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The role of dopamine in the regulation of insulin secretion in horses is poorly understood and requires further investigation. Pituitary pars intermedia dysfunction (PPID) is associated with decreased activity of dopaminergic neurons which normally suppress peptide hormone secretion from the pituitary pars intermedia. A high proportion of horses with PPID also have insulin dysregulation (ID), characterised by post-prandial hyperinsulinaemia and/or tissue insulin resistance, which are risk factors for the development of laminitis. The aim of this study was to investigate the effects of alpha-methyl-para-tyrosine (AMPT), a tyrosine hydroxylase inhibitor that reduces dopamine production, on insulin sensitivity and the post-prandial insulin response to a glucose-containing meal. Six healthy Standardbred horses were enrolled in a placebo-controlled randomised crossover study, in which one dose of AMPT (40 mg/kg BW) or placebo was administered orally, prior to performing an in-feed oral glucose test (OGT) and a frequently sampled intravenous glucose tolerance test (FSIGTT). Dopamine reduction by AMPT was confirmed by an increase in plasma prolactin concentration and the lack of post-prandial increase in plasma dopamine concentration compared to placebo. Post-prandial insulin responses, both peak and AUCi, were increased after AMPT compared to placebo (P=0.048 and P=0.005, respectively), without affecting blood glucose concentrations. However, one dose of AMPT did not appear to affect tissue sensitivity as assessed by the FSIGTT. This study confirmed that dopamine plays a role in the regulation of insulin secretion in horses, as it does in other species, whereby the post-prandial release of dopamine into the circulation may inhibit pancreatic insulin secretion. Further studies are required to evaluate different dosing protocols for AMPT, and to further investigate the links between PPID, ID and laminitis risk in horses., (Copyright © 2024. Published by Elsevier Inc.)

Alpha-methyl-para-tyrosine (AMPT) is a reversible inhibitor of tyrosine hydroxylase, the rate-limiting enzyme in catecholamine synthesis. This study aimed to determine whether AMPT could reduce dopamine concentrations in horses. Six healthy adult Standardbred geldings were administered AMPT (40 mg/kg BW, orally) or placebo in a randomised crossover study design. Clinical examination findings were recorded, and blood samples were collected for up to 6 h after administration of AMPT or placebo, for measurement of blood glucose, plasma ACTH and cortisol concentrations, and plasma metabolomic analysis. Plasma prolactin concentration was determined as a proxy index of central dopamine reduction. No adverse clinical effects were detected after oral administration of AMPT, with heart rate, mean arterial pressure and blood glucose concentration not differing between AMPT treatment or placebo. Plasma prolactin concentration peaked 1 h after AMPT administration before returning to baseline at 2 h (for five horses) or 6 h (for one horse). Metabolomic analysis demonstrated a reduction in plasma dopamine (0.72-fold change; P=0.016) 1 h after AMPT treatment. Plasma ACTH and cortisol concentrations were not different between AMPT and placebo over time. A few metabolites associated with ketogenesis were increased, and certain amino acids decreased, at 1 h compared with baseline, for both AMPT treatment and placebo. Therefore, AMPT was effective in reducing both central and circulating dopamine concentrations in healthy horses following a single oral dose. Further pharmacokinetic and pharmacodynamic studies are warranted to optimise the dose and duration of AMPT treatment to achieve longer-term dopamine reduction. Plasma metabolomic findings suggested an interruption to energy flux at the time of sample collection, which may be relevant to nutritional studies in horses and warrants further investigation., (Copyright © 2024. Published by Elsevier Inc.)

Pituitary pars intermedia dysfunction (PPID) is the most common endocrine disorder of older horses. Immune dysfunction in horses with PPID could increase susceptibility to infectious diseases, including strongyle infections; however, few data are available. The aim of this study was to determine if horses with PPID had increased strongyle faecal egg counts (FEC) compared with control horses, over a fourteen-week period in Victoria, Australia. Clinical signs and plasma adrenocorticotropic hormone (ACTH) concentrations were used to categorise horses into PPID (n=14) or control (n=31) groups. Faecal samples were collected for FEC determination prior to anthelmintic treatment, and fortnightly post-treatment for each horse. Generalised linear mixed modelling, using a gamma distribution, was used to compare differences between groups in the repeated measures study. The confounding variable of age was controlled for as a fixed effect. Following anthelmintic treatment, mean FEC was greater for the PPID group compared to the control group on day 56 (405 ± 756 eggs per gram [EPG] vs 40 ± 85 EPG, p=0.05) and day 70 (753 ±1598 EPG vs 82 ±141 EPG, p=0.04). There were no differences in mean FEC between groups on days 84 and 98. Cumulative FEC (day 14 to day 98) was significantly greater for the PPID horses than control horses (2118 ± 4016 EPG vs 798 ± 768 EPG, p<0.0001). Group egg reappearance period was shorter for PPID horses (day 56 post-anthelmintic treatment) compared to control horses (day 70) and 30% of the PPID horses reached a FEC threshold of >200 EPG on day 42, compared to 0% of control horses (p=0.02). These results suggest that the rate of a re-established patent infection between groups could be different due to a comprised immune response in PPID horses or differences in the host-parasite relationship regarding encysted stage larvae. However, despite differences between groups, some horses with PPID consistently had no detectable or low FEC (<200 EPG) during the study period. These findings highlight the importance of individual FEC monitoring to determine if anthelmintic treatment is required, in line with sustainable parasite management practices., Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 The Authors. Published by Elsevier B.V. All rights reserved.)

Background: The thyrotropin-releasing hormone (TRH) stimulation test is used to diagnose pituitary pars intermedia dysfunction (PPID) using 10- or 30-min protocols. Imprecise sampling time for the 10-min protocol can lead to misdiagnoses., Objectives: To determine the effect of imprecise sampling time for the 30-min protocol of the TRH stimulation test., Study Design: In vivo experiment., Methods: Plasma immunoreactive adrenocorticotropin (ACTH) concentrations were measured 9, 10, 11, 29, 30 and 31 min after intravenous administration of 1 mg of TRH in 15 control and 12 PPID horses. Differences in ACTH concentrations between sampling times, variability in ACTH concentrations between protocols, and diagnostic classification of PPID were assessed using Friedman's test, Bland-Altman plots, and Fisher's exact test, respectively, with 95% confidence intervals reported and significance set at p < 0.05., Results: Imprecise sampling time resulted in variable ACTH concentrations, but significant differences in absolute ACTH concentrations were not detected for imprecise sampling within each protocol or between protocols. Imprecise sampling changed PPID diagnostic classification for 3/27 (11 [4-28] %) horses for both protocols. Using the 30-min protocol as a reference, 1/12 (8 [1-35] %) horses returned a negative test result and 5/12 (42 [19-68] %) horses returned equivocal test results that would be considered positive in practice due to the presence of supportive clinical signs., Main Limitations: Limited sample size and inter-horse variability reduced the ability to detect small but potentially relevant differences., Conclusions: Overall, the impact of imprecise sampling was not significantly different between the 10- and 30-min TRH stimulation test protocols. However, diagnostic classification for PPID would have varied between the 10- and 30-min protocols in this population, if clinical signs had been ignored. Precise timing during TRH stimulation tests and contextual interpretation of ACTH concentrations remain fundamental for the diagnosis of PPID., (© 2023 The Authors. Equine Veterinary Journal published by John Wiley & Sons Ltd on behalf of EVJ Ltd.)

Background: Insulin dysregulation (ID) is central to equine metabolic syndrome. There are limited epidemiological studies investigating dynamic testing of ID in ponies., Objectives: To evaluate prevalence and risk factors for ID through dynamic testing of hyperinsulinaemia (DHI) and insulin resistance (IR)., Study Design: Cross-sectional., Methods: Sex, age, breed, height, cresty neck score (CNS), body condition score (BCS), laminitis, HMGA2:c.83G>A genotype and pituitary pars intermedia dysfunction (PPID) status were documented. Dynamic hyperinsulinaemia was diagnosed with an oral sugar test (OST) and IR with an insulin tolerance test (ITT). Owners completed surveys reporting activity, laminitis history and perception of body condition using a (1-9) visual analogue scale (VASo). Ordinal scores were converted to binary outcomes for CNS (≤2/5 or ≥3/5), BCS and VASo (≤6/9 or ≥7/9). Variables associated with insulin concentrations, glucose reduction after the ITT and laminitis were evaluated with mixed effects regression models accounting for random effects of farms., Results: Among 167 ponies tested, median (range) age was 9 (4-21) years and BCS was 6 (4-8). Prevalence (95% confidence interval [CI]) of ID was 61 (53-68)%. Factors associated with insulin concentrations (estimate [95% CI]; μIU/mL) 60 min post-OST were: age (1.07 [1.02-1.11]), CNS (≥3/5, 1.52 [1.04-2.23]) and VASo (≥7/9, 1.75 [1.09-2.79]); and 90 min post-OST were: age (1.08 [1.03-1.12]), CNS (≥3/5, 1.80 [1.22-2.64]), VASo (≥7/9, 2.49 [1.52-4.08]) and sex (male, 0.64 [0.45-0.91]). Factors associated with glucose reduction after the ITT (estimate [95% CI]; %) were: age (-1.34 [-2.01 to -0.67]), sex (female, -6.21 [-11.68 to -0.74]) and VASo (≥7/9, -1.74 [-18.89 to -4.78]). Factors associated with laminitis (odds ratio [95% CI]) were DHI (4.60 [1.68-12.58]), IR (3.66 [1.26-10.61]) and PPID (11.75 [1.54-89.40])., Main Limitations: Single time-point sampling, laminitis definition and diet analysis., Conclusions: Ageing, being female and owner-perceived obesity were associated with ID., (© 2024 The Authors. Equine Veterinary Journal published by John Wiley & Sons Ltd on behalf of EVJ Ltd.)

Background: There is a high prevalence of obesity in ponies and pleasure horses. This may be associated with equine metabolic syndrome and an increased risk of laminitis. Body condition scoring (BCS) systems are widely used but are subjective and not very sensitive., Objectives: To derive a body condition index (BCI), based on objective morphometric measurements, that correlates with % body fat., Study Design: Retrospective cohort study., Methods: Morphometric measurements were obtained from 21 ponies and horses in obese and moderate body condition. Percentage body fat was determined using the deuterium dilution method and the BCI was derived to give the optimal correlation with body fat, applying appropriate weightings. The index was then validated by assessing inter-observer variation and correlation with % body fat in a separate population of Welsh ponies; and finally, the correlation between BCI and BCS was evaluated in larger populations from studies undertaken in Australia, the United Kingdom and the United States., Results: The BCI correlated well with adiposity in the ponies and horses, giving a Pearson r value of 0.74 (P < 0.001); however, it was found to slightly overestimate the % body fat in leaner animals and underestimate in more obese animals. In field studies, the correlation between BCI and BCS varied particularly in Shetlands and miniature ponies, presumably due to differences in body shape., Main Limitations: Further work may be required to adapt the BCI to a method that is more applicable for Shetlands and miniature ponies., Conclusions: This BCI was able to provide an index of adiposity which compared favourably with condition scoring in terms of accuracy of estimating adiposity; and was more consistent and repeatable when used by inexperienced assessors. Therefore, this may be a useful tool for assessing adiposity; and may be more sensitive than condition scoring for tracking weight gain or weight loss in individual animals., (© 2023 Mars Horsecare UK Ltd and The Authors. Equine Veterinary Journal published by John Wiley & Sons Ltd on behalf of EVJ Ltd.)

Insulin dysregulation in horses is characterised by hyperinsulinaemia and/or tissue insulin resistance and is associated with increased risk of laminitis. There is growing evidence in other species that dopamine attenuates insulin release from the pancreas; however, this has yet to be examined in horses. The present study aimed to identify whether there are cells capable of producing or responding to dopamine within the equine gastrointestinal mucosa and pancreas. Tissue samples were collected from the stomach, small and large intestines, and pancreas of six mature horses following euthanasia. Samples of stomach contents and faeces were also collected. Immunohistochemistry was performed to identify tyrosine hydroxylase (TH), the rate-limiting enzyme for dopamine production, and dopamine D2 receptors in tissue sections. Additional immunostaining for glucagon, insulin and chromogranin A was performed to identify α cells, β cells and enteroendocrine cells, respectively. Gastric parietal cells expressed both TH and D2 receptors, indicating that they are capable of both producing and responding to dopamine. Dopamine was quantified in stomach contents and faeces by high-performance liquid chromatography with electrochemical detection, with similar concentrations found at both sites. Dopamine D2 receptors were expressed in duodenal epithelial cells but not more distally. A subset of enteroendocrine cells, located sporadically along the gastrointestinal tract, were found to be immunopositive for the D2 receptor. In pancreatic islets, TH was present in α cells, while D2 receptors were strongly expressed in β cells and variably expressed in α cells. These findings are consistent with studies of other species; however, dynamic studies are required to further elucidate the role of dopamine in the modulation of insulin and glucagon secretion in horses. This descriptive study provides preliminary evidence for a potential role of dopamine to act as a paracrine messenger in the gastrointestinal mucosa and endocrine pancreas of horses., Competing Interests: The authors have declared that no competing interests exist., (Copyright: © 2024 Galinelli et al. This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.)

Field tests and their association with laminitis have not been evaluated in large cohorts. The objectives of this study were to evaluate the performance of basal insulin (BI), the oral sugar test (OST) and the insulin tolerance test (ITT) to diagnose ID and investigate their association with laminitis. Insulin dysregulation status was determined in 146 ponies using BI (insulin concentration >20 µIU/mL), an OST (insulin concentration >65 µIU/mL at 60 or 90 min after oral administration of 0.45 mL/kg corn syrup) and an ITT (< 50% reduction in glucose concentration 30 min after intravenous administration of 0.1 IU/kg insulin). Laminitis was identified using modified-Obel scores. A Bayesian approach was used to define the characteristics of the tests and receiver operating characteristic curves were used to assess their association with laminitis. All tests were well tolerated and laminitis was diagnosed in 9% of ponies. Insulin dysregulation was diagnosed in 15% of ponies using BI, 38% using the OST and 54% using the ITT with 11% of ponies positive for all three tests. The sensitivities and specificities of BI, the OST and the ITT to diagnose ID were 0.52 (95% confidence interval [CI], 0.35-0.79) and 0.97 (95% CI, 0.91 - 1.00), 0.84 (95% CI, 0.70 - 0.94) and 0.60 (95% CI, 0.49 - 0.71), and 0.85 (95% CI, 0.68-0.96) and 0.88 (95% CI, 0.75 - 0.97), respectively. Only BI and the OST were associated with laminitis (P = 0.003 and 0.015, respectively)., Competing Interests: Declaration of Competing Interest None of the authors has any other financial or personal relationships that could inappropriately influence or bias the content of the paper., (Copyright © 2023 Elsevier Ltd. All rights reserved.)

Plasma adrenocorticotropic hormone (ACTH) concentration is commonly measured to diagnose pituitary pars intermedia dysfunction (PPID). Several intrinsic and extrinsic factors affect ACTH concentrations, including breed. The objective of this study was to prospectively compare plasma ACTH concentrations among different breeds of mature horses and ponies. Three breed groups comprised Thoroughbred horses (n = 127), Shetland ponies (n = 131) and ponies of non-Shetland breeds (n = 141). Enrolled animals did not show any signs of illness, lameness or clinical signs consistent with PPID. Blood samples were collected 6 months apart, around the autumn equinox and spring equinox, and plasma concentrations of ACTH were measured by chemiluminescent immunoassay. Pairwise breed comparisons within each season were performed on log transformed data using the Tukey test. Estimated mean differences in ACTH concentrations were expressed as fold difference with 95 % confidence intervals (CI). Reference intervals for each breed group per season were calculated using non-parametric methods. In autumn, higher ACTH concentrations were found among non-Shetland pony breeds compared with Thoroughbreds (1.55 fold higher; 95 % CI, 1.35-1.77; P < 0.001), and in Shetland ponies compared with Thoroughbreds (2.67 fold higher; 95 % CI, 2.33-3.08; P < 0.001) and non-Shetland pony breeds (1.73 fold higher; 95 % CI, 1.51-1.98; P < 0.001). In spring, no differences were identified among breed groups (all P > 0.05). Reference intervals were similar among breed groups in spring, but upper limits for ACTH concentrations were markedly different between Thoroughbred horses and pony breeds in autumn. These findings emphasise that breed should be accounted for when determining and interpreting reference intervals for ACTH concentrations among healthy horses and ponies in autumn., Competing Interests: Conflict of Interest Statement None of the authors has any financial or personal relationships that could inappropriately influence or bias the content of the paper., (Copyright © 2023 Elsevier Ltd. All rights reserved.)

Background: The HMGA2:c.83G>A variant was identified in Welsh ponies having pleiotropic effects on height and insulin concentration., Objective: Determine whether the HMGA2:c.83G>A variant is associated with decreased height and higher basal insulin concentrations across pony breeds., Animals: Two hundred thirty-six ponies across 6 breeds., Methods: Cross-sectional study. Ponies were genotyped for the HMGA2:c.83G>A variant and phenotyped for height and basal insulin concentrations. Stepwise regression was performed for model analysis using a linear regression model for height and mixed linear model for insulin with farm as a random effect. Coefficient of determination, pairwise comparison of the estimated marginal means and partial correlation coefficients (parcor) were calculated to assess the relationship between HMGA2 genotype and height or insulin., Results: Breed and genotype accounted for 90.5% of the variation in height across breeds, and genotype explained 21% to 44% of the variation within breeds. Breed, genotype, cresty neck score, sex, age, and farm accounted for 45.5% of the variation in insulin, with genotype accounting for 7.1%. The HMGA2 A allele frequency was 62% and correlated with both height (parcor = -0.39; P < .001) and insulin (parcor = 0.22; P = .02). Pairwise comparisons found A/A ponies were >10 cm shorter than other genotypes. Compared with G/G individuals, A/A and G/A individuals had 4.3 μIU/mL (95% confidence interval [CI]: 1.8-10.5) and 2.7 μIU/mL (95% CI: 1.4-5.3) higher basal insulin concentrations, respectively., Conclusions and Clinical Importance: These data demonstrate the pleiotropic effects of the HMGA2:c.83G>A variant and its role in identifying ponies at increased risk for insulin dysregulation., (© 2023 The Authors. Journal of Veterinary Internal Medicine published by Wiley Periodicals LLC. on behalf of the American College of Veterinary Internal Medicine.)

Ponies and some horse breeds such as Andalusians exhibit an 'easy keeper' phenotype and tend to become obese more readily than other breeds such as Standardbreds. Various hypotheses have been proposed, including differences in appetite or metabolic efficiency. This study aimed to investigate the effect of breed on nutrient digestibility. Ponies, Standardbreds and Andalusian horses were adapted to consuming either a control fibre-based diet ( n = 9), a hypercaloric cereal-rich diet ( n = 12) or a hypercaloric fat-rich diet ( n = 12) over 20 weeks. Total faecal collection was performed over 24 h to determine apparent total tract digestibility of gross energy, dry matter (DM), neutral detergent fibre (NDF), starch, crude protein and crude fat. There was no effect of breed on apparent digestibility for any of the nutrients studied (all p > 0.05). However, there was a significant effect of diet, with animals consuming the cereal-rich or fat-rich diets demonstrating higher digestibility of gross energy, DM, NDF and crude protein compared with those consuming the control diet (all p < 0.05). Animals adapted to the cereal-rich diet demonstrated higher digestibility of starch ( p < 0.001) and animals adapted to the fat-rich diet demonstrated higher digestibility of fat ( p < 0.001). This study found that horses and ponies had similar nutrient digestibility when adapted to the same diets and management conditions. Limitations included the relatively small number of animals from each breed per diet group and the short period of total faecal collection. The tendency towards increased adiposity in ponies and Andalusian-type horse breeds is more likely to reflect differences in metabolism, rather than differences in feed digestibility.

Ross River virus (RRV) is a mosquito-borne arbovirus of the genus Alphavirus that causes disease in humans and horses in Australia. A temporal association of RRV infection in horses with clinical signs including pyrexia, malaise, and polyarthralgia has been reported, along with reduced athletic performance, often for extended periods. Despite these reports, disease due to RRV remains somewhat controversial as experimental infection of horses has resulted in obvious viraemia yet minimal signs of clinical disease. The relatively high viraemia demonstrated by horses infected with RRV has led to speculation that they could act as an important reservoir host of the virus, although this remains unclear. This review sought to appraise the existing literature relating to RRV infection of horses and to summarize the ecological and clinical consequences of RRV of relevance to the equine industry and to public health more broadly., (Copyright © 2020 The Authors. Published by Elsevier Inc. All rights reserved.)

Background: Pituitary pars intermedia dysfunction (PPID) is a commonly described endocrine disorder in higher latitudes of the Northern hemisphere but the description of the disease at lower latitudes and in the Southern hemisphere is limited., Objectives: Document the clinical features of PPID at different Australian latitudes and climates, and investigate factors associated with survival, laminitis and insulin dysregulation (ID)., Study Design: Retrospective study of 274 equids from eight institutions across Australia., Methods: A diagnosis of PPID was based on endogenous ACTH, overnight dexamethasone suppression test, thyrotropin-releasing hormone stimulation test or necropsy. Clinical and clinicopathologic characteristics of PPID and therapeutic responses were investigated. Laminitis was diagnosed by radiographic or histologic changes and ID was diagnosed based on endogenous insulin, an oral glucose test or a 2-step insulin-response test., Results: Being a pony, having a higher body condition score and pergolide administration were associated with survival. The clinical presentation of PPID changed with latitude and climate, with anhidrosis and polyuria/polydipsia more commonly recognised at lower latitudes. Laminitis was diagnosed in 89.9% of cases and ID was present in 76.5% of cases in which they were investigated., Main Limitations: Despite the sample size, the lack of uniform testing at all locations (primary or referral cases) and the incompleteness of data sets limited the power of the statistical analyses., Conclusions: PPID can present with variable signs at different latitudes and climates, and ID should be investigated in equids diagnosed with PPID. Adequate body condition and administration of pergolide are fundamental in PPID management., (© 2018 EVJ Ltd.)

Background: The importance of including exercise with dietary modification for the management of obese equids is not clearly understood., Objectives: To evaluate the effect of a practical low-intensity exercise regimen, in addition to dietary restriction, on indices of insulin sensitivity (SI) and plasma adipokine concentrations in obese equids., Animals: Twenty-four obese (body condition score [BCS] ≥ 7/9) horses and ponies., Methods: Over a 12-week period, animals received either dietary restriction only (DIET) or dietary restriction plus low-intensity exercise (DIET+EX). All animals were provided with a restricted ration of grass hay at 1.25% body weight (BW) on a dry matter basis, providing 82.5% estimated digestible energy requirements. The DIET+EX group undertook low-intensity exercise 5 days per week on an automated horse walker. Before and after weight loss, total body fat mass (TBFM) was determined, indices of SI were calculated using minimal model analysis of a frequently sampled IV glucose tolerance test, and adipokines plus inflammatory biomarkers were measured using validated assays., Results: Decreases in BCS, BW, and TBFM were similar between groups (all P > .05). After weight loss, animals in both groups had decreased basal insulin and leptin concentrations, and increased adiponectin concentrations (all P < .001). Furthermore, animals in the DIET+EX group had significantly improved SI and decreased serum amyloid A concentrations relative to animals in the DIET group (both P = .01)., Conclusions and Clinical Importance: Regular low-intensity exercise provided additional health benefits compared with dietary restriction alone in this population of obese equids., (© 2018 The Authors. Journal of Veterinary Internal Medicine published by Wiley Periodicals, Inc. on behalf of the American College of Veterinary Internal Medicine.)

Collaborative learning activities are an increasingly prominent feature of veterinary curricula that have been redesigned to achieve competency-based graduate learning outcomes. This evolution challenges the traditional individualistic approach to veterinary education and necessitates revisions to assessment and feedback practices to ensure constructive alignment. Peer feedback has been widely reported in the medical education literature as a teaching intervention in collaborative learning settings, with learning gains reported for students who receive and provide peer feedback. In this setting, peer feedback has been demonstrated to provide valuable formative feedback on professional behaviors and skills. However, there are very few such reports in the veterinary education literature to date. Barriers to the introduction of this approach can include teacher and student perceptions, and concerns around validity and reliability. This review aimed to provide an overview of current evidence regarding peer feedback on collaborative learning activities in higher education, and to explore opportunities and challenges for the introduction of peer feedback in the context of veterinary education. We contend that early and repeated provision of formative peer feedback can provide an opportunity to scaffold the development of crucial core competencies within veterinary education, including the self-regulated learning skills required to work in collaborative teams, and interpret and act on feedback.

Background: Snake envenomation is a cause of morbidity and mortality in domestic animals worldwide. The clinical features of crotalid snake (pit viper) envenomation are widely reported and well described in horses but elapid snake envenomation is poorly characterised., Objectives: To describe the presentation, clinical and laboratory findings, treatment and outcome of horses with a diagnosis of elapid snake envenomation in Australia., Study Design: Retrospective case series., Methods: Medical records of horses with a diagnosis of elapid snake envenomation (2006-2016) at several university and private veterinary practices were reviewed. Inclusion criteria comprised one or more of the following: 1) observed snakebite, 2) positive snake venom detection kit (SVDK) result, 3) appropriate clinical response to treatment with antivenom or 4) supportive post-mortem findings., Results: Fifty-two cases met the inclusion criteria. Most cases (94%) demonstrated clinical signs of neurotoxicity, characterised by generalised neuromuscular weakness. Associated neurologic signs included staggering gait, muscle fasciculations, recumbency, mydriasis, ptosis and tongue paresis. Concurrent clinically important conditions included rhabdomyolysis (50%) and haemolysis (19%). Of 18 urine samples evaluated with a SVDK, only three (17%) were positive. Overall survival was favourable (86%) among 49 horses who received antivenom. Eighteen surviving horses (43%) required more than one vial of antivenom., Main Limitations: Possible cases within the searchable database were not included if horses died acutely or responded to symptomatic treatment without receiving antivenom., Conclusions: Elapid snake envenomation is primarily a syndrome of neuromuscular weakness. Supportive anamnesis or an obvious bite site is rarely encountered. In endemic areas, this diagnosis should be considered for horses with generalised neuromuscular weakness, altered mentation, rhabdomyolysis and/or haemolysis; especially during spring and summer months. Diagnostic suspicion is best confirmed by response to treatment with antivenom., (© 2017 EVJ Ltd.)

Insulin-like growth factor-1 (IGF-1) plays several important physiological roles, and IGF-related pathways have been implicated in developmental osteochondral disease and endocrinopathic laminitis. This factor is also a downstream marker of growth hormone activity and its peptide mimetics. Unfortunately, previously used assays for measuring equine IGF-1 (radioimmunoassays and ELISAs) are no longer commercially available, and many of the kits on the market give poor results when used on horse samples. The aim of the present study was to compare three different ELISA assays (two human and one horse-specific). Plasma samples from six Standardbreds, six ponies and six Andalusians were used. The human IGF-1 ELISA kit from Immunodiagnostic Systems (IDS) proved to be the most accurate and precise of the three kits; the other two assays gave apparently much lower concentrations, with poor recovery of spiked recombinant human IGF-1 and unacceptably poor intra-assay coefficients of variation (CV). The IDS assay gave an intra-assay CV of 3.59 % and inter-assay CV of 7.31%. Mean percentage recovery of spiked IGF-1 was 88.82%, and linearity and dilutional parallelism were satisfied. The IGF-1 plasma concentrations were 123.21 ±8.24 ng/mL for Standardbreds, 124.95 ±3.69 ng/mL for Andalusians and 174.26 ±1.94 ng/mL for ponies. Therefore of the three assays assessed, the IGF-1 ELISA manufactured by IDS was the most suitable for use with equine plasma samples and may have many useful applications in several different research areas. However, caution should be used when comparing equine studies where different analytical techniques and assays may have been used to measure this growth factor.

The relationships between diet, obesity and insulin dysregulation in equids require further investigation due to their association with laminitis. This study examined the effect of dietary glycaemic load and increased adiposity on insulin sensitivity and adipokine concentrations in different equine breeds. Equal numbers of Standardbred horses, mixed-breed ponies and Andalusian horses were provided with ad libitum hay plus either cereal-rich (CHO; n = 12), fat-rich (FAT; n = 12) or control (CON; n = 9) meals over 20 weeks. The isocaloric CHO and FAT diets were fed to induce obesity by gradually increasing the supplementary feeds to provide 200% of daily digestible energy requirements by Week 20. The CON group were fed a basal ration only and maintained moderate body condition. At Week 20, the CHO and FAT groups demonstrated significantly increased body condition score, bodyweight, total body fat mass and plasma leptin concentrations compared with the CON group (P <0.001). The CHO group had lower insulin sensitivity (SI; P <0.001) and higher acute insulin response to glucose (P = 0.002) than the CON group. In contrast, the FAT group was no different to the control group. Ponies and Andalusians had lower SI values compared with Standardbreds, regardless of diet group (P = 0.001). Adiponectin concentrations were similar between the FAT and CON groups, but were significantly lower in the CHO group (P = 0.010). The provision of cereal-rich meals appeared to be a more important determinant of insulin sensitivity than the induction of obesity per se. Whether hypoadiponectinaemia is a cause or consequence of insulin dysregulation warrants further investigation., (Copyright © 2016 Elsevier Ltd. All rights reserved.)

Reasons for Performing Study: The relative influences of obesity and adaptation to high glycaemic diets on the development of insulin dysregulation in equids are unclear., Objectives: To determine whether increased adiposity per se is responsible for the decreased insulin sensitivity often observed in obese horses or whether a dietary glycaemic response is critically important., Study Design: Randomised controlled trial., Methods: Eighteen horses and ponies were studied over a 20-week period. They received ad libitum hay plus either a high fat (low glycaemic) diet (FAT; n = 6) or a similar (isocaloric) diet containing 1.5 g/kg bwt once daily glucose (GLU; n = 6) to induce obesity. A third group received a control ration (CON; n = 6). Adiposity was monitored using body condition score (BCS) and total body fat mass percentage (TBFM) determined using a deuterium oxide dilution technique. Insulin sensitivity was assessed using a frequently sampled i.v. glucose tolerance test. Plasma concentrations of glucose, insulin, leptin, adiponectin, tumour necrosis factor-α (TNF-α) and serum amyloid A (SAA) were measured., Results: The FAT and GLU groups became obese (BCS ≥7) whereas the CON group maintained moderate condition (BCS ≤6). Total body fat mass and leptin concentrations were increased in the FAT and GLU groups than in the CON group (P<0.001 and P = 0.003, respectively). Values for both insulin-dependent (SI) and insulin-independent (Sg) glucose disposal were higher in the GLU group compared with the FAT and CON groups (P = 0.006 and P = 0.03, respectively). There were no differences in adiponectin, TNF-α or SAA between groups (all P≥0.4)., Conclusions: Increased adiposity did not reduce insulin sensitivity in either the FAT or the GLU diet groups, suggesting that obesity per se might not be responsible for the lower SI values reported in previous studies. Contrary to expectations, once daily glucose appeared to increase insulin sensitivity. Further work is required into the dietary causes of insulin resistance in equids., (© 2015 EVJ Ltd.)

The enteroinsular axis is a complex system that includes the release of incretin hormones from the gut to promote the absorption and utilization of glucose after a meal. The insulinogenic effect of incretin hormones such as glucagon-like peptide-1 (GLP-1) remains poorly characterized in the horse. The aim of this study was to compare postprandial glucose, insulin, and GLP-1 responses of different equine breeds adapted to twice-daily meals containing micronized maize. Four Standardbred horses, 4 mixed-breed ponies, and 4 Andalusian cross horses in moderate BCS (5.5 ± 0.2 out of 9) were fed meals at 0800 and 1600 h each day. The meals contained micronized maize (mixed with soaked soybean hulls and lucerne chaff), with the amount of maize gradually increased over 12 wk to reach a final quantity of 1.7 g/kg BW (1.1 g/kg BW starch) in each meal. Animals had ad libitum access to the same hay throughout. After 12 wk of acclimation, serial blood samples were collected from all animals over a 14-h period to measure concentrations of glucose, insulin, and GLP-1, with meals fed immediately after the 0 and 8 h samples. Glucose area under the curve (AUC) values were similar between breed groups (P = 0.41); however, ponies and Andalusian horses exhibited significantly higher insulin AUC values after both meals compared with Standardbred horses (both P < 0.005). Postprandial GLP-1 AUC values were also significantly higher in ponies and Andalusian horses compared with Standardbred horses (breed × time interaction; P < 0.001). Correlation analysis demonstrated a strong positive association between concentrations of insulin and GLP-1 over time (rs = 0.752; P < 0.001). The increased insulin concentrations in ponies and Andalusian horses may partly reflect lower insulin sensitivity but could also be attributed to increased GLP-1 release. Given that hyperinsulinemia is a recognized risk factor for the development of laminitis in domestic equids, this study provides evidence that the enteroinsular axis warrants further investigation.

Breed-related differences may occur in the innate insulin sensitivity (SI) of horses and ponies, an important factor believed to be associated with the risk of laminitis. The aim of this study was to measure the glucose and insulin responses of different breeds of horses and ponies in moderate body condition to a glucose-containing meal and to compare these responses with the indices of SI as determined by a frequently sampled intravenous glucose tolerance test (FSIGT). Eight Standardbred horses, 8 mixed-breed ponies, and 7 Andalusian-cross horses with a mean ± SEM BCS 5.0 ± 0.3 of 9 were used in this study. Each animal underwent an oral glucose tolerance test (OGTT) in which they were fed a fiber-based ration (2.0 g/kg BW) containing 1.5 g/kg BW added glucose, as well as a standard FSIGT with minimal model analysis. The glucose response variables from the OGTT were similar between groups; however, the peak insulin concentration was higher in ponies (94.1 ± 29.1 μIU/mL; P = 0.003) and Andalusians (85.3 ± 18.6; P = 0.004) than in Standardbreds (21.2 ± 3.5). The insulin area under the curve was also higher in ponies (13.5 ± 3.6 IU · min · L(-1); P = 0.009) and Andalusians (15.0 ± 2.7; P = 0.004) than in Standardbreds (3.1 ± 0.6). Insulin sensitivity, as determined by the FSIGT, was lower in Andalusians (0.99 ± 0.18 × 10(-4)/[mIU · min]) than in Standardbreds (5.43 ± 0.94; P < 0.001) and in ponies (2.12 ± 0.44; P = 0.003) than in Standardbreds. Peak insulin concentrations from the OGTT were negatively correlated with SI (P < 0.001; rs = -0.75). These results indicate that there are clear breed-related differences in the insulin responses of horses and ponies to oral and intravenous glucose. All animals were in moderate body condition, indicating that breed-related differences in insulin dynamics occurred independent of obesity., (Copyright © 2014 Elsevier Inc. All rights reserved.)