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.

Effects of photoperiod on food intake, activity and metabolic rate in adult neutered male cats.

With the continued rise in feline obesity, novel weight management strategies are needed. To date, strategies aimed at altering physical activity, an important factor in weight maintenance, have been lacking. Photoperiod is known to cause physiological changes in seasonal mammals, including changes in body weight (BW) and reproductive status. Thus, our objective was to determine the effect of increased photoperiod (longer days) on voluntary physical activity levels, resting metabolic rate (RMR), food intake required to maintain BW, and fasting serum leptin and ghrelin concentrations in adult cats. Eleven healthy, adult, neutered, male domestic shorthair cats were used in a randomized crossover design study. During two 12-week periods, cats were exposed to either a short-day (SD) photoperiod of 8 h light: 16 h dark or a long-day (LD) photoperiod of 16 h light: 8 h dark. Cats were fed a commercial diet to maintain baseline BW. In addition to daily food intake and twice-weekly BW, RMR (via indirect calorimetry), body composition [via dual-energy X-ray absorptiometry (DEXA)] and physical activity (via Actical activity monitors) were measured at week 0 and 12 of each period. Fasting serum leptin and ghrelin concentrations were measured at week 0, 6 and 12 of each period. Average hourly physical activity was greater (p = 0.008) in LD vs. SD cats (3770 vs. 3129 activity counts/h), which was primarily due to increased (p < 0.001) dark period activity (1188 vs. 710 activity counts/h). This corresponded to higher (p < 0.0001) daily metabolizable energy intake (mean over 12-week period: 196 vs. 187 kcal/day), and increased (p = 0.048) RMR in LD cats (9.02 vs. 8.37 kcal/h). Body composition, serum leptin and serum ghrelin were not altered by photoperiod. More research is needed to determine potential mechanisms by which these physiological changes occurred and how they may apply to weight management strategies.

Skeletal muscle tissue transcriptome differences in lean and obese female beagle dogs.

Skeletal muscle is a large and insulin-sensitive tissue that is an important contributor to metabolic homeostasis and energy expenditure. Many metabolic processes are altered with obesity, but the contribution of muscle tissue in this regard is unclear. A limited number of studies have compared skeletal muscle gene expression of lean and obese dogs. Using microarray technology, our objective was to identify genes and functional classes differentially expressed in skeletal muscle of obese (14.6 kg; 8.2 body condition score; 44.5% body fat) vs. lean (8.6 kg; 4.1 body condition score; 22.9% body fat) female beagle adult dogs. Alterations in 77 transcripts was observed in genes pertaining to the functional classes of signaling, transport, protein catabolism and proteolysis, protein modification, development, transcription and apoptosis, cell cycle and differentiation. Genes differentially expressed in obese vs. lean dog skeletal muscle indicate oxidative stress and altered skeletal muscle cell differentiation. Many genes traditionally associated with lipid, protein and carbohydrate metabolism were not altered in obese vs. lean dogs, but genes pertaining to endocannabinoid metabolism, insulin signaling, type II diabetes mellitus and carnitine transport were differentially expressed. The relatively small response of skeletal muscle could indicate that changes are occurring at a post-transcriptional level, that other tissues (e.g., adipose tissue) were buffering skeletal muscle from metabolic dysfunction or that obesity-induced changes in skeletal muscle require a longer period of time and that the length of our study was not sufficient to detect them. Although only a limited number of differentially expressed genes were detected, these results highlight genes and functional classes that may be important in determining the etiology of obesity-induced derangement of skeletal muscle function.

Commercial kefir products assessed for label accuracy of microbial composition and density.

Kefirs are fermented beverages containing yeast and bacteria produced by the fermentation of water or milk with kefir grains. Because microorganism density may influence a product's health benefits, label accuracy regarding viable bacterial density and taxonomy of fermented foods is important. In this study, the microbiota of 5 commercial kefir products were measured quantitatively using standard plating techniques and characterized using high-resolution, long-read 16S rRNA gene amplicon sequencing. To enumerate viable lactic acid bacteria, 2 lots of each product were plated on de Man, Rogosa and Sharpe agar upon opening and following 14 d and incubated under anaerobic and aerobic conditions. Results revealed that 66% of products with a guaranteed count of colony-forming units per gram overstated microorganism density by at least 1 log, with only product E exceeding 1 × 109 cfu/g. Sequencing results demonstrated moderate product label accuracy in regard to taxonomy, yet several products contained bacterial species above the minimum detectable threshold (0.001% relative abundance) that were not included on the labels (e.g., Streptococcus salivarius, Lactobacillus paracasei). Our results demonstrate a moderate level of labeling accuracy for commercial kefir products intended for human consumption. Regulatory agencies and consumers must continue to scrutinize these products and demand a higher level of accuracy and quality.

Effect of leukoreduction on transfusion-induced inflammation in dogs.

BACKGROUND: Removal of leukocytes (LR) has been shown to eliminate or attenuate many of the adverse effects of transfusion in experimental animals and humans. HYPOTHESIS/OBJECTIVES: Transfusion of stored packed red blood cells (pRBCs) is associated with an inflammatory response in dogs and prestorage LR attenuates the inflammatory response. ANIMALS: Thirteen random-source, clinically healthy, medium and large breed dogs. METHODS: Experimental study. On day 0, animals were examined and baseline blood samples were collected for analysis. Whole blood was then collected for processing with and without LR, and stored as pRBC. Twenty-one days later, stored pRBCs were transfused back to the donor. Blood samples were collected before and 1 and 3 days after transfusion. RESULTS: In the dogs that received non-LR pRBCs (n = 6) there was a significant increase from baseline in white blood cell count from a mean (SD) of 8.20 (2.74) to 13.95 (4.60) × 10(3) cells/µL (P < .001) and in segmented neutrophil count from a mean (SD) of 5.76 (2.70) to 11.91 (4.71) × 10(3) cells/µL (P < .001). There were also significant increases in fibrinogen from a mean (SD) of 129.7 (24.2) to 268.6 (46.7) mg/dL (P < .001) and C-reactive protein from a mean (SD) of 1.9 (2.1) to 78.3 (39.3) µg/mL (P < .001). There was no significant increase from baseline in any of the markers in the dogs that received LR pRBC (n = 5). CONCLUSIONS AND CLINICAL IMPORTANCE: There is a profound inflammatory response to transfusion in normal dogs, which is eliminated by LR of the pRBC units.

Effect of fructans, prebiotics and fibres on the human gut microbiome assessed by 16S rRNA-based approaches: a review.

The inherent and diverse capacity of dietary fibres, nondigestible oligosaccharides (NDOs) and prebiotics to modify the gut microbiota and markedly influence health status of the host has attracted rising interest. Research and collective initiatives to determine the composition and diversity of the human gut microbiota have increased over the past decade due to great advances in high-throughput technologies, particularly the 16S ribosomal RNA (rRNA) sequencing. Here we reviewed the application of 16S rRNA-based molecular technologies, both community wide (sequencing and phylogenetic microarrays) and targeted methodologies (quantitative PCR, fluorescent in situ hybridisation) to study the effect of chicory inulin-type fructans, NDOs and specific added fibres, such as resistant starches, on the human intestinal microbiota. Overall, such technologies facilitated the monitoring of microbiota shifts due to prebiotic/fibre consumption, though there are limited community-wide sequencing studies so far. Molecular studies confirmed the selective bifidogenic effect of fructans and galactooligosaccharides (GOS) in human intervention studies. Fructans only occasionally decreased relative abundance of Bacteroidetes or stimulated other groups. The sequencing studies for various resistant starches, polydextrose and beta-glucan showed broader effects with more and different types of gut microbial species being enhanced, often including phylotypes of Ruminococcaceae. There was substantial variation in terms of magnitude of response and in individual responses to a specific fibre or NDO which may be due to numerous factors, such as initial presence and relative abundance of a microbial type, diet, genetics of the host, and intervention parameters, such as intervention duration and fibre dose. The field will clearly benefit from a more systematic approach that will support defining the impact of prebiotics and fibres on the gut microbiome, identify biomarkers that link gut microbes to health, and address the personalised response of an individual's microbiota to prebiotics and dietary fibres.

Dietary protein concentration affects intestinal microbiota of adult cats: a study using DGGE and qPCR to evaluate differences in microbial populations in the feline gastrointestinal tract.

The objective of this study was to identify qualitative and quantitative differences in microbial populations of adult cats fed diets containing different protein concentrations. Following a 4 week baseline period, eight healthy adult domestic short-hair queens (>1-year-old) were randomly allotted to a moderate-protein (MP; n = 4) or high-protein (HP; n = 4) diet for 8 weeks. Fresh faecal samples were collected after baseline and 8 weeks on treatment and stored at -80 degrees C. Following DNA extraction, samples were analyzed using denaturing gradient gel electrophoresis to distinguish qualitative changes between diets. Quantitative polymerase chain reaction was used to measure E. coli, Bifidobacterium, Clostridium perfringens, and Lactobacillus populations. Compared to baseline, cats fed MP had a bacterial similarity index of 66.7% as opposed to 40.6% similarity for those fed HP, exhibiting marked changes in intestinal bacteria of cats fed HP. Bifidobacterium populations were greater (p < 0.05) in cats fed MP versus HP (9.44 vs. 5.63 CFU/g). Clostridium perfringens populations were greater (p < 0.05) in cats fed HP than MP (12.39 vs. 10.83 CFU/g). In this experiment, a high-protein diet resulted in a dramatic shift in microbial populations. Decreased Bifidobacterium population in cats fed HP may justify prebiotic supplementation for such diets.

Fish protein substrates can substitute effectively for poultry by-product meal when incorporated in high-quality senior dog diets.

An experiment was conducted to analytically define several novel fish substrates and determine the effects of feeding diets containing these substrates on total tract nutrient digestibilities and on immune status of senior dogs. The control diet contained poultry by-product meal while test diets contained 20% milt meal (MM), pink salmon hydrolysate (PSH) and white fish meal (WFM) added at the expense of poultry by-product meal. Concentrations of lymphocytes positive for CD3, CD4, CD8 and CD21 cell-surface markers and immunoglobulin concentrations were measured. Gene expression of cytokines tumour necrosis factor (TNF)-, interleukin (IL)-6, interferon (IFN)-, IL-10 and transforming growth factor (TGF)-ß was determined by quantitative real-time polymerase chain reaction. Major compositional differences were noted among fish substrates but apparent nutrient digestibility coefficients and immune indices were not affected by treatment. Fish protein substrates were found to be effective substitutes for poultry by-product meal, providing diets of high nutritive value for senior dogs.

Using genomic biology to study liver metabolism.

The liver plays a central role in coordinating the body's metabolism, including glucose homeostasis, xenobiotic metabolism and detoxification, and steroid hormone synthesis and degradation. Many of the regulatory effects in response to diet initially occur in the liver, which then modulates the activities of other organs in terms of nutrient utilization and metabolism. The health consequences of abnormal liver function are widespread, many of which are not entirely understood. Recent advances in genomic biology, nanotechnology, computer science and related fields have supplied researchers with a powerful set of tools for the laboratory and clinic. Because nutrient status has been proven to be an important factor in health and disease, the use of these tools to identify nutrient-gene interactions and their association with disease has greatly increased over the past decade. Given its great importance to intermediary metabolism, the liver has been one of the primary organs of focus in recent nutrigenomic experiments. This paper will provide a brief synopsis of the recent technological advancements that may be applied to nutrition research, common mechanisms by which nutrients and genes interact with one another, a few examples pertaining to hepatic function, and future directions in the field.

The Gastrointestinal Microbiome: A Review.

The gastrointestinal microbiome is a diverse consortium of bacteria, archaea, fungi, protozoa, and viruses that inhabit the gut of all mammals. Studies in humans and other mammals have implicated the microbiome in a range of physiologic processes that are vital to host health including energy homeostasis, metabolism, gut epithelial health, immunologic activity, and neurobehavioral development. The microbial genome confers metabolic capabilities exceeding those of the host organism alone, making the gut microbiome an active participant in host physiology. Recent advances in DNA sequencing technology and computational biology have revolutionized the field of microbiomics, permitting mechanistic evaluation of the relationships between an animal and its microbial symbionts. Changes in the gastrointestinal microbiome are associated with diseases in humans and animals including inflammatory bowel disease, asthma, obesity, metabolic syndrome, cardiovascular disease, immune-mediated conditions, and neurodevelopmental conditions such as autism spectrum disorder. While there remains a paucity of data regarding the intestinal microbiome in small animals, recent studies have helped to characterize its role in host animal health and associated disease states. This review is intended to familiarize small animal veterinarians with recent advances in the field of microbiomics and to prime them for a future in which diagnostic tests and therapies will incorporate these developments into clinical practice.

Physiological effects of stress related to helicopter travel in Federal Emergency Management Agency search-and-rescue canines.

Working canines are deployed by the Federal Emergency Management Agency (FEMA), as part of a National Disaster Response Plan. Stress associated with helicopter flight and the resulting physical effects on the dog are unknown. Our objective was to test the hypotheses that (1) helicopter travel affects the physiology and faecal microbiota of working canines, but that (2) physiological consequences of helicopter travel will not negatively affect their work performance. A total of nine FEMA canines were loaded onto helicopters and flown for 30 min in July 2015. Rectal temperature, behavioural stress indicators and saliva swabs (for cortisol) were collected at baseline, loading, mid-flight and post-flight. After flight, canines completed a standardised search exercise to monitor work performance. Faecal samples were collected for microbial DNA extraction and Illumina sequencing. All canines were on a standardised diet (CANIDAE® Grain Free PURE Land®) for 3 weeks prior to the study. Visible indicators of stress were observed at loading and at mid-flight and corresponded with an increase (P < 0·05) in salivary cortisol from 5·4 µg/l (baseline) to 6·4 µg/l (loading). Additionally, rectal temperature increased (P < 0·05) from 38·61°C (baseline) to 39·33°C (mid-flight) and 39·72°C (post-flight). Helicopter travel did not affect search performance (P > 0·05). We found that α- and ß-diversity measures of faecal microbiota were not affected (P > 0·05). Our data suggest that although helicopter travel may cause physiological changes that have been associated with stress in working dogs, it does not make an impact on their search performance or the stability of faecal microbiota.

Effects of dietary calcium fructoborate supplementation on joint comfort and flexibility and serum inflammatory markers in dogs with osteoarthritis.

Our objective was to evaluate the short-term effects of calcium fructoborate (CFB) on gait, joint range of motion, serum inflammatory markers, and owner perception of pain in client-owned dogs. We used 59 osteoarthritic dogs with impairment, with dogs being randomly assigned to 4 treatments: placebo (60 mg fructose; = 15), low dose (69 mg CFB; = 14), high dose (127 mg CFB; = 14), or combination (69 mg CFB, 500 mg glucosamine hydrochloride and 200 mg chondroitin sulfate; = 16). Dogs up to 22.9 kg received 1 capsule/d, while dogs weighing 23 to 50 kg received 2 capsules/d. A physical examination, radiographs, goniometry measurements, gait analysis, blood sample collection, and a canine brief pain inventory questionnaire were performed on d 0 and 28. Change from baseline values were statistically analyzed among groups. After 28 d, dogs fed the low and high doses had an improved ( < 0.05) ability to rise from a lying position compared to placebo. Dogs fed the high dose also had a greater ( = 0.05) increase in soluble receptor for advanced glycation end products concentration than dogs fed the placebo. Sub-analysis of only large dogs (> 23 kg) showed that dogs fed the low dose had decreased ( < 0.05) pain severity score and pain at its worst compared to dogs fed the placebo. Large dogs fed the low dose also were shown to improve ( < 0.05) in their ability to rise from a lying position compared to dogs fed the placebo. Overall, CFB supplementation was well-tolerated and may aid in mitigating joint discomfort in dogs.

Chemical composition, true nutrient digestibility, and true metabolizable energy of novel pet food protein sources using the precision-fed cecectomized rooster assay.

A wide variety of animal protein-based ingredients is commonly used in the pet food products. The raw ingredients and processing procedures used may greatly affect protein quality. Testing the quality of alternative protein sources is necessary and contributes to the sustainability of pet foods. The objective of this study was to test the chemical composition of 8 protein sources intended for use in dog and cat foods (calamari meal, pork peptone, alligator meal, lamb meal, venison meal, chicken meal, and 2 duck meals), and evaluate their true nutrient digestibility and nitrogen-corrected true ME (TMEn) using the precision-fed cecectomized rooster assay. Calamari meal and pork peptone had lower ash (4.4 and 3.6% of DM, respectively) but greater CP (88.1 and 80.5% of DM, respectively) and either greater or similar GE (5.6 and 5.3 kcal/g of DM, respectively) compared with alligator, lamb, venison, chicken, and duck meals (11.8 to 24.5% ash, 58.7 to 65.9% CP, and 4.6 to 5.3 kcal GE/g). Acid-hydrolyzed fat (AHF) was lower in calamari meal (8.7% of DM) compared with the other proteins tested (15.5-22.1% of DM). True nutrient digestibility was variable among the protein sources (52 to 79% of DM, 60 to 83% of OM, 78 to 92% of AHF, and 70 to 89% of GE) with pork peptone having the highest DM, AHF, and GE digestibility and calamari meal having the highest OM digestibility. True indispensable AA digestibility was highest for calamari meal, with all AA having a digestibility greater than 90%. Except for histidine, all indispensable AA had a digestibility over 85% for pork peptone. In contrast, true indispensable AA digestibility was lowest for lamb meal, with histidine having digestibility less than 70% and the other entire indispensable AA having digestibility between 72 and 88%. The TMEn of calamari meal (4.82 kcal/g DM and 86.9% of GE) was greater ( < 0.05) than the other protein sources. The lamb meal had the lowest TMEn value (3.12 kcal/g DM and 66.9% of GE), with others being intermediate (3.46-4.09 kcal/g DM and 71.2-77.9% of GE). This study demonstrates the considerable variability that exists not only in the chemical composition but also in the true nutrient digestibility among protein sources intended for use in dog and cat foods and justifies further in vivo testing of novel protein sources.

Apparent total tract macronutrient digestibility, fecal characteristics, and fecal fermentative end-product concentrations of healthy adult dogs fed bioprocessed soy protein.

Animal proteins are commonly used in extruded dog foods. Plant-based proteins have a more consistent nutrient profile than animal sources but may contain antinutritional factors, including trypsin inhibitors and oligosaccharides. Bioprocessed soy protein (SP; HP-300; Hamlet Protein, Inc., Findlay, OH) is a processed soy-based product with low antinutritional factor concentrations and high protein quality. The objective was to evaluate the effects of SP on apparent total tract macronutrient digestibility, fecal characteristics, and fecal fermentative end products. Furthermore, this study aimed to identify if SP can be a replacement for poultry byproduct meal (PBPM) in dog food and determine if there are practical limits to its use. Three palatability experiments were conducted to evaluate 1) 0 vs. 12% SP, 2) 0 vs. 48% SP, and 3) 12 vs. 48% SP. For digestibility, 48 healthy adult Beagle dogs (20 females and 28 males; 3.4 yr mean age and 10.0 kg mean BW) were randomly allotted to 1 of 6 dietary treatments, 0 (control), 4, 8, 12, 24, and 48% SP, in a completely randomized design. All diets were formulated to meet Association of American Feed Control Officials nutrient profiles and contained approximately 30% CP and 16% fat. The treatment period consisted of a 10-d diet adaptation phase followed by a 4-d fresh and total fecal collection phase. The palatability results suggest that of the 3 inclusion levels tested (0, 12, or 48% SP), the best inclusion of SP is 12%, which was preferred over 0 and 48% SP. Digestibility and fecal data were evaluated for linear and quadratic effects using SAS. Stool output (on both an as-is and a DM basis) did not differ from the control except for the 48% SP treatment ( < 0.01). Fecal output per unit food intake differed ( < 0.01) from the control only at the 24 and 48% SP inclusion rates. No significant effects of feeding SP were found on stool consistency scores. Digestibility of DM, OM, and energy did not differ from the control at any inclusion rate, except for a decrease ( < 0.01) at 48% SP. Apparent total tract CP digestibility was not affected by treatment and ranged from 82.9 to 86.2%. Fecal short-chain fatty acid concentrations were greater ( < 0.01) in dogs fed 24 and 48% SP compared with the control. Conversely, branched-chain fatty acid concentrations were lower ( < 0.01) in dogs fed 8 to 48% SP compared with the control. These data suggest that SP is a suitable replacement for PBPM in dog diets up to a 24% inclusion level.

COMPANION ANIMALS SYMPOSIUM: Future aspects and perceptions of companion animal nutrition and sustainability.

Companion animals play an important role in our lives and are now considered to be and treated as family members in a majority of households in the United States. Because of the high number of pets that now exist, an increasingly stronger pet-human bond, and the importance placed on health and longevity, the pet food industry has realized steady growth over the last few decades. Despite past successes and opportunities that exist in the future, there are also challenges that must be considered. This review will present a brief overview of the current pet food industry and address some of the key issues moving forward. In regards to companion animal research, recent advances and future needs in the areas of canine and feline metabolism, aging, clinical disease, and the gut microbiome using molecular and high-throughput assays; chemical, in vitro, and in vivo testing of feed ingredients; and innovative pet food processing methods is discussed. Training the future workforce for the pet food industry is also of great importance. Recent trends on student demographics and their species and careers of interest, changing animal science department curricula, and technology's impact on instruction are provided. Finally, the sustainability of the pet food industry is discussed. Focus was primarily placed on the disconnect that exists between opinions and trends of consumers and the nutrient recommendations for dogs and cats, the desire for increasing use of animal-based and human-grade products, the overfeeding of pets and the pet obesity crisis, and the issues that involve the evaluation of primary vs. secondary products in terms of sustainability. Moving forward, the pet food industry will need to anticipate and address challenges that arise, especially those pertaining to consumer expectations, the regulatory environment, and sustainability. Given the already strong and increasingly dynamic market for pet foods and supplies, an academic environment primed to supply a skilled workforce, and continued industry support for basic and applied research initiatives, the future of the pet food industry looks very bright.

Feeding frequency, but not dietary water content, affects voluntary physical activity in young lean adult female cats.

The objective of this study was to investigate whether increased dietary water content and feeding frequency increased voluntary physical activity of young, lean adult female cats. A replicated 4 × 4 Latin square design with a 2 × 2 factorial treatment arrangement (feeding frequency and water content) was used. The 4 treatments consisted of 1 meal daily dry pet food without added water (1D; 12% moisture as is), 1 meal daily dry pet food with added water (1W; 70% total water content), 4 meals daily dry pet food without added water (4D; 12% moisture as is), and 4 meals daily dry pet food with added water (4W; 70% total water content). Eight healthy adult, lean, intact, young, female domestic shorthair cats were used in this experiment. Voluntary physical activity was evaluated using Actical activity monitors placed on collars and worn around the cats' necks for the last 7 d of each experimental period of 14 d. Food anticipatory activity (FAA) was calculated based on 2 h prior to feeding periods and expressed as a percentage of total daily voluntary physical activity. Increased feeding frequency (4 vs. 1 meal daily) resulted in greater average daily activity (P = 0.0147), activity during the light period (P = 0.0023), and light:dark activity ratio (P = 0.0002). In contrast, physical activity during the dark period was not altered by feeding frequency (P > 0.05). Cats fed 4 meals daily had increased afternoon FAA (P= 0.0029) compared with cats fed once daily. Dietary water content did not affect any measure of voluntary physical activity. Increased feeding frequency is an effective strategy to increase the voluntary physical activity of cats. Thus, it may assist in the prevention and management of obesity.

In vitro fermentation characteristics of novel fibers, coconut endosperm fiber and chicory pulp, using canine fecal inoculum.

The objective of this experiment was to determine the effects of in vitro fermentation of coconut endosperm fiber (CEF), chicory pulp (CHP), and selective blends of these substrates on SCFA production and changes in microbiota using canine fecal inocula. A total of 6 individual substrates, including short-chain fructooligosaccharide (scFOS; a well-established prebiotic source), pectin (PEC; used as a positive control), pelletized cellulose (PC; used as a negative control), beet pulp (BP; considered the gold standard fiber source in pet foods), CEF, and CHP, and 3 CEF:CHP blends (75:25% CEF:CHP [B1], 50:50% CEF:CHP [B2], and 25:75% CEF:CHP [B3]) were tested. Triplicate samples of each substrate were fermented for 0, 8, and 16 h after inoculation. A significant substrate × time interaction (P < 0.05) was observed for pH change and acetate, propionate, butyrate, and total SCFA concentrations. After 8 and 16 h, pH change was greatest for scFOS (-2.0 and -3.0, respectively) and smallest for PC (0.0 and -0.1, respectively). After 16 h, CEF had a greater butyrate concentration than CHP and all the CEF:CHP blends and it was not different than PEC. The substrate × time interaction was significant for bifidobacteria (P < 0.05) and lactobacilli (P < 0.05). After 8 h, bifidobacteria was greatest for BP and lowest for PC (12.7 and 10.0 log10 cfu/tube, respectively). After 16 h, PC had the lowest and scFOS had the greatest bifidobacteria (6.7 and 13.3 log10 cfu/tube, respectively). In general, CEF, CHP, and their blends had similar bifidobacteria populations after 8 and 16 h of fermentation when compared with BP and scFOS. After 16 h, lactobacilli populations were greatest for B1, B2, B3, BP, and scFOS, intermediate for PEC, and lowest for PC (P < 0.05). Overall, our data suggest that CEF had a butyrogenic effect and that CEF, CHP, and their blends had similar bifidobacteria and lactobacilli populations as popular prebiotic and fiber substrates. Future research should investigate the effects of CEF, CHP, and their blends on gastrointestinal health and fecal quality in dogs.

Evaluation of soluble corn fiber on chemical composition and nitrogen-corrected true metabolizable energy and its effects on in vitro fermentation and in vivo responses in dogs.

Dietary fermentable fiber is known to benefit intestinal health of companion animals. Soluble corn fiber (SCF) was evaluated for its chemical composition, nitrogen-corrected true ME (TMEn) content, in vitro digestion and fermentation characteristics, and in vivo effects on nutrient digestibility, fecal fermentation end products, and modulation of the fecal microbiome of dogs. Soluble corn fiber contained 78% total dietary fiber, all present as soluble dietary fiber; 56% was low molecular weight soluble fiber (did not precipitate in 95% ethanol). The SCF also contained 26% starch and 8% resistant starch and had a TMEn value of 2.6 kcal/g. Soluble corn fiber was first subjected to in vitro hydrolytic-enzymatic digestion to determine extent of digestibility and then fermented using dog fecal inoculum, with fermentative outcomes measured at 0, 3, 6, 9, and 12 h. Hydrolytic-enzymatic digestion of SCF was only 7%. In vitro fermentation showed increased (P < 0.05) concentrations of short-chain fatty acids through 12 h, with acetate, propionate, and butyrate reaching peak concentrations of 1,803, 926, and 112 µmol/g DM, respectively. Fermentability of SCF was higher (P < 0.05) than for cellulose but lower (P < 0.05) than for pectin. In the in vivo experiment, 10 female dogs (6.4 ± 0.2 yr and 22 ± 2.1 kg) received 5 diets with graded concentrations of SCF (0, 0.5, 0.75, 1.0, or 1.25% [as-is basis]) replacing cellulose in a replicated 5 × 5 Latin square design. Dogs were first acclimated to the experimental diets for 10 d followed by 4 d of total fecal collection. Fresh fecal samples were collected to measure fecal pH and fermentation end products and permit a microbiome analysis. For microbiome analysis, extraction of DNA was followed by amplification of the V4 to V6 variable region of the 16S rRNA gene using barcoded primers. Sequences were classified into taxonomic levels using a nucleotide basic local alignment search tool (BLASTn) against a curated GreenGenes database. Few changes in nutrient digestibility or fecal fermentation end products or stool consistency were observed, and no appreciable modulation of the fecal microbiome occurred. In conclusion, SCF was fermentable in vitro, but higher dietary concentrations may be necessary to elicit potential in vivo responses.

Diet affects nutrient digestibility, hematology, and serum chemistry of senior and weanling dogs.

The objective of this experiment was to determine the effects of age and diet on serum chemistry, hematology, and nutrient digestibility in healthy dogs. Twelve senior (11 yr old; six males and six females) and 12 weanling (age = 8 wk old; six males and six females) beagles were randomly assigned to one of two dietary treatments: 1) an animal product-based (APB) diet or 2) a plant product-based (PPB) diet. The APB diet was primarily composed of brewer's rice, chicken by-product meal, and poultry fat, whereas the primary ingredients of the PPB diet included corn, soybean meal, wheat middlings, and meat and bone meal. Dogs remained on experiment for 12 mo. A 4-d total fecal collection was performed to determine apparent macronutrient digestibilities after 3 and 10 mo. Blood samples were collected at baseline and after 3, 6, 9, and 12 mo on study. After 3 mo, dogs fed the APB diet had greater (P < 0.001) DM (6 percentage units) and OM (7 percentage units) digestibilities than dogs fed the PPB diet. Senior dogs had greater DM (2.5 percentage units; P = 0.07) and OM (3 percentage units; P < 0.01) digestibilities than young dogs. Dogs fed the PPB diet had a lower (P < 0.001) fecal DM percentage (7.5 percentage units) and greater (P < 0.001) fecal output (253 vs. 97 g/d, as-is basis). After 10 mo, age did not affect nutrient digestibility or fecal characteristics. However, the effect of diet after 10 mo was similar to that observed after 3 mo, as dogs fed the PPB diet had a lower (P < 0.001) fecal DM percentage (7 percentage units), lower OM (4 percentage units; P = 0.09) and fat (6 percentage units; P < 0.001) digestibilities, and greater (P < 0.005) fecal output (235 vs. 108 g/d, as-is basis). At baseline, most serum metabolites were different between age groups, with weanlings having several metabolite concentrations outside the reference ranges for adult dogs. Blood cholesterol, red blood cells, hemoglobin, hematocrit, creatinine, total protein, albumin, bilirubin, sodium, chloride, and alanine transaminase were present in greater (P < 0.05) concentrations in senior dogs, but weanling dogs had greater (P < 0.05) concentrations of glucose, platelets, Ca, P, K, and alkaline phosphatase. Over time, blood cholesterol concentrations were affected by age (P < 0.05) and diet (P < 0.01). Senior dogs had greater (P < 0.05) cholesterol concentrations than weanling dogs. Moreover, dogs fed the APB diet had greater (P < 0.05) cholesterol concentrations than dogs fed the PPB diet. Overall, although serum metabolite concentrations of weanlings were different from senior dogs at baseline, as weanlings matured into young adults, metabolite concentrations were similar to those of senior dogs. Diet had the largest effects on nutrient digestibilities and fecal characteristics. Canine age and diet must be considered when interpreting experimental and clinical data.

Fruit and vegetable fiber fermentation by gut microflora from canines.

The objective of this study was to assess fermentability by canine gut microflora to include shortchain fatty acid (SCFA) production, organic matter (OM) disappearance, and gas production of vegetable and fruit fiber sources compared to fiber standards (psyllium, citrus pectin, and Solka Floc). Fiber sources included apple pomace, carrot pomace, flaxseed, fruit blend (mixture of peach, almond, nectarine, and plum), grape pomace, pea hulls, pistachio, and tomato pomace. Substrates were fermented in vitro for 4, 12, and 24 h with fecal flora obtained from three healthy dogs. Citrus pectin had the highest OM disappearance, SCFA production, and gas production at all times of fermentation; psyllium was intermediate and Solka Floc was lowest. A wide variation in fermentability was noted among the vegetable and fruit fiber sources. Apple pomace, carrot pomace, and flaxseed had the greatest fermentability as assessed by OM disappearance. Pea hulls and tomato pomace had intermediate OM disappearances, and fruit blend, grape pomace, and pistachio were poorly fermented. Carrot pomace produced the largest amounts of gas and SCFA. Apple pomace produced high concentrations of gas but intermediate concentrations of SCFA. Pea hulls and tomato pomace produced intermediate concentrations of gas and SCFA, whereas flaxseed, fruit blend, grape pomace, and pistachio produced low amounts of these fermentation products. For all substrates collectively, OM disappearance was highly correlated with both gas production (r2 = 0.782 and 0.723 for 12- and 24-h values, respectively) and SCFA production (r2 = 0.737 and 0.738 for 12- and 24-h values, respectively). In general, OM disappearance, gas production, and SCFA production were related to the insoluble:soluble fiber ratio in the samples; as the insoluble:soluble ratio decreased (increased soluble fiber), the OM disappearance, gas production, and SCFA production increased.