Molecular characterisation of fructose transport in equine small intestine

REASONS FOR PERFORMING STUDY: Fructose can be a suitable carbohydrate supplement for horses before and/or during endurance exercise. In comparison to glucose, the ingestion of fructose results in a lower insulin peak and less marked fluctuations in blood glucose during exercise, potentially avoiding hypoglycaemia-induced exhaustion. OBJECTIVES: To assess the capacity of the equine small intestine to absorb fructose and to determine the mechanism, molecular structure and properties of equine intestinal fructose transport. METHODS: Using PCR-based strategies, RNA isolated from equine small intestine and primers designed to homologous regions of the fructose transporter, GLUT5, cDNA of other species, we cloned and sequenced equine GLUT5 (eGLUT5). Northern and western blot analyses, in conjunction with immunohistochemistry, utilising eGLUT5 cDNA and antibodies, assessed expression of eGLUT5 along the longitudinal and radial axes of the small intestine. Functional properties of fructose transport in intestinal brush-border membrane vesicles were measured using the rapid-filtration technique. RESULTS: eGLUT5 is expressed in the villus enterocytes with highest levels in duodenum>jejunum and lowest in the ileum. Kinetic studies indicate eGLUT5 is a low affinity, high capacity transporter. CONCLUSIONS: Equine small intestine has the capacity to absorb fructose. POTENTIAL RELEVANCE: The molecular probes produced in these studies can be used as diagnostic aids to determine equine intestinal monosaccharide malabsorption.     

Attachment of E. coli-bearing K88 antigen to equine brush-border membranes

Equine small intestinal brush-border membranes, from 40 adult horses were tested in vitro for the presence of receptors for the Escherichia coli adhesive antigens K88ab, K88ac and K99. Only K88-positive strains of E. coli adhered strongly to horse brush-border membranes. In contrast, a K88-negative mutant strain J2, 2 K99-positive strains and 3 E. coli strains isolated from foals failed to adhere to horse brush-border membranes. Purified K88ac pili when reacted with equine brush-border membranes inhibited to a great extent the adhesion of K88-positive E. coli. Similarly, K88-positive E. coli previously reacted with K88 antibody, did not attach to equine brush-border membranes. Oral inoculation of 4 newborn foals with strains of K88-positive enterotoxigenic E. coli, producing either heat-stable or heat-labile enterotoxin, caused diarrhoea in 1 animal.     

Influence of abomasal carbohydrates on small intestinal sodium-dependent glucose cotransporter activity and abundance in steers

Most animals adapt readily to increased supplies of carbohydrate in the intestinal lumen by increasing enzymes for degradation and increasing glucose transporter activity. However, the extent of upregulation of Na+-dependent glucose cotransporter 1 (SGLT1) activity and content in response to increased delivery of carbohydrate to the small intestinal lumen of ruminants is unclear. Therefore, an experiment was conducted to determine the effect of glucose and starch hydrolysate on the activity and abundance of SGLT1 in the small intestine of steers. In a randomized complete block design, 40 crossbred beef steers (243+/-2 kg BW) were fed 0.163 Mcal of ME/(kg BW0.75(d; W), 0.215 Mcal of ME/(kg BW0.75 x d; 2M), or 0.163 Mcal ME/(kg BW0.75 x d) and infused for 35 d into the rumen (R) or abomasum (A) with 12.6 g/(kg BW0.75 x d) of starch hydrolysate (S) or into the abomasum with 14.4 g/(kg BW0.75 x d) of glucose (G). Steers were slaughtered, and brush-border membrane vesicles were prepared from the small intestinal samples obtained from five equidistant sites along the intestine. Maltase activity in vesicles and homogenates differed with intestinal sampling site (quadratic, P < 0.001). Steers on the AG treatment yielded a greater intestinal maltase activity (38 nmol glucose x mg protein(-1) x min(-1)) compared with the AS, RS, W, or 2M treatments (34, 26, 23, and 23 nmol glucose x mg protein(-1) x min(-1) respectively [SEM = 3; P = 0.02]). Sodium-dependent glucose uptake averaged 18.4+/-3.94 pmol glucose/(mg protein x s) and was not affected by treatment, but uptake decreased distally along the intestine (P < 0.001). There was no effect of treatment on SGLT1 protein abundance, but SGLT1 protein abundance increased linearly from the duodenum to the ileum (P = 0.05). The inverse relationship between glucose uptake and SGLT1 abundance suggests that the regulation of brush border Na+-dependent glucose transport capacity is complex, involving factors other than the presence of luminal carbohydrate.     

Nonruminant Nutrition Symposium: intestinal glucose sensing and regulation of glucose absorption: implications for swine nutrition

The Na(+/)glucose cotransporter (SGLT1) is the major route for the transport of dietary sugars from the lumen of the intestine into enterocytes. Regulation of this protein is essential for the provision of glucose to the body and avoidance of intestinal malabsorption. This has important nutritional implications in particular for young and growing animals. It has been demonstrated that dietary sugars and artificial sweeteners increase SGLT1 expression and the capacity of the gut to absorb monosaccharides. Furthermore, diets supplemented with artificial sweeteners have been shown to improve growth and performance of weaning piglets. In this review, after describing the organization of intestinal epithelium, the type of gut hormones released in response to dietary carbohydrates, the mechanism underlying the transcellular transport of glucose in the intestine is outlined. Next, a historical background to the work carried out in various laboratories aimed at identifying molecular mechanisms involved in regulation of intestinal glucose transporter, SGLT1, is described. Subsequently, the more recent data on the role of intestinal glucose, or sweet, sensor T1R2 + T1R3, a G protein-coupled receptor, required for upregulation of SGLT1 by dietary sugars and artificial sweeteners, are presented. The glucose sensor subunits, T1R2 + T1R3, are members of the taste receptor family 1, T1R, and are expressed in the gut enteroendocrine cells. Sensing of dietary sugars and artificial sweeteners by T1R2 + T1R3 activates a pathway in endocrine cells leading to secretion of gut hormones. Finally, after describing molecular mechanisms by which a specific gut hormone released by endocrine cells may regulate SGLT1 expression in the neighboring absorptive enterocytes, the application of these findings to enhancing intestinal capacity to absorb dietary sugars in weaning piglets is presented. A better understanding of the molecular events involved in regulation of SGLT1 will allow the identification of nutritional targets with attendant promise of avoiding nutrient malabsorption and enhancing growth and well-being of species.     

Distribution of the neurokinin-1 receptor in equine intestinal smooth muscle

REASON FOR PERFORMING STUDY: Tachykinins have profound effects on equine intestinal motility, but the distribution of the neurokinin receptors (NKRs) through which they act is unknown. This study reports the distribution of one of these receptors, the neurokinin-1 receptor (NK1R), in smooth muscle throughout the equine intestinal tract. OBJECTIVES: To quantify the distribution of the NK1R, based upon mRNA expression, in smooth muscle of different regions of the equine intestinal tract. METHODS: Nine regions of the intestinal tract were sampled in 5 mature horses. Total RNA was isolated from smooth muscle and reverse transcribed; NK1R mRNA was then quantified using real-time PCR. RESULTS: NK1R mRNA was found at all levels of the sampled intestinal tract. The smooth muscle of the proximal small intestine and the ventral colon exhibited the highest level of NK1R mRNA expression in the equine intestinal tract. CONCLUSIONS: Tachykinins probably affect intestinal contractility and propulsion in the proximal small intestine and in the ventral colon.     

Abundance of intestinal Na+/glucose cotransporter (SGLT1) in roe deer (Capreolus capreolus)

Introduction Based on morphological and physiological differences in their digestive systems H ofmann and S tewart (1972) classified ruminants into three feeding types: concentrate selectors (CS), grass and roughage eaters (GR) and intermediate, opportunistic, mixed feeders (IM). In evolutionary terms CS most closely resemble the original ruminants (H ofmann 1989). They have a relatively small forestomach with large openings between the different parts of the stomach. The retention time of ingesta is short and therefore less suited to optimizing cellulose digestion. They have relatively large saliva glands, producing high volumes of saliva (F ickel et al. 1998), which may facilitate the passage of soluble nutrients down their highly developed ventricular groove. The CS ruminants choose easily digestible forage, especially dicotyledons, which are rich in soluble plant cell contents (PCC, T ixier et al. 1997; D uncan et al. 1998). With evolution, the forestomach of the ruminants became larger relative to body size, and also more subdivided. These evolutionary adaptations optimized the selective retention of feed particles and increased retention time, leading to improvement of cellulose digestion. Large GR are well adapted to digest plant cell walls (PCW), i.e. structural carbohydrates (cellulose); they consequently feed mainly on monocotyledons. Roe deer (Capreolus capreolus) are very small ruminants which select concentrated feed. As energy requirements increase proportional to metabolic body weight (K leiber 1961) roe deer require relatively more energy per unit body mass for maintenance compared to that required by large ruminants (V an S oest 1994; D uncan et al. 1998). Easily digestible forage is not sufficient to satisfy the energy requirements of roe deer. It is proposed therefore that these animals may have other methods of avoiding energy losses due to microbial fermentation, either bypassing nutrients down the ventricular groove (rumen bypass) or by ruminal escape of unfermented and/or partially fermented nutrients (H ofmann 1989). The relatively high content of polyunsaturated fatty acids present in the depot fat of roe deer due to only partial rumen biohydrogenation (M eyer et al. 1998) supports the alternative hypothesis of rumen bypass or ruminal escape. Once reaching the small intestine, partially fermented or bypassed soluble carbohydrates can be further hydrolysed by maltase and sucrase to monosaccharides. These monosaccharides are then available for absorption. The intestinal sodium-dependent glucose cotransporter (SGLT1) in the brush border membrane (BBM) of the enterocytes is a stable indicator for the presence of sugars in the small intestine. The expression and activity of SGLT1 protein are regulated by the level of sugars reaching the small intestine (F erraris and D iamond 1989). Infusion of d -glucose into the intestinal lumen of ruminant sheep for 2 h stimulates the expression of SGLT1 which can be detected 4 days later in the newly formed mature enterocytes (S hirazi -B eechey et al. 1995). When dietary carbohydrate is removed, it takes 3 days before the brush border glucose uptake capacity decreases significantly from control values (F erraris 1994). This reflects the time of physiological cell renewal. In GR, such as sheep, the capacity of the intestine to absorb sugars decreases up to 500-fold during development (S hirazi -B eechey et al. 1995). This decrease in the intestinal absorptive capacity is a reflection of the decline in SGLT1 transport activity and protein abundance. It is not due to modifications in the structure of the absorptive surface and cannot be explained in terms of an age-related process (S hirazi -B eechey et al. 1991). It has been shown that there is a direct correlation between the level of monosaccharides reaching the lumen of the small intestine and the expression of functional SGLT1 protein (D yer et al. 1997). Therefore in this study we aimed to investigate the presence of functional SGLT1 in the small intestine of roe deer as a stable indicator of the availability of glucose in the luminal content of the small intestine. The presence of SGLT1 protein in the small intestine will support the hypothesis of rumen bypass and/or ruminal escape of nutrients. Furthermore we measured the maltase activities in the BBM, as part of the carbohydrates reach the intestinal lumen as polysaccharides and have to be broken down to monosaccharides before absorption.     

Molecular insights into dietary induced colic in the horse

Equine colic, a disorder manifested in abdominal pain, is the most frequent cause of emergency treatment and death in horses. Colic often requires intestinal surgery, subsequent hospitalisation and post operative care, with a strong risk of complications arising from surgery. Therefore strategies that explore approaches for preventing the condition are essential. To this end, a better understanding of the factors and mechanisms that lead to the development of colic and related intestinal diseases in the horse allows the design of preventive procedures. Colic is a multifactorial disorder that appears to be induced by environmental factors and possibly a genetic predisposition. One factor that seems to influence the risk of developing colic is the excessive consumption of diets containing high levels of carbohydrates. Therefore, major efforts have been made by various laboratories and institutions across the world to study the type and digestibility of various feed in order to formulate accurate and safe feed components and proportions. However, relatively little work has been carried out to characterise, in detail, the carbohydrate digestive and absorptive capacity and mechanisms underlying the potential adaptive response of equine gut epithelium to a changing diet. This review focuses on advances made towards understanding the molecular and cellular mechanisms involved in digestion and absorption of dietary carbohydrates in the equine gastrointestinal tract and the implication of these processes for the whole body physiology. It addresses the underlying mechanisms that may govern the adaptive response of equine small intestine to increased dietary hydrolysable carbohydrates. Furthermore, it describes changes that occur in the equine large intestinal microbiology and host tissue biology brought about by alterations in diet and in colic. It is hoped that a better understanding of the molecular and cellular processes that play important roles in the physiology and pathology of the equine gastrointestinal tract will assist the development of effective strategies to prevent equine colic.     

Intestinal decompression: preliminary study in the horse

A technique of nasoduodenal (N-D) intubation and intestinal decompression was developed and used in the horse to explore the prevention of gastric and intestinal distention after abdominal surgical operation. Three styles of tubes (2 single-lumen tubes and 1 double-lumen tube) were positioned in the duodenum of 12 mature horses (10 experimental and 2 clinical) during laparotomy (without enterotomy), and an iatrogenic occlusion at the small intestine was created and later released in the 10 experimental horses. The 2 clinical horses had an exploratory laparotomy to correct a natural obstruction of the small intestine. After each horse recovered from surgical manipulation, suction was used to keep fluids from accumulating in the cranial part of the gastrointestinal tract. In 5 of the 12 horses, the most simple N-D tube was positioned successfully and functioned properly. Three of the 5 horses which were fasted before surgical manipulation (to obtain an empty stomach) survived without postsurgical complications. Volume of reflux material was measured. Clinical data, such as periods of comfort during decompression without giving analgesics, were recorded. Necropsies were done on 10 of the 12 horses (9 experimental and 1 clinical). Although already tested in 2 clinical horses, use of the N-D tube remains experimental, and the N-D tube functioned only in horses which were fasted before surgical manipulation. Perfection of a safe and dependable means of emptying the equine stomach of its solid ingesta before gastrointestinal intubation is done, is the next step in affording greater clinical application of the N-D tube for gastrointestinal decompression.     

Myeloperoxidase assay in plasma and peritoneal fluid of horses with gastrointestinal disease

Gastrointestinal disorders, especially strangulating intestinal obstructions, are still a major cause of illness and death in the horse. Circulating lipopolysaccharides may activate both neutrophils and monocytes. The activated neutrophils release myeloperoxidase (MPO), a specific enzyme with strong oxidative activity. The aim of this study was to evaluate MPO concentrations in the plasma and peritoneal fluid (PF) of horses with colic and to check the hypothesis that these concentrations would be higher in a case of strangulating obstruction than in cases of nonstrangulating disease. By using a specific enzyme-linked immunosorbent assay for equine MPO, we determined the MPO concentrations in horses admitted to a clinic for colic. Horses with nonstrangulating or strangulating obstruction of the large intestine (NSLI or SLI), strangulating obstruction of the small intestine (SSI), or inflammatory bowel disease (IBD) were compared with healthy horses. The horses with SLI, SSI, or IBD had significantly higher MPO levels in plasma and PF than did those in the other 2 groups. The mean plasma level was significantly higher in the horses with NSLI than in the healthy horses. High MPO values in PF indicated necrotic bowel. These results show that neutrophil activation occurs during nonstrangulating and strangulating intestinal obstruction in horses and that the plasma and PF MPO concentrations may be a marker of the severity of the disease.     

Effect of Omentectomy on Adhesion Formation in Horses

Objective —To determine if omentectomy would decrease the frequency of postoperative intraabdominal adhesions. Study Design —Retrospective study. Animals or Sample Population—44 horses that had either two ventral median celiotomies or a ventral median celiotomy and a necropsy more than 4 days later; 19 of these horses had their omentum removed at the initial surgery. Methods —Data retrieved from the records included location and type of intraabdominal adhesions; location of the surgical lesion; relationship of adhesions to the surgical lesion; surgical procedures; duration of initial surgery; time interval between procedures; age, gender, and breed of the horse; and clinical outcome. Fisher's exact test was used to evaluate the association between categorical explanatory and outcome variables. The effect of potential risk factors on the incidence rate of adhesion formation was estimated using a proportional hazards regression model. Results —Of 25 horses in the nonomentectomy group, 15 (60%) had postoperative adhesions that resulted in the need for a second surgical intervention, whereas of 19 horses that had omentectomy initially, only 4 (21%) had postoperative adhesions that required a second procedure. Rate of adhesion formation was higher in horses that did not have omentectomy initially (incidence ratio rate [IRR], 0.46; 90% confidence interval [CI], 0.18 to 1.19). At initial surgery, 24 horses had a small intestinal lesion, and 20 horses had a large intestinal lesion. Fifteen horses (63%) with small intestinal lesions subsequently developed adhesions compared with four horses (20%) with an initial large intestinal lesion (P= .006). At the second procedure, small intestine lesions were identified in 32 horses and large intestine lesions in 12 horses (1 horse had both small and large intestine lesions), and 1 horse had a gastric lesion. Adhesions were identified as the cause of colic signs in 19 (61%) horses with small intestinal lesions and in none of the horses with large intestine lesions. The frequency of adhesion development leading to colic associated with only the small intestine at the second surgery or necropsy was significantly greater (P= .001) than the frequency only in the large intestine. Conclusions —Omentectomy reduced the rate of postoperative adhesion formation. Adhesions are more likely to occur after small intestinal surgery and if they do occur likely involve the small intestine. Clinical Relevance —Omentectomy is a safe procedure and should be considered prophylactically for reduction of adhesion formation after abdominal surgery in horses.     

Small intestinal malabsorption in the horse: an assessment of the specificity of the oral glucose tolerance test

Specificity of the oral glucose tolerance test (OGTT) for the diagnosis of small intestinal malabsorption in the horse was assessed by comparing the results of OGTT with the results of a histopathological examination of the small intestine in 42 adult horses affected by chronic weight loss. The horses were assigned to three groups on the basis of the results of the test. Five horses were considered to have a normal OGTT absorption result (Group 1); all the horses had a histologically normal small intestine. Twenty-five horses had a partial malabsorption result (Group 2) seven of which had normal small intestinal morphology, whereas the remaining 18 had a variety of pathological lesions including lymphosarcoma, villous atrophy, granulomatous enteritis and eosinophilic gastroenteritis. Twelve of the 42 horses had a total malabsorption result (Group 3), and all had a severe infiltrative lesion in the small intestinal wall (either lymphosarcoma or granulomatous enteritis).     

Strangulating obstruction caused by intestinal herniation through the proximal aspect of the cecocolic fold in 9 horses

OBJECTIVE: To report the clinical and surgical findings and outcome for horses with strangulating obstruction caused by herniation through the proximal aspect of the cecocolic fold. STUDY DESIGN: Retrospective study. ANIMALS: Nine horses. METHODS: Medical records were reviewed for clinical signs, surgical findings and technique, and outcome. Cadaver ponies and necropsy specimens were also used to study the regional anatomy of the cecocolic fold. RESULTS: The ileum and distal jejunum were strangulated in 8 horses, whereas in 1 horse the small intestine and the left ascending colons were incarcerated in a rent in the cecocolic fold. Two horses were euthanatized at surgery, 6 horses had a small intestinal resection (mean length, 3 m; range, 1.5-6.4 m) and an end-to-side jejunocecostomy, and the entrapment was reduced without resection in the horse that had small intestine and ascending colon incarceration; cecocolic fold defects were not closed. One horse was euthanatized 36 hours after surgery because of endotoxemia. Six horses were discharged; 4 were available for long-term follow-up, of which 2 were euthanatized, and 2 were euthanatized 12 and 18 months after surgery because of colic signs. Variations in thickness of the cecocolic fold were observed in specimens obtained from necropsy of other horses and ponies. CONCLUSIONS: Reasons for this defect are unknown, although observed anatomic differences in cecocolic fold thickness may contribute to the development of defects. CLINICAL RELEVANCE: Reduction of the entrapped bowel is easiest when traction is placed on the bowel at a 90 degrees to the base of the cecum. Intestinal incarceration through rents within the proximal part of the cecocolic fold should be considered as a differential diagnosis for strangulating obstruction in horses.     

Idiopathic muscular hypertrophy of the equine small intestine: 11 cases (1980-1991).

The medical records of 11 horses with idiopathic muscular hypertrophy (MH) of the small intestine were reviewed to determine the clinical and pathological features of the disease. The median age of affected horses was 10.0 years (range 5-18 years). No breed or sex predisposition was apparent. Ten horses (91%) had chronic (23 days to 2.4 years) signs of mild, intermittent colic, and 1 horse had signs of severe colic of only 3 days' duration. Partial anorexia and chronic weight loss of variable duration (1-6 months) were prominent historical findings in 5 (45%) horses. Diagnostic tests, with the exception of exploratory caeliotomy, were ineffective for definitive diagnosis of intestinal MH as a cause of colic. In 2 horses, however, a thickened, rigid ileum was detected by palpation per rectum, and in 5 horses, multiple loops of distended small intestine were detected by palpation per rectum. Hypertrophy of both the circular and longitudinal layers of muscularis was determined as the cause of intestinal thickening in all horses. Muscular hypertrophy of the ileum was present in 9 (82%) horses. Two horses (18%) had MH of a section of jejunum only, and 4 (36%) horses had MH of the ileum in combination with MH of other sections of small intestine. Two (18%) horses had MH of the entire small intestine. In 9 (82%) horses, intestinal MH resulted in narrowing of the luminal diameter at the site of MH. Small diverticula were present on the mesenteric border of the hypertrophied ileum of 5 (45%) horses. Five linear (up to 150-cm) diverticula were present in the hypertrophied jejunum of 1 (9%) horse. Haemomelasma ilei was present on the antimesenteric serosal surface of affected intestine of 8 (73%) horses. Full-thickness rupture of the ileum with subsequent diffuse, septic peritonitis occurred in 3 (27%) horses.     

Influence of dietary fiber on luminal environment and morphology in the small and large intestine of sows

In this study, the effect of feeding different types and amounts of dietary fiber (DF) on luminal environment and morphology in the small and large intestine of sows was studied. Three diets, a low-fiber diet (LF) and 2 high-fiber diets (high fiber 1, HF1, and high fiber 2, HF2) were used. Diet LF (DF, 17%; soluble DF 4.6%) was based on wheat and barley, whereas the 2 high-fiber diets (HF1: DF, 43%; soluble DF, 11.0%; and HF2: DF, 45%; soluble DF, 7.6%) were based on wheat and barley supplemented with different coproducts from the vegetable food and agroindustry (HF1 and HF2: sugar beet pulp, potato pulp, and pectin residue; HF2: brewers spent grain, seed residue, and pea hull). The diets were fed for a 4-wk period to 12 sows (4 receiving each diet). Thereafter, the sows were killed 4 h postfeeding, and digesta and tissue samples were collected from various parts of the small and large intestine. The carbohydrates in the LF diet were well digested in the small intestine, resulting in less digesta in all segments of the intestinal tract. The fermentation of nonstarch polysaccharides in the large intestine was affected by the chemical composition and physicochemical properties. The digesta from pigs fed the LF diet provided low levels of fermentable carbohydrates that were depleted in proximal colon, whereas for pigs fed the 2 high-DF diets, the digesta was depleted of fermentable carbohydrates at more distal locations of the colon. The consequence was an increased retention time, greater DM percentage, decreased amount of material, and a decreased tissue weight after feeding the LF diet compared with the HF diets. The concentration of short-chain fatty acids was consistent with the fermentability of carbohydrates in the large intestine, but there was no effect of the dietary composition on the molar short-chain fatty acid proportions. It was further shown that feeding the diet providing the greatest amount of fermentable carbohydrates (diet HF1, which was high in soluble DF) resulted in significant morphological changes in the colon compared with the LF diet.     

Mesenteric rents as a source of small intestinal strangulation in horses: 15 cases (1990-1997)

OBJECTIVE: To describe the clinical findings in horses with small intestinal strangulation through mesenteric rents, and to determine the recurrence and survival rates after surgery. DESIGN: Retrospective study. ANIMALS: 15 horses with small intestinal obstruction via a mesenteric rent. PROCEDURE: Medical records of horses with obstruction of the small intestine via a mesenteric rent between January 1990 and December 1997 were reviewed. The signalment, history, initial physical examination findings, results of abdominocentesis, and clinical laboratory values were recorded. Surgical findings, including location of the mesenteric rent and surgical procedure performed, were recorded. Short- and long-term survival rates were calculated. RESULTS: Most mesenteric rents were located in the mesentery of the small intestine (13 horses). Two horses had multiple mesenteric defects. Seven horses were euthanatized at surgery because of an inability to reduce the entrapped intestine (3 horses), uncontrollable hemorrhage (2), inability to close the rent (1), and the amount of compromised intestine involved (1). Seven horses required intestinal resection and anastomosis. The median length of intestine resected was 2.6 m (range, 0.6 to 4.5 m). The mesenteric rents created during resection were not closed in 2 horses. One of these 2 horses subsequently developed a strangulating obstruction through the open rent. Seven of 15 horses in our study were discharged from the hospital (i.e., short-term survival rate of 47% [7/15]). Long-term follow-up information was available for 5 of the 7 horses (follow-up duration of 5 months to 9 years), of which 2 died as a result of colic, and 1 horse was euthanatized because of severe arthritis (i.e., long-term survival rate of 40% [2/5]). CONCLUSIONS AND CLINICAL RELEVANCE: Inability to reduce the intestinal obstruction, severe hemorrhage from the mesentery, and the length of intestine involved are the main factors that decrease survival rates in horses with small intestinal strangulation caused by mesenteric rents.     

Effect of venous strangulation obstruction on length of equine jejunum and relevance to small-intestinal resection

OBJECTIVE--To determine if venous strangulation obstruction (VSO) of the distal half of the equine small intestine would increase length of that segment. STUDY DESIGN--Halothane-anesthetized horses were assigned randomly to 3 groups of 5 horses: Group 1 (controls)--the entire small intestine was measured and rubber-shod clamps were applied to mark each end of the most distal 50% of the small intestine; Group 2--same procedure, except that VSO was induced in the distal 50% of the small intestine for 180 minutes; and Group 3--same initial procedure, except that VSO was induced for 90 minutes and followed by reperfusion for 90 minutes. ANIMALS OR SAMPLE POPULATION--Fifteen horses. METHODS--The proximal and distal halves of the small intestine were measured before and at 180 minutes after clamps and ligatures were applied. At the end of the study, biopsies were taken to assess mucosal epithelial damage by light microscopy, and horses were euthanatized while under general anesthesia. RESULTS--Intestine subjected to VSO and VSO and reperfusion had marked hemorrhagic changes and thickening in the intestinal wall. Both groups had incurred a grade 2.8 of 5 mucosal injury by 180 minutes. Total length of small intestine and length of the distal 50% did not change in the control group, but intestine subjected to VSO only and VSO and reperfusion had increased in length by 29% (P <.05) and 36% (P <.05), respectively. CONCLUSIONS--Small intestine of horses subjected to VSO can increase in length, and this change could cause an overestimate of the amount of intestine involved in an extensive strangulating lesion. CLINICAL RELEVANCE--An overestimate of the amount of intestine involved in an extensive strangulating lesion could lead to an overly pessimistic assessment of a horse's risk for postresection malabsorption and maldigestion. Therefore, estimates of the proportion of small intestine that is strangulated should be corrected for this potential error and the risk of malabsorption determined accordingly.     

Diagnostic value of intestinal alkaline phosphatase in horse serum

Antiserum directed against equine intestinal Alkaline Phosphatase (ALP) was produced in rabbits and used to develop a sensitive and quantitative assay for the detection of intestinal ALP in equine serum. This assay was then used to measure the half-life of intravenously injected intestinal ALP and to determine if the intestinal ALP was present in normal horse sera, sera from horses presented for lesions not involving the gastrointestinal tract and sera from horses presented with lesions involving the gastrointestinal tract. The results suggest that intestinal ALP is not likely to appear in equine serum even when gastrointestinal disease is present and, therefore, appears to be of no diagnostic value.     

Mesenteric strangulation by pedunculated lipomas without involvement of associated intestine in four horses

An unusual form of strangulation of mesentery only by pedunculated lipoma was identified as the cause of moderate to severe colic in four horses. The small intestinal mesentery was involved in three horses and the small colon mesentery in the fourth horse, but the associated intestine was not strangulated, haemorrhagic, nor obviously obstructed in any horse. In all horses, a patch of haemorrhagic mesentery of variable size was evident around the origin of a mesenteric lipoma and a major mesenteric vessel. One horse was subjected to euthanasia at the owner's request and the remaining three had surgery from which they made a complete recovery after the removal of the lipoma. Intestinal resection was not performed in any of the three horses undergoing surgery. An isolated mesenteric strangulation by lipoma is an uncommon cause of colic in older horses that have the typical presentation of a strangulating lipoma. The removal of the involved lipoma without mesenteric or intestinal resection can be associated with complete recovery.     

Evaluation of glucose tolerance and intestinal luminal membrane glucose transporter function in horses with equine motor neuron disease

OBJECTIVE: To confirm whether the plasma glucose concentration curve obtained during oral glucose tolerance tests (OGTTs) in horses with equine motor neuron disease (EMND) is decreased, compared with that obtained in clinically normal horses, and determine whether that decrease is a result of defective glucose metabolism or intestinal glucose transport dysfunction. ANIMALS: 8 horses with EMND and 44 matched control horses. PROCEDURE: Electromyography and OGTTs were performed in all 8 affected horses and 10 control horses. Intravenous GTTs (IVGTTs) were performed in 6 affected horses and another 11 control horses. The activity and levels of jejunal luminal membrane glucose transporter (Na+ / glucose cotransporter isoform 1 [SGLT1]) were measured in 2 affected horses and 23 control horses. RESULTS: In horses with EMND, generalized neuropathy was detected via quantitative electromyography; the mean increase in plasma glucose concentration during the OGTT was significantly decreased, compared with the value in control horses. During the IVGTT the mean increase in plasma glucose concentration was significantly lower than that of control horses. The activity and levels of SGLT1 in 2 affected horses were similar to those of control horses. Diagnosis of EMND was confirmed postmortem in all affected horses. CONCLUSIONS AND CLINICAL RELEVANCE: Data suggest that the decreased plasma glucose curve obtained in horses with EMND during OGTTs (compared with control horses) is a result of overall enhanced glucose metabolism or abnormalities in the facilitated glucose transporters; definitive identification of the underlying mechanisms could aid in the development of appropriate treatments of EMND in horses.