Gastrointestinal health in horses encompasses the study of the structure, function, and disorders of the equine digestive system. The equine gastrointestinal tract is complex, consisting of the stomach, small intestine, cecum, and large intestine, each playing a specific role in digestion and nutrient absorption. Research in this area often focuses on common disorders such as colic, gastric ulcers, and parasitic infections, which can impact a horse's overall health and performance. Investigations examine factors affecting gastrointestinal health, including diet, management practices, and the microbiome. This page compiles peer-reviewed research studies and scholarly articles that explore the physiology, pathology, and management of gastrointestinal health in horses.
Roberts MC, Kidder DE, Hill FW.Two enzymes having lactase activity are present in the equine small intestine. The first, the digestive enzyme, neutral beta-galactosidase, declines in activity from birth to three years, disappearing completely between 3 and 4 years of age. The other, the soluble lysosomal enzyme, acid beta-galactosidase, having affinity for lactose and a synthetic beta-galactoside, shows a decrease in activity in the first three months of life and thereafter varies little in activity and represents the lactase enzyme in the adult horse. This pattern may parallel the development of lactase activity in many ot...
Phaneuf LP, Grivel ML, Ruckebusch Y.The electrical potentials were recorded from the antrum, the duodenum, the ileum and the first part of the colon of ponies under (a) normal resting conditions, (b) during nonpainful colic and (c) after intravenous morphine administration. The normal pony, at rest, had five contractions of the antrum per minute. On the small intestine, the basal electrical activity decreased from the duodenum (14-15/min) to the ileum (10-11/min). The small bowel also had three types of motility: peristaltic waves, rhythmic segmentations and random contractions. On the colon, bursts of potentials indicating inte...
Schryver HF, Hintz HF, Craig PH, Hogue DE, Lowe JE.The site of phosphorus absorption was studied by comparing the absorption of 32P placed directly into the cecum of fistulated ponies, with that absorbed from an intragastric dose and by estimating apparent absorption in different areas of the intestinal tract of ponies using Cr2O3 as an unabsorbable marker. There was no difference in the absorption of 32P following gastric or cecal administration indicating that phosphorus may be absorbed from the large intestine. The Cr2O3/nutrient ratio technique indicated that phosphorus was secreted into the upper half of the small bowel and that a nearly ...
Wolf P, Kamphues J.Nutritional disorders in domestic or pet animals depend not seldom on special situations, for example when different influences coincide concerning keeping, housing and offering of feed or water. These lead suddenly to high-risk situations, that can cause sometimes the death of the animal. The following case report deals with two ponies, that were kept on a so-called "petting zoo" and showed repeatedly colic symptoms (always after a weekend). During surgery in the stomach light yellow balls were found, that can be explained by ingestion of 1.0 to 1.5 kg wheat. This cereals consist--depending o...
Hansen TL, Bobel JM, Rankins EM, Sanchez LC, Warren LK.Digesta retention time within specific segments of the equine gastrointestinal tract (GIT) may be more relevant to scientific inquiries than total tract mean retention time (TTMRT); however, measuring retention time in individual segments requires access to the digestive tract. The objective of this study was to compare prececal, cecal, and colonic mean retention time (MRT) with model-derived compartment MRT. A cecally fistulated gelding was fed indigestible particulate and liquid markers to determine TTMRT and dosed with different pairs of particulate and liquid markers into the cecum (hindgu...
Wellard L, Medyk K, Pearson W.Feed additives that accelerate gastrointestinal transit time may help support normal gastrointestinal function in horses at risk for impaction colic. Previous research has demonstrated significant stimulatory effect of a hemp-based nutraceutical product (Gs Formula; GF) on contractility of gastric smooth muscle and gastrin production in vitro. Objective: To quantify effects of GF on indicators of GIT transit time and tight junction proteins. Methods: Randomized placebo-controlled cross-over study. Methods: Eight Standardbreds were administered 200 plastic beads by nasogastric tube before (base...
Shibahara T, Kuwano A, Ueno T, Anzai T, Kuwamoto Y, Sato H, Maeda T, Ishikawa Y, Kadota K.A 21-month-old Thoroughbred colt showed continuous diarrhea and developmental retardation for 7 months, and was thereafter subjected to euthanasia for necropsy and laboratory examinations. At necropsy, the cecal and colonic mucosae were diffusely rough and hyperemic. Histopathologically, the mucosa and submucosa were edematous and were infiltrated by numerous lymphocytes and macrophages. Meanwhile, three morphological types of Brachyspira antigen-containing spirochetes were found to be numerous in the crypts and in the mucus layer over the epithelium in the cecal and colonic lesions. They were...
Bertone AL, Cockerell GL, Lee RE, Stashak TS.Light microscopy, morphometry, and scanning electron microscopy were used to examine the mucosal morphologic features of 7 intestinal specimens (3 from the small intestine; 4 from the large intestine) from each of 8 horses 1 year after sham operation (group 1; n = 3) or extensive large-colon resection (group 2; n = 5). Qualitative light microscopic examination did not reveal differences between groups, but morphometry revealed significantly (P less than 0.05) greater intercrypt area and distance in horses with colon resection and this was most pronounced in the cecum and remaining right ventra...
Takehana K, Abe M, Iwasa K, Hiraga T.Complex carbohydrates were examined in glandular cells of the horse duodenal gland by using lectin histochemical techniques. In the horse, the duodenal gland was distributed in the area from the uppermost part of the small intestine to a point about 6m caudal to the pylorus. It consisted of two types of cells, mucous and serous cells. The former was found in glands distributed almost all over this part, but the latter was present in glands distributed restrictedly to the uppermost part of the small intestine at a point about 10 cm caudal to the pylorus. The cytoplasm of the mucous cell contain...
Viljoen A, Saulez MN, Carstens A, Gummow B.Clinical use of diagnostic ultrasound at point-of-care or emergency situations, although common, has not been well documented in veterinary medicine. Medical records of after-hour emergency equine admissions during a 10-year period were reviewed and horses that received ultrasound scans were identified. Data sheets for each ultrasound scan performed during emergency clinical evaluation were collected and reviewed. Data extracted included anatomical region imaged, body system affected, documented ultrasonographic diagnosis and final diagnosis. Six hundred and nine records were available of whic...
Sandin A, Girma K, Sjöholm B, Lindholm A, Nilsson G.Plasma gastrin concentrations were determined in 6 Standardbreds (4 geldings and 2 mares) after 3 different meals consisting of unlimited amounts of hay (8-9 kg per horse), a restricted amount of hay (0.6 kg/100 kg body-weight) and grain (0.2 kg/100 kg body-weight) in combination or of grain alone (0.2 kg/100 kg body-weight). In another series of experiments the possible role of gastrin as a stress hormone was investigated. Plasma gastrin and cortisol concentrations were determined during fasting and compared with concentrations during hay feeding. In addition, gastrin and cortisol concentrati...
Bester RC, Coetzer JA.A case of granulomatous enteritis in a 2 year-old Thoroughbred colt is reported. Clinically the horse showed chronic wasting and subcutaneous oedema of the ventral parts of the body and legs. Grossly the wall of the jejunum and ileum was uniformly thickened. Microscopically the lamina propria, submucosa and the tunica muscalaris of the small intestine were infiltrated with lymphocytes, plasma cells, epithelioid cells and occasional multinucleated giant cells. The granulomatous reaction was most marked in the muscular layers of the gut wall.
Sullins KE, Stashak TS.Six normal adult horses had large colon resections at the sternal and diaphragmatic flexures. Stainless steel staples were used to close the stumps of the dorsal and ventral colons in all six. Intestinal continuity was restored with a side-to-side anastomosis of the dorsal and ventral colons. Three of these anastomoses were performed with staples, and three with a double inverting suture pattern. After one month, the horses were surgically reevaluated, and the anastomotic sites were examined. There was no significant difference between the stoma sizes in the two groups. No complications were o...
Grenager NS, Durham MG.This report describes the use of ultrasound to diagnose right dorsal displacement of the large colon (RDDLC) in 13 horses prior to surgery. Horses had ultrasonographic examinations performed of the right lateroventral aspect of the abdomen upon admission to the hospital with a 2-5 MHz broadband curvilinear sector scanning transducer after alcohol was used to wet the hair. First, the caecal vessels were identified in the right flank and followed medially and cranially. Next, each intercostal space, from caudal to cranial, was scanned from dorsal to ventral evaluating for abnormally-located mese...
Freeman DE, Richardson DW, Tulleners EP, Orsini JA, Donawick WJ, Madison JB, Ross MW, Beroza GA.Loop colostomy was performed in 10 horses as treatment for grade-III rectal tears (n = 6 horses), small-colon infarction (n = 2 horses), perirectal abscess and stenosis (n = 1 horse), and small-colon stricture (n = 1 horse). In 7 horses, the colostomy was constructed through a single incision low in the left flank, with closure of the incision around the stoma (single-incision technique). In 3 horses, 2 of which had colostomy performed as a standing procedure, the selected segment of small colon was placed from a flank incision into a separate, small incision low in the left flank (double-inci...
Engiles JB, Uzal FA, Navarro MA, Reef VB, Bender SJ.Phlegmonous gastritis was diagnosed in 2 yearling fillies that were presented with a 1-wk history of fever, lethargy, and hypoproteinemia, associated with a previous diagnosis of equine proliferative enteropathy based on clinical signs and PCR assay detection of Lawsonia intracellularis in fecal samples. Abdominal ultrasound revealed enlargement of the stomach and expansion of its submucosal layer with hypoechoic fluid, as well as thickened hypomotile small intestinal segments. Given the poor prognosis and poor response to treatment, both horses were euthanized, one on the day of presentation ...
Ralston SL, Freeman DE, Baile CA.The roles of volatile fatty acids (VFA) and of the large intestine in the control of feeding in ponies were investigated. Ponies with cecal fistulas were adapted to ad libitum access to pelleted feed. Treatment solutions were given as a bolus 15 min before the animals were allowed free access to feed after a 4-h fast. Each dose of VFA solution was tested in a crossover design with a water control. When the ponies were permitted to eat after the treatments, the latency to eat, first meal size, and duration and first intermeal interval were recorded. Feed intakes were measured at 3 and 18 h afte...
Bertone AL, Toofanian F, Stashak TS.Lactase, maltase, sucrase, and alkaline phosphatase activities were determined in the intestinal mucosa from 3 locations in the small intestine and 4 locations in the large intestine 1 year after extensive large-colon resection (group 1; n = 5) and 1 year after sham operation (group 2; n = 3) in horses. Lactase, maltase, and sucrase activities were similar (P greater than 0.05) between group-1 and group-2 horses in all locations measured in the intestinal tract. Alkaline phosphatase activity in the remaining large colon of group-1 horses was significantly (P less than 0.05) greater than the ac...
Bombardi C, Grandis A, Gardini A, Sorteni C, Clavenzani P, Chiocchetti R.The activity of the gastrointestinal tract is regulated through the activation of adrenergic receptors (ARs). Since data concerning the distribution of ARs in the horse intestine is virtually absent, we investigated the distribution of β2-AR in the horse ileum using double-immunofluorescence. The β2-AR-immunoreactivity (IR) was observed in most (95%) neurons located in submucosal plexus (SMP) and in few (8%) neurons of the myenteric plexus (MP). Tyrosine hydroxylase (TH)-IR fibers were observed close to neurons expressing β2-AR-IR. Since β2-AR is virtually expressed in most neurons located...
Flota-Burgos GJ, Rosado-Aguilar JA, Rojas-Becerril R, Rodríguez-Vivas RI, Trinidad-Martínez I.Gastrointestinal nematodes (GIN) are a major impediment to breeding and exploitation of horses. Traditional control of GIN has generated resistance to main anthelmintics, including ivermectin. An analysis of five ranches with a history of IVM use was done to determine the efficacy and resistance of GIN to IVM treatment in horses from the Mexican southeast. Predesigned questionnaires were applied to collect information on previous treatment protocols. The fecal egg count reduction test (FECRT) was applied to determine resistance. Before IVM application, a McMaster test was used to diagnose GIN ...
Murray MJ, Ball MM, Parker GA.A 3-month-old foal with a history of persistent fever and leukocytosis was found to have pneumonia, ulceration of the squamous portion of the stomach, and dilatation of the distal portion of the esophagus. The foal was euthanatized and necropsied. The distal portion of the esophagus was severely dilated, and there was severe ulceration and mural thickening of the stomach at the cardia. Because of the severe gastric ulceration and mural thickening, the gastroesophageal junction was fixed in an open position, permitting gastroesophageal reflux. The megaesophagus and pneumonia were considered to ...
Bustamante CC, de Paula VB, Rabelo IP, Fernandes CC, Kishi LT, Canola PA, Lemos EGM, Valadão CAA.Starch overload in horses causes gastrointestinal and metabolic disorders that are associated with microbiota changes. Therefore, we identified the fecal microbiota and hypothesized that intracecal injection of alkaline solution (buffer; Mg(OH)2 + Al(OH)3) could stabilize these microbiota and clinical changes in horses submitted to corn starch overload. Ten crossbred horses (females and geldings) were allocated to group I (water−saline and starch−buffer treatments) and group II (water−buffer and starch−saline treatments). Clinical signs, gross analysis of the feces, and fecal microbiot...
Sanchez LC, Giguère S, Javsicas LH, Bier J, Walrond CJ, Womble AY.Gastric tonometry is commonly used in humans as an assessment of intestinal mucosal perfusion. Values in healthy foals are currently unknown. Objective: Age, enteral feeding, and omeprazole administration would significantly alter gastric tonometry measurements in neonatal foals. Methods: Nine clinically normal foals were used to assess the effect of age and feeding, and 8 similar foals were used to assess the effect of omeprazole. Methods: At 1, 7, and 14 days of age, gastric intramucosal PCO2 (PgCO2) and arterial blood gas samples were obtained at baseline, immediately after feeding milk, an...
Jacobs CC, Stefanovski D, Southwood LL.To determine whether perioperative variables can be used to differentiate a medical vs a surgical reason for postoperative reflux (POR) after small intestinal (SI) surgery in horses. Methods: Retrospective study. Methods: Horses >1 year of age that recovered from SI surgery and had POR. Methods: Medical records of horses that underwent SI surgery and developed POR from 2009-2015 were reviewed. Surgical reasons for POR were defined as an anastomosis complication, mechanical obstruction, or nonviable intestine identified at repeat celiotomy/necropsy. A medical reason for POR was presumed wh...
Blake KR, Affolter VK, Lowenstine LJ, Vilches-Moure JG, le Jeune SS.A 10-year-old Lipizzaner stallion was evaluated over the course of 1.5 years because of intermittent, recurrent colic. Results: The horse was initially treated medically for gastric ulcers; dietary changes were made, and a deworming protocol was instituted, without resolution of colic episodes. Subsequently, the horse underwent exploratory celiotomy and a large colon volvulus was identified with diffuse colonic wall thickening. A pelvic flexure biopsy sample was submitted for histologic examination, which revealed lymphocytic (CD3-positive T cells) myenteric ganglionitis (MG). The horse develo...
Richter RA, Freeman DE, Wallig M, Whittem T, Baker GJ.To study the functional and structural responses of the right dorsal colon (RDC) of ponies to phenylbutazone (PBZ) in vitro at a concentration that could be achieved in vivo. Methods: 8 adult ponies. Methods: Short circuit current and conductance were measured in mucosa from the RDC. Tissues incubated with and without HCO3- were exposed to PBZ, bumetanide, or indomethacin. Bidirectional Cl- fluxes were determined. After a baseline flux period, prostaglandin E2 (PGE2) was added to the serosal surfaces and a second flux period followed. Light and transmission electron microscopy were performed. ...
Drudge JH, Lyons ET, Tolliver SC.Four controlled tests (experiments A, B, C, and D) were conducted in naturally infected yearling equids to evaluate activity of ivermectin (0.2 mg/kg IM) against migrating Strongylus vulgaris and S edentatus in mesenteric arteries and ventral abdominal wall, respectively. Data were also obtained on activity against other internal parasites of the gastrointestinal tract and eyeworms. The type and number of equids in the experiments were as follows: experiment A-3 ponies, 2 treated and 1 non-treated; experiment B-4 mixed-bred horses, 2 treated and 2 nontreated; experiment C-5 mixed-bred horses, ...
Lloyd KC.Despite clinical signs compatible with obstruction or ischemia of the gastrointestinal tract, the clinician occasionally is unable to identify a gastrointestinal cause for colic. In this article, disorders not originating from obstruction or ischemia of the gastrointestinal tract but causing real or apparent abdominal pain are presented as alternative causes of colic. In addition, colic of gastrointestinal origin may be the primary inciting factor or a secondary complication of an alternative disorder, causing colic-like signs. Recognition of alternative diagnoses relies on a thorough and cons...
Snyder JR, Tyler WS, Pascoe JR, Olander HJ, Bleifer DR, Hinds DM, Neves JW.Microvascular circulation of the ascending colon in healthy horses was studied using microangiography, light microscopy, and scanning electron microscopy. The pelvic flexure with 30 cm of ventral and dorsal colon attached was removed from 14 adult horses immediately after horses were euthanatized. The lumen was flushed with warm water, and this section of the ascending colon was placed in a 37-C bath of isotonic NaCl. In sections from 8 horses, colic vessels were perfused with a radio-opaque medium for microangiography. After angiographic evaluation, tissue sections were prepared for light mic...
Reed L, MacNicol JL, Charchoglyan A, Brewer D, Murrant C, Pearson W.The objective of this study was to evaluate the effect of a botanical-based equine nutraceutical on contractility of gastric smooth muscle in vitro. Gastric ulcers are prevalent in performance horses and negatively impact horse welfare. Gastric hypermotility has been positively associated with the development of gastric ulceration in nonequine species, and reduction of hypermotility may be protective against their development. Stomachs from 12 pigs processed for food at a provincially inspected abattoir were collected within 1 hour of slaughter. Explants of nonglandular gastric tissue were p...
A 25-year-old pony mare was presented to the clinic with preliminarily reported severe acute colic. The pony during the previous week had shown inappetence, apathy and fever of unknown origin. Clinical examination and placement of a gastric tube were indicative of a secondary gastric dilation. Rectal exploration found moderate caecal meteorism with a tensed and painful medial taenia as well as a dilated and fluid-filled small intestine. In addition, a solid, mobile, non-painful structure of approximately 10 cm diameter was palpated ventrally. A hyperechogenic mass close to the caecum was detec...
Cottrell DF, Jones AF, Potter KE.Electromanometric recordings of caecal pressures were made in chronically cannulated ponies. Endoscopy allowed direct observation of the caecal base and cupola while recording intracaecal pressures and enabled a functional interpretation of caecal pressure profiles. Using gas-tight seals, the caecal gas cap baseline pressure (tone) was usually below atmosphere, becoming less negative postprandially. Diurnal variations were observed in the amplitude and frequency of caecal pressure profiles and the direction of caecal movements, during which intra-caecal gas cap pressures briefly became positiv...
Malberg JA, Webb BT, Hackett ES.A 14-year-old Trakehner gelding was evaluated for recurrent colic, with episodes occurring over 1 year. Signs were consistent with intermittent ascending colon obstruction and hematochezia. Necropsy examination revealed an ulcerated mass extending into the lumen of the right dorsal ascending colon. Gross and histologic appearance and immunoreactivity to c-kit (CD117), desmin, vimentin, and smooth muscle actin, were consistent with a diagnosis of gastrointestinal stromal tumor. Tumeur ventrale gastro-intestinale du côlon produisant des coliques et de l’hématochézie et des coliques récurre...
