The Establishment of Fibrolytic Bacteria in the Foal Gastrointestinal Tract Is Related to the Occurrence of Coprophagy by Foals.

The consumption of maternal feces (coprophagy) is commonly observed in healthy foals and is a proposed contributor to microbial colonization of the foal's gastrointestinal tract (GIT). This study investigated the role of coprophagy in the establishment of fibrolytic bacteria in the foal GIT. Nine thoroughbred mares were dosed with chromic oxide, an indigestible marker, as a method to detect the occurrence of coprophagy by their foals. Foal fecal samples were collected from 12 h to 21 d after birth to measure chromic oxide and neutral detergent fiber (NDF) and to enumerate cellulolytic bacteria using culture-based techniques. Milk yield was estimated at 7 and 14 d postpartum. Coprophagy was detected as early as 3 d after birth and detected in all foals by 7 d of age. There were strong relationships between coprophagy and cellulolytic bacteria and NDF in foal feces at 7 d of age (r = 0.9703 and r = 0.7878, respectively; p < 0.05). Fecal NDF and chromic oxide concentrations were negatively related to milk yield (r = -0.8144 and r = -0.6966, respectively; p < 0.05), suggesting milk availability affected the incidence of coprophagy. Based on the relationships identified, maternal feces are an important source of fiber and live microbes for the foal, contributing to the development of the microbial community.

Improved methods for mare milk analysis: Extraction and quantification of mare milk carbohydrates and assessment of FTIR-based macronutrient quantification.

Accurately determining the macronutrient profile of mare milk is a precursor to studying how milk composition affects foals' growth and development. This study optimized and validated an extraction and quantification method for mare milk oligosaccharides, which make up a portion of the carbohydrate fraction of mare milk. Mare milk was extracted with chloroform and methanol, and oligosaccharides were selectively isolated from the carbohydrate fraction using porous-graphitized carbon solid-phase-extraction (SPE). Good recovery rates for milk oligosaccharides (between 70 and 100%) were achieved with the optimized method. This study also compared the use of Fourier-Transform infrared (FTIR) spectroscopy versus wet chemistry quantification methods for protein, fat, and lactose. The FTIR method produced statistically equivalent protein contents to the wet chemistry method, along with substantial savings in both analyst time and consumable consumption. FTIR analysis slightly underestimated the fat content of mare milk relative to the official wet chemistry method, with the difference between the methods increasing at higher fat contents. FTIR also overestimated the lactose content of mare milk and appeared to generate "lactose" values that included the milk oligosaccharides and thus represented the total carbohydrate (lactose and milk oligosaccharides) content of mare milk.

The nutrient requirements of horses: historical perspectives.

The National Research Council (NRC) published the Recommended Nutrient Allowances for Horses in 1949. The subsequent publication was renamed the Nutrient Requirements of Horses and the 6th revised edition was published in 2007. The document has increased in size and scope from the initial publication in 1949 that contained 29 pages to the most recent version with 341 pages. Several formats for expressing requirements (dietary concentrations or daily amounts) have been utilized. In addition, a variety of methods have been employed to determine the nutrient requirements of horses since 1949. Many of the requirement estimates are based on research studies with the target class of horse. However, some estimates have been derived from practical experience or extrapolated from other species and there is ample opportunity for future research related to many nutrients. Equine nutritionists may also explore additional methods to express the recommended daily nutrient intakes of horses.

Technical Note: A method for determination of titanium dioxide concentration in fecal samples.

Titanium dioxide has been used as a marker for determining diet digestibility indirectly, but some authors have expressed difficulty in measuring TiO2 concentrations in fecal material. We developed an accurate and precise method to determine TiO2 concentrations in equine feces. The method includes dry-ashing samples, digestion with (NH4)2SO4 in concentrated sulfuric acid, followed by the addition of H2O2 to produce a yellow to orange color that can be read spectrophotometrically. Accuracy was tested by spike recovery, and precision was tested by examining the coefficient of variation (CV) between duplicates of 449 individual samples. The method described here was compared with a previously published method by examining CV between duplicates of samples analyzed using both methods and comparing them using a paired t-test. Titanium dioxide spike recovery averaged 106%, and the CV between duplicates averaged 4.0%, with 79% of sample pairs having a CV of <5%. When compared with a previously published method, the method described here had a lower CV between duplicates (P < 0.0001). The method described here provides an accurate and precise quantitative analytical procedure for TiO2 in equine fecal samples.

Titanium dioxide is a marker fed to animals to help determine diet digestibility indirectly by measuring the concentration of TiO2 in fecal samples. This paper describes an accurate and precise method to analyze TiO2 in equine feces. The precision of this method is demonstrated by the low variation between sample duplicates. This method requires fewer sample replicates for analysis, leading to less labor, expense, and waste in the laboratory.

Ethanol-Soluble Carbohydrates of Cool-Season Grasses: Prediction of Concentration by Near-Infrared Reflectance Spectroscopy (NIRS) and Evaluation of Effects of Cultivar and Management.

Ethanol-soluble carbohydrates (ESCs) of cool-season grasses include mono- and disaccharides and sometimes short-chain fructans, which may exacerbate the risk of pasture-associated laminitis. A calibration for prediction of ESC concentrations by near-infrared reflectance spectroscopy (NIRS) was developed from 323 samples of four cool-season grass species (orchardgrass, Kentucky bluegrass, tall fescue, and perennial ryegrass) across 10 cultivars collected in central Kentucky in the morning and afternoon over two growing seasons. The calibration, which had accuracy above 95%, was used to predict ESC concentrations of 1,532 samples from the second growing season. ESC concentrations increased in the afternoon compared to the morning across all cultivars. In the majority of samples, ESC concentrations were not affected by nitrogen application to plots. Use of NIRS has the potential to evaluate management and cultivar effects on ESC concentrations in cool-season grass pastures.

Relationships between blood and follicular fluid urea nitrogen concentrations and between blood urea nitrogen and embryo survival in mares.

High blood urea nitrogen (BUN) concentration is linked to low fertility in cows and ewes; however, this relationship has not been reported in mares. The study characterized the relationship between BUN and follicular fluid urea nitrogen (FUN) during follicle growth (Experiment 1) and the impact of BUN from embryo donors on the pregnancy outcome of recipient mares (Experiment 2). In experiment one, follicular fluid and blood samples were collected from mares during diestrus with growing follicles and during estrus with pre-ovulatory follicles (n = 16 and 10 mares, respectively). In experiment two, BUN concentrations of embryo donors were related to pregnancy outcome after embryo transfer. In experiment one, there was a strong positive correlation between BUN and FUN (R = 0.83; P < 0.0001), with higher BUN in mares with growing follicles than with preovulatory follicles (P = 0.004) and higher FUN in growing follicles than in preovulatory follicles (P = 0.031). In experiment two, BUN was higher in donor mares that produced unsuccessful embryos compared to donor mares that produced embryos resulting in successful pregnancies at D14 (P < 0.03). Additionally, there was an effect of age (P = 0.01) and interaction between age and lactation (P = 0.009) in donor mares for embryo survival after embryo transfer. Donor mares with unsuccessful embryos were older than donor mares with successful embryos. Therefore, these experiments showed that BUN was related to follicular fluid environment as well as to the survival of Day 7-8 embryos after transfer to recipient mares.

Elevated blood urea nitrogen alters the transcriptome of equine embryos.

High blood urea nitrogen (BUN) in cows and ewes has a negative effect on embryo development; however, no comparable studies have been published in mares. The aims of the present study were to evaluate the effects of high BUN on blastocoele fluid, systemic progesterone and Day 14 equine embryos. When a follicle with a mean (±s.e.m.) diameter of 25±3mm was detected, mares were administered urea (0.4g kg-1) with sweet feed and molasses (n=9) or sweet feed and molasses alone (control; n=10). Blood samples were collected every other day. Mares were subjected to AI and the day ovulation was detected was designated as Day 0. Embryos were collected on Day 14 (urea-treated, n=5 embryos; control, n=7 embryos). There was an increase in systemic BUN in the urea-treated group compared with control (P<0.05), with no difference in progesterone concentrations. There were no differences between the two groups in embryo recovery or embryo size. Urea concentrations in the blastocoele fluid tended to be higher in the urea-treated mares, with a strong correlation with plasma BUN. However, there was no difference in the osmolality or pH of the blastocoele fluid between the two groups. Differentially expressed genes in Day 14 embryos from urea-treated mares analysed by RNA sequencing were involved in neurological development, urea transport, vascular remodelling and adhesion. In conclusion, oral urea treatment in mares increased BUN and induced transcriptome changes in Day 14 equine embryos of genes important in normal embryo development.

In-Flight Emergency: A Simulation Case for Emergency Medicine Residents.

Introduction: In-flight medical emergencies are common occurrences that require medical professionals to manage patients in an unfamiliar setting with limited resources. Emergency medicine (EM) residents should be well prepared to care for patients in unusual environments such as on an aircraft. Methods: We developed a simulation case for EM residents featuring a 55-year-old male passenger who suffers a cardiac arrest secondary to a tension pneumothorax. We conducted this case eight times during a 5-hour block of scheduled simulation time. Participants included EM residents of all training levels from one residency program. We arranged the simulation lab as an airplane cabin, with rows of chairs representing airplane seats and a mannequin in a window seat as the patient. Residents were expected to manage cardiac arrest and perform needle thoracostomy on the patient. Residents also evaluated and treated a flight attendant with a near syncopal episode. Throughout the case, residents were expected to practice teamwork skills, including leadership, communication, situational awareness, and resource utilization. Participants were debriefed and completed voluntary anonymous evaluations of the session. Results: Seventeen EM residents participated in the simulation. Overall, all 17 found the simulation to be a valuable educational experience. In addition, all agreed or strongly agreed that they felt more prepared to respond to an in-flight emergency after participating in the simulation. Discussion: This simulation was determined to be a valuable part of EM resident education. The challenges presented and skills practiced in this in-flight medical emergency simulation case are transferable to other resource-limited environments.

Water-Soluble Carbohydrates of Cool-Season Grasses: Prediction of Concentrations by Near-Infrared Reflectance Spectroscopy and Evaluation of Effects of Genetics, Management, and Environment.

An excess of water-soluble carbohydrates (WSCs) can present a risk for horses prone to pasture-associated laminitis or some other metabolic conditions. Determining WSC concentrations in commonly grazed cool-season grasses, at different times of day and under different fertilization treatments, can help optimize grazing times and management strategies. The goals of this study were to develop a near-infrared reflectance spectroscopy (NIRS) calibration curve for WSC and to apply it to four cool-season grass species. Tall fescue, Kentucky bluegrass, orchardgrass, and perennial ryegrass (10 cultivars) were sampled every two to four weeks from plots with or without added nitrogen, in the morning and afternoon. WSCs were quantified colorimetrically for a sample subset, and these values were used to develop an NIRS calibration predicting WSC concentrations with 90% accuracy. An interaction of species, nitrogen treatment, time of day, and harvest date influenced WSC concentrations in 10 harvests (P = .040). A modest positive relationship was observed between photosynthetically active radiation and WSC concentration when morning and afternoon samples were included (r = 0.503; P = .024). On nine harvest dates, perennial ryegrass or tall fescue were highest in WSC. High-WSC cultivars included "Aberzest" and "Calibra" perennial ryegrass, "Ginger" Kentucky bluegrass, and "Bronson" and "Cajun II" tall fescue. Water-soluble carbohydrates did not exceed 150 g/kg freeze-dried weight, possibly due to assay method, sampling times, or defoliation. The results suggest that minimizing WSC intake for horses may be possible by cultivar choice, grazing time, or mowing frequency.

Effect of oral urea supplementation on the endometrial transcriptome of mares.

An intravenous large dose of protein led to an increased blood urea nitrogen (BUN), resulting in a lesser uterine pH and altered uterine gene expression in mares. The objective of the present study was to evaluate effects of a more physiological methodology to increase BUN on the endometrium of mares. Mares were fed hay and a treatment or control diet (n = 11 mares/treatment) in a crossover design starting at time of ovulation detection (D0) and continuing until D7. Mares of the treated group were fed urea (0.4 g/kg BW) with sweet feed and molasses, and those of the control group were fed sweet feed and molasses. Blood samples were collected daily, 1 hour after feeding, for BUN determination. Uterine and vaginal pH were determined after the last feeding on D7, and endometrial biopsies were performed. The RNA sequencing of the endometrium of a subset of mares (n = 6/treatment) was conducted. Differentially expressed genes (DEGs) between treatments were calculated (FDR-adjusted P-value<0.1). Urea-treated mares had greater BUN (P < 0.05), with no differences in uterine and vaginal pH compared to control mares. A total of 60 DEGs were characterized, those with largest fold change were SIK1, ATF3, SPINK7, NR4A1 and EGR3. Processes related to necrosis and cellular movement were predicted with the DEGs. Dietary administration of urea resulted in transcriptomic changes in the endometrium of mares related to necrosis, tissue remodeling and concentration of lipids. The observed changes in gene expression after an increased BUN might result in a disruption to the endometrium.

Relationships Between Measurements of Body Fat in Thoroughbred Horses.

Equine obesity is increasing in prevalence, and weight loss diets are frequently recommended for these horses. However, there are also management situations in which horses are deemed to be too thin. To monitor the efficacy of weight change programs, estimates of body fat are often made. There are several systems available to estimate body fat, and there are benefits and challenges to using each method. The objective of this study was to compare four different methods of estimating body fat in Thoroughbred horses. In 14 mature Thoroughbred horses, relationships among body condition score (BCS), morphometric measurements, ultrasonic measures of subcutaneous fat depots, and estimation of total body fat (BFD) via measurement of total body water through deuterium oxide dilution were evaluated. Body condition scores ranged from 4.5 to 6.5 on a 9-point scale. Body condition score, heart girth-to-body weight ratio, and BFD were all positively correlated with each other (P < .05). Subcutaneous fat depth at the tailhead tended to be positively related to BFD when only horses with BCS ≥ 5 were included (P = .0680). These data suggest that BCS remains a simple means of monitoring adiposity in mature horses in moderate condition. Tailhead fat depots may become useful for monitoring changes in body fat in Thoroughbreds with a BCS above 5, although more work with animals of higher adiposity is required and at different times of year.

Phosphorus excretion by mares post-lactation.

Across the equine literature, estimates of true P digestibility range from -23% to 79%. This large range cannot be explained by differences in P intake or phytate-P intake alone. However, differences in endogenous P secretion into the GI tract may explain the variation. In horses, excess absorbed P is not excreted in the urine but is re-secreted into the GI tract, increasing faecal P and leading to estimates of low P digestibility. Thus, accurate estimates of P digestibility can only be obtained if absorbed P is retained in the horse. The objective of this study was to examine P digestibility in post-lactational mares and control mares that were fed similar amounts of P. It was hypothesized that post-lactational mares would have greater P retention and higher apparent P digestibility than control mares. Prior to the study, four lactating and four non-lactating mares were fed a diet that provided 100% of the control mares' P requirement, but only 55% of the lactating mares' P requirement. During the study, both groups were fed P at the rate recommended for non-lactating mares. Post-lactational mares did not retain more P than control mares but tended to excrete more P than control mares (p = .082), presumably due to differences in endogenous P secretion into the GI tract. Metabolic changes occurring during mammary gland involution may have contributed to the increase in P excretion. However, faecal P excretion exceeded P intake in both groups (p = .08) and both groups lost weight during the study. Tissue mobilization during weight loss may have influenced P secretion into the GI tract.

Seasonal and Diurnal Variation in Water-Soluble Carbohydrate Concentrations of Repeatedly Defoliated Red and White Clovers in Central Kentucky.

Nonstructural carbohydrates of pasture plants, comprising water-soluble carbohydrates (WSCs) and starch, may contribute to excessive consumption of rapidly fermentable carbohydrates by grazing horses. Seasonal and diurnal variation in WSCs were studied in red (Trifolium pratense L.) and white clovers (Trifolium repens L.) subjected to a typical management regime of rotationally grazed horse pastures. Two red and two white clover cultivars from monoculture plots were harvested after 4 weeks of growth from April to October of 2015, in the morning and afternoon of each harvest date. Water-soluble carbohydrates were quantified for each harvest, and starch was quantified for two harvests. Mean monthly WSC concentrations ranged from 80 to 99 mg/g (freeze-dried weight basis), whereas mean starch concentrations were 31 and 40 mg/g. In September, white clover had 14% more WSCs than red clover (P < .0001). Water-soluble carbohydrate concentrations were 10% higher in the afternoon than in the morning (P < .0001). Starch concentrations were 290% higher in the afternoon than in the morning (P < .0001), and nonstructural carbohydrate concentrations in the afternoon averaged 150 mg/g. Further studies are needed to determine whether the mixed grass-legume pastures of central Kentucky accumulate enough nonstructural carbohydrates to present risk factors for equine metabolic or digestive dysfunction.

Effects of Harvest Date, Sampling Time, and Cultivar on Total Phenolic Concentrations, Water-Soluble Carbohydrate Concentrations, and Phenolic Profiles of Selected Cool-Season Grasses in Central Kentucky.

Grasses are a source of nutrients for grazing horses. However, water-soluble carbohydrates (WSCs) of grasses have been implicated in some equine health issues. Grasses also contain phenolic compounds, whose sensory and antimicrobial properties may affect forage intake by horses and horse health. The goals of this study were to assess factors affecting phenolic and WSC concentrations in selected cultivars of cool-season grasses and profile the phenolic compounds. Total phenolics and WSC were quantified in "Linn" and "Calibra" perennial ryegrass (PRG), "Cajun II" tall fescue (Cajun TF), "Persist" orchardgrass (OG), and "Ginger" Kentucky bluegrass (BG), collected in the morning and afternoon of late April, early May, and late May. WSCs were higher in the afternoon (P < .0001), and afternoon concentrations differed among cultivars (P = .011) and decreased by late May (P < .0001). Total phenolics, initially highest in Calibra PRG and Persist OG, decreased or remained constant from late April to late May, except in Persist OG (P < .0001). Total phenolics decreased in the afternoon in Persist OG and Calibra PRG (P = .015). High-performance liquid chromatography revealed similar phenolic profiles in Calibra PRG, Linn PRG, and Cajun TF. These differed from the profiles of Ginger BG and Persist OG. Major peaks were characterized by liquid chromatography coupled to mass spectrometry. The cultivars had a diversity of phenolic compounds possibly worth exploring for properties that may interact with those of WSC to impact equine health.

A High Protein Model Alters the Endometrial Transcriptome of Mares.

High blood urea nitrogen (BUN) decreases fertility of several mammals; however, the mechanisms have not been investigated in mares. We developed an experimental model to elevate BUN, with urea and control treatments (7 mares/treatment), in a crossover design. Urea-treatment consisted of a loading dose of urea (0.03 g/kg of body weight (BW)) and urea injections over 6 hours (0.03 g/kg of BW/h). Control mares received the same volume of saline solution. Blood samples were collected to measure BUN. Uterine and vaginal pH were evaluated after the last intravenous infusion, then endometrial biopsies were collected for RNA-sequencing with a HiSeq 4000. Cuffdiff (2.2.1) was used to identify the differentially expressed genes (DEG) between urea and control groups (false discovery rate-adjusted p-value < 0.1). There was a significant increase in BUN and a decrease of uterine pH in the urea group compared to the control group. A total of 193 genes were DEG between the urea and control groups, with five genes identified as upstream regulators (ETV4, EGF, EHF, IRS2, and SGK1). The DEG were predicted to be related to cell pH, ion homeostasis, changes in epithelial tissue, and solute carriers. Changes in gene expression reveal alterations in endometrial function that could be associated with adverse effects on fertility of mares.

Effect of Starch Source in Pelleted Concentrates on Fecal Bacteria in Prepartum and Postpartum Mares.

Dietary starch source has been shown to affect fecal bacterial communities of horses fed minimally processed cereal grains. However, processing may increase foregut starch digestibility, reducing effects of starch source on fecal bacterial communities. This study aimed to determine the effect of starch source in pelleted concentrates on fecal Lactobacillus spp., amylolytic bacteria, and cellulolytic bacteria in broodmares mares, during the prepartum and postpartum period. Thoroughbred mares (n = 18) were paired by last breeding date then randomly assigned to either an oat-based or a corn and wheat middlings-based pelleted concentrate fed with forage. Mares were fed their assigned concentrates beginning on 310 days of gestation, and fecal samples were collected at 324 days of gestation, before parturition, 1 day, 14 days, and 28 days postpartum. Fecal samples were enumerated by serial dilution and inoculation into selective, enriched media for Lactobacillus spp., amylolytic bacteria, and cellulolytic bacteria. Data were log transformed then analyzed using a mixed model ANOVA with repeated measures (SAS 9.3) to test the main effects of treatment, time of sample, and treatment by time interaction. Starch source did not affect enumerated bacterial communities (P > .05); thus, pelleting concentrates may alter some of the effects of starch sources on the hindgut microbiota. Sample date did not affect amylolytic bacteria (P > .05); however, lactobacilli and cellulolytic bacteria decreased 1 day postpartum (P < .05). Although we did not observe an effect of starch source on fecal bacteria in mares, parturition did appear to alter the hindgut microbiota.

Effect of maternal diet on select fecal bacteria of foals.

Adult horses depend on the microbial community in the hindgut to digest fiber and produce short-chain fatty acids that are use for energy. Colonization of the foal gastrointestinal tract is essential to develop this symbiosis. However, factors affecting colonization are not well understood. The objectives of this study were to evaluate the age-related changes and effects of maternal diet on select fecal bacterial groups in foals from 1 to 28 d of age. Thoroughbred foals (n = 18) were from dams fed forage and one of two concentrates: an oat-based (OB) or corn and wheat middlings-based (CWB) pelleted concentrate. The mares had access to assigned concentrates, along with a mixed hay and cool-season grass pasture, 28 d before and 28 d after parturition. Fecal samples were collected from foals at 1 d (14 to 36 h), 4, 14, and 28 d after birth. Fecal samples were serially diluted with phosphate-buffered saline before inoculation of enriched, selective media to enumerate Lactobacillus spp., amylolytic bacteria, and cellulolytic bacteria. Enumeration data were log-transformed then analyzed with mixed model analysis of variance with repeated measures (SAS 9.3) to test the main effects of maternal diet (OB or CWB), time of sample, and interaction between maternal diet and time. Cellulolytic bacteria first appeared in foal feces between 4 and 14 d of age and increased with age (P < 0.05). Amylolytic bacteria and lactobacilli were abundant at 1 d and then increased with age (P < 0.05). There was an interaction between maternal diet and time for Lactobacillus spp. with OB foals having more lactobacilli than CWB foals at 1 and 4 d (P < 0.05); however, there were no differences observed at 14 d (P > 0.05). Maternal diet did not influence amylolytic or cellulolytic bacteria (P > 0.05). These results indicate that colonization of the hindgut is a sequential process beginning early in the foal's life and that maternal diet may influence some bacteria in the gastrointestinal tract of foals.

Exogenous lactobacilli mitigate microbial changes associated with grain fermentation (corn, oats, and wheat) by equine fecal microflora ex vivo.

Cereal grains are often included in equine diets. When starch intake exceeds foregut digestion starch will reach the hindgut, impacting microbial ecology. Probiotics (e.g., lactobacilli) are reported to mitigate GI dysbioses in other species. This study was conducted to determine the effect of exogenous lactobacilli on pH and the growth of amylolytic and lactate-utilizing bacteria. Feces were collected from 3 mature geldings fed grass hay with access to pasture. Fecal microbes were harvested by differential centrifugation, washed, and re-suspended in anaerobic media containing ground corn, wheat, or oats at 1.6% (w/v) starch and one of five treatments: Control (substrate only), L. acidophilus, L. buchneri, L. reuteri, or an equal mixture of all three (107 cells/mL, final concentration). After 24 h of incubation (37°C, 160 rpm), samples were collected for pH and enumerations of total amylolytics, Group D Gram-positive cocci (GPC; Enterococci, Streptococci), lactobacilli, and lactate-utilizing bacteria. Enumeration data were log transformed prior to ANOVA (SAS, v. 9.3). Lactobacilli inhibited pH decline in corn and wheat fermentations (P < 0.0001). Specifically, addition of either L. reuteri or L. acidophilus was most effective at mitigating pH decline with both corn and wheat fermentation, in which the greatest acidification occurred (P < 0.05). Exogenous lactobacilli decreased amylolytics, while increasing lactate-utilizers in corn and wheat fermentations (P < 0.0001). In oat fermentations, L. acidophilus and L. reuteri inhibited pH decline and increased lactate-utilizers while decreasing amylolytics (P < 0.0001). For all substrates, L. reuteri additions (regardless of viability) had the lowest number of GPC and the highest number of lactobacilli and lactate-utilizers (P < 0.05). There were no additive effects when lactobacilli were mixed. Exogenous lactobacilli decreased the initial (first 8 h) rate of starch catalysis when wheat was the substrate, but did not decrease total (24 h) starch utilization in any case. These results indicate that exogenous lactobacilli can impact the microbial community and pH of cereal grain fermentations by equine fecal microflora ex vivo. Additionally, dead (autoclaved) exogenous lactobacilli had similar effects as live lactobacilli on fermentation. This latter result indicates that the mechanism by which lactobacilli impact other amylolytic bacteria is not simple resource competition.

Effect of Dietary Starch Source and Concentration on Equine Fecal Microbiota.

Starch from corn is less susceptible to equine small intestinal digestion than starch from oats, and starch that reaches the hindgut can be utilized by the microbiota. The objective of the current study was to examine the effects of starch source on equine fecal microbiota. Thirty horses were assigned to treatments: control (hay only), HC (high corn), HO (high oats), LC (low corn), LO (low oats), and LW (low pelleted wheat middlings). Horses received an all-forage diet (2 wk; d -14 to d -1) before the treatment diets (2 wk; d 1 to 14). Starch was introduced gradually so that horses received 50% of the assigned starch amount (high = 2 g starch/kg BW; low = 1 g starch/kg BW) by d 4 and 100% by d 11. Fecal samples were obtained at the end of the forage-only period (S0; d -2), and on d 6 (S1) and d 13 (S2) of the treatment period. Cellulolytics, lactobacilli, Group D Gram-positive cocci (GPC), lactate-utilizers and amylolytics were enumerated. Enumeration data were log transformed and analyzed by repeated measures ANOVA. There were sample day × treatment interactions (P < 0.0001) for all bacteria enumerated. Enumerations from control horses did not change during the sampling period (P > 0.05). All treatments except LO resulted in increased amylolytics and decreased cellulolytics, but the changes were larger in horses fed corn and wheat middlings (P < 0.05). Feeding oats resulted in increased lactobacilli and decreased GPC (P < 0.05), while corn had the opposite effects. LW had increased lactobacilli and GPC (P < 0.05). The predominant amylolytic isolates from HC, LC and LW on S2 were identified by 16S RNA gene sequencing as Enterococcus faecalis, but other species were found in oat fed horses. These results demonstrate that starch source can have a differential effect on the equine fecal microbiota.