providing novel bacterial-host information for eight viral clusters, and Hi-C proximity ligation data linked the six potential plasmids to their bacterial host. Long-read metagenomics and Hi-C proximity ligation are likely to become a comprehensive approach to HQ MAG discovery and assignment of extra-chromosomal elements to their bacterial host. This will provide essential information for studying the canine gut microbiome in veterinary medicine and animal nutrition.

Noninsect-Based Diet Leads to Structural and Functional Changes of Acidic Chitinase in Carnivora

Acidic chitinase (Chia) digests the chitin of insects in the omnivorous stomach and the chitinase activity in carnivorous Chia is significantly lower than that of the omnivorous enzyme. However, mechanistic and evolutionary insights into the functional changes in Chia remain unclear. Here we show that a noninsect-based diet has caused structural and functional changes in Chia during the course of evolution in Carnivora. By creating mouse-dog chimeric Chia proteins and modifying the amino acid sequences, we revealed that F214L and A216G substitutions led to the dog enzyme activation. In 31 Carnivora, Chia was present as a pseudogene with stop codons in the open reading frame (ORF) region. Importantly, the Chia proteins of skunk, meerkat, mongoose, and hyena, which are insect-eating species, showed high chitinolytic activity. The cat Chia pseudogene product was still inactive even after ORF restoration. However, the enzyme was activated by matching the number and position of Cys residues to an active form and by introducing five meerkat Chia residues. Mutations affecting the Chia conformation and activity after pseudogenization have accumulated in the common ancestor of Felidae due to functional constraints. Evolutionary analysis indicates that Chia genes are under relaxed selective constraint in species with noninsect-based diets except for Canidae. These results suggest that there are two types of inactivating processes in Carnivora and that dietary changes affect the structure and activity of Chia.

Unraveling differences in fecal microbiota stability in mammals: from high variable carnivores and consistently stable herbivores

BACKGROUND

Through the rapid development in DNA sequencing methods and tools, microbiome studies on a various number of species were performed during the last decade. This advance makes it possible to analyze hundreds of samples from different species at the same time in order to obtain a general overview of the microbiota. However, there is still uncertainty on the variability of the microbiota of different animal orders and on whether certain bacteria within a species are subject to greater fluctuations than others. This is largely due to the fact that the analysis in most extensive comparative studies is based on only a few samples per species or per study site. In our study, we aim to close this knowledge gap by analyzing multiple individual samples per species including two carnivore suborders Canoidea and Feloidea as well as the orders of herbivore Perissodactyla and Artiodactyla held in different zoos. To assess microbial diversity, 621 fecal samples from 31 species were characterized by sequencing the V3-V4 region of the 16S rRNA gene using Illumina MiSeq.

RESULTS

We found significant differences in the consistency of microbiota composition and in fecal microbial diversity between carnivore and herbivore species. Whereas the microbiota of Carnivora is highly variable and inconsistent within and between species, Perissodactyla and Ruminantia show fewer differences across species boundaries. Furthermore, low-abundance bacterial families show higher fluctuations in the fecal microbiota than high-abundance ones.

CONCLUSIONS

Our data suggest that microbial diversity is significantly higher in herbivores than in carnivores, whereas the microbiota in carnivores, unlike in herbivores, varies widely even within species. This high variability has methodological implications and underlines the need to analyze a minimum amount of about 10 samples per species. In our study, we found considerable differences in the occurrence of different bacterial families when looking at just three and six samples. However, from a sample number of 10 onwards, these within-species fluctuations balanced out in most cases and led to constant and more reliable results.

The Fecal Microbiota of Dogs Switching to a Raw Diet Only Partially Converges to That of Wolves

The genomic signature of dog domestication reveals adaptation to a starch-rich diet compared with their ancestor wolves. Diet is a key element to shape gut microbial populations in a direct way as well as through coevolution with the host. We investigated the dynamics in the gut microbiota of dogs when shifting from a starch-rich, processed kibble diet to a nature-like raw meat diet, using wolves as a wild reference. Six healthy wolves from a local zoo and six healthy American Staffordshire Terriers were included. Dogs were fed the same commercial kibble diet for at least 3 months before sampling at day 0 (DC), and then switched to a raw meat diet (the same diet as the wolves) for 28 days. Samples from the dogs were collected at day 1 (DR1), week 1 (DR7), 2 (DR14), 3 (DR21), and 4 (DR28). The data showed that the microbial population of dogs switched from kibble diet to raw diet shifts the gut microbiota closer to that of wolves, yet still showing distinct differences. At phylum level, raw meat consumption increased the relative abundance of Fusobacteria and Bacteroidetes at DR1, DR7, DR14, and DR21 (q < 0.05) compared with DC, whereas no differences in these two phyla were observed between DC and DR28. At genus level, Faecalibacterium, Catenibacterium, Allisonella, and Megamonas were significantly lower in dogs consuming the raw diet from the first week onward and in wolves compared with dogs on the kibble diet. Linear discriminant analysis effect size (LEfSe) showed a higher abundance of Stenotrophomonas, Faecalibacterium, Megamonas, and Lactobacillus in dogs fed kibble diet compared with dogs fed raw diet for 28 days and wolves. In addition, wolves had greater unidentified Lachnospiraceae compared with dogs irrespective of the diets. These results suggested that carbohydrate-fermenting bacteria give way to protein fermenters when the diet is shifted from kibble to raw diet. In conclusion, some microbial phyla, families, and genera in dogs showed only temporary change upon dietary shift, whereas some microbial groups moved toward the microbial profile of wolves. These findings open the discussion on the extent of coevolution of the core microbiota of dogs throughout domestication.

Wolves, dogs and humans in regular contact can mutually impact each other's skin microbiota

In contrast to humans and dogs, the skin microbiota of wolves is yet to be described. Here, we investigated the skin microbiota of dogs and wolves kept in outdoor packs at the Wolf Science Center (WSC) via 16S rRNA gene amplicon sequencing. Skin swab samples were also collected from human care takers and their pet dogs. When comparing the three canine groups, representing different degrees of human contact to the care takers and each other, the pet dogs showed the highest level of diversity. Additionally, while human skin was dominated by a few abundant phylotypes, the skin microbiota of the care takers who had particularly close contact with the WSC animals was more similar to the microbiota of dogs and wolves compared to the humans who had less contact with these animals. Our results suggest that domestication may have an impact on the diversity of the skin microbiota, and that the canine skin microbiota can be shared with humans, depending on the level of interaction.

Unveiling the Fecal Microbiota in Two Captive Mexican Wolf (Canis lupus baileyi) Populations Receiving Different Type of Diets

Simple Summary

The Mexican wolf (Canis lupus baileyi) is an endangered canine. Both Mexico and the United States are currently collaborating to reproduce and reintroduce individuals to their original habitats. However, keeping these wolves in captivity represents a great commitment to meet their basic needs. Diet is a determining factor that is closely related to health and reproductive fitness. The type of diet that is fed to canines in captivity must provide the required nutrients for their development and welfare. The study of the fecal microbiota is a non-invasive way to establish the abundance and diversity of bacterial communities to determine if they are in a healthy condition. We analyzed data from two captive populations of Mexican wolves (i.e., northern and central Mexico) receiving different type of diets (Michilia population: mainly kibble vs. Ocotal population: mainly raw meat). The operational taxonomic units (OTUs) in Michilia resulted in 204 genera and 316 species, while in Ocotal there were 232 genera and 379 species. In the Michilia, dominance of bacteria that degrade carbohydrates was observed (related to kibble diet). In contrast, the Ocotal microbiota was dominated by protein-degrading bacteria (related to raw meat diet). The main outcomes generated in this study should help to enhance the welfare of the captive Mexican wolves to increase its numbers.

Abstract

The Mexican wolf (Canis lupus baileyi) was once distributed in southern United States and northern Mexico. It is an endangered subspecies detached from the gray wolf, and likely exemplifies one of the original migration waves of C. lupus into the new world. This is a canine whose individuals survive in specialized facilities, zoos, and museums as part of captive-breeding programs. In order to contribute to the improvement of the management of this species and favor its long-term conservation in Mexico, we aimed to evaluate the diversity and abundance of the fecal bacterial microbiota in two populations exposed to different types of diet: (1) Michilia (23° N, 104° W); kibble daily and raw meat sporadically, and (2) Ocotal (19° N, 99° W); raw meat daily and live animals periodically. Next generation sequencing (V3-V4 16S rRNA gene) by Illumina was implemented. The operational taxonomic units (OTUs) in Michilia resulted in 9 phyla, 19 classes, 34 orders, 61 families, 204 genera, and 316 species, while in Ocotal there were 12 phyla, 24 classes, 37 orders, 69 families, 232 genera, and 379 species. Higher estimated Chao1 richness, Shannon diversity, and core microbiota were observed in Ocotal. Differences (p < 0.05) between populations occurred according to the Bray–Curtis beta diversity index. In the Michilia, dominance of bacteria that degrade carbohydrates (Firmicutes, Lachnospiraceae, Blautia, Clostrodium, Eisenbergiella, Romboutsia, and Ruminococcus) was observed; they are abundant in kibble diets. In contrast, the Ocotal microbiota was dominated by protein-degrading bacteria (Fusobacteria, Fusobacteriaceae, and Fusobacteria), indicating a possible positive relation with a raw meat diet. The information generated in this study is fundamental to support the implementation of better management plans in the two populations considered here, as well as in different facilities of southern United States and Mexico, where this subspecies is kept in captivity for conservation purposes.

The gut microbiome buffers dietary adaptation in Bronze Age domesticated dogs

In an attempt to explore the role of the gut microbiome during recent canine evolutionary history, we sequenced the metagenome of 13 canine coprolites dated ca. 3,600–3,450 years ago from the Bronze Age archaeological site of Solarolo (Italy), which housed a complex farming community. The microbiome structure of Solarolo dogs revealed continuity with that of modern dogs, but it also shared some features with the wild wolf microbiome, as a kind of transitional state between them. The dietary niche, as also inferred from the microbiome composition, was omnivorous, with evidence of consumption of starchy agricultural foods. Of interest, the Solarolo dog microbiome was particularly enriched in sequences encoding alpha-amylases and complemented a low copy number of the host amylase gene. These findings suggest that Neolithic dogs could have responded to the transition to a starch-rich diet by expanding microbial functionalities devoted to starch catabolism, thus compensating for delayed host response.

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Ancient DNA of Bronze Age canine coprolites from Solarolo was sequenced

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Solarolo dogs share gut microbiome features with modern wolves and dogs

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The gut microbiome of Solarolo dogs shows high number of reads for alpha-amylase

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Neolithic canine gut microbiome complemented delay in host genome adaptation

Correction to: Changes in feeding habits promoted the differentiation of the composition and function of gut microbiotas between domestic dogs (Canis lupus familiaris) and gray wolves (Canis lupus)

An amendment to this paper has been published and can be accessed via the original article.

Comparison of Canine and Human Physiological Factors: Understanding Interspecies Differences that Impact Drug Pharmacokinetics

This review is a summary of factors affecting the drug pharmacokinetics (PK) of dogs versus humans. Identifying these interspecies differences can facilitate canine-human PK extrapolations while providing mechanistic insights into species-specific drug in vivo behavior. Such a cross-cutting perspective can be particularly useful when developing therapeutics targeting diseases shared between the two species such as cancer, diabetes, cognitive dysfunction, and inflammatory bowel disease. Furthermore, recognizing these differences also supports a reverse PK extrapolations from humans to dogs. To appreciate the canine-human differences that can affect drug absorption, distribution, metabolism, and elimination, this review provides a comparison of the physiology, drug transporter/enzyme location, abundance, activity, and specificity between dogs and humans. Supplemental material provides an in-depth discussion of certain topics, offering additional critical points to consider. Based upon an assessment of available state-of-the-art information, data gaps were identified. The hope is that this manuscript will encourage the research needed to support an understanding of similarities and differences in human versus canine drug PK.

Metabolomics shows the Australian dingo has a unique plasma profile

Dingoes occupy a wide range of the Australian mainland and play a crucial role as an apex predator with a generalist omnivorous feeding behaviour. Dingoes are ecologically, phenotypically and behaviourally distinct from modern breed dogs and have not undergone artificial selection since their arrival in Australia. In contrast, humans have selected breed dogs for novel and desirable traits. First, we examine whether the distinct evolutionary histories of dingoes and domestic dogs has lead to differences in plasma metabolomes. We study metabolite composition differences between dingoes (n = 15) and two domestic dog breeds (Basenji n = 9 and German Shepherd Dog (GSD) n = 10). Liquid chromatography mass spectrometry, type II and type III ANOVA with post-hoc tests and adjustments for multiple comparisons were used for data evaluation. After accounting for within group variation, 62 significant metabolite differences were detected between dingoes and domestic dogs, with the majority of differences in protein (n = 14) and lipid metabolites (n = 12), mostly lower in dingoes. Most differences were observed between dingoes and domestic dogs and fewest between the domestic dog breeds. Next, we collect a second set of data to investigate variation between pure dingoes (n = 10) and dingo-dog hybrids (n = 10) as hybridisation is common in regional Australia. We detected no significant metabolite differences between dingoes and dingo-dog hybrids after Bonferroni correction. However, power analysis showed that increasing the sample size to 15 could result in differences in uridine 5′-diphosphogalactose (UDPgal) levels related to galactose metabolism. We suggest this may be linked to an increase in Amylase 2B copy number in hybrids. Our study illustrates that the dingo metabolome is significantly different from domestic dog breeds and hybridisation is likely to influence carbohydrate metabolism.

The Gut Microbiome of Dogs and Cats, and the Influence of Diet

The gut microbiome is a functional organ, and responds metabolically to the nutrient composition within the diet. Fiber, starch, and protein content have strong effects on the microbiome composition, and changes in these nutrient profiles can induce rapid shifts. Due to functional redundancy of bacteria within microbial communities, important metabolites for health can be produced by different bacteria. Microbiome alterations associated with disease are of greater magnitude than those seen in healthy dogs on different diets. Dietary changes, addition of prebiotics, and probiotics, can be beneficial to improve microbial diversity and to normalize metabolite production in diseased dogs.

Catching a glimpse of the bacterial gut community of companion animals: a canine and feline perspective

Dogs and cats have gained a special position in human society by becoming our principal companion animals. In this context, efforts to ensure their health and welfare have increased exponentially, with in recent times a growing interest in assessing the impact of the gut microbiota on canine and feline health. Recent technological advances have generated new tools to not only examine the intestinal microbial composition of dogs and cats, but also to scrutinize the genetic repertoire and associated metabolic functions of this microbial community. The application of high-throughput sequencing techniques to canine and feline faecal samples revealed similarities in their bacterial composition, with Fusobacteria, Firmicutes and Bacteroidetes as the most prevalent and abundant phyla, followed by Proteobacteria and Actinobacteria. Although key bacterial members were consistently present in their gut microbiota, the taxonomic composition and the metabolic repertoire of the intestinal microbial population may be influenced by several factors, including diet, age and anthropogenic aspects, as well as intestinal dysbiosis. The current review aims to provide a comprehensive overview of the multitude of factors which play a role in the modulation of the canine and feline gut microbiota and that of their human owners with whom they share the same environment.

The canine gastrointestinal microbiota: early studies and research frontiers

The canine gut microbiota is a complex microbial population that is potentially related to metabolism, immunologic activity and gastrointestinal (GI) diseases. Early studies revealed that the canine gut microbiota was dynamic, and bacterial populations in the adjacent gut segments were similar, with anaerobes predominating. Metagenomics analysis revealed that nutrient contents in the diet modulated bacterial populations and metabolites in the canine gut. Further research revealed significant correlations between dietary factors and canine gut core microbiomes. Canine GI diseases are closely correlated with gut microbiota dysbiosis and metabolic disorders. Probiotic-related therapies can effectively treat canine GI diseases. Recent studies have revealed that the canine gut microbiota is similar to the human gut microbiota, and dietary factors affect both. Studying canine intestinal microorganisms enables clarifying changes in the canine intestinal bacteria under different conditions, simulating human diseases in dog models, and conducting in-depth studies of the interactions between intestinal bacteria and disease.

The impact of human-facilitated selection on the gut microbiota of domesticated mammals

Domestication is the process by which anthropogenic forces shape lifestyle and behavior of wild species to accommodate human needs. The impact of domestication on animal physiology and behavior has been extensively studied, whereas its effect on the gut microbiota is still largely unexplored. For this reason, 16S rRNA gene-based and internal transcribed spacer-mediated bifidobacterial profiling, together with shotgun metagenomics, was employed to investigate the taxonomic composition and metabolic repertoire of 146 mammalian fecal samples, corresponding to 12 domesticated-feral dyads. Our results revealed that changes induced by domestication have extensively shaped the taxonomic composition of the mammalian gut microbiota. In this context, the selection of microbial taxa linked to a more efficient feed conversion into body mass and putative horizontal transmission of certain bacterial genera from humans were observed in the fecal microbiota of domesticated animals when compared to their feral relatives and to humans. In addition, profiling of the metabolic arsenal through metagenomics highlighted extensive functional adaptation of the fecal microbial community of domesticated mammals to changes induced by domestication. Remarkably, domesticated animals showed, when compared to their feral relatives, increased abundance of specific glycosyl hydrolases, possibly due to the higher intake of complex plant carbohydrates typical of commercial animal feeds.

Gut Microbiota Plasticity Influences the Adaptability of Wild and Domestic Animals in Co-inhabited Areas

Due to the increased economic demand for livestock, the number of livestock is increasing. Because of human interference, the survival of wild animals is threatened in the face of competition, particularly in co-inhabited grazing pastures. This may lead to differences in the adaptability between wild and domestic animals, as well as nutritional deficiencies in wild animals. The gut microbiota is closely associated with host health, nutrition, and adaptability. However, the gut microbiota diversity and functions in domestic and wild animals in co-inhabited areas are unclear. To reveal the adaptability of wild and domestic animals in co-inhabited areas based on gut microbiota, we assessed the gut microbiota diversity. This study was based on the V3–V4 region of 16S rRNA and gut microbiota functions according to the metagenome analysis of fresh fecal samples in wild goitered gazelles (Gazella subgutturosa) and domestic sheep (Ovis aries) in the Qaidam Basin. The wild and domestic species showed significant differences in alpha- and beta-diversities. Specifically, the alpha-diversity was lower in goitered gazelles. We speculated that the nutritional and habitat status of the goitered gazelles were worse. The gut microbiota functions in the gazelles were enriched in metabolism and cellular processes based on the KEGG database. In summary, we reasoned that gut microbiota can improve the adaptability of goitered gazelles through energy maintenance by the functions of gut microbiota in the face of nutritional deficiencies. These findings highlight the importance of gut microbiota diversity to improve the adaptability of goitered gazelles, laying a foundation for the conservation of wild goitered gazelles. In addition, we further provide management suggestions for domestic sheep in co-inhabited grazing pastures.

The Role of the Canine Gut Microbiome and Metabolome in Health and Gastrointestinal Disease

The gut microbiome contributes to host metabolism, protects against pathogens, educates the immune system, and, through these basic functions, affects directly or indirectly most physiologic functions of its host. Molecular techniques have allowed us to expand our knowledge by unveiling a wide range of unculturable bacteria that were previously unknown. Most bacterial sequences identified in the canine gastrointestinal (GI) tract fall into five phyla: Firmicutes, Fusobacteria, Bacteroidetes, Proteobacteria, and Actinobacteria. While there are variations in the microbiome composition along the GI tract, most clinical studies concentrate on fecal microbiota. Age, diet, and many other environmental factors may play a significant role in the maintenance of a healthy microbiome, however, the alterations they cause pale in comparison with the alterations found in diseased animals. GI dysfunctions are the most obvious association with gut dysbiosis. In dogs, intestinal inflammation, whether chronic or acute, is associated with significant differences in the composition of the intestinal microbiota. Gut dysbiosis happens when such alterations result in functional changes in the microbial transcriptome, proteome, or metabolome. Commonly affected metabolites include short-chain fatty acids, and amino acids, including tryptophan and its catabolites. A recently developed PCR-based algorithm termed “Dysbiosis Index” is a tool that allows veterinarians to quantify gut dysbiosis and can be used to monitor disease progression and response to treatment. Alterations or imbalances in the microbiota affect immune function, and strategies to manipulate the gut microbiome may be useful for GI related diseases. Antibiotic usage induces a rapid and significant drop in taxonomic richness, diversity, and evenness. For that reason, a renewed interest has been put on probiotics, prebiotics, and fecal microbiota transplantation (FMT). Although probiotics are typically unable to colonize the gut, the metabolites they produce during their transit through the GI tract can ameliorate clinical signs and modify microbiome composition. Another interesting development is FMT, which may be a promising tool to aid recovery from dysbiosis, but further studies are needed to evaluate its potential and limitations.

The Australian dingo: untamed or feral?

BACKGROUND

The Australian dingo continues to cause debate amongst Aboriginal people, pastoralists, scientists and the government in Australia. A lingering controversy is whether the dingo has been tamed and has now reverted to its ancestral wild state or whether its ancestors were domesticated and it now resides on the continent as a feral dog. The goal of this article is to place the discussion onto a theoretical framework, highlight what is currently known about dingo origins and taxonomy and then make a series of experimentally testable organismal, cellular and biochemical predictions that we propose can focus future research.

DISCUSSION

We consider a canid that has been unconsciously selected as a tamed animal and the endpoint of methodical or what we now call artificial selection as a domesticated animal. We consider wild animals that were formerly tamed as untamed and those wild animals that were formerly domesticated as feralized. Untamed canids are predicted to be marked by a signature of unconscious selection whereas feral animals are hypothesized to be marked by signatures of both unconscious and artificial selection. First, we review the movement of dingo ancestors into Australia. We then discuss how differences between taming and domestication may influence the organismal traits of skull morphometrics, brain and size, seasonal breeding, and sociability. Finally, we consider cellular and molecular level traits including hypotheses concerning the phylogenetic position of dingoes, metabolic genes that appear to be under positive selection and the potential for micronutrient compensation by the gut microbiome.

CONCLUSIONS

Western Australian Government policy is currently being revised to allow the widespread killing of the Australian dingo. These policies are based on an incomplete understanding of the evolutionary history of the canid and assume the dingo is feralized. However, accumulated evidence does not definitively show that the dingo was ever domesticated and additional focused research is required. We suggest that incorporating ancient DNA data into the debate concerning dingo origins will be pivotal to understanding the evolutionary history of the canid. Further, we advocate that future morphological, behavioural and genetic studies should focus on including genetically pure Alpine and Desert dingoes and not dingo-dog hybrids. Finally, we propose that future studies critically examine genes under selection in the dingo and employ the genome from a wild canid for comparison.