Background: Diagnosis of pituitary pars intermedia dysfunction (PPID) is problematic because of large variations in ACTH concentrations. Hypothesis/Objectives: Compare the test characteristics of baseline and post-thyrotropin-releasing hormone (TRH) stimulation plasma ACTH concentrations in horses using diagnostic cutoff values (DCOVs) and reference intervals (RIs) and determine the clinical consequences of using each method. Animals: One hundred six mature horses: 72 control cases and 34 PPID cases. Methods: Prospective case-controlled study. Horses underwent monthly TRH stimulation tests. Diagnostic cutoff values were determined monthly by receiver operating characteristic curves using the Youden index. Reference intervals were determined monthly by a robust method. For each case age, sex and body condition score (BCS) were recorded. Results: Baseline ACTH concentrations varied by month (P < .001) with significant "month × age" (P = .003), "month × sex" (P = .003), and "month × BCS" (P = .007) effects. Baseline ACTH concentrations were accurate to diagnose PPID (0.91 ± 0.06) with DCOVs increasing the test sensitivity (0.61 ± 0.21 to 0.87 ± 0.05, P = .002) and RI increasing test specificity (0.85 ± 0.12 to 0.98 ± 0.01, P = .01). Thyrotropinreleasing hormone stimulation improved test accuracy (0.91 ± 0.06 to 0.97 ± 0.03, P = .004). Conclusions and Clinical Importance: ACTH concentrations follow a circannual rhythm and vary with physiological factors. As using DCOVs increases the ability to detect mild cases and using RI decreases the risk of unnecessary treatments, ACTH concentrations should be interpreted within a specific clinical context. The TRH stimulation test improves the diagnosis of PPID.

This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain. Abstract 19Failure of lamellar energy metabolism may contribute to the pathophysiology of equine 20 laminitis. Tissue microdialysis has the potential to dynamically monitor lamellar energy 21 balance over time. The objectives of this study were to develop a minimally invasive lamellar 22 microdialysis technique and use it to measure normal lamellar energy metabolite 23 concentrations over 24 h. Microdialysis probes were placed (through the white line) into 24 either the lamellar dermis (LAM) (n = 6) or the sublamellar dermis (SUBLAM) (n = 6) and 25 perfused continuously over a 24 h study period. Probes were placed in the skin dermis 26 (SKIN) for simultaneous comparison to LAM (n = 6). Samples were collected every 2 h and 27 analysed for glucose, lactate, pyruvate, urea and glycerol concentrations. LAM was further 28 compared with SUBLAM by simultaneous placement and sampling in four feet from two 29 horses over 4 h. Horses were monitored for lameness, and either clinically evaluated for 1 30 month after probe removal (n = 4) or subjected to histological evaluation of the probe site (n 31 = 10). 32 33 There were no deleterious clinical effects of probe placement and the histological 34 response was mild. Sample fluid recovery and metabolite concentrations were stable for 24 h. 35Glucose was lower (and lactate:glucose ratio higher) in LAM compared with SUBLAM and 36 SKIN (P < 0.05). Pyruvate was lower in SUBLAM than SKIN and urea was lower in LAM 37 than SKIN (P < 0.05). These differences suggest lower perfusion and increased glucose 38 consumption in LAM compared with SUBLAM and SKIN. In conclusion, lamellar tissue 39 microdialysis was well tolerated and may be useful for determining the contribution of 40 energy failure in laminitis pathogenesis. 41 42

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SummaryReasons for performing study: Prophylactic digital hypothermia reduces the severity of acute laminitis experimentally but there is no evidence for its efficacy as a treatment once lameness has already developed. Objectives: To investigate the therapeutic effects of digital hypothermia, applied after the onset of lameness, in an experimental acute laminitis model. Study design: Randomised, controlled (within subject), blinded, experimental trial. Methods: Eight Standardbred horses underwent laminitis induction using the oligofructose model. Once lameness was detected at the walk, one forelimb was continuously cooled (CRYO), with the other forelimb maintained at ambient temperature (NON-RX). Dorsal lamellar sections (proximal, middle and distal) harvested 36 h after the onset of lameness/initiation of cryotherapy were analysed by 2 blinded observers: laminitis pathology was scored . There was complete physical separation of lamellar dermis from epidermis (score of 4) in 4 of the NON-RX feet at one or more section level(s), which was not observed in any CRYO sections. Histomorphometry was thus limited to sections that remained intact; there was a trend of increased total (TELL) and secondary (SELL) epidermal lamellar length and decreased secondary epidermal lamellar width (SELW) in NON-RX limbs compared with CRYO at all 3 levels; differences were significant (P<0.05) for SELL and SELW in the distal sections. Conclusions: Digital hypothermia reduced the severity of lamellar injury and prevented lamellar structural failure (complete dermoepidermal separation) when initiated at the detection of lameness in an acute laminitis model. This study provides the first evidence to support the use of therapeutic digital hypothermia as a treatment for acute laminitis.

Summary Background Continuous digital hypothermia can prevent the development and progression of laminitis associated with sepsis but its effects on laminitis due to hyperinsulinaemia are unknown. Objectives To determine the effects of continuous digital hypothermia on laminitis development in the euglycaemic hyperinsulinaemic clamp model. Study design Randomised, controlled (within subject), blinded, experiment. Methods Eight clinically normal Standardbred horses underwent laminitis induction using the euglycaemic hyperinsulinaemic clamp model (EHC). At initiation of the EHC, one forelimb was continuously cooled (ICE), with the other maintained at ambient temperature (AMB). Dorsal lamellar sections (proximal, middle, distal) were harvested 48 h after initiation of the EHC and were analysed using histological scoring (0–3) and histomorphometry. Cellular proliferation was quantified by counting epidermal cell nuclei staining positive with an immunohistochemical proliferation marker (TPX2). Results Severe elongation and disruption of SEL with dermo‐epidermal separation (score of 3) was observed in all AMB feet at one or more section locations, but was not observed in any ICE sections. Overall 92% of the AMB sections received the most severe histological score (grade 3) and 8% were grade 2, whereas ICE sections were classified as either grade 1 (50%) or grade 2 (50%). Relative to AMB feet, ICE sections were 98% less likely to exhibit grades 2 or 3 (OR: 0.02, 95% CI 0.001, 0.365; P<0.01). Histomorphometry measurements of total and nonkeratinised primary epidermal lamellar length were significantly increased (P<0.01) in AMB limbs compared with ICE. TPX2 positive cell counts were significantly increased (P<0.01) in AMB limbs compared with ICE. Main limitations Continuous digital hypothermia was initiated before recognition of laminitis and therefore the clinical applicability requires further investigation. Conclusions Continuous digital hypothermia reduced the severity of laminitis in the EHC model and prevented histological lesions compatible with lamellar structural failure.