Hindgut Fermentation Research Articles

The effect of sainfoin (Onobrychis viciifolia Scop.) drying temperature and pelleting on in vitro fermentation characteristics using equine faecal inocula

This study was conducted to determine the effects of drying temperature and pelleting of the tanniniferous forage legume sainfoin (Onobrychis viciifolia Scop.) on the in vitro fermentation characteristics by equine faecal inocula. The sainfoin used for the experiment was air dried on the land and oven dried at 30, 70 and 130 °C for 2.5 h. Part of the dried sainfoin samples was left as dried hay, another part was pelleted, resulting in 6 different samples. The hay and pellets were tested for particle size distribution and pellets were tested for their pellet quality in terms of hardness, durability and bulk density. The gas production technique was used to simulate fermentation and faecal samples of eight randomly selected horses were used to create four independent inocula mixtures that were examined in two subsequent gas production runs. Per inocula mixture, the hay and pellet samples were incubated in triplicate as is, or in combination with polyethylene glycol to inactivate the tannins. Cumulative gas production, a proxy for the organic matter (OM) fermentation, was measured for 72 h, whereafter fermentation fluids were sampled and analysed for volatile fatty acids (VFA) and pH. The results of the pellet quality measurements showed that the particle sizes of the sainfoin particles in the pellets were decreased by a higher drying temperature or by the pelleting process, indicating a loss of fibre physical effectiveness, a factor that may be indicative for chewing activity and hence saliva production. The gas production results showed a significant (P < 0.05) effect of drying temperature and the addition of polyethylene glycol on the cumulative gas production, the VFA production and the percentage of branched chain VFA produced. Hay dried at 130 °C had a lower (P < 0.05) gas production compared to hay dried at 30 and 70 °C, which indicates a lower OM fermentability. The addition of polyethylene glycol increased the gas and total VFA production, which indicates that tannins in sainfoin decrease the production of gas and VFA in hay pellets compared to the hay product. The pelleting process had no effect on the fermentation characteristics, but pelleting conditions strongly decreased the level of the amino acid lysine and its reactivity. The results indicate the increase in drying temperature to cause a decrease in the OM hindgut fermentation and the total and reactive lysine contents of sainfoin. The positive effects of the tannins (a higher proportion of propionic acid relative to acetic acid and a lower protein fermentation) remain, despite of technological treatments.

Patterns and determinants of the global herbivorous mycobiome

Despite their role in host nutrition, the anaerobic gut fungal (AGF) component of the herbivorous gut microbiome remains poorly characterized. Here, to examine global patterns and determinants of AGF diversity, we generate and analyze an amplicon dataset from 661 fecal samples from 34 mammalian species, 9 families, and 6 continents. We identify 56 novel genera, greatly expanding AGF diversity beyond current estimates (31 genera and candidate genera). Community structure analysis indicates that host phylogenetic affiliation, not domestication status and biogeography, shapes the community rather than. Fungal-host associations are stronger and more specific in hindgut fermenters than in foregut fermenters. Transcriptomics-enabled phylogenomic and molecular clock analyses of 52 strains from 14 genera indicate that most genera with preferences for hindgut hosts evolved earlier (44-58 Mya) than those with preferences for foregut hosts (22-32 Mya). Our results greatly expand the documented scope of AGF diversity and provide an ecologically and evolutionary-grounded model to explain the observed patterns of AGF diversity in extant animal hosts.

Temporal progression of anaerobic fungal communities in dairy calves from birth to maturity.

Establishment of microbial communities in neonatal calves is vital for their growth and overall health. While this process has received considerable attention for bacteria, our knowledge on temporal progression of anaerobic gut fungi (AGF) in calves is lacking. Here, we examined AGF communities in faecal samples from six dairy cattle collected at 24 different time points during the pre-weaning (days 1-48), weaning (days 48-60), and post-weaning (days 60-360) phases. Quantitative polymerase chain reaction indicated that AGF colonisation occurs within 24 h after birth, with loads slowly increasing during pre-weaning and weaning, then drastically increasing post-weaning. Culture-independent amplicon surveys identified higher alpha diversity during pre-weaning/weaning, compared to post-weaning. AGF community structure underwent a drastic shift post-weaning, from a community enriched in genera commonly encountered in hindgut fermenters to one enriched in genera commonly encountered in adult ruminants. Comparison of AGF community between calves day 1 post-birth and their mothers suggest a major role for maternal transmission, with additional input from cohabitating subjects. This distinct pattern of AGF progression could best be understood in-light of their narrower niche preferences, metabolic specialisation, and physiological optima compared to bacteria, hence eliciting a unique response to changes in feeding pattern and associated structural GIT development during maturation.

Dietary supplementation of Allium mongolicum modulates rumen-hindgut microbial community structure in Simmental calves.

Compared to traditional herbage, functional native herbage is playing more important role in ruminant agriculture through improving digestion, metabolism and health of livestock; however, their effects on rumen microbial communities and hindgut fermentation are still not well understood. The objective of present study was to evaluate the effects of dietary addition of Allium mongolicum on bacterial communities in rumen and feces of claves. Sixteen 7-month-old male calves were randomly divided into four groups (n = 4). All calves were fed a basal ration containing roughage (alfalfa and oats) and mixed concentrate in a ratio of 60:40 on dry matter basis. In each group, the basal ration was supplemented with Allium mongolicum 0 (SL0), 200 (SL200), 400 (SL400), and 800 (SL800) mg/kg BW. The experiment lasted for 58 days. Rumen fluid and feces in rectum were collected, Rumen fluid and hindgut fecal were collected for analyzing bacterial community. In the rumen, Compared with SL0, there was a greater relative abundance of phylum Proteobacteria (p < 0.05) and genera Rikenellaceae_RC9_gut_group (p < 0.01) in SL800 treatment. In hindgut, compared with SL0, supplementation of A. mongolicum (SL200, SL400, or SL800) decreased in the relative abundances of Ruminococcaceae_UCG-014 (p < 0.01), Ruminiclostridium_5 (p < 0.01), Eubacterium_coprostanoligenes_group (p < 0.05), and Alistipes (p < 0.05) in feces; Whereas, the relative abundances of Christensenellaceae_R-7_group (p < 0.05), and Prevotella_1 (p < 0.01) in SL800 were higher in feces, to maintain hindgut stability. This study provided evidence that A. mongolicum affects the gastrointestinal of calves, by influencing microbiota in their rumen and feces.

Apparent total tract digestibility and palatability of extruded diets with graded levels of whole soybeans by dogs.

Fat has high energy density and is considered one of the primary energy sources for dogs, however, increasing fat level in dry dog food has been challenging due to the lubrication and limitation of the coating system. The objective was to determine the effect of whole soybeans (WSB) on nutrient digestibility, stool quality, and palatability by dogs. The corn gluten meal, chicken fat, and brewers rice were replaced by WSB at 10, 20, and 30% (WSB10, WSB20, and WSB30, respectively) in the base diet (WSB0). Twelve beagles were randomly assigned. The digestibility trial was duplicated 4 × 4 Latin square design where dogs were allowed a 9-d adaptation followed by a 5-d total fecal collection for each period. Least-square means were analyzed with a single degree of freedom contrasts and significance at α = 0.05. Palatability was determined with a 2-bowl test by 20 beagles for 2 d with each WSB diet compared to the WSB0. First choice preference between two diets and total food consumption were recorded. Individual intake ratios (IR) were calculated (intake of each diet/total intake) for each dog. First choice (FC) was analyzed by a Chi-square probability, and the diet consumption was compared by a Wilcoxon signed rank test and a 2-way analysis of variance. Fecal moisture, output, and defecation frequency increased linearly (P < 0.05) as WSB increased. Apparent total tract digestibility of dry matter, organic matter, crude protein, fat, and gross energy decreased linearly (P < 0.05) as dogs fed the increased level of WSB. The fresh fecal pH in dogs decreased linearly (P < 0.05) as WSB content increased. The acetate, propionate, and the total short-chain fatty acid concentration increased linearly (P < 0.05) while the total branched-chain fatty acid concentration decreased linearly (P < 0.05) as WSB increased. Dogs had greater (P < 0.05) FC for WSB diets than WSB0, but there was no difference among treatments for diet consumption and IR. In conclusion, additional thermal processing before extrusion may improve nutrient digestibility of WSB. The stool quality and palatability were not affected, and fermentation in hindgut increased by WSB by dogs.

Equid nutritional physiology and behavior: an evolutionary perspective.

Like other members of the even-toed ungulates (the perissodactyls), equids once had a higher species diversity in the fossil record than they have today. This is generally explained in comparison to the enormous diversity of bovid ruminants. Theories on putative competitive disadvantages of equids include the use of a single toe as opposed to two toes per leg, the lack of a specific brain cooling (and hence water-saving) mechanism, longer gestation periods that delay reproductive output, and in particular digestive physiology. To date, there is no empirical support for the theory that equids fare better on low-quality forage than ruminants. In contrast to the traditional juxtaposition of hindgut and foregut fermenters, we suggest that it is more insightful to sketch the evolution of equid and ruminant digestive physiology as a case of convergence: both evolved a particularly high chewing efficacy in their respective groups, which facilitates comparatively high feed and hence energy intakes. But because the ruminant system, less based on tooth anatomy but more on a forestomach sorting mechanism, is more effective, equids depend more on high feed intakes than ruminants and may well be more susceptible to feed shortages. Arguably, the most under-emphasized characteristic of equids may be that in contrast to many other herbivores including ruminants and coprophageous hindgut fermenters, equids do not use the microbial biomass growing in their gastrointestinal tract. Equids display behavioral and morphophysiological adaptations to high feed intakes, and their cranial anatomy that facilitates the cropping of forage while performing grinding chewing at the same time might be unique. Rather than looking for explanations how equids are better adapted to their present niches than other organisms, considering them remnants of a different morphophysiological solution may be more appropriate.

51 Estimation of in vitro digestibility measures within equine fecal inoculum using feedstuff fiber composition

Previous studies support the use of equine fecal microbes to simulate hindgut fermentation to calculate in vitro true digestibility (IVTD) of feedstuffs. Neutral detergent fiber (NDF) and acid detergent fiber (ADF) composition have been shown to predict IVTD, in vitro NDF digestibility (IVNDFD), and in vitro ADF digestibility (IVADFD). However, little work has been done to predict these digestibility measures within horses. Thus, the study objective was to determine correlation and estimation of in vitro digestibility measures using equine fecal inoculum from feedstuff NDF and ADF composition. Four mature stock-type geldings (8.5 ± 3.9yr; 558.4 ± 31.0kg; 6.0 ± 0.4 BCS) were used in a duplicated 4 × 6 Factorial Design. Horses were acclimated to a basal diet of 1.8% BW as-fed of Coastal Bermudagrass hay (Cynodon dactylon)and 0.2% BW as-fed of Bluebonnet® Equilene® Pellets for 21d. Feces were collected on d22 via rectal-grab for use as incubation inoculum. Dried, ground feed samples (0.5g: alfalfa hay, Coastal Bermudagrass hay, soybean meal, rice bran, hempseed meal, Bluebonnet® Equilene® Pellets), sealed in ANKOM filter bags, were placed in duplicate within 2 DaisyII incubators for 48hr. After incubation, fiber bags were removed and dried, then analyzed for NDF composition to determine IVTD. Split samples were analyzed to determine pre-incubation NDF composition of feedstuffs. Correlations and linearregressions were performed within R Statistical Program©. Both NDF (r = −0.936) and ADF (r = −0.897) were highly correlated to IVTD. However, ADF had a greater correlation to both IVNDFD (r = −0.807) and IVADFD (r = −0.848) than NDF (r = −0.684; r = −0.720). A linear regression between NDF and IVTD produced the model: IVTD (g/kg DM) = 1052.30 – 0.932 * NDF (g/kg DM); R2 = 0.930; P < 0.001. A lower goodness-of-fit was found between ADF and IVTD: IVTD (g/kg DM) = 1033.25 – 1.528 * ADF (g/kg DM); R2 = 0.866; P < 0.001. An additive model of IVTD versus NDF+ADF mildly increased goodness-of-fit (R2 = 0.953). Sample ADF strongly predicted IVADFD (IVADFD (g/kg ADF) = 881.91 – 1.595 * ADF (g/kg DM); R2 = 0.835; P < 0.001) but only moderately predicted IVNDFD (IVNDFD (g/kg NDF) = 855.15 – 1.518 * ADF (g/kg DM); R2 = 0.749; P < 0.001). These results indicate the effectiveness of using feedstuff NDF to predict IVTD when using equine fecal inoculum. Feedstuff IVNDFD and IVADFD are predicted with less precision, likely due to the lack of foregut digestion of feedstuffs that would occur in vivo. The use of in vitro total-tract digestion modeling in horses may estimate equine hindgut fiber digestion with greater precision.

Effect of supplementing live Saccharomyces cerevisiae yeast on performance, rumen function, and metabolism during the transition period in Holstein dairy cows

Dairy cows have to face several nutritional challenges during the transition period, and live yeast supplementation appears to be beneficial in modulating rumen activity. In this study, we evaluated the effects of live yeast supplementation on rumen function, milk production, and metabolic and inflammatory conditions. Ten Holstein multiparous cows received either live Saccharomyces cerevisiae (strain Sc47; SCY) supplementation from -21 to 21 d from calving (DFC) or a control diet without yeast supplementation. Feed intake, milk yield, and rumination time were monitored until 35 DFC, and rumen fluid, feces, milk, and blood samples were collected at different time points. Compared with the control diet, SCY had increased dry matter intake (16.7 vs. 19.1 ± 0.8 kg/d in wk 2 and 3) and rumination time postpartum (449 vs. 504 ± 19.9 min/d in wk 5). Milk yield tended to be greater in SCY (40.1 vs. 45.2 ± 1.7 kg/d in wk 5), protein content tended to be higher, and somatic cell count was lower. In rumen fluid, acetate molar proportion was higher and that of propionate lower at 21 DFC, resulting in increased acetate:propionate and (acetate + butyrate):propionate ratios. Cows in the SCY group had lower fecal dry matter but higher acetate and lower propionate proportions on total volatile fatty acids at 3 DFC. Plasma analysis revealed a lower degree of inflammation after calving in SCY (i.e., lower haptoglobin concentration at 1 and 3 DFC) and a likely better liver function, as suggested by the lower γ-glutamyl transferase, even though paraoxonase was lower at 28 DFC. Plasma IL-1β concentration tended to be higher in SCY, as well as Mg and P. Overall, SCY supplementation improved rumen and hindgut fermentation profiles, also resulting in higher dry matter intake and rumination time postpartum. Moreover, the postcalving inflammatory response was milder and liver function appeared to be better. Altogether, these effects also led to greater milk yield and reduced the risk of metabolic diseases.

Effects of abomasally infused rumen fluid from corn-challenged donor cows on production, metabolism, and inflammatory biomarkers in healthy recipient cows

Subacute rumen acidosis may cause postruminal intestinal barrier dysfunction, but this does not appear to be due to increased hindgut fermentation. Alternatively, intestinal hyperpermeability may be explained by the plethora of potentially harmful substances (e.g., ethanol, endotoxin, and amines) produced in the rumen during subacute rumen acidosis, which are difficult to isolate in traditional in vivo experiments. Therefore, objectives were to evaluate whether abomasal infusion of acidotic rumen fluid collected from donor (Donor) cows elicits systemic inflammation or alters metabolism or production in healthy recipients. Ten rumen-cannulated lactating dairy cows [249 ± 63 d in milk; 753 ± 32 kg of body weight (BW)] were randomly assigned to 1 of 2 abomasal infusion treatments: (1) healthy rumen fluid (HF; 5 L/h; n = 5) or (2) acidotic rumen fluid (AF; 5 L/h; n = 5) infused. Eight rumen-cannulated cows [4 dry, 4 lactating (lactating = 391 ± 220 d in milk); 760 ± 70 kg of BW] were used as Donor cows. All 18 cows were acclimated to a high-fiber diet (46% neutral detergent fiber; 14% starch) during an 11-d prefeeding period during which rumen fluid was collected for the eventual infusion into HF cows. During period (P) 1 (5 d), baseline data were obtained and on d 5 Donor were corn-challenged (2.75% BW ground corn after 16 h of 75% feed restriction). Cows were fasted until 36 h relative to rumen acidosis induction (RAI), and data were collected through 96 h RAI. At 12 h RAI, an additional 0.50% BW of ground corn was added, and acidotic fluid collections began (7 L/Donor every 2 h; 6 M HCl was added to collected fluid until pH was between 5.0 and 5.2). On d 1 of P2 (4 d), HF/AF cows were abomasally infused with their respective treatments for 16 h, and data were collected for 96 h relative to the first infusion. Data were analyzed in SAS (SAS Institute Inc.) using PROC MIXED. Following the corn challenge in the Donor cows, rumen pH only mildly decreased at nadir (pH = 5.64 at 8 h RAI) and remained above the desired threshold for both acute (5.2) and subacute (5.6) acidosis. In contrast, fecal and blood pH markedly decreased to acidotic levels (nadir = 4.65 and 7.28 at 36 and 30 h RAI, respectively), and fecal pH remained below 5 from 22 to 36 h RAI. In Donor cows, dry matter intake remained decreased through d 4 (36% relative to baseline) and serum amyloid A and lipopolysaccharide-binding protein markedly increased by 48 h RAI in Donor cows (30- and 3-fold, respectively). In cows that received the abomasal infusions, fecal pH decreased in AF from 6 to 12 h relative to the first infusion (7.07 vs. 6.33) compared with HF; however, milk yield, dry matter intake, energy-corrected milk, rectal temperature, serum amyloid A, and lipopolysaccharide-binding protein were unaffected. Overall, the corn challenge did not cause subacute rumen acidosis but markedly decreased fecal and blood pH and stimulated a delayed inflammatory response in the Donor cows. Abomasal infusion of rumen fluid from corn-challenged Donor cows decreased fecal pH but did not cause inflammation, nor did it create an immune-activated phenotype in recipient cows.

Undernutrition Disrupts Cecal Microbiota and Epithelium Interactions, Epithelial Metabolism, and Immune Responses in a Pregnant Sheep Model.

Undernutrition may change cecal microbiota-epithelium interactions to influence cecal feed fermentation, nutrient absorption and metabolism, and immune function. Sixteen late-gestation Hu-sheep were randomly divided into control (normal feeding) and treatment (feed restriction) groups to establish an undernourished sheep model. Cecal digesta and epithelium were collected to analyze microbiota-host interactions based on 16S rRNA gene and transcriptome sequencing. Results showed that cecal weight and pH were decreased, volatile fatty acids and microbial proteins concentrations were increased, and epithelial morphology was changed upon undernutrition. Undernutrition reduced the diversity, richness, and evenness of cecal microbiota. The relative abundances of cecal genera involved in acetate production (Rikenellaceae dgA-11 gut group, Rikenellaceae RC9 gut group, and Ruminococcus) and negatively correlated with butyrate proportion (Clostridia vadinBB60 group_norank) were decreased, while genera related to butyrate (Oscillospiraceae_uncultured and Peptococcaceae_uncultured) and valerate (Peptococcaceae_uncultured) production were increased in undernourished ewes. These findings were consistent with the decreased molar proportion of acetate and the increased molar proportions of butyrate and valerate. Undernutrition changed the overall transcriptional profile and substance transport and metabolism in cecal epithelium. Undernutrition suppressed extracellular matrix-receptor interaction and intracellular phosphatidyl inositol 3-kinase (PI3K) signaling pathway then disrupted biological processes in cecal epithelium. Moreover, undernutrition repressed phagosome antigen processing and presentation, cytokine-cytokine receptor interaction, and intestinal immune network. In conclusion, undernutrition affected cecal microbial diversity and composition and fermentation parameters, inhibited extracellular matrix-receptor interaction and the PI3K signaling pathway, and then disrupted epithelial proliferation and renewal and intestinal immune functions. Our findings exposed cecal microbiota-host interactions upon undernutrition and contribute to their further exploration. IMPORTANCE Undernutrition is commonly encountered in ruminant production, especially during pregnancy and lactation in females. Undernutrition not only induces metabolic diseases and threatens pregnant mothers' health, but also inhibits fetal growth and development, leading to weakness or even death of fetuses. Cecum works importantly in hindgut fermentation, providing volatile fatty acids and microbial proteins to the organism. Intestinal epithelial tissue plays a role in nutrient absorption and transport, barrier function, and immune function. However, little is known about cecal microbiota and epithelium interactions upon undernutrition. Our findings showed that undernutrition affected bacterial structures and functions, which changed fermentation parameters and energy regimens, and therefore affected the substance transport and metabolism in cecal epithelium. Extracellular matrix-receptor interactions were inhibited, which repressed cecal epithelial morphology and cecal weight via the PI3K signaling pathway and lowered immune response function upon undernutrition. These findings will help in further exploring microbe-host interactions.

Comparison of the gut microbiome and resistome in captive African and Asian elephants on the same diet.

Elephants are endangered species and threatened with extinction. They are monogastric herbivorous, hindgut fermenters and their digestive strategy requires them to consume large amounts of low quality forage. The gut microbiome is important to their metabolism, immune regulation, and ecological adaptation. Our study investigated the structure and function of the gut microbiota as well as the antibiotic resistance genes (ARGs) in captive African and Asian elephants on the same diet. Results showed that captive African and Asian elephants had distinct gut bacterial composition. MetaStats analysis showed that the relative abundance of Spirochaetes (FDR = 0.00) and Verrucomicrobia (FDR = 0.01) at the phylum level as well as Spirochaetaceae (FDR = 0.01) and Akkermansiaceae (FDR = 0.02) at the family level varied between captive African and Asian elephants. Among the top ten functional subcategories at level 2 (57 seed pathway) of Kyoto Encyclopedia of Genes and Genomes (KEGG) database, the relative gene abundance of cellular community-prokaryotes, membrane transport, and carbohydrate metabolism in African elephants were significantly lower than those in Asian elephants (0.98 vs. 1.03%, FDR = 0.04; 1.25 vs. 1.43%, FDR = 0.03; 3.39 vs. 3.63%; FDR = 0.02). Among the top ten functional subcategories at level 2 (CAZy family) of CAZy database, MetaStats analysis showed that African elephants had higher relative gene abundance of Glycoside Hydrolases family 28 (GH 28) compared to Asian elephants (0.10 vs. 0.08%, FDR = 0.03). Regarding the antibiotic resistance genes carried by gut microbes, MetaStats analysis showed that African elephants had significantly higher relative abundance of vanO (FDR = 0.00), tetQ (FDR = 0.04), and efrA (FDR = 0.04) than Asian elephants encoding resistance for glycopeptide, tetracycline, and macrolide/rifamycin/fluoroquinolone antibiotic, respectively. In conclusion, captive African and Asian elephants on the same diet have distinct gut microbial communities. Our findings established the ground work for future research on improving gut health of captive elephants.

Yeast Cell Wall Compounds on The Formation of Fermentation Products and Fecal Microbiota in Cats: An In Vivo and In Vitro Approach.

The effects of yeast cell wall compounds (YCWs) being added to cat food on hindgut fermentation metabolites and fecal microbiota were assessed in in vivo Experiment 1 (Exp. 1) and in vitro Experiments 2 and 3 (Exp. 2 and 3). In Exp. 1, the cats' diets were supplemented with two dietary concentrations (46.2 and 92.4 ppm) of YCWs (YCW-15 and YCW-30, respectively), and a negative control diet with no compound in three groups (six cats per group) was used to assess the fecal score, pH, digestibility, fermentation products, and microbiota. In Exp. 2, feces from the cats that were not supplemented with YCWs (control) were used as an inoculum. A blend of pectin, amino acids, and cellulose was used as a substrate, and the YCW compound was added at two levels (5 and 10 mg). In Exp. 3, feces from cats fed YCWs were used as an inoculum to test three different substrates (pectin, amino acids, and cellulose). In Exp. 2 and 3, the gas production, pH, and fermentation products (ammonia, SCFAs, and BCFAs) were assessed. YCW-30 resulted in a higher digestibility coefficient of the crude protein, organic matter (OM) (p < 0.05), and energy of the diet (p < 0.10). Regarding the fermentation products, YCW-15 showed a trend toward higher concentrations of propionate, acetate, lactate, ammonia, isobutyrate, and valerate, while YCW-30 showed a trend (p < 0.10) toward higher levels of butyrate and pH values. The bacteroidia class and the genus Prevotella were increased by using YCW-30 and the control. At the gender level, decreased (p < 0.01) Megasphaera was observed with YCW inclusion. The microbiota differed (p < 0.01) among the groups in their Shannon indexes. For beta diversity, YCW-30 showed higher indexes (p = 0.008) than the control. The microbiota metabolic profile differed in the pathway CENTFERM-PWY; it was more expressed in YCW-30 compared to the control. In Exp. 2, the YCWs showed a higher ratio (p = 0.006) of the fermentation products in the treatments with additives with a trend towards a high dose of the additive (10 mg). In Exp. 3, the effects of the substrates (p < 0.001), but not of the YCWs, on the fermentation products were observed, perhaps due to the low dietary concentrations we used. However, the marked responses of the fermentation products to the substrates validated the methodology. We could conclude that the YCWs, even at low dietary concentrations, affected fecal SCFA production, reduced the fecal pH, and modulated the fecal microbiota in the cats. These responses were more pronounced under in vitro conditions.

Forages and Pastures Symposium: revisiting mechanisms, methods, and models for altering forage cell wall utilization for ruminants.

Several ruminant animals rely almost exclusively on the complex polysaccharide matrix from the plant cell wall (CW) as their primary energy source via volatile fatty acids produced through ruminal and some hindgut fermentation processes. The CW contains different types and proportions of polysaccharides, proteins, phenolic compounds, and minerals in their macromolecular structure that influence the rate and extent of fiber digestion and selective retention of particulate matter due to its physical characteristics (buoyancy and comminuting) in the reticulorumen. The biosynthetic formation of the CW dictates possible manipulation mechanisms (targeted plant and microbes selection) and processing methods (physical, chemical, microbial, and enzymatic treatments and the use of genetically engineered bacteria) to increase its digestibility, leading to better utilization of the CW by the ruminant animal and hopefully lower the contribution of ruminants' greenhouse gas emissions. Early studies on lignin biosynthesis have led to more advanced studies focusing on replacing traditional monolignols with homopolymers that are easier to deconstruct or degrade. Concurrently, laboratory methods must be developed, evaluated, and modified to accurately reflect the digestibility and nutritive value of CW brought about by modern manipulation mechanisms or processing methods. However, the laboratory methods must also be reliable, precise, feasible, trivial, easy to implement, and cost-effective, but at the same time environmentally friendly and aware. For instance, although the acid detergent lignin has been demonstrated to behave uniformly as a nutritional entity, its chemical determination and association with carbohydrates still lack consensus. Spectroscopy (near-infrared and Raman) and in vitro gas production techniques have been adopted to assess plant chemical composition and nutritive value, but an incomplete understanding of the impacts caused by disrupting the CW for sample processing still exists. Different variations of multicompartmental and time- and age-dependent mathematical models have been proposed to determine the ruminal rates of degradation and passage of fiber. However, low-quality and incomplete data due to inconsistent marker results used to determine passage rates and transit time of fiber in the gastrointestinal tract have hindered advancements and adoptions of the next generation of computer models to understand ruminal fiber degradation.

Effect of increasing dietary fermentable fiber on diet nutrient digestibility and estimation of endogenous phosphorus losses in growing pigs.

Fermentable fiber may increase endogenous losses of phosphorus (EPL) and amino acids (AA), thereby reducing apparent nutrient digestibility. Acacia gum with medium-to-high fermentability and low viscosity was increasingly included in diets to investigate its effect on apparent ileal digestibility (AID) and apparent total tract digestibility (ATTD) of nutrients, gross energy (GE), and standardized total tract digestibility (STTD) of P in growing pigs. A control diet (49% cornstarch; 18% bovine plasma protein) was formulated to measure basal EPL. Three additional diets were formulated to include 2.5%, 5.0%, or 7.5% acacia gum at the expense of cornstarch. Diets contained 16.1% to 17.4% CP and 0.31% to 0.33% total P (DM-basis). The four diets were fed to eight ileal-cannulated barrows (initial BW, 54.6 kg) for four 9 d periods in a double 4 × 4 Latin square. Apparent hindgut fermentation (AHF) was calculated as ATTD minus AID. Feeding increasing acacia gum quadratically affected (P < 0.05) AID of DM, GE, linearly decreased (P < 0.05) ATTD of DM, crude protein (CP), GE, digestible (DE) and predicted net energy (NE) value of diets, and linearly increased (P < 0.001) AHF of DM and GE. Increasing acacia gum did not affect AID and standardized ileal digestibility (SID) of CP and AA. Basal EPL was 377 mg/kg DM intake (DMI) and increasing acacia gum linearly increased (P < 0.05) total tract EPL. Increasing acacia gum linearly decreased (P < 0.05) diet ATTD of P, and STTD of P based on either the calculated EPL or NRC (2012) recommended value (190 mg P/kg DMI). Increasing acacia gum did not affect AID and ATTD of Ca of diets. In conclusion, feeding increasing dietary fermentable, low-viscous acacia gum decreased diet AID and ATTD of DM and GE, but did not affect AID or SID of CP and AA. Increasing acacia gum decreased ATTD of P, which might have been due to increased specific endogenous losses of P in the total tract of growing pigs.

Sorghum tannin extract impedes in vitro digestibility and fermentability of nutrients in the simulated porcine gastrointestinal tract.

The site and extent of digestion of sorghum nutrients affected by tannins in the intestine are not clarified. Porcine small intestine digestion and large intestine fermentation were simulated in vitro to determine the effects of sorghum tannin extract on the digestion and fermentation characteristics of nutrients in the mimicked porcine gastrointestinal tract. In experiment 1, low-tannin sorghum grain without or with 30 mg/g sorghum tannin extract were digested by porcine pepsin and pancreatin to measure in vitro digestibility of nutrients. In experiment 2, the lyophilized porcine ileal digesta from 3 barrows (Duroc × Landrace × Yorkshire, 27.75 ± 1.46 kg) fed the low-tannin sorghum grain without or with 30 mg/g sorghum tannin extract and the undigested residues from experiment 1 were, individually, incubated with fresh pig cecal digesta as inoculums for 48 h to simulate the porcine hindgut fermentation. The results revealed that sorghum tannin extract decreased in vitro digestibility of nutrients both by pepsin hydrolysis or pepsin-pancreatin hydrolysis (P < 0.05). Although enzymatically unhydrolyzed residues provided more energy (P = 0.09) and nitrogen (P < 0.05) as fermentation substrates, the microbial degradation of nutrients from unhydrolyzed residues and porcine ileal digesta were both decreased by sorghum tannin extract (P < 0.05). Regardless of unhydrolyzed residues or ileal digesta as fermentation substrates, microbial metabolites including the accumulative gas production excluding the first 6 h, total short-chain fatty acid and microbial protein content in the fermented solutions were decreased (P < 0.05). The relative abundances of Lachnospiraceae AC2044 and NK4A136 and Ruminococcus_1 was decreased by sorghum tannin extract (P < 0.05). In conclusion, sorghum tannin extract not only directly decreased the chemical enzymatic digestion of nutrients in the simulated anterior intestine, but also directly inhibited the microbial fermentation including microbial diversities and metabolites in the simulated posterior intestine of pigs. The experiment implies that the decreased abundances of Lachnospiraceae and Ruminococcaceae by tannins in the hindgut may weaken the fermentation capacity of microflora and thus impair the nutrient digestion in the hindgut, and ultimately reduce the total tract digestibility of nutrients in pigs fed high tannin sorghum.

Cellulose Butyrate as a Potent Fiber Supplement for Mono-Gastric Animals to Modulate Hindgut Microbiota and Fermentation: In Vitro Evaluations

To evaluate the function of cellulose butyrate (CB), a new synthetic, fibrous, candidate food additive, a series of batch culture study was carried out. Fecal cultures were prepared using fresh feces from human volunteers and swines, and anaerobically incubated to characterize the effect of CB on hindgut fermentation and microbial community, and thereby evaluate the potential use of CB as a food additive in mono-gastric animals. Three types of CB differing in the degree of substitution and in the carbon position of glucose residue where butyl groups are substituted were tested to proceed multiple comparisons for measured parameters. Among three types of CB tested, partially water-soluble CB3 was associated with the highest increase in butyrate production in human and swine fecal cultures. CB3 supplementation shifted fecal microbiota toward greater abundance of bacteria in the Bacteroidetes phylum, in particular the genus Parabacteroides, in which the increase of Parabacteroides distasonis was remarkable even with individual variations. CB3 also lowered putrefactive products, including ammonia, indole and skatole, in the cultures. Dietary use of partially water-soluble CB3 might be expected to have useful effects in humans and other mono-gastric animals, judging from the present results of enhanced butyrate production and lowered putrefactive products with CB3 addition to feces. The results might be partly attributable to a shift in hindgut microbiota, represented by the increased abundance of Bacteroidetes, especially Parabacteroides species. Therefore, CB3 can be considered as a functional additive candidate for the use in mono-gastric animals such as human and pigs.

Effects of Cashew Nut Shell Liquid on Hindgut Fermentation and Microbiota of Chickens

Cashew nut shell liquid (CNSL), a feed additive for chickens, was evaluated for its influence on the hindgut environment by determining fermentation and bacterial profiles using cecal contents, fecal slurry and pure cultures. A farm-scale study showed that CNSL feeding to broiler chickens from 0 to 42 days of age improved body weight gain and lowered mortality. Cecal levels of short chain fatty acids increased with CNSL feeding, while ammonia and indole levels decreased. Feeding CNSL decreased the relative abundance of cecal bacteria belonging to some clostridial groups and Ruminococcaceae. In particular, Clostridium perfringens was undetectable following CNSL feeding. A pure culture study showed that CNSL (≥ 6.25 μg/ml) inhibited C. perfringens growth, accompanied by cell surface disruption based on electron microscopic observation. Fermentation profiles of slurry cultures prepared from feces of chickens were altered by CNSL supplementation toward less ammonia production. The lowered ammonia was correlated positively with the abundance of unclassified Lachnospiraceae and unclassified Ruminococcaceae, and negatively with unclassified Enterobacteriaceae and Sutterella. These results suggest that CNSL could exert its beneficial influence on the hindgut health of chickens through impacting the microbiota.

Quantification of relative stock units for horses to permit correct application within pasture-based production systems

Context Overseer® is the primary software tool used to estimate farm-level nutrient cycle and management for regulatory purposes in New Zealand. The model compares feed demand among different livestock by using ‘revised stock units’ (RSUs, the annual energy requirement of a mature ewe to raise a single lamb to weaning; 6000 MJ metabolisable energy). The RSUs for several common equine stock classes are not yet available, while those currently available within the model are based on the linear scaling of feed demand to liveweight, which does not consider allometric scaling of metabolism to liveweight or the differences in digestive physiology and nutrient metabolism between ruminants and monogastric hindgut fermenters (horses). Aim To compare the current RSU values used in Overseer® for different equine stock classes, with the equineRSU values calculated using equine-specific models. Methods Weighted average estimates of the bodyweight for the different equine livestock classes were calculated from the published literature. These weighted average estimates of bodyweight were used to estimate the energy requirements on the basis of data published by National Research Council. The resulting dry-matter intake and N intake from the equineRSU values and the current RSU values in use within Overseer® were modelled using published data on diet composition, crude protein content and the digestibility of the different feeds offered. Results The current RSUs in Overseer were 2.5–6.8 units higher than the equineRSU values obtained from the equine-specific models. This overestimation in feed demand resulted in N-intake estimates at an animal level being 52–108% higher than values derived using the equine-specific estimates. Conclusion The use of RSUs based on linear scaling of feed demand from ruminants on the basis of liveweight overestimates feed demand and N intake in horses. If horses are to be included within nutrient management models, feed demand must be based on published equine data for energy requirements to avoid over-inflation of N excretion. The equineRSUs calculated in this study reduce the risk of over-inflation of N intake and excretion, and subsequently the N leaching estimations. Implication Failure to accurately model feed demand of horses within nutrient management software would unfairly compromise stocking density and horse management on large commercial breeding farms. The implication for these errors on economic impact and restricted livestock number is greatest for the Thoroughbred breeding industry due to the scale of the operations.

Truly dorsostable runners: Vertebral mobility in rhinoceroses, tapirs, and horses.

The vertebral column is a hallmark of vertebrates; it is the structural basis of their body and the locomotor apparatus in particular. Locomotion of any vertebrate animal in its typical habitat is directly associated with functional adaptations of its vertebrae. This study is the first large-scale analysis of mobility throughout the presacral region of the vertebral column covering a majority of extant odd-toed ungulates from 6 genera and 15 species. In this study, we used a previously developed osteometry-based method to calculate available range of motion. We quantified all three directions of intervertebral mobility: sagittal bending (SB), lateral bending (LB), and axial rotation (AR). The cervical region in perissodactyls was found to be the most mobile region of the presacral vertebral column in LB and SB. Rhinoceroses and tapirs are characterized by the least mobile necks in SB among odd-toed and even-toed ungulates. Equidae are characterized by very mobile necks, especially in LB. The first intrathoracic joint (T1-T2) in Equidae and Tapiridae is characterized by significantly increased mobility in the sagittal plane compared to the typical thoracic joints and is only slightly less mobile than typical cervical joints. The thoracolumbar part of the vertebral column in odd-toed ungulates is very stiff. Perissodactyls are characterized by frequent fusions of vertebrae with each other with complete loss of mobility. The posterior half of the thoracic region in perissodactyls is characterized by especially stiff intervertebral joints in the SB direction. This is probably associated with hindgut fermentation in perissodactyls: the sagittal stiffness of the posterior thoracic region of the vertebral column is able to passively support the hindgut heavily loaded with roughage. Horses are known as a prime example of a dorsostable galloper among mammals. However, based on SB in the lumbosacral part of the backbone, equids appear to be the least dorsostable among extant perissodactyls; the cumulative SB in equids and tapirs is as low as in the largest representatives of artiodactyls, while in Rhinocerotidae it is even lower representing the minimum across all odd-toed and even-toed ungulates. Morphological features of small Paleogene ancestors of rhinoceroses and equids indicate that dorsostability is a derived feature of perissodactyls and evolved convergently in the three extant families.

Effects of hindgut acidosis on metabolism, inflammation, and production in dairy cows consuming a standard lactation diet

Postruminal intestinal barrier dysfunction caused by excessive hindgut fermentation may be a source of peripheral inflammation in dairy cattle. Therefore, the study objectives were to evaluate the effects of isolated hindgut acidosis on metabolism, inflammation, and production in lactating dairy cows. Five rumen-cannulated lactating Holstein cows (32.6 ± 7.2 kg/d of milk yield, 242 ± 108 d in milk; 642 ± 99 kg of body weight; 1.8 ± 1.0 parity) were enrolled in a study with 2 experimental periods (P). During P1 (4 d), cows were fed ad libitum a standard lactating cow diet (26% starch dry matter) and baseline data were collected. During P2 (7 d), all cows were fed the same diet ad libitum and abomasally infused with 4 kg/d of pure corn starch (1 kg of corn starch + 1.25 L of H2O/infusion at 0600, 1200, 1800, and 0000 h). Effects of time (hour relative to the first infusion or day) relative to P1 were evaluated using PROC MIXED in SAS (version 9.4; SAS Institute Inc.). Infusing starch markedly reduced fecal pH (5.84 vs. 6.76) and increased fecal starch (2.2 to 9.6% of dry matter) relative to baseline. During P2, milk yield, milk components, energy-corrected milk yield, and voluntary dry matter intake remained unchanged. At 14 h, plasma insulin and β-hydroxybutyrate increased (2.4-fold and 53%, respectively), whereas circulating glucose concentrations remained unaltered. Furthermore, blood urea nitrogen increased at 2 h (23%) before promptly decreasing below baseline at 14 h (13%). Nonesterified fatty acids tended to decrease from 2 to 26 h (40%). Circulating white blood cells and neutrophils increased on d 4 (36 and 73%, respectively) and somatic cell count increased on d 5 (4.8-fold). However, circulating serum amyloid A and lipopolysaccharide-binding protein concentrations were unaffected by starch infusions. Despite minor changes in postabsorptive energetics and leukocyte dynamics, abomasal starch infusions and the subsequent hindgut acidosis had little or no meaningful effects on biomarkers of immune activation or production variables.