Topic:Hindgut
The hindgut of horses is a critical component of their digestive system, responsible for the fermentation of fibrous plant materials. It consists primarily of the cecum and colon, where a complex community of microorganisms breaks down cellulose and other fibers into volatile fatty acids, which are then absorbed as a significant energy source for the horse. The hindgut also plays a role in water absorption and the synthesis of certain vitamins. Disruptions in hindgut function can lead to digestive disorders such as colic or laminitis. This page gathers peer-reviewed research studies and scholarly articles that explore the anatomy, function, and health implications of the equine hindgut, as well as management practices to maintain its optimal function.
In vitro analysis of the effect of supplementation with activated charcoal on the equine hindgut. The present study uses in vitro analytical techniques to investigate the effect of activated charcoal on the microbial community of the equine hindgut and the metabolites they produce. Incubations were performed in Wheaton bottles using a 50 ml incubation of a high-energy feed or a low-energy feed, plus bottles with no added food source, together with five levels of activated charcoal (0, 10, 25, 50 or 100 mg per bottle) and fecal samples as a bacterial inoculum. Using this method the rate of gas production, volatile fatty acid and ammonia concentrations, and pH values were analyzed and found ...
Equids. Alongside domestic horses and donkeys, the horse family, also known as equids, comprises six extant wild species of asses and zebras (Figure 1). Equids are extremely well represented in the fossil record, comprising a 55 million-year evolutionary history, punctuated by many episodes of innovation, extinction and migration. Limited to the single genus Equus today, in the Miocene (23.0–5.3 million years ago) the equid family flourished, comprising more than twenty genera. The group originated in Northern America, where the earliest fossil forms have been found, the so-called Hyracotheres, no l...
Impact of barley form on equine total tract fibre digestibility and colonic microbiota. This study aimed at assessing the impact of four barley forms on total tract apparent digestibility of dietary fibre in horses fed a large amount of starch in the morning meal (0.27% BW). Processed barley forms had a greater pre-caecal starch digestibility than the whole form. Based on this result, we hypothesised that using barley-processing methods would limit the potential dumping of undegraded starch in the hindgut of horses and, consequently, the potential negative effect on fibre degradation in the hindgut. In a 4×4 latin square design, four mature geldings fitted with a right ventral c...
In vitro simulation of the equine hindgut as a tool to study the influence of phytosterol consumption on the excretion of anabolic-androgenic steroids in horses. Traditionally, steroids other than testosterone are considered to be synthetic, anabolic steroids. Nevertheless, in stallions, it has been shown that β-Bol can originate from naturally present testosterone. Other precursors, including phytosterols from feed, have been put forward to explain the prevalence of low levels of steroids (including β-Bol and ADD) in urine of mares and geldings. However, the possible biotransformation and identification of the precursors has thus far not been investigated in horses. To study the possible endogenous digestive transformation, in vitro simulations of t...
Comparison of the bacterial community structure within the equine hindgut and faeces using Automated Ribosomal Intergenic Spacer Analysis (ARISA). The horse's hindgut bacterial ecosystem has often been studied using faecal samples. However few studies compared both bacterial ecosystems and the validity of using faecal samples may be questionable. Hence, the present study aimed to compare the structure of the equine bacterial community in the hindgut (caecum, right ventral colon) and faeces using a fingerprint technique known as Automated Ribosomal Intergenic Spacer Analysis (ARISA). Two DNA extraction methods were also assessed. Intestinal contents and faeces were sampled 3 h after the morning meal on four adult fistulated horses fed mea...
Inhibition of fructan-fermenting equine faecal bacteria and Streptococcus bovis by hops (Humulus lupulus L.) β-acid. The goals of this study were to determine if β-acid from hops (Humulus lupulus L.) could be used to control fructan fermentation by equine hindgut micro-organisms, and to verify the antimicrobial mode of action on Streptococcus bovis, which has been implicated in fructan fermentation, hindgut acidosis and pasture-associated laminitis (PAL) in the horse. Results: Suspensions of uncultivated equine faecal micro-organisms produced fermentation acids when inulin (model fructan) was the substrate, but β-acid (i.e. lupulone) concentrations ≥9 ppm inhibited lactate production and mitigated the d...
Effect of grass hay intake on fiber digestion and digesta retention time in the hindgut of horses. Eight Thoroughbred horses were used to examine the effects of grass hay intake on the fiber digestion and the retention time of digesta in the total gastrointestinal tract and the hindgut segments. The horses were randomly assigned to 2 groups and offered 2.0 (high intake [HI]) or 1.3 kg DM/(100 kg BW • d; low intake [LI]) of timothy hay in equal amounts every 3 h for 17 d. The digestibility and total tract mean retention time of digesta (tMRT) in the total gastrointestinal tract were measured from d 11 to d 15. To measure the mean retention time of digesta in each hindgut segment (sMRT), th...
Feed restriction enhances the depressive effects of erythromycin on equine hindgut microbial metabolism in vitro. Equine typholocolitis is a sporadic diarrheal disease causing high mortality rates. One of the risk factors responsible for this is the oral application of the macrolide antibiotic erythromycin. The aim of the present in vitro study was to investigate whether erythromycin in combination with feed restriction provokes changes in microbial hindgut metabolism and could therefore be involved in the pathogenesis of equine typhlocolitis. As application of erythromycin and feed restriction are risk factors for equine typhlocolitis, both factors were chosen to investigate their individual and combined...
A comparison of the microbiome and the metabolome of different regions of the equine hindgut. The microbiome and associated metabolome of faecal samples were compared to those from the caecum and right dorsal colon of horses and ponies euthanised for nonresearch purposes by investigating the microbial population community structure as well as their functional metabolic products. Through the use of 16S rRNA gene dendrograms, the caecum microbiome was shown to cluster separately from the other gut regions. 16S rRNA gene-based quantitative PCR (q-PCR) also demonstrated differences between the caecum and the other gut regions. Metabolites as identified by Fourier transform infrared cluster...
[Occurence of the hindgut ciliates Paraisotricha colpoidea and P. minuta (Ciliophora: Paraisotrichidae) in horses in Turkey]. The aim of this study was to determine the cytological features of 2 endocommensal ciliates, P. colpoidea and P. minuta belonging to genus Paraisotricha found in the hindgut of 15 Turk rahvan and 15 English and Arabic horses from Izmir, compare the morphological characters of species with their original descriptions and previous reports and discuss the similarities and differences. Methods: The cytological features of two endocommensal ciliates were investigated with the pyridinated silver carbonate impregnation and silver nitrate impregnation techniques at the level of light microscopy. Resul...
Fermentation of six different forages in the semi-continuous fermentation technique Caesitec. The aim of the present study was to compare carbohydrate degradation of forages which store carbohydrates either predominantly as fructan or starch, in horses' hindgut. The effects of an abrupt change from hay-based feeding to green fodder-based feeding on the caecal flora were tested with the in vitro hindgut simulation technique 'Caesitec'. Six trials with different forages (English ryegrass, tall fescue, grass mixture-horses, grass mixture-cows, lucerne, white clover) were conducted. During a 4-day stabilisation period, samples were taken once a day before loading the fermenters with hay. A...
Investigation of the effect of pasture and stable management on large intestinal motility in the horse, measured using transcutaneous ultrasonography. Management regimes have been identified as risk factors for equine intestinal motility disorders. However, it is not known how management factors affect gastrointestinal motility. Objective: Large intestinal motility was similar in horses on a stabled and a pastured management regime. Objective: To investigate the effect of 2 different management regimes on large intestinal motility assessed with ultrasonography. Methods: A within-subjects crossover design was used to compare large intestinal motility between a stabled and a pastured regime in 16 working horses. Group A was managed under a sta...
Understanding the equine cecum-colon ecosystem: current knowledge and future perspectives. Having evolved as a grazing animal, a horse's digestive physiology is characterized by rapid gastric transit, a rapid but intense enzymatic digestion along the small intestine, and a long and intense microbial fermentation in the large intestine. The process of understanding and describing feed degradation mechanisms in the equine digestive system in general, and in the hindgut ecosystem in particular, is essential. Regardless of its importance for the nutritional status of the host, the significance of the cecum-colon ecosystem has not yet been fully understood, and few reports have focused d...
Microbial events in the hindgut during carbohydrate-induced equine laminitis. Equine laminitis is the most serious foot disease of the horse, often resulting in death or euthanasia. Laminitis has long been recognized as an affliction of horses, as has the association of this condition with the ingestion of carbohydrates. Research into the pathophysiology of this condition has been facilitated by the development of reliable models for experimentally inducing laminitis, and DNA-based techniques for profiling complex microbiomes have dramatically increased the knowledge of the microbiology of this disease. Recent studies have provided substantial evidence showing equine hi...
Medial collateral ligament desmitis of the distal interphalangeal joint in the hindlimb of a horse: treatment with cast immobilisation. A 12-year-old show-jumping mare was presented for investigation of a chronic hindlimb lameness of 16 weeks duration. Perineural anaesthesia and ultrasonography localised the lesion to the medial collateral ligament of the distal interphalangeal joint of the left hindlimb. Treatment consisted of a heavily padded distal limb cast for 6 weeks, strict box rest and a strictly regulated hand walking program. Serial ultrasonographic examinations were performed throughout the rehabilitation period. Collateral ligament desmitis of the distal interphalangeal joint is a commonly diagnosed condition of th...
The bacterial community of the horse gastrointestinal tract and its relation to fermentative acidosis, laminitis, colic, and stomach ulcers. The gastrointestinal tract of the horse has unique characteristics that make it well suited for the ingestion and utilization of roughage. The horse is considered a simple-stomached herbivore and is classed as a hindgut fermenter. The upper segments of the gastrointestinal tract resemble those of a typical simple-stomached animal. The lower have undergone modification to become voluminous and host to a large number of microbial populations similar to those of the compartmental stomach of ruminant animals. The main advantage of this arrangement is the ability of the horse to extract valuable nu...
Morphometric data on the accessory ligament of the deep digital flexor tendon in the equine hindlimb. Desmopathy of the accessory ligament of the deep digital flexor tendon (ALDDFT) in the hindlimb has recently been described as a cause of lameness in horses. However, there is limited morphometric data on this ligament. In the present study, the ALDDFT was carefully dissected in 165 hindlimbs that were collected from an abattoir. Length, width (lateral-to-medial) and thickness (plantar-to-dorsal) of the ligament were measured. It was found that the ALDDFT may be absent in a minority of horses, but when it was present the general morphology was variable. The ALDDFT can be a single rectilinear s...
The role of nutrition in colic. Nutritional intolerances manifesting as colic in the horse may be largely explained by divergence from the diet and ingestive behaviors to which the feral ancestors of modern domesticated equids had become accustomed and adapted. High-starch diets and abrupt dietary changes are probably foremost in the risk factors for diet-associated colic in the horse and have their basis in disruption of the stability of microbial populations resident within the equine hindgut. Although some general associations between colic and diet may be inferred from several epidemiologic studies, data derived from stu...
Use of kinetic gait analysis for detection, quantification, and differentiation of hind limb lameness and spinal ataxia in horses. To evaluate use of kinetic gait analysis for detection, quantification, and differentiation of hind limb lameness and spinal ataxia in horses. Methods: Prospective clinical study. Methods: 36 horses. Procedures-Kinetic gait analysis with a force plate was performed for 12 clinically normal horses, 12 horses with hind limb lameness, and 12 horses with spinal ataxia. Kinetic variables were compared among groups, correlated to subjective grading, and used to build predictive models to assess the accuracy of discrimination. Results: Subsets of kinetic variables were characteristically altered in a...
Fluorescence in situ hybridization analysis of hindgut bacteria associated with the development of equine laminitis. Carbohydrate-induced laminitis in horses is characterized by marked changes in the composition of the hindgut microbiota, from a predominantly Gram-negative population to one dominated by Gram-positive bacteria. The objective of this study was to monitor changes in the relative abundance of selected hindgut bacteria that have previously been implicated in the pathophysiology of equine laminitis using fluorescence in situ hybridization (FISH). Caecal cannulae were surgically implanted in five Standardbred horses and laminitis induced by oral administration of a bolus dose of oligofructose. Caec...
Gastrointestinal derived factors are potential triggers for the development of acute equine laminitis. Equine laminitis is the painful and debilitating condition resulting from cellular damage and inflammation of the tissues comprising the bonds supporting the pedal bone within the hoof capsule. One of the reasons why this condition is so complicated and enigmatic is its association with gastrointestinal disturbances, particularly a diet of lush grass at certain times of the year. Determining the link between disturbances to the hindgut flora and pathophysiology in the foot is one of the keys to preventing this condition. Therefore, one of the biggest challenges in equine laminitis research is ...
The effects of vasoactive amines found in the equine hindgut on digital blood flow in the normal horse. Disturbances of digital blood flow are thought to be fundamental to the pathophysiology of acute laminitis. However, factors linking the initiating events in the equine hindgut with these disturbances in the foot remain to be determined. Objective: Amine compounds, formed by bacteria in the equine hindgut, have digital vasoconstrictor effects in vivo. Methods: Tryptamine (1.6 microg/kg/min) and phenylethylamine (2.13 microg/kg/min) were infused i.v. into standing nonsedated horses. Digital blood flow was measured by Doppler ultrasound and foot surface temperature was monitored. Plasma 5-hydrox...
Effects of hay intake and feeding sequence on variables in faeces and faecal water (dry matter, pH value, organic acids, ammonia, buffering capacity) of horses. To investigate effects of hay intake and feeding sequence on indicators of the microbial activity within the hindgut, six horses were fed 1.00 kg oats plus 0.50, 0.67, 0.83 or 1.00 kg hay/100 kg body weight (BW) x day, each for 14 days. Oats was offered either 30 min prior to hay (OA) or in the reversed sequence (HA) in a 2 x 8-week crossover design. Because typically exercised horses should be subjected to the study, faeces was used as substrate. Faecal dry matter (DM), the faecal waters' short-chain fatty acids (SCFA, in mmol/1) and molar percentages (mol%) of propionate and iso-butyrate wer...
Identification of equine cecal bacteria producing amines in an in vitro model of carbohydrate overload. Acute laminitis has been associated with the overgrowth of gram-positive bacteria within the equine hindgut, causing the release of factor(s) leading to ischemia-reperfusion of the digits. The products of fermentation which trigger acute laminitis are, as yet, unknown; however, vasoactive amines are possible candidates. The objectives of this study were to use an in vitro model of carbohydrate overload to study the change in populations of cecal streptococci and lactobacilli and to establish whether certain species of these bacteria were capable of producing vasoactive amines from amino acids....
Identification and quantification of amines in the equine caecum. Acute laminitis has been associated with the release of compounds, as yet unidentified, produced by hindgut fermentation which affect blood flow to the digit. The objectives of this study were to identify amine compounds in equine caecal and colonic contents, some of which are known to have vasoactive properties. In addition, the concentrations of amines in caecal contents of horses fed either grass or hay diets were compared. Fifteen amines were identified in equine hindgut contents in concentrations greater than 1 microM. The caecal concentrations of phenylethylamine, isoamylamine, cadaverin...
Functional morphology of the equine pelvic flexure and its role in disease. A review. The hindgut is the major site in the horse for nutrient digestion and absorption. Most of this activity occurs in the large intestinal compartments, i.e., cecum, right and left ventral colon and left and right dorsal colon. The colonic pelvic flexure is a short and narrow loop connecting the left ventral and left dorsal colon. It is not significant directly in digestive and absorptive processes but plays an important functional role in regulating colonic aboral and retropropulsive transit of digesta through its motility pacemaker activity. The pelvic flexure also contributes to the pathophysio...
The effect of dietary fibre on hydration status after dehydration with frusemide. Three diets were fed to 6 horses in a 3 x 6 Latin rectangle experiment to determine if dietary fibre could improve hydration status in response to dehydration with frusemide. Frusemide was used to simulate dehydration from exercise-induced sweat loss. Diets contained similar dry matter (DM), energy, protein and electrolyte content, but differed in total dietary fibre (TDF) and/or soluble fibre (SDF). The 3 diets were: 1) HIGH-HIGH (high TDF, high SDF); 2) HIGH-LOW (high TDF, low SDF); and 3) LOW-LOW (low TDF, low SDF). In each 10 day period, water intake and faecal moisture content were assess...
Abnormal bone scan findings of the equine ischial tuberosity and third trochanter. Obtaining high-quality radiographs of the proximal aspect of equine limbs is difficult because of the large muscles in these regions. The use of scintigraphy may provide further information. Abnormal bone scan findings of the ischial tuberosity or the third trochanter were found in 29 adult horses with obscure hind limb lameness between 1986 and 1996 at the Large Animal Clinic of the University of Bern. Each had abnormal radiopharmaceutical uptake but not all had radiographic changes. Radiopharmaceutical uptake ratios between the ischial tuberosity and the greater trochanter were calculated. T...
Methanogenesis in monogastric animals. Studies of methanogenic bacteria present in monogastric animals are still scarce. Methanogens have been isolated from faeces of rat, horse, pig, monkey, baboon, rhinoceros, hippopotamus, giant panda, goose, turkey and chicken. The predominant methanogen in all except the chicken and turkey is species of Methanobrevibacterium. The chicken and turkey harbour species of Methanogenium. In pig the population of methanogenic bacteria is more than 30 times as dense in the distal colon as in the caecum. This finding is in agreement with the finding that the rate of methane production is much higher in...