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1.
OBJECTIVE: To determine whether pasture, and specifically the addition of fructan carbohydrate to the diet, induces exaggerated changes in serum insulin concentration in laminitispredisposed (LP) ponies, compared with ponies with no history of the condition, and also to determine insulin responses to the dexamethasone suppression test. DESIGN: Prospective study. ANIMALS: 10 LP and 11 control adult nonobese mixed-breed ponies. PROCEDURES: Insulin-modified IV glucose tolerance tests were performed (5 ponies/group). In diet studies, ponies were kept on pasture and then changed to a hay diet (10 ponies/group). Second, ponies were maintained on a basal hay diet (4 weeks) before being fed a hay diet supplemented with inulin (3 g/kg/d [1.4 g/lb/d]). Serum insulin and plasma glucose concentrations were analyzed before and after dietary changes. Serum cortisol and insulin concentrations were also measured in a standard dexamethasone suppression test. RESULTS: The LP ponies were insulin resistant (median insulin sensitivity of 0.27 x 10(4) L min(-1) mU(-1) in LP ponies, compared with 0.64 x 10(4) L min(-1) mU(-1) in control ponies). Median insulin concentration in LP ponies was significantly greater than that in control ponies at pasture, decreased in response to feeding hay, and was markedly increased (5.5-fold) following the feeding of inulin with hay. The LP ponies had a greater increase in serum insulin concentration at 19 hours after dexamethasone administration (median, 222.9 mU/L), compared with control ponies (45.6 mU/L). CONCLUSIONS AND CLINICAL RELEVANCE: Nonobese ponies predisposed to develop laminitis had compensated insulin resistance, and this phenotype was revealed by feeding plant fructan carbohydrate or by dexamethasone administration.  相似文献   

2.
OBJECTIVE: To determine the metabolic phenotype of a group of laminitis-prone ponies when at pasture in summer, compared with when at pasture in winter. ANIMALS: 40 ponies of various breeds predisposed to recurrent pasture-associated laminitis and 40 unaffected control ponies. PROCEDURES: Body condition score and size of the crest of the neck were assessed, blood samples obtained, and blood pressure measured by use of an indirect oscillometric technique, while ponies were kept on winter pasture (last week of November or beginning of December) and again on summer pasture (June). Serum insulin concentration and plasma glucose, triglyceride, uric acid, and ACTH concentrations were measured. Insulin sensitivity was calculated with proxies derived from basal serum insulin and plasma glucose concentrations. RESULTS: No significant differences were apparent between ponies predisposed to laminitis and control ponies during winter. However, in June, laminitis-prone ponies had increased serum insulin concentration and plasma triglyceride and uric acid concentrations, compared with control ponies. Also, laminitis-prone ponies were relatively insulin resistant, compared with control ponies. Mean blood pressure was significantly higher during summer in laminitis-prone ponies (median [interquartile range], 89.6 mm Hg [78.3 to 96.9 mm Hg]), compared with control ponies (76.8 mm Hg [69.4 to 85.2 mm Hg]). CONCLUSIONS AND CLINICAL RELEVANCE: Summer pastures appear to induce metabolic responses in some ponies, leading to expression of the prelaminitic phenotype, which includes hypertension as well as insulin resistance. Signs of this metabolic syndrome may not be apparent in affected ponies during periods of grazing winter pasture. Understanding this syndrome may enable improved countermeasures to be devised to prevent laminitis.  相似文献   

3.
OBJECTIVE: To evaluate genetic and metabolic predispositions and nutritional risk factors for development of pasture-associated laminitis in ponies. DESIGN: Observational cohort study. ANIMALS: 160 ponies. PROCEDURES: A previous diagnosis of laminitis was used to differentiate 54 ponies (PL group) from 106 nonlaminitic ponies (NL group). Pedigree analysis was used to determine a mode of inheritance for ponies with a previous diagnosis of laminitis. In early March, ponies were weighed and scored for body condition and basal venous blood samples were obtained. Plasma was analyzed for glucose, insulin, triglycerides, nonesterified fatty acids, and cortisol concentrations. Basal proxies for insulin sensitivity (reciprocal of the square root of insulin [RISQI]) and insulin secretory response (modified insulin-to-glucose ratio [MIRG]) were calculated. Observations were repeated in May, when some ponies had signs of clinical laminitis. RESULTS: A previous diagnosis of laminitis was consistent with the expected inheritance of a dominant major gene or genes with reduced penetrance. A prelaminitic metabolic profile was defined on the basis of body condition, plasma triglyceride concentration, RISQI, and MIRG. Meeting > or = 3 of these criteria differentiated PL- from NL-group ponies with a total predictive power of 78%. Determination of prelaminitic metabolic syndrome in March predicted 11 of 13 cases of clinical laminitis observed in May when pasture starch concentration was high. CONCLUSIONS AND CLINICAL RELEVANCE: Prelaminitic metabolic syndrome in apparently healthy ponies is comparable to metabolic syndromes in humans and is the first such set of risk factors to be supported by data in equids. Prelaminitic metabolic syndrome identifies ponies requiring special management, such as avoiding high starch intake that exacerbates insulin resistance.  相似文献   

4.
Pituitary adenomas are commonly reported in older horses. The typical clinical signs associated with this condition, also known as equine Cushing's disease (ECD), are related to increased adrenocorticotropin (ACTH) production resulting in hyperadrenocorticism. The primary purpose of this study was to determine whether plasma ACTH concentrations differed between cushingoid and healthy horses. The second objective was to determine the effects of blood sample handling techniques on ACTH concentrations. A commercial human ACTH radioimmunoassay (RIA) was used to quantify equine plasma ACTH. Intra-assay and interassay variations, as well as dilutional parallelism were determined during the RIA validation. Plasma ACTH concentrations were evaluated in a group of healthy equids composed of 18 horses and 9 ponies, and in 22 equids with a clinical diagnosis of hyper adrenocorticism (11 horses and 11 ponies). The mean plasma ACTH concentrations in healthy horses and ponies, (18.68 ± 6.79 pg/mL (mean ± SD) and 8.35 ± 2.92 pg/mL, respectively), were significantly different (P = .009). The mean plasma ACTH concentration in horses and ponies with ECD, (199.18 ± 182.82 pglmL and 206.21 ± 319.56 pg/mL, respectively), were significantly higher than the mean ACTH concentration in the control animals (P < .001). Plasma ACTH concentrations appeared to be a sensitive and specific indicator of ECD in horses and ponies. ACTH concentrations measured in plasma samples kept at room temperature (19°C) as long as 3 hours after blood collection were not statistically different from those of samples kept at 1°C. J Vet Intern Med 1996;10:1–6. Copyright 1996 by the American College of Veterinary Internal Medicine .  相似文献   

5.
Ponies were evaluated for their response to feed withholding and exogenous administration of corticosteroids (dexamethasone 0.04 mg/kg intramuscular [IM]) in an attempt to reproduce the hyperlipemia syndrome. Because insulin resistance has been associated with hyperlipemia, all ponies were initially evaluated for insulin response to an oral glucose load and normal dexamethasone suppression of serum cortisol. Four ponies were identified as hyperinsulinemic reflecting insulin resistance. All ponies had suppressed cortisol concentrations following dexamethasone administration. Feed withdrawal resulted in hypertriglyceridemia by 48 hours in all ponies. Very low density lipoprotein-triglyceride (VLDL) fraction was primarily elevated. The administration of dexamethasone failed to increase the degree of triglyceridemia. Although insulin resistance has been proposed as the likely cause of the hypertriglyceridemia in ponies, in this study four of eight ponies were considered to have normal insulin responses and yet still developed hypertriglyceridemia.  相似文献   

6.
Hyperlipemia in horses is a disorder of lipid metabolism peculiar to ponies. This study reports changes of blood biochemical values from the acute to the postconvalescent phases in 3 Shetland ponies with hyperlipemia in Japan. Diseased ponies (all 7 to 9 years old, in late pregnancy, and obese) were fed in the same farm. The periods of their hospitalizations ranged from 30 to 45 days. Twelve well-conditioned ponies (3 to 13 years old) around parturition were used to establish baseline values for blood test results. Main clinical findings in the affected ponies were depression, dysphagia, anorexia, ventral edema and milky-appearing plasma. Hypertriglyceridemia (40- to 70-fold rise of controls) was found in the acute phase of the disease in the affected ponies, and was derived from increased very-low density lipoproteins. Aspartate transaminase and gamma-glutamyl transpeptidase activities, blood urea nitrogen, and creatinin concentrations were increased in acute ponies compared to controls, suggesting impairment of liver and kidney functions. However, these values gradually recovered until the end of postconvalescent phase. Hyperinsulinemia was observed in the acute phase of the hyperlipemia of all affected ponies. And an exaggerated insulin response to intravenous glucose was observed in the 2 ponies given intravenous glucose tolerance tests. These findings suggest decreased insulin sensitivity in hyperlipemic ponies.  相似文献   

7.
To investigate the influence of overweight and dietary fat supplementation on lipid and insulin glucose metabolism of Shetland ponies, eight Shetland pony geldings were fed a hypercaloric (30 MJ DE/150 kg bwt. and day) fat diet (10% fat as soybean oil) or a carbohydrate control diet for nine months until ponies gained an overweight of 15%. Afterwards oral glucose tolerance tests (oGTT; 5, 6 mmol/kg bwt.) were performed after a 12 hour fast and after a fast which led to an increase of plasma triglyceride concentrations to a threshold of 3 mmol/l (36-65 hrs.). Plasma concentrations of glucose, insulin, triglycerides and non esterified fatty acids (NEFA) were determined for 480 minutes after the glucose load. Ponys having had received the control diet tended to a higher insulin secretion in case of both oGTTs, whereas the glucose tolerance was similar in both groups but lower than in ponies of normal weight. During the oGTTs after fasting leading to the plasma triglyceride threshold, triglyceride concentrations decreased significantly (p < 0.05) faster and stronger in fat fed ponies. Additionally, fat fed pony showed significantly (p < 0.05) lower NEFA levels. The results of this study demonstrate a positive effect of fat feeding on the triglyceride clearance of overweight Shetland ponies.  相似文献   

8.
Identification of ponies (Equus caballus) at increased risk of pasture-associated laminitis would aid in the prevention of the disease. Insulin resistance has been associated with laminitis and could be used to identify susceptible individuals. Insulin resistance may be diagnosed by feeding supplementary water-soluble carbohydrate (WSC) and measuring blood glucose and insulin concentrations. The aim of this study was to assess the glycemic and insulinemic responses of 7 normal (NP) and 5 previously laminitic (PLP), mixed breed, native UK ponies fed glucose, fructose, and inulin [1 g/(kg(.)d) for 3 d] or no supplementary WSC (control) in spring and fall after a 7-d adaptation to a pasture or hay diet. Blood samples were taken for 12 h after feeding on each day, and baseline and peak concentrations and area under the curve (AUC) for glucose and insulin were recorded. Linear mixed models were used for statistical analysis. Differences between PLP and NP groups were most marked after glucose feeding with differences in peak glucose (P = 0.02) and peak insulin (P = 0.016) concentrations. Season and diet adaptation also affected results. Peak concentrations of glucose and insulin occurred 2 to 4 h after WSC feeding. Peak insulin concentration was greater and more variable in fall, particularly in PLP adapted to fall pasture. Baseline glucose and insulin concentrations varied between individuals and with season and diet adaptation but were not greater in PLP than NP. Insulin AUC was greater in PLP than NP after feeding both glucose and fructose (P = 0.017), but there were no differences between PLP and NP in glucose AUC. Glycemic and insulinemic changes were less (P ≤ 0.05) after feeding fructose than glucose, although differences between PLP and NP were still evident. Minimal changes in glucose and insulin concentrations occurred after inulin feeding. Measurement of peak insulin 2 h after feeding of a single dose of glucose (1 g/kg) may be a simple and practical way to aid identification of laminitis-prone ponies before the onset of clinical disease, particularly when ponies are adapted to eating fall pasture.  相似文献   

9.
The purpose of this study was to determine the effects of prolonged administration of insulin, whilst maintaining normal glucose concentrations, on hoof lamellar integrity in vivo on healthy ponies with no known history of laminitis or insulin resistance. Nine clinically healthy, unrelated ponies were randomly allocated to either a treatment group (n =5; 5.9+/-1.7 years) or control group (n =4; 7.0+/-2.8 years). The treatment group received insulin via a euglycaemic hyperinsulinaemic clamp technique modified and prolonged for up to 72 h. Control ponies were infused with an equivalent volume of 0.9% saline. Ponies were euthanized at the Obel grade 2 stage of clinical laminitis and hoof lamellar tissues were harvested and examined for histopathological evidence of laminitis. Basal serum insulin and blood glucose concentrations were 15.7+/-1.8 microU/mL and 5.2+/-0.1 mmol/L, respectively (mean+/-SE) and were not significantly different between groups. Mean serum insulin concentration in treatment ponies was 1036+/-55 microU/mL vs. 14.6 microU/mL in controls. All ponies in the treatment group developed clinical and histological laminitis (Obel grade 2) in all four feet within 72 h (55.4+/-5.5h), whereas none of the control ponies developed laminitis. There was no clinical evidence of gastrointestinal involvement and the ponies showed no signs of systemic illness throughout the experiment. The data show that laminitis can be induced in healthy young ponies, with no prior history of laminitis, by maintaining prolonged hyperinsulinaemia with euglycaemia. This suggests a role for insulin in the pathogenesis of laminitis, independent of hyperglycaemia, or alterations in hind-gut fermentation. For the clinician, early detection and control of hyperinsulinaemia may facilitate management of endocrinopathic laminitis.  相似文献   

10.
Metformin may be an effective therapeutic option for insulin-resistant (I-R) horses/ponies because, in humans, it reportedly enhances insulin sensitivity (SI) of peripheral tissues without stimulating insulin secretion. To determine the effect of metformin on insulin and glucose dynamics in I-R ponies, six ponies were studied in a cross-over design by Minimal Model analysis of a frequently-sampled intravenous glucose tolerance test (FSIGT). Metformin was administered at 15 mg/kg bodyweight (BW), orally, twice-daily, for 21 days to the metformin-treated group. The control group received a placebo. A FSIGT was conducted before and after treatment. The Minimal Model of glucose and insulin dynamics rendered indices describing SI, glucose effectiveness (Sg), acute insulin response to glucose (AIRg) and the disposition index (DI). The body condition score (BCS), BW and cresty neck score (CNS) were also assessed. There was no significant change in SI, Sg, AIRg, DI, BW, BCS or CNS in response to metformin, or over time in the control group. There were no measurable benefits of metformin on SI, consistent with recent work showing that the bioavailability of metformin in horses is poor, and chronic dosing may not achieve therapeutic blood concentrations. Alternatively, metformin may only be effective in obese ponies losing weight or with hyperglycaemia.  相似文献   

11.
Reasons for performing study: Anatomical changes in the hoof lamellar tissue induced by prolonged hyperinsulinaemia have not been described previously. Analysis of the induced lesions may promote understanding of hyperinsulinaemic laminitis pathogenesis and produce clinical benefit. Objectives: To use light and transmission electron microscopy (TEM) to document hoof lamellar lesions in ponies clinically lame after prolonged hyperinsulinaemia. Methods: Nine clinically normal, mature ponies were allocated randomly to either a treatment group (n = 5) or control group (n = 4). The treatment group received insulin via a modified, prolonged euglycaemic hyperinsulinaemic clamp technique (EHCT) and were subjected to euthanasia when clinical signs of Obel grade II laminitis occurred. The control group was sham treated with an equivalent volume of 0.9% saline and killed at 72 h. Lamellar tissues of the right front feet were harvested and processed for TEM. Results: Lamellae from insulin treated ponies were attenuated and elongated with many epidermal basal cells (EBC) in mitosis. Unlike carbohydrate induced laminitis in horses there was no global separation at the lamellar dermal/epidermal interface among ponies. Sporadic EBC basement membrane (BM) separation was associated with the proximity of infiltrating leucocytes. In 2 ponies, the lamellar BM was thickened. The number of hemidesmosomes/μm of BM was decreased in all insulin treated ponies. Conclusions: Prolonged hyperinsulinaemia causes unique lamellar lesions normally characteristic of acute and chronic laminitis. Lamellar proliferation may be an insulin effect through its mitogenic pathway. Aberrant lamellar mitosis may lengthen and weaken the lamellar, distal phalanx attachment apparatus and contribute to the clinical signs that developed. Potential relevance: The study shows that insulin alone, in higher than normal circulating concentrations, induces profound, changes in lamellar anatomy. Medical control of insulin resistance and hyperinsulinaemia may ameliorate lesions and produce clinical benefit.  相似文献   

12.
Reasons for performing study: The ability to predict ponies at increased risk of laminitic episodes, when exposed to nutrient dense pasture, would facilitate management to avoid disease. Objectives: To identify variables and clinically useful cut‐off values with reproducible diagnostic accuracy for the prediction of ponies that subsequently developed laminitis when exposed to nutrient dense pasture. Methods: A cohort of predominantly Welsh and Dartmoor ponies from a closed herd was evaluated in March 2006 (n = 74) and March 2007 (n = 57). Ponies were categorised as never laminitic or previously laminitic according to reported laminitic history and as clinically laminitic (CL) if laminitis was observed within 3 months following evaluation. Body condition score (BCS), cresty neck score (CNS), girth and neck circumferences (NC), withers height, blood pressure and hoof surface temperature, and plasma insulin, glucose, triglyceride, leptin, cortisol, ACTH, uric acid and TNF‐α concentrations were measured. Analysis of sensitivity, specificity and receiver operating characteristic curves was used to evaluate the diagnostic accuracy for a variable to predict CL ponies. Results: Variables with diagnostic accuracy for the prediction of CL ponies included insulin, leptin, BCS, CNS, and NC:height ratio. Specific cut‐off values of insulin (>32 mu/l), leptin (>7.3 ng/ml), BCS (≥7), CNS (≥4) and NC:height ratio (>0.71) had reproducible diagnostic accuracy for the prediction of laminitis. Combining tests did not result in higher diagnostic accuracy than individual tests of insulin or leptin during either evaluation. Conclusions: Tests of insulin and leptin concentrations and measures of generalised (BCS) and localised (CNS or NC:height ratio) obesity were beneficial in the prediction of laminitic episodes. Potential relevance: These results highlight the importance of monitoring and reducing insulin concentration, and generalised and regional obesity in ponies to reduce risk of laminitis.  相似文献   

13.
Equine metabolic syndrome (EMS) is important because of its association with laminitis. Obesity and insulin resistance are two important components of EMS, and the underlying cause of this syndrome is likely to be enhanced metabolic efficiency. Affected horses are often referred to as “easy keepers” because they require fewer calories to maintain body condition, and enhanced metabolic efficiency is an inherent risk factor for EMS that may be genetically determined. Pony breeds, Morgan horses, and Paso Finos are predisposed to EMS, but this problem can be prevented through effective management. Overfeeding, abundant pasture grass, and inadequate exercise are risk factors that relate to modern management practices. Obesity and adiposity induce insulin resistance, and recent research suggests that this is the determinant of laminitis susceptibility in ponies. Increased plasma insulin concentrations are detected in most affected horses and ponies, so this serves as a useful screening test for EMS. Physical characteristics also should be examined because horses with EMS exhibit regional adiposity in the form of a cresty neck or abnormal adipose tissue deposits close to the tailhead. All horses with enhanced metabolic efficiency, obesity, or regional adiposity should be screened for EMS. The combined intravenous glucose−insulin test can be performed to diagnose insulin resistance in mildly affected horses and quantify insulin sensitivity. Most horses with EMS can be effectively managed by reducing caloric intake, decreasing the starch and sugar content of the diet, increasing exercise, and limiting or eliminating access to pasture, but medical therapy is warranted in select cases.  相似文献   

14.
To determine whether plasma leptin concentrations and glucose tolerance are affected by changes in energy balance, nine healthy Shetland ponies were fed at 140% followed by 75% of their maintenance requirements for 13 days in each of the two periods. Bodyweight was recorded every three days. Blood samples were taken every two days and analysed for leptin and cortisol. An oral glucose tolerance test was performed on day 7 of each period. Serial blood samples were analysed for glucose and insulin. Although bodyweight was not affected, plasma leptin concentrations increased (P<0.001) initially during overfeeding, but returned to previous values after 7 days. During underfeeding, plasma leptin concentrations decreased (P<0.001). Underfeeding was associated with a higher AUC for plasma glucose (P=0.02) and plasma insulin (P=0.05) resulting in a decreased glucose tolerance (AUC glucose/AUC insulin; P=0.008), probably due to a plasma cortisol increase caused by the reduced feed intake. It is concluded that changes in energy balance, without altering bodyweight, can influence plasma leptin concentrations in ponies.  相似文献   

15.
Laminitis is a painful, inflammatory disease of the equine hoof that often results in euthanasia. Elevated plasma insulin concentrations are a predictive factor for laminitis, and in previously healthy horses and ponies, laminitis was induced by infusion of insulin. Thus, we chose to determine if an infusion of insulin would increase plasma concentrations of inflammatory cytokines and cytokine mRNA abundance in subcutaneous adipose tissue, skeletal muscle, and white blood cells. Ten mature Thoroughbred mares received an insulin infusion that elevated plasma insulin concentrations for 6h or an equivalent volume of isotonic saline in a switchback design. Insulin infusion altered plasma concentrations of both TNF (P=0.037) and IL-6 (P=0.044), but did not result in consistent changes to either skeletal muscle or adipose tissue cytokine mRNA. Insulin may be involved in the production of inflammatory cytokines, and this could be a mechanism for insulin increasing the risk of laminitis.  相似文献   

16.
OBJECTIVE: To determine effects of dexamethasone on glucose dynamics and insulin sensitivity in healthy horses. ANIMALS: 6 adult Standardbreds. PROCEDURES: In a balanced crossover study, horses received dexamethasone (0.08 mg/ kg, IV, q 48 h) or an equivalent volume of saline (0.9% NaCl) solution (control treatment) during a 21-day period. Horses underwent a 3-hour frequently sampled IV glucose tolerance test (FSIGT) 2 days after treatment. Minimal model analysis of glucose and insulin data from FSIGTs were used to estimate insulin sensitivity (Si), glucose effectiveness (Sg), acute insulin response to glucose (AIRg), and disposition index. Proxies for Si (reciprocal of the inverse square of basal insulin concentration [RISQI]) and beta-cell responsiveness (modified insulin-to-glucose ratio [MIRG]) were calculated from basal plasma glucose and serum insulin concentrations. RESULTS: Mean serum insulin concentration was significantly higher in dexamethasone-treated horses than control horses on days 7, 14, and 21. Similarly, mean plasma glucose concentration was higher in dexamethasone-treated horses on days 7, 14, and 21; this value differed significantly on day 14 but not on days 7 or 21. Minimal model analysis of FSIGT data revealed a significant decrease in Si and a significant increase in AIRg after dexamethasone treatment, with no change in Sg or disposition index. Mean RISQI was significantly lower, whereas MIRG was higher, in dexamethasone-treated horses than control horses on days 7, 14, and 21. CONCLUSIONS AND CLINICAL RELEVANCE: The study revealed marked insulin resistance in healthy horses after 21 days of dexamethasone administration. Because insulin resistance has been associated with a predisposition to laminitis, a glucocorticoid-induced decrease in insulin sensitivity may increase risk for development of laminitis in some horses and ponies.  相似文献   

17.
REASONS FOR PERFORMING STUDY: Elevated plasma homocysteine (HCy) concentration is a risk factor for cardiovascular diseases associated with endothelial dysfunction, including the human digital ischaemic disease, Raynaud's phenomenon. HYPOTHESIS: HCy causes dysfunction of equine vascular endothelium and elevated plasma concentrations predispose to laminitis. OBJECTIVES: To determine 1) the concentration of HCy in vitro, which inhibits equine vascular endothelial cell function and 2) any association between risk of laminitis and plasma HCy concentration. METHODS: Endothelial function was studied by measuring endothelium-dependent vasodilatory responses of the equine isolated perfused digit and basal nitric oxide (NO) production by cultured equine digital vein endothelial cells (EDVECs). Total plasma HCy (tHCy) concentrations were measured in samples collected in the winter and spring from normal ponies and ponies predisposed to laminitis. RESULTS: HCy (10 and 100 micromol/l) inhibited endothelial function and, at concentrations above 100 micromol/l, inhibited NO production by EDVECs. Plasma tHCy concentration ranged from 13 to 14.7 micromol/l. There was no effect of season or disease status on the concentration measured. CONCLUSIONS: In vitro, HCy was shown to interfere with endothelial cell function at physiologically relevant concentrations. No evidence was found for an association between risk of laminitis and high plasma concentrations of HCy. POTENTIAL RELEVANCE: Elevated plasma HCy concentrations could adversely affect endothelial cell function and mangement regimens that lead to increases in plasma HCy concentration should be avoided in ponies predisposed to laminitis.  相似文献   

18.
Reasons for performing study: Ponies with laminitis associated with insulin resistance and hyperinsulinaemia lack systemic and/or intestinal inflammatory signs, suggesting a different pathogenesis potentially reflected in differing histopathology. Objectives: To describe the histological appearance and quantify morphological changes in primary and secondary epidermal lamellae (PEL and SEL) of laminitis lesions from ponies with insulin‐induced laminitis. Methods: Equine hoof lamellar tissue was obtained from 4 control ponies and 5 ponies with laminitis induced following infusion of insulin (1036 ± 55 µU/ml) while maintaining euglycaemia for 55.4 ± 5.5 h. Sections from all 4 hooves were stained and examined by a veterinary pathologist. Measurements of lamellar length (PEL and SEL) were made in mid‐dorsal sections of the right forefeet by 2 blinded observers. Immunolabelling for calprotectin was performed using a monoclonal antibody. Results: No lesions were detected in normal ponies. Lesions detected in ponies with laminitis were variable in severity between ponies. Within ponies, SEL lesions were more severe along the axial region of PEL. Lesions included swelling, disorganisation and abnormal keratinisation of epidermal cells, increased mitotic activity and apoptosis. Separation of basement membranes was minimal. Immunostaining revealed inflammatory cells within the lamellar dermis. SEL were significantly elongated in laminitic hooves relative to controls, with the greatest elongation in those attached to abaxial and middle regions of PEL. Conclusions: Laminitis induced by prolonged infusion of insulin lacked widespread basement membrane disintegration, and increases in epidermal cellular proliferation at axial aspects were marked for this acute stage of disease. Potential relevance: Defining equine laminitis entirely in terms of separation of the basement membrane may not be appropriate for laminitis associated with hyperinsulinaemia.  相似文献   

19.
Dried tansy ragwort, which contains pyrrolizidine alkaloids, was fed as 10% of a complete diet to ponies, with and without a mixture of additives. The additives provided a dietary supplement equivalent to 1% cysteine, 0.75% butylated hydroxyanisole, 200 micrograms of vitamin B12/kg of feed, and 5 mg of folic acid/kg of feed. The additives did not alter tansy ragwort toxicity, as assessed by survival time, liver changes, sulfobromophthalein (BSP) clearance rate, serum gamma-glutamyl transpeptidase activity, and plasma amino acid patterns. In ponies fed tansy ragwort, BSP clearance rate was a sensitive indicator of liver damage, and decreased to about 20% of control values. gamma-Glutamyl transpeptidase activities showed considerable variability, but generally were elevated in animals fed tansy ragwort. Liver iron and copper concentrations increased, and liver zinc concentrations decreased in tansy ragwort-fed ponies. Plasma amino acid patterns in tansy ragwort-fed ponies showed changes typical of those observed in liver disease.  相似文献   

20.
Four ileal cannulated ponies (average weight, 136 kg) were used in a replicated Latin Square experiment to determine the site and extent of calcium, magnesium and phosphorous absorption in the presence of elevated amounts of dietary aluminum. During each experimental period, ponies were fed 1.25 kg of a basal diet with or without 0.45% added aluminum as aluminum sulfate. Following an 8-day adjustment, ileal, fecal and feed samples were collected for 6-days collection. Chromic oxide (0.2% of diet) was used as an indicator to measure flow through the digestive tract. The primary site of calcium absorption was the small intestine. Adding 0.45% aluminum to the diet of ponies did not alter (P>.05) the site or efficiency of calcium absorption. Ponies fed 0.45% aluminum tended (P>.05) to absorb larger quantities of magnesium from the total digestive tract. This is probably an indirect response of aluminum on magnesium absorption rather than a direct interaction of these minerals. The major site of apparent phosphorus absorption in ponies was the large intestine with a net secretion of phosphorus into the small intestine. Aluminum decreased (P<.05) the percentage of phosphorus absorbed from the large intestine by 59%. Equine grazing forages which contain elevated concentrations of aluminum or are contaminated with aluminum-containing soil may need phosphorus supplementation.  相似文献   

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