Onset Of Laminitis Research Articles

Preliminary Investigation of the Changes in Fecal Streptococcal Population due to Diet and Time of Day in Horses

A growing number of equine studies examine management factors that influence the microbial populations in regions of the gastrointestinal tract using culture-independent molecular techniques. We used quantitative polymerase chain reaction (qPCR) to evaluate changes in fecal streptococcal populations in horses fed different maturities of teff hay with fecal samples collected at 7 AM, 12 PM, and 7 PM. The objective of this study was to use qPCR and species-specific probes for 16S ribosomal DNA to quantify the percentage of equine hindgut streptococcal species (EHSS) relative to the total bacterial load in the feces. Feces from horses fed the most mature teff hay had the lowest %EHSS, and feces collected at 12:00 had the highest %EHSS (P < .05). Our interest in investigating %EHSS developed out of research that examined associations between changes in EHSS populations and the onset of laminitis. Although we expected almost no risk of laminitis in these forage fed horses, our hypothesis was that the different carbohydrate fractions in the three maturities of hay would result in differences in %EHSS in horses fed these hay maturities. The supply of carbohydrates, nonstructural or structural, influences the microbial species composition through the gastrointestinal tract. This study highlights the occurrence of measurable changes in %EHSS due to subtle changes in dietary nonstructural carbohydrate and also changes in samples taken at different times of day. This information is useful to others considering investigations of dietary influences on gastrointestinal microbial populations, particularly those that plan to use feces as their main sample medium.

No Evidence That Therapeutic Systemic Corticosteroid Administration is Associated With Laminitis in Adult Horses Without Underlying Endocrine or Severe Systemic Disease.

Clinical bottom line&#x0D; &#x0D; There is currently no conclusive evidence to support a causal association between therapeutic systemic corticosteroid administration and the development of laminitis in healthy adult horses/ponies.&#x0D; There is weak evidence of an association between administration of multiple doses of systemic corticosteroid and the onset of laminitis in adult horses/ponies with underlying endocrine disorders or severe systemic disease.&#x0D;

Comparison of a colorimetric and a high‐performance liquid chromatography method for the determination of fructan in pasture grasses for horses

Pasture (fresh or conserved as hay/haylage) forms the basis of most equid diets and contains varying amounts (0 to ≥ 200 g kg⁻¹ dry matter (DM) or more) of fructans. Over-consumption of fructan is associated with the onset of laminitis in equids, an agonizing condition that may necessitate euthanasia. To enable appropriate dietary management of animals susceptible to laminitis, it is essential that fructans can be properly quantified in fresh and conserved pasture. For research purposes, fructans are frequently quantified by high-performance liquid chromatography (HPLC), but these methods are costly for routine screening. However, an inexpensive colorimetric method for measuring fructans in human foods is commercially available. The aim here was to determine the suitability of the commercially available colorimetric method for determining the fructan content of pasture grasses for horses. Pasture grasses (Phleum pretense, Festuca rubra, Dactylis glomerata, Lolium perenne) managed for grazing (sampled from April to November) and a further set managed for conservation (sampled in July) were analysed for fructan content by HPLC and the colorimetric technique. HPLC values ranged from 83 to 299 g fructan kg⁻¹ DM (mean 154); corresponding colorimetric values were 5-238 g fructan kg⁻¹ DM (mean 82). Discrepancies in values between the two methods varied with time of sampling and plant species. Comparison of selected samples before and after incubation with the fructan hydrolases used in the colorimetric method revealed incomplete fructan hydrolysis from the pasture grasses, resulting in underestimates of their fructan content. The colorimetric technique was not a reliable substitute for HPLC to quantify the fructan content of pasture grasses.

An investigation into daily fluctuations in faecal pH in healthy equine

Laminitis is often recognised as one of the most common causes of lameness in horses. This painful condition has obvious far-reaching implications for the welfare of affected animals, yet, despite the prevalence and seriousness of laminitis, the exact aetiology of the disease has still to be unanimously identified. It is generally accepted that acidosis within the hind gut of the horse is a predisposing factor to the onset of laminitis (Bailey et al., 2003). Fast digestive transit times and low production rates of α-amylase, result in the horse being relatively inefficient at the breakdown of starch within the small intestine. Rapid fermentation of cereal starch in the caecum and dorsal colon will ultimately yield lactic acid and can culminate in changes to the caecal bacterial populations (Bailey et al, 2003). Rising lactic acid levels, coupled with a drop in pH will result in the development of acidosis. It is believed that a window of opportunity exists between the occurrence of acidosis and the development of the symptoms associated with laminitis (Al Jassim, 2005) in which changes to diet could be made, thus preventing the eventual onset of the disease. It has been established that faecal pH is intrinsically linked to caecal pH, and studies reporting diet-induced pH changes in both horses (McLean et al., 2000) and pigs (Cahn et al., 1998), have shown close correlation between faecal and caecal pH. It is therefore postulated that faecal pH may be an indication of acidotic conditions within the hindgut of the horse and a faecal test to indicate acidotic status would obviously be of benefit. The aim of this study was to investigate optimal collection times of faecal samples destined for pH analysis, and to establish whether time of feeding significantly altered faecal pH, thus enabling further work to be carried out on the development of a faecal test for acidosis.

Unilateral Basement Membrane Zone Alteration of the Regenerated Laminar Region in Equine Chronic Laminitis

Between the laminar epidermis and the laminar dermis of laminar region (LR) in equine foot, it can be observed the basement membrane zone (BMZ), which is composed of a basement membrane and its accompaniments like the hemidesmosome and anchoring fibril. Alteration in the BMZ in equine laminitis is possibly related with not only development but also recovery outcome and recurrence of this disease. However, there is little known about the structure of the BMZ during the recovery phase of this disease. To assess the condition of the BMZ of LR affected by chronic laminitis, the tissue was examined in three cases at two weeks, four weeks and three months after the onset of laminitis, using pathological, immunohistochemical and electron microscopic techniques. Histologically in all laminitis cases, there was a regenerated laminar epidermis with proliferating keratinocytes between the Stratum medium and the dermis, but it included the undeveloped secondary epidermal laminae (ud-SELs) structure in one side of the primary epidermal laminae, especially in the part of the deep area of LR. Immunohistochemical results were positive for the anti-type IV collagen, anti-type VII collagen and anti-laminin 5 antibodies in the most BMZs. However, partial BMZs adjacent to the ud-SELs were negative for the anti-type VII collagen and anti-laminin 5 antibodies. Ultrastructurally, in the BMZ of the ud-SEL, the lamina densa and the lamina lucida were present. In contrast, the anchoring fibrils and the hemidesmosomes were either absent, or present at lower than normal levels. In conclusion, the present study indicated that the part of regenerated LR in chronic laminitis was not able to fully restore to construct the BMZ for a long time, especially in the unilateral side of laminar epidermis. It might be related with recurrence of this disease.

Localisation of gelatinase activity in epidermal hoof lamellae by in situ zymography.

In situ gelatin zymography is a technique, which utilises a gelatin-based emulsion overlay to detect and, more importantly, localise the gelatinase activity in underlying tissue. Gelatinase A [matrix metalloproteinase-2 (MMP-2)] and gelatinase B [matrix metalloproteinase-9 (MMP-9)] are present in equine hoof homogenates and supernatants from cultured hoof explants by SDS-PAGE gelatin zymography, and it has been assumed that the enzymes are derived solely from matrix and epithelia and not from other sources such as leucocytes. Using in situ zymography, gelatinases are shown to be localised within the equine epidermal hoof lamellae and, more specifically, are apparently produced by epidermal basal and/or parabasal cells. The pattern of expression correlates with that expected based on the progression of pathological changes observed during the onset of laminitis, thus providing further evidence that laminitis pathology probably arises as a result of inadequate local MMP regulation.

Gamma scintigraphic analysis of the distribution of perfusion of blood in the equine foot during black walnut (Juglans nigra)-induced laminitis

SUMMARY Twelve horses, with acute laminitis (primarily in the forefeet) at 12 hours after intragastric dosing with an aqueous extract of black walnut (Juglans nigra) heartwood, were studied. The distribution of perfusion of blood to the foot and to outlined regions within the foot was quantified, using γ scintigraphy of regionally infused 99mTc-labeled macroaggregated albumin, before and 12 hours after extract administration. Horses 1 to 3 were not studied further. Perfusion was quantified again for horses 4 to 12 at 84 hours after extract administration. At the onset of acute laminitis, horses 7 to 12 were administered a single dose of prazosin (0.025 mg/kg of body weight, iv) immediately after scintigraphy of the right forelimb and before scintigraphy of the left forelimb. When compared with baseline images, perfusion to the forefoot of horses after the development of acute laminitis was quantitatively decreased vs perfusion to the entire distal portion of the forelimb. Also with the onset of laminitis, perfusion also decreased to the dorsal laminar and coronary corium regions vs the distal portion of the forelimb. The acute laminitis-associated deficit in perfusion to the dorsal lamina was greater in magnitude than the deficit in perfusion to either the coronary corium or the entire forefoot. Equivalent deficits in the distribution of perfusion were not detected in forelimbs from horses with acute laminitis and which had been treated with prazosin. When compared with baseline images, perfusion to the dorsal lamina was increased in relation to perfusion to the distal portion of the limb at postdosing hour 84. Prazosin treatment did not influence that increase in perfusion to the dorsal lamina.

Circulatory and blood gas changes accompanying the development and treatment of induced laminitis

Summary A peripheral vasodilatory agent, isoxsuprine hydro-chloride, was evaluated in a controlled study for its efficacy in the treatment of acute equine laminitis. Eight healthy, adulthorses of variable age and sex were used in the trial. Acute laminitis was induced in 5 of the horses by oral carbohydrate overload. Intravenous isoxsuprine therapy (1.8 mg/kg) was initiated in 3 of the horses receiving carbohydrate overload at first sign of clinical lameness and repeated at 12-hour intervals. Intravenous saline placebos were administered on a similar schedule to 2 control horses which also received a carbohydrate overload. The remaining 3 horses served as further controls. Local and systemic responses to induction of laminitis and isoxsuprine administration were assessed by subjective evaluation of clinical lameness in a double blind trial; nuclear scintigraphy and radiography of the distal forelimbs; and assessment of physical, hematological and biochemical parameters. Pronounced tachycardia, hypotension and sweating accompanied the intravenous infusion of isoxsuprine. The 3 horses treated with isoxsuprine following the induction of laminitis showed a more rapid improvement in soundness than horses receiving saline placebos. No horse developed rotation of the third phalanx in response to the diet Nuclear scintigraphy indicated that blood perfusion patterns within the hoof of laminitic horses altered with isoxsuprine therapy, but an overall increase or decrease in perfusion was not apparent. Alterations in serum enzyme and electrolyte profiles with the onset of laminitis generally concurred with findings previously reported for this model of the disease. No change in coagulation profiles accompanied the onset of laminitis or isoxsuprine administration. Blood gas analysis indicated an increase in median palmar vein oxygen partial pressure (PO 2 ) levels with onset of laminitis. A concurrent decrease in the median palmar arteriovenous oxygen partial pressure difference (AVO 2 ) was significant at the P 2 values between thoseanimals receiving isoxsuprine and those receiving saline placebo therapy. Results of the trialindicated that isoxsuprine may be beneficial in the treatment of acute laminitis. Further controlled studies are appropriate.

Changes in the caecal flora associated with the onset of laminitis.

Caecal fluid samples collected 8 and 24 hours after carbohydrate overload were quantitatively compared to control samples in terms of aerobic and anaerobic bacteria. Concomitant increases in lactic acid-producing bacteria and decreases in Gram negative bacteria were substantiated during the onset of acute laminitis. Progressive decreases in caecal fluid pH were also quantitated. Although endotoxin assays of caecal fluid and blood were not done, the caecal flora changes suggest its presence during the onset of acute laminitis.