Fumonisin B1 concentrations in feeds from 45 confirmed equine leukoencephalomalacia cases

During the fall of 1989 and winter of 1990, numerous reports of equine leukoencephalomalacia (ELEM) occurred from many regions of the United States. Typically, horses were consuming feed partially or entirely composed of corn and/or corn screenings. From October 1989 through May 1990, samples from 55 confirmed or suspected ELEM cases were received at the National Veterinary Services Laboratories, Ames, Iowa, for fumonisin B1 analysis. Samples from 9 cases in 1984-1985 were also obtained. Fumonisin B1, a mycotoxin produced by Fusarium moniliforme, causes ELEM, but little is known of naturally occurring toxic or safe levels in feeds. To determine what levels of fumonisin B1 in feeds are associated with ELEM, 45 selected cases were studied. The fumonisin B1 concentrations ranged from less than 1 ppm to 126 ppm, with the majority of the samples above 10 ppm. All types of feeds were included: corn, screenings, sweet feeds, and commercially pelleted rations. The length of exposure varied from 7 to greater than 35 days. Horse feed samples not associated with ELEM were also collected and analyzed. None of the nonproblem feed samples contained fumonisin B1 levels greater than 8 ppm.     

Cardiovascular changes associated with intravenous administration of fumonisin B1 in horses

OBJECTIVE: To determine whether cardiovascular dysfunction is evident in horses with leukoencephalomalacia experimentally induced by administration of fumonisin B1. ANIMALS: 11 healthy horses of various breeds (body weight, 252 to 367 kg). PROCEDURE: Horses were randomly assigned to 3 groups and administered fumonisin B1 daily. Horses received IV injections of 0 (control horses; n = 4), 0.01 (3), or 0.20 mg (4) of fumonisin B1/kg for 7 to 28 days. Horses were examined daily for evidence of neurologic disease. When neurologic signs consistent with leukoencephalomalacia were evident, horses were anesthetized, and catheters were inserted for evaluation of the cardiovascular system. After recovery from anesthesia, hemodynamic measurements were obtained. RESULTS: Fumonisin-treated horses with clinical signs of neurologic disease had evidence of cardiovascular dysfunction manifested as decreases in heart rate, cardiac output, right ventricular contractility (assessed by measuring the maximal rate of change of right ventricular pressure), coccygeal artery pulse pressure, and pH and base excess in venous blood as well as increases in systemic vascular resistance, compared with values for control horses. Fumonisin-treated horses with and without clinical signs of neurologic disease also had higher serum and right ventricular sphinganine and sphingosine concentrations than control horses. CONCLUSIONS AND CLINICAL RELEVANCE: An association was detected among fumonisin-induced neurologic disease, increased serum and myocardial sphinganine and sphingosine concentrations, and decreased cardiovascular function in horses. Fumonisin-induced decreases in cardiovascular function may contribute to the pathophysiologic development of leukoencephalomalacia in horses.     

Leukoencephalomalacia in a horse induced by fumonisin B1 isolated from Fusarium moniliforme

Each of two horses was dosed by stomach tube with culture material on maize of Fusarium moniliforme MRC 826. One horse developed severe hepatosis and mild oedema of the brain after 6 doses of 2.5 g of culture material/kg body mass/day in 7 days. The second horse, in a similar experiment but at a dosage rate of 1.25 g/kg/day, developed mild hepatosis and moderate oedema of the brain. In both animals the brain oedema was particularly noticeable in the medulla oblongata. The mycotoxin fumonisin B1 was extracted and purified from the culture material of F. moniliforme MRC, 826 which contained approximately 1 g/kg of this compound. A horse was injected intravenously 7 times from Day 0-Day 9 with 0.125 mg of fumonisin B1/kg body mass/day. Clinical signs of neurotoxicosis, which appeared on Day 8, included nervousness followed by apathy, a wide-based stance, trembling, ataxia, reluctance to move, paresis of the lower lip and tongue, and an inability to eat or drink. Euthanasia was performed on the horse on Day 10 while the animal was in a tetanic convulsion. The principal lesions were severe oedema of the brain and early, bilaterally symmetrical, focal necrosis in the medulla oblongata. This report provides experimental evidence that fumonisin B1, produced by F. moniliforme, causes equine leukoencephalomalacia.     

A rapid, sensitive thin layer chromatography procedure for the detection of fumonisin B1 and B2.

A thin layer chromatography (TLC) method was developed for the detection of fumonisin B1 and B2 in corn and corn-based feedstuffs. Finely ground samples were extracted with acetonitrile:water (1:1), filtered, and applied to C18 cleanup columns. The columns were washed with 1% aqueous KCl followed by acetonitrile: 1% aqueous KCl (1:9), and the fumonisins were eluted with acetonitrile:water (7:3). The eluants were concentrated and spotted on reverse-phase C18 TLC plates along with fumonisin B1 and B2 standards, and the plates were developed in methanol: 4% aqueous KCl (3:2). The fumonisins were visualized by spraying the TLC plates successively with 0.1 M sodium borate buffer, fluorescamine, and 0.01 M boric acid. The plates were then dried and examined under longwave ultraviolet light. Fumonisin B1 and B2 appeared as bright yellowish-green fluorescent bands at Rfs of 0.5 and 0.1, respectively. The detection limit for the fumonisins on the TLC plate was 0.1 ppm in corn. Recoveries from spiked samples averaged greater than 80%. The identification of the fumonisins was confirmed by hydrolyzing the parent compounds of B1 and B2 to their respective C22 amino-alcohols and reexamining by TLC with the same visualizing reagents. This procedure was used to survey 193 corn samples collected from University of Missouri test plots in 1990 for fumonisin B1. Fumonisin B1 was detected in 15% of the corn samples.     

Age-related and non-age-related changes in 100 surveyed horse brains

Brains from 100 horses, aged 2-25 years, were systematically examined by histopathology at 46 different neuroanatomical sites. The horses were sourced from a slaughterhouse (group A, n = 57), from a kennel that collected dead animals, and from 2 diagnostic laboratories (group B, n = 43). All horses from group A and 26 horses from group B were examined by a veterinarian in the period before death. None of the horses were known to exhibit clinical signs suggestive of neurologic disease. Among the main changes identified were vacuolation in the neuropil (n = 73), neurons (n = 32), white matter (n = 31), and focal perivascular lymphoid cell infiltrates (n = 35). Spheroids were frequently seen (n = 91), and 10 horses each had more than 10 spheroids in the cuneate or gracile nucleus. Statistically significant age-related changes noted included intraneuronal (n = 97) and glial or extracellular lipofuscin deposition (n = 41), hemosiderin deposition around blood vessels (n = 60), and calcium depositions (n = 24). One horse had low-grade nonsuppurative meningoencephalitis; Alzheimer type II cells were detected in the brains of 2 horses. Hyalinized vessel walls in the cerebellum were observed in 1 horse. It was concluded that some histopathologic changes are a frequent feature in equine brains, which has implications for the pathologists involved in equine neurology and disease surveillance.     

Clinical and epidemiologic features of an epizootic of equine leukoencephalomalacia

A herd of 15 mature riding horses with a history of anorexia, weight loss, and lethargy was examined. The animals had been fed a 50/50 mixture of commercial sweet feed and corn screenings contaminated with a heavy growth of Fusarium moniliforme. Thirteen of the horses had one or more neurologic signs. The most characteristic signs were profound depression and mild ataxia. Over the 19-day course of the epizootic, the horses had increasing severe neurologic deficits, including unilateral blindness and delirium. Despite the clinical appearance of dehydration, 12 horses had low PCV (16 to 27%), hematocrit (21.2 to 31.0%; determined by automated cell counter), and RBC counts (3.76 to 5.5 x 10(6) RBC/microliters). White blood cell counts were variable (4,900 to 17,000 WBC/microliters). Necropsy findings included diffuse malacia of the white matter of the frontal cortex and severe multifocal perivascular hemorrhage in the white matter of the temporal cortex, basal ganglia, anterior medulla, and pons. One horse had a hepatic lesion consisting of a mixed inflammatory cell infiltrate and bile duct proliferation. The attack rate of this epizootic was 100%. The course of disease was unusually long in some animals. In an experiment, the fusarium-infected corn screenings were fed to horses and did not cause clinical signs or alterations in blood or serum biochemical values.     

ABNORMAL IMAGING FINDINGS OF THE FEMORAL THIRD TROCHANTER IN 20 HORSES

Injuries involving the femoral third trochanter are an uncommon but important source of equine lameness; however, clinical localization can be challenging. The purpose of this retrospective study was to describe ultrasonographic and scintigraphic findings in a group of horses with presumed third trochanter injury. Medical records of an equine referral hospital were searched from 2004–2014, and 20 horses met the inclusion criteria. Lesions consistent with third trochanter fracture were identified with ultrasound in 14/20 horses. Onset of lameness was acute (11), insidious (2), or unknown (1). All but one horse was lame at presentation, ranging from Grade 2–4/5. Ultrasound was the primary diagnostic modality in 5/14 horses with fragmentation, while scintigraphic findings of intense (3), moderate (5), and mild (1) increased radiopharmaceutical uptake (IRU) prompted ultrasonographic examinations in 9/14 fractured horses. A nondisplaced fracture was suspected in an additional horse with intense IRU and negative ultrasound findings. In the remaining five horses, imaging findings included only mild IRU. Lameness was localized to other regions in these cases. Six of 12 fractured horses with available outcome data were returned to function after a prolonged rehabilitation of 8–18 months. Scintigraphic findings helped to direct focused ultrasound exams in the majority of fracture cases. Horses with evidence of third trochanter fracture had similar clinical characteristics to that reported for pelvic fractures and authors therefore recommend ultrasonographic examination of both regions, especially when scintigraphy is unavailable. Prognosis for return to function in horses of the current study was less favorable than previously reported.     

The density of equine tissue at 37 degrees C.

The density of the following equine tissues was measured: white and grey brain matter, myocardium, lung parenchyma, liver, spleen, gastrointestinal tract and contents, renal medulla and cortex, muscle, fat, tendon and bone. Statistical analysis indicated that there were highly significant differences in the values for density between horses and between tissues within horses. Values for density of eight different muscles were obtained for 18 horses and these were shown to differ highly significantly between horses and between muscles within horses. The values for splenic density differed highly significantly between those for knackery killed horses and for the barbiturate killed post morten room horses.     

The influence of dietary fiber digestibility on the nitrogen requirements of mature horses

Mature geldings at maintenance were fed different diets in a 4 x 4 Latin square design balanced to account for residual effects in an attempt to determine whether differences in the digestibility of the fibrous portions of feedstuffs would influence dietary nitrogen (N) requirements. Diet 1 contained corn and soybean meal (SBM); diet 2, corn, corn oil and urea; diet 3, corn, SBM, straw and urea; diet 4, corn, alfalfa and urea. Urea supplied 50% of the total N in diets 2 and 3 and 39% of the total N in diet 4. The diets were fed in amounts that met National Research Council (NRC) recommendations for daily digestible energy intakes by mature horses at maintenance and met or exceeded total daily N requirements. True absorbed N was calculated by subtracting the fecal N associated with neutral detergent fiber (NDF-N) from total N intakes; true digestibilities of N ranged from 92.4 to 95.9%. Endogenous and metabolic fecal N excretions ranged from .37 to .56 g N/100 g dry matter intake. Although none of the diets as fed were deficient in N, apparent N digestibility was only 64% of N intake when the horses were fed the diet containing straw (diet 3), compared with 72.5 to 79.6% of total N intake among diets 1, 2 and 4 (P less than .01). Fecal excretions of water soluble, bacterial cell-associated and intestinal cell-associated N fractions were greatest when diet 3 was fed.(ABSTRACT TRUNCATED AT 250 WORDS)     

Effect of Mineral Block Supplementation on In Vivo Digestibility and In Vitro Gas Production With Equine Fecal Bacteria

The effects of a mineral block for horses on in vivo digestibility and in vitro fermentability with equine fecal inoculum were evaluated. Fifty healthy horses from three groups (lactating mares n = 19, working horses n = 18, and maintenance horses n = 13) were randomly assigned to two treatment groups (with or without the mineral block; Ca 10.0%, P 12.0%, Zn 12.1 mg/kg, Cu 2,050 mg/kg, Mn 4,050 mg/kg, Se 30 mg/kg, and I 105 mg/kg). Dry matter digestibility was estimated with an internal marker. Samples of diet were incubated with equine fecal bacteria with varying amounts of mineral block (0, 1.1, 3.6, and 6.2 mg/g dry matter [DM]) to record gas production and to estimate in vitro DM digestibility. The results showed that mineral supplementation with the blocks increased in vivo DM digestibility (P < .01) in all groups, but there was an interaction (P < .01) with a greater response in the maintenance horses (55.5% vs. 78.0%) compared to lactating mares (62.8% vs. 79.6%) and working (70.3% vs. 75.1%). Block consumption was lowest in the lactating mares (12.8 g/d), intermediate in the working horses (44.6 g/d), and highest in the maintenance horses (74.2 g/d). The mineral supplementation did not affect the kinetics of gas production but tended (P = .10) to improve the in vitro DM digestibility (37.01% vs. 38.34%). Mineral block supplementation increased dry matter digestibility in horses. The unsupplemented control diet was deficient in several minerals, and block intake was not proportional to the mineral requirements.     

Genetic Analyses of an H3N8 Influenza Virus Isolate, Causative Strain of the Outbreak of Equine Influenza at the Kanazawa Racecourse in Japan in 2007

In August 2007, an outbreak of equine influenza occurred among vaccinated racehorses with Japanese commercial equine influenza vaccine at Kanazawa Racecourse in Ishikawa prefecture in Japan. Apparent symptoms were pyrexia (38.2-41.0 degrees C) and nasal discharge with or without coughing, although approximately half of the infected horses were subclinical. All horses had been shot with a vaccine that contained two inactivated H3N8 influenza virus strains [A/equine/La Plata/93 (La Plata/93) of American lineage and A/equine/Avesta/93 (Avesta/93) of European lineage] and an H7N7 strain (A/equine/Newmarket/1/77). Influenza virus, A/equine/Kanazawa/1/2007 (H3N8) (Kanazawa/07), was isolated from one of the nasal swab samples of diseased horses. Phylogenetic analysis indicated that Kanazawa/07 was classified into the American sublineage Florida. In addition, four amino acid substitutions were found in the antigenic sites B and E in the HA1 subunit protein of Kanazawa/07 in comparison with that of La Plata/93. Hemagglutination-inhibition (HI) test using 16 serum samples from recovering horses revealed that 1.4- to 8-fold difference in titers between Kanazawa/07 and either of the vaccine strains. The present findings suggest that Japanese commercial inactivated vaccine contributed to reducing the morbidity rate and manifestation of the clinical signs of horses infected with Kanazawa/07 that may be antigenically different from the vaccine strains.     

Characterization of an epizootic of pulmonary edema in swine associated with fumonisin in corn screenings.

In 1989, corn screenings were associated with acute interstitial pulmonary edema, hydrothorax, and death in swine. Attack rate was 5-50%, case fatality rate was 50-90%, and clinical course was 1-2 days. Screenings from farms with pigs affected with pulmonary edema contained 20-330 micrograms fumonisin B1 per gram. Screenings containing 92 micrograms fumonisin B1 per gram fed to weanling pigs caused pulmonary edema and death. Sterilized corn inoculated with Fusarium moniliforme and diluted 1:1 with clean corn contained fumonisin B1 (17 micrograms/g) and caused acute pulmonary edema when fed for 5 days. Survivors developed subacute hepatotoxicosis with individual hepatocellular necrosis, hepatomegalocytosis, and increased numbers of mitotic figures. Similar liver lesions occurred in pigs given fumonisin B1 intravenously at 0.8 mg/kg body weight for 14 days.     

Ataxia and weakness associated with fourth ventricle vascular anomalies in two horses

Two adult horses with progressive neurologic signs were examined clinically and at necropsy. Both horses had signs of progressive ataxia and weakness, clinically diagnosed as spinal cord in origin. Differential diagnoses for cervical spinal ataxia in horses included cervical vertebral malformation, equine degenerative myeloencephalopathy, equine herpes-virus-I myeloencephalopathy, and equine protozoal myeloencephalopathy. Necropsy findings in both horses were similar and consisted of a large hematoma in the fourth ventricle, with upward compression of the cerebellum and downward compression of the pons and rostral portion of the medulla.     

Doxycycline levels in preocular tear film of horses following oral administration

Objective To determine the concentration of doxycycline in preocular tear film following oral administration in horses as a possible therapeutic modality for infectious and keratomalacic equine keratitis. Procedure Eight broodmares without ocular disease from a Thoroughbred breeding facility were included in this study. Each mare received 20 mg/kg of doxycycline by mouth once daily in the morning for five consecutive days. Tears were collected 1 h after doxycycline administration starting on day one of administration and continuing for 10 consecutive days. Doxycycline levels in the tears were measured using liquid chromatography with tandem mass spectrometric detection (LC-MS/MS). Results Doxycycline was present in the tears of each mare at low µg/mL levels with the highest concentration appearing on the third to fifth days (8.21–9.83 µg/mL). Doxycycline levels had fallen below quantifiable ranges by day 10. No systemic side-effects were noted in any of the horses included in this study. Conclusions Oral doxycycline is present in preocular tear film of normal horses with noninflamed eyes and may be useful as treatment in equine ulcerative keratomalacia. The oral dose listed was tolerated well by the horses in this study. The drug levels attained at 20 mg/kg once daily orally of doxycycline may aid in the treatment of corneal ulceration in horses, but further study is warranted.     

Determination of the lactate breakpoint during incremental exercise in horses adapted to dietary corn oil

OBJECTIVE: To determine lactate breakpoint of horses and test for effects of training and dietary supplementation with corn oil on that breakpoint. ANIMALS: 7 healthy Arabian horses. PROCEDURES: Horses received a control diet (n = 4) or a diet supplemented with 10% corn oil (4). A training program, which comprised two 5-week conditioning periods with 1 week of rest, was initiated. Submaximal incremental exercise tests (IET) were conducted before the first and after both conditioning periods. Blood samples for determination of blood lactate and plasma glucose concentrations were collected 1 minute before IET and during the 15 seconds immediately preceding each speed change. Data collected were fit to one- and two-slope broken-line models and an exponential model. RESULTS: Good fits were obtained by application of the broken-line models (adjusted R2 > 0.92) to blood lactate concentration versus speed curves. Lactate breakpoints increased 41% after training. After training, slope 2 and peak blood lactate concentrations were greater in the corn oil group, compared with controls. Mean blood lactate concentration at the breakpoint was not affected by training or diet. Plasma glucose concentration versus speed curves also fit the broken-line models, and glucose breakpoints preceded lactate breakpoints by approximately 1 m/s in the second and third IET. CONCLUSIONS AND CLINICAL RELEVANCE: Lactate breakpoints can be determined for horses, using blood lactate concentration versus speed curves generated during submaximal IET and may be useful for assessing fitness and monitoring training programs in equine athletes.     

Equine herpesvirus type 1 (EHV-1) myeloencephalopathy: a case report

An outbreak of neurological disease occurred in a well-managed riding school. Ataxia and paresis were observed in several horses, five of which became recumbent and were euthanized. Post-mortem analysis revealed scattered haemorrhages along the spinal cord, that were reflected by multiple haemorrhagic foci on formalin-fixed sections, with the thoracic and lumbar segments being the most affected. Pathohistologically, perivascular mononuclear cuffing and axonal swelling, especially in the white matter, were evident. Parallel to the course of disease, alterations in myelin sheets and activation of astrocytes and microglial cells were also observed. Virological findings confirmed an acute equine herpesvirus type 1 infection and virus was isolated from the spinal cord of a 26-year-old mare.     

Evaluation of the opsonic capacity of core lipopolysaccharide antiserum of equine origin against smooth Escherichia coli 0111:B4, using macrophage chemiluminescence

A study was performed to determine whether equine antiserum to core lipopolysaccharide (LPS) would enhance phagocytosis of smooth gram-negative (GN) organisms by equine macrophages. Five healthy adult horses (group A) were immunized with a bacterin prepared from the J-5 mutant of Escherichia coli 0111:B4 and Salmonella minnesota R595 to produce antibodies to core LPS. Five horses (group B) served as nonimmunized controls and were given physiologic saline solution instead of the rough mutant bacterin. Serum antibody titers to core LPS and to smooth E coli 0111:B4 were determined by indirect ELISA. Four serum pools were prepared: pool 1 = sera from horses in group B prior to immunization; pool 2 = sera from horses in group A prior to immunization (preimmune serum); pool 3 = sera from horses in group B, 7 days after the last saline injection; pool 4 = sera from horses in group A, 7 days after the last immunization (core LPS antiserum). The serum pools, either unheated or heated 30 minutes at 56 C, in 3 dilutions (1/50, 1/100, 1/500) were used to opsonize smooth E coli 0111:B4 in an assay of equine peritoneal macrophage chemiluminescence (CL). Peritoneal fluid was collected from clinically normal horses and the macrophages were purified by adherence to borosilicate glass scintillation vials. Each serum type and dilution was added to triplicate vials containing 10(7) colony-forming units of E coli 0111:B4. Luminol-dependent CL was measured with a liquid scintillation counter in the out-of-coincidence mode. Each serum dilution was tested in duplicate vials without bacteria to asses serum-induced nonspecific CL.(ABSTRACT TRUNCATED AT 250 WORDS)     

Lack of Detectable Equine Herpesviruses 1 and 2 in Paraffin-Embedded Specimens of Equine Sarcoidosis

Background: Equine sarcoidosis is a rare, multisystemic, noncaseating, granulomatous and lymphoplasmacytic disease of unknown etiology. A recent report described a horse with granulomatous skin disease displaying histologic, electron microscopic, and polymerase chain reaction (PCR) findings consistent with equine herpesvirus 2 (EHV-2).
Objective: To investigate the presence of EHV-2 and equine herpesvirus 1 (EHV-1) in 8 horses with sarcoidosis.
Animals: Eight horses with sarcoidosis, reported previously.
Methods: Retrospective study. PCR assays of the tissues were performed to detect DNA associated with EHV-1 and EHV-2. For both herpesviruses the target was their respective glycoprotein B gene. Positive controls consisted of DNA from viral cultures of culturettes from naturally occurring respiratory infections of EHV-1 and EHV-2.
Results: The PCR analyses for both equine herpesviruses' DNA were negative in all 8 horses.
Conclusion: The failure to detect DNA from EHV-1 and EHV-2 in paraffin-embedded skin of these 8 horses does not discount EHV-1 or EHV-2 as causing some cases of ES, but lends support to the presumably multifactorial etiologic nature of the disease.     

新疆昭苏地区马梨形虫病病原及抗体检测

马梨形虫病是由马驽巴贝斯虫和马泰勒虫寄生于马属动物的红细胞内所引起的一类血液原虫病,呈全球性分布,尤其在新疆发病率更高,处于逐年上升趋势,对区域性马产业的发展影响极大。为了解2018年新疆昭苏养马区域马梨形虫的感染情况,随机采集昭苏县18个乡镇的马全血及血清各858份,采用PCR和间接ELISA分别进行检测,对两种方法检测的18个地区、不同年龄阶段的马驽巴贝斯虫、马泰勒虫及混合感染情况进行统计学分析。结果显示,PCR检测马驽巴贝斯虫、马泰勒虫及混合感染的阳性率分别为12.12%、13.87%和2.80%;间接ELISA检测马驽巴贝斯虫、马泰勒虫及混合感染的抗体阳性率分别为15.50%、10.14%和2.56%;不同年龄阶段筛查结果显示,在6岁以下的马匹感染马驽巴贝斯虫、马泰勒虫及混合感染的阳性率较高,并且不同地区的不同年龄阶段马匹的马梨形虫感染率存在不同程度的差异。此次获得的昭苏县马梨形虫感染情况的一线数据,可为当地养马区域马梨形虫病的综合防控提供技术支撑。     

Clinical nutrition of adult horses

Horses suffering from trauma, sepsis, and severe burns need 12% to 16% of protein (dry matter basis) in their diet. Since reduced appetite may be a problem, relatively energy dense (greater than 2 Mcal DE/kg) feeds should be offered. In hepatic failure, maintenance protein requirements (8% on a dry matter basis for adult horses) should be met with feeds that are high in short branched-chain amino acids and arginine but low in aromatic amino acids and tryptophan (for example, milo, corn, soybean, or linseed meal) in addition to grass hay. Vitamins A, C, and E should also be supplemented. In cases with renal failure, protein, calcium, and phosphorus should be restricted to maintenance or lower levels. Grass hay and corn are the best feeds for horses with reduced renal function. Do not offer free-choice salt to horses with dependent edema from uncompensated chronic heart failure. Following gastrointestinal resection, legume hay and grain mixtures are the feeds of choice. Horses with diarrhea should not be deprived or oral or enteral alimentation for prolonged periods of time. Liquid formulas may be used if bulk or gastrointestinal motility are a problem. Apple cider vinegar and a high grain diet may reduce the incidence of enteroliths in horses prone to this problem. Pelleted feeds will reduce fecal volume and produce softer feces for horses that have had rectovaginal lacerations or surgery. Horses with small intestinal dysfunction or resection should be offered low residue diets initially, but long-term maintenance requires diets that promote large intestinal digestion (alfalfa hay, vegetable oil, restricted grain). Geriatric horses (greater than 20 years old need diets similar to those recommended for horses 6 to 18 months old.