Prospective cohort study evaluating risk factors for the development of pasture-associated laminitis in the United Kingdom

Sodium-glucose transport protein 2 inhibitor use in the management of insulin dysregulation in ponies and horses

Laminitis is a common and painful condition of the equine foot and approximately 90% of cases are associated with insulin dysregulation (ID) that is a central feature of the common endocrine disorder equine metabolic syndrome (EMS) and occurs in a subset of animals with pituitary pars intermedia dysfunction. Additional features of EMS include obesity, altered circulating concentrations of adipokines (particularly adiponectin and leptin) and hypertriglyceridaemia. Obesity, ID, hypoadiponectinaemia, hyperleptinaemia and an altered plasma lipid profile are also features of human metabolic syndrome (HMS) alongside hyperglycaemia. Sodium-glucose cotransporter 2 inhibitors (SGLT2i) are a novel class of oral hypoglycaemic agents used in combination with lifestyle changes in the management of HMS. SGLT2 receptors are responsible for 90% of the renal glucose reabsorption that occurs in the proximal convoluted tubule. Thus, these drugs increase urinary glucose excretion by suppressing glucose reabsorption from the glomerular filtrate resulting in urinary calorie loss with consequent weight loss and improvements in ID, hyperglycemia, hypoadiponectinaemia and hyperleptinaemia. There are no licenced veterinary drugs available for treating ID and preventing insulin-associated laminitis in horses. Thus, the use of SGLT2i for the control of equine hyperinsulinaemia with the goal of improving recovery from associated active laminitis or preventing future laminitis has recently been advocated. There are a small number of published studies reporting the use of the SGLT2i canagliflozin, ertugliflozin and velagliflozin to aid the management of equine ID. However, the doses used are largely extrapolated from human studies with limited consideration of species-specific variations. In addition, there is limited evaluation of the fundamental differences between ID in horses and humans, particularly the fact that most horses with ID remain hyperinsulinaemic but normoglycaemic such that increased urinary loss of glucose may not explain the beneficial effects of these drugs. Further study of the potential deleterious effects of treatment-associated hypertriglyceridaemia is required together with the effect of SGLT2i therapy on circulating concentrations of adipokines in horses.

Evaluating insulindysregulation in horses: A two-step insulin-tolerance test using porcine zinc insulin

In insulin dysregulation, hyperinsulinemia (HI) can be accompanied by peripheral insulin resistance (IR) in horses, which can be diagnosed with an insulin-tolerance test (ITT). The administration of 0.1 IU/kg body weight of recombinant regular human insulin (RHI) should elicit a 50 % reduction of the initial blood glucose concentration at 30 min after insulin administration in insulin sensitive horses. Compared to RHI, porcine zinc insulin (PZI) is veterinary-approved and therefore easier accessible for many practitioners. The aim of this study was to compare the insulin and glucose dynamics during a standard ITT with RHI to an ITT performed with PZI. Twelve Icelandic horses were subjected to an ITT with RHI (ITT-RHI) and with PZI (ITT-PZI) at same dosages in a randomised crossover design. The insulin and glucose dynamics that resulted from these tests were compared, and the consistency of classification into insulin-sensitive and IR categories was evaluated. No complications were observed with the use of either RHI or PZI in ITT. A good correlation of the test results was observed (r = 0.88; P < 0.001). The blood glucose concentrations and the percentage reduction in glucose concentration did not differ significantly between the two tests (P = 0.053), but four out of twelve horses were classified as IR in the ITT-RHI whereas with the ITT-PZI seven out of twelve horses were classified as IR with the 50 % glucose reduction from baseline. Based on the Youden index, when using the ITT-PZI, an adjusted cut-off value for blood glucose reduction of 40 % at 30 min resulted in better test performance. With consideration for the seemingly weaker effect of PZI and the adjusted cut-off value, PZI can be an appropriate substitute to RHI in an ITT.

Insulin, but not adiponectin, is detectable in equine saliva using an automated, commercial assay

BACKGROUND

The hormones insulin and adiponectin are commonly measured in equids because of their involvement in endocrinopathic laminitis. These are currently measured in serum/plasma, although jugular venipuncture can cause stress in some animals and may be impossible in needle-shy individuals. However, both hormones can be measured in saliva in other species.

OBJECTIVES

To determine whether [insulin] and [total adiponectin] are detectable in equine saliva using automated assays and whether saliva collection is associated with changes in stress indicators. Additionally, the correlation between serum and salivary [insulin] was investigated.

STUDY DESIGN

In vivo experiment.

METHODS

Paired blood and saliva samples were collected from eight adult ponies at multiple time-points (n = 45 paired samples). [Insulin] and [total adiponectin] were measured using automated assays validated for equine serum/plasma. Blink rates and heart rates were determined, using video recordings and a wearable heart rate monitor respectively, to assess the effects of sample collection on stress indicators compared with a control situation without a stressful stimulus.

RESULTS

[Total adiponectin] was undetectable in saliva. However, salivary [insulin] was measurable with acceptable inter-assay (1.3 ± 0.9%) and intra-assay (1.1 ± 0.6%) variability. Blink and heart rates during saliva collection did not differ significantly from those in the control setting. Serum and salivary [insulin] were not significantly correlated.

MAIN LIMITATIONS

Small sample size comprising native UK ponies; potential sampling bias as animals were recruited to the study partly based on their behaviour during blood sampling; saliva collected from unfasted animals.

CONCLUSIONS

Insulin is measurable in equine saliva using an automated assay currently available in the UK, but further validation and the determination of specific diagnostic thresholds are required. Saliva collection was not associated with changes in stress indicators. Further research is therefore needed to determine the potential of equine saliva as a non-invasive alternative to blood for insulin determination.

Short-term induced hyperinsulinaemia and dexamethasone challenge do not affect circulating total adiponectin concentrations in insulin-sensitive ponies

BACKGROUND

Hypoadiponectinaemia is a risk factor for endocrinopathic laminitis, but the directionality and nature of its association with insulin dysregulation is unclear.

OBJECTIVES

To investigate the effects of short-term induced hyperinsulinaemia and dexamethasone challenge on circulating [total adiponectin] and whole blood expression of adiponectin (AdipoR1 and AdipoR2), insulin, and insulin-like growth factor 1 (IGF-1) receptors in insulin-sensitive ponies.

STUDY DESIGN

In vivo experiment.

METHODS

Six never-laminitic, insulin-sensitive, native-breed UK ponies first underwent a dexamethasone challenge (0.08 mg/kg i.v.) with blood samples collected every 15 min over 3 h. After a 14-day washout period, hyperinsulinaemia was induced for 9 h via a euglycaemic-hyperinsulinaemic clamp (EHC), with blood samples collected every 30 min. Serum [insulin], plasma [total adiponectin], and plasma [IGF-1] were measured using validated assays and receptor gene expression was assessed via quantitative polymerase chain reaction (qPCR). Finally, whole blood was incubated with 10-1000 ng/mL dexamethasone for 3 h at 37°C to investigate its direct effects on gene expression.

RESULTS

There were no adverse effects observed during either protocol. Dexamethasone challenge did not alter circulating [insulin] or [total adiponectin] at any time-point, but significantly upregulated AdipoR1 and IGF-1R expression at 150 and 180 min. Ex vivo incubation of whole blood with dexamethasone did not alter expression of the genes examined. There was no change in [total adiponectin] or expression of the genes examined associated with EHC-induced hyperinsulinemia.

MAIN LIMITATIONS

This was a small sample size that included only native-breed ponies; total adiponectin was measured rather than high-molecular-weight adiponectin.

CONCLUSIONS

Short-term induced hyperinsulinaemia and dexamethasone challenge did not affect circulating [total adiponectin] in insulin-sensitive ponies. However, dexamethasone administration was associated with upregulation of two receptors linked to adiponectin signalling, suggesting that a physiological response occurred possibly to counteract dexamethasone-associated changes in tissue insulin sensitivity.

Relationships between total adiponectin concentrations and obesity in native-breed ponies in England

BACKGROUND

Equine metabolic syndrome is a collection of risk factors associated with an increased risk of endocrinopathic laminitis. All affected animals display insulin dysregulation and some may show adiponectin dysregulation and/or excessive adiposity. However, the relationship between obesity and hypoadiponectinaemia in equids remains unclear.

OBJECTIVES

To investigate the relationship between obesity and circulating plasma total adiponectin (TA) concentrations in native-breed ponies in England.

STUDY DESIGN

Secondary data analysis.

METHODS

Data collected for three previous studies were retrospectively analysed and cohorts were pooled where possible (maximum sample size: n = 734 ponies). Correlations between [TA], age, and morphometric measures were assessed using Spearman's correlation coefficient. [TA] was compared between animals of different body condition score (BCS) classification (ideal-weight, overweight, and obese), breed, and body shape using Kruskal-Wallis with Dunn's post hoc tests, and sex using Mann-Whitney U test. The proportions of obese and ideal-weight ponies with basal hyperinsulinaemia and/or hypoadiponectinaemia were compared using a Chi-square test of homogeneity and post hoc z-test. Logistic regression was used to identify factors that may discriminate ponies with hypoadiponectinaemia.

RESULTS

[TA] was weakly positively correlated with BCS, height, weight, and weight:height ratio (Spearman's ρ = 0.14-0.29, p < 0.05). There were significant differences in [TA] in ponies with different BCS group classification, body shape, and breed. A greater percentage of obese (54.6%) than ideal-weight ponies (33.1%, p < 0.001) had both normal [TA] and [basal insulin], and a greater percentage of ideal-weight (38.6%) than obese ponies (16.5%, p < 0.001) showed hypoadiponectinaemia. Weight:height and BCS group were significant variables in a logistic regression of hypoadiponectinaemia but model fit and predictive accuracy were poor.

MAIN LIMITATIONS

Retrospective study design, only native-breed ponies included.

CONCLUSIONS

Morphometric measures such as BCS do not closely reflect [TA]. Circulating [TA] and [basal insulin] should be determined in all animals with predisposing factors, regardless of obesity status.

Metabolic and Endocrine Insights in Donkeys

Donkey medicine is gaining attention due to their increased use as companion animals, in shows, asinotherapy, etc. The increasing demand and unique aspects call for specialized care, requiring new information (physiology, infectious disorders, pharmacology, etc.). Since obesity is common in this species, hyperlipemia, metabolic syndrome and insulin dysregulation (ID) are common disorders in donkeys, in some cases with high mortality, either directly (multiorgan dysfunction) or indirectly due to poor quality of life (chronic laminitis). Donkeys have long-life expectancy and are often afflicted with pituitary pars intermedia dysfunction (PPID), a neurodegenerative and endocrine disease. Hyperlipemia is diagnosed based on high plasma triglyceride concentration in association with clinical findings and laboratory abnormalities from affected tissues (liver, kidney and pancreas). The measurement of resting serum insulin and plasma ACTH concentrations is the first step in ID and PPID diagnosis. In donkeys with clinical signs of ID (obesity or recurrent laminitis) or PPID (hypertrichosis, regional adiposity, laminitis and weight loss), where these hormones are in the normal or non-diagnostic range (donkey-specific cut-off values and reference ranges need to be established), dynamic tests are recommended (oral sugar test or thyrotropin-releasing hormone, respectively). Equine treatment protocols apply to donkeys, although pharmacological studies for most drugs, except pergolide, are lacking.

Comparison of one novel and four established diagnostic tests for insulin dysregulation in ponies

Several tests have been advocated for diagnosis of insulin dysregulation (ID). Tests using simple sugars may not reflect the response to naturally ingested carbohydrates. This study aimed to evaluate agreement between the oral glucose test (OGT), the oral sugar test (OST), a novel oral test using a proprietary cereal (WEET), the IV combined glucose-insulin tolerance test (CGIT) and fasted basal insulin (FI) for diagnosis of ID. Each of the five tests above was performed on a group of six normal and six insulin dysregulated mixed-breed ponies in a randomised crossover study. Area under the curve (AUC) and maximum concentration of insulin from OGT, OST and WEET showed strong to very strong bivariate correlations (r = 0.85-0.94, and r = 0.87-0.92, respectively; P ≤ 0.001) and were significantly different between tests (associated with dose of carbohydrate) and between CGIT-positive and -negative ponies. Dichotomous results showed substantial agreement between OST and both WEET (κ = 0.65; P = 0.02) and OGT (κ = 0.67; P = 0.01) and between CGIT and both OST (κ = 0.63; P = 0.03) and OGT (κ = 0.67; P = 0.01), and no agreement between FI, which had low sensitivity, and all other tests (κ = 0.15 - 0.31; P > 0. 05). Palatability of WEET was variable, resulting in one pony being excluded for analysis of WEET data. Further work on development of an oral test using a more palatable feedstuff and appropriate cut-offs or diagnostic thresholds for tests of ID is warranted.

Strip grazing: Changes in biomass, nutrient content and digestibility of temperate, midsummer pasture by strip-grazed or 'free'-grazing ponies, over 4 weeks

The digestibility and nutritive values of pastures that were either freely or strip-grazed for 28 days were compared. Twelve ponies were individually grazed in adjacent, 10 m wide, rectangular paddocks. On day -1, each paddock length was adjusted to contain a 28-day supply of herbage DM at 1.5 % of pony BW/d. Ponies, (4/treatment) either accessed the entire 28-day supply from day 1 (TA), or gradually via strip-grazing treatments, SG1 and SG2. SG1 had a 'lead' fence spanning the paddock width that from day 3 was moved forward 1/26th of the paddock length daily, whereas SG2 had an additional 'back fence', that was advanced the same distance as the lead fence daily. Pasture nutrient contents and estimated nutrient digestibilities (eD) were determined weekly. From weeks 1-4, mean strip-grazed pasture contents (% DM) of water-soluble carbohydrate (WSC) and crude protein declined from 15.7-10.2 and 9.4-8.7, respectively, whereas neutral- and acid-detergent fibre increased from 53.6-60.5 and 35.2-38.0, respectively. Corresponding values for TA pastures were 17.7-5.2, 8.9-8.7, 54.6-69.2 and 35.7-43.6. Concomitantly, calculated digestible energy (cDE) (MJ/kg DM) of strip-grazed and TA pastures declined from 9.7-8.9 and 9.6-7.8, respectively and eDMD of all treatments declined (P<0.05). By week 4, TA pasture WSC, cDE and eDMD were lower and fibre contents higher (P<0.05) than the strip-grazed pastures. TA animal cDE intakes in weeks 1 and 2 exceeded requirements by 42 % vs. 8 % by strip-grazed animals. Strip-grazing delivered a steadier nutrient supply than TA, potentially conferring health benefits to animals prone to metabolic dysfunction.

Confidence does not mediate a relationship between owner experience and likelihood of using weight management approaches for native ponies

Native ponies are at increased risk of obesity and metabolic perturbations, such as insulin dysregulation (ID), a key risk factor for endocrinopathic laminitis. Management and feeding practices can be adapted to maintain healthy body condition and support metabolic health, but owners may inadvertently provide their ponies with inappropriate management leading to obesity and exacerbating risk of metabolic disease. Adoption of preventative weight management approaches (WMAs), including regular monitoring of body condition, providing appropriate preserved forage, promoting seasonal weight loss, and using exercise accordingly, are key in supporting native ponies' metabolic health. The factors influencing the adoption of WMAs, such as owners' experience and confidence, require exploration. The aim of the current study was to understand factors influencing owners' likelihood to undertake certain WMAs, to develop our understanding of suitable intervention targets. A total of 571 responses to an online cross-sectional questionnaire were analysed. Mediation analysis revealed that whilst long term (≥20 years) experience caring for native ponies was associated with owners increased, self-reported confidence in identifying disease and managing their native ponies, this did not translate to an increased likelihood of implementing WMAs. Conversely, respondents who managed ponies with dietary requirements related to obesity, laminitis, or equine metabolic syndrome were more likely to use WMAs related to feeding, seasonal weight management and exercise. Owner confidence was assessed and rejected as a mediator of the relationship between experience and WMA use. These results highlight the need for further work that elucidates the pathways leading owners to undertake action against obesity without the need for ponies to develop overt disease, as well as suggesting a need for long term managers of native ponies to update management practices with preventative care as the focus.

Development of a Web App to Convert Blood Insulin Concentrations among Various Immunoassays Used in Horses

The measurement of the blood insulin concentration, and comparison to cut-offs, is essential in diagnosing insulin dysregulation, a common equine endocrinopathy. However, different insulin assays provide disparate results. We aimed to ease comparison between assays by compiling original and published data into a web app to convert insulin measurements from one assay to another. Data were available for ADVIA Centaur insulin chemiluminescent immunoassay (CLIA), Beckman Coulter insulin radioimmunoassay (RIA), Immulite 1000 CLIA, Immulite 2000 CLIA, Immulite 2000 XPi CLIA, Mercodia equine insulin enzyme-linked immunosorbent assay (ELISA), and Millipore porcine insulin RIA. Linear models were fitted for 13 assay pairs using non-decreasing splines, and integrated into this app. Assay comparisons including data from several studies showed a lower performance. This indicates technical variation between laboratories, which has not been described before, but is relevant when diagnostic measurements and cut-offs are provided by different laboratories. Nevertheless, the models' overall high performance (median r2 = 0.94; range 0.57-1.00) supports their use to interpret results from diagnostic insulin measurements when the reference assay is unavailable, and to compare values obtained from different assays.

Evaluation of field-testing protocols to diagnose insulin dysregulation in ponies using a Bayesian approach

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).

Occurrence of equine metabolic syndrome, clinical manifestations, and associated risk factors in Nigeria

Insulin dysregulation (ID) is central to the pathophysiology of equine metabolic syndrome (EMS), putting the horse at risk of laminitis. There is a paucity of information on the status of EMS in Nigeria. This study aimed to determine the occurrence of EMS, clinical manifestations, and associated risk factors in Nigeria. A cross-sectional study was carried out. Selected horses underwent an insulin 2-step response test to ascertain insulin dysregulation; a physical examination was carried out to diagnose laminitis and obesity. Risk factors were assessed using a questionnaire. The overall prevalence of EMS was 43.10%. Breed and sex were significantly associated with EMS, but age was not. Horses diagnosed with laminitis showed two signs of laminitis, namely, divergent hoof rings and widened white lines. Risk factors significantly associated with the prevalence of EMS were as follows: being a West African Barb horse (60.00%), being a stallion (67.86%), being a leisure horse (67.86%), only walking horses during exercise (68.00%), exercising horses once every 5 months (82.76%), tethering horses to a stake in the ground (67.86%), obesity (92.86%), and abnormal neck crest (83.33%). The risk of ID remains higher in obese horses. However, some of the horses with ID were not obese, indicating that there are other possible underlying causes of EMS.

Equine Endocrine Disease: Challenges With Case Definition for Research

Equine endocrine disease is an important area for equine research, requiring an appropriate case definition for inclusion and criteria for exclusion from disease. Defining a case for research may be different from criteria for clinical diagnosis. Further, clinical diagnosis recommendations have been changing regularly, making this area challenging for equine scientists. This review discusses the diagnosis of major equine endocrine diseases, pituitary pars intermedia dysfunction, equine metabolic syndrome and insulin dysregulation, focusing on the most appropriate diagnostic methods for research case definitions. Different diagnostic methods, including use of reference intervals and clinical decision limits, will be discussed with their relative merits for use in case definition for research.

Equine metabolic syndrome: Role of the enteroinsular axis in the insulin response to oral carbohydrate

Equine insulin dysregulation (ID) comprises amplified insulin responses to oral carbohydrates or insulin resistance, or both, which leads to sustained or periodic hyperinsulinaemia. Hyperinsulinaemia is important in horses because of its clear association with laminitis risk, and the gravity of this common sequela justifies the need for a better understanding of insulin and glucose homoeostasis in this species. Post-prandial hyperinsulinaemia is the more commonly identified component of ID and is diagnosed using tests that include an assessment of the gastrointestinal tract (GIT). There are several factors present in the GIT that either directly, or indirectly, enhance insulin secretion from the endocrine pancreas, and these factors are collectively referred to as the enteroinsular axis (EIA). A role for key components of the EIA, such as the incretin peptides glucagon-like peptide-1 and 2, in the pathophysiology of ID has been investigated in horses. By comparison, the function (and even existence) of many EIA peptides of potential importance, such as glicentin and oxyntomodulin, remains unexplored. The incretins that have been examined all increase insulin responses to oral carbohydrate through one or more mechanisms. This review presents what is known about the EIA in horses, and discusses how it might contribute to ID, then compares this to current understanding derived from the extensive studies undertaken in other species. Future directions for research are discussed and knowledge gaps that should be prioritised are suggested.

A review of cellular and molecular mechanisms in endocrinopathic, sepsis-related and supporting limb equine laminitis

Equine laminitis has both fascinated and frustrated veterinary researchers and clinicians for many years. The recognition that many ponies suffering from pasture-associated laminitis have an insulin-dysregulated phenotype (endocrinopathic laminitis, EL) and that prolonged insulin and glucose infusions can experimentally induce laminar pathology and functional failure are seminal discoveries in this field. Researchers have studied the molecular basis for disease pathogenesis in models of EL, sepsis-related laminitis and supporting limb laminitis and generated much data over the last 15 years. This review attempts to synthesise those data, drawing comparisons between models and naturally occurring laminitis. A hypothesis is proposed that the basal epithelial cell stress is a central event in each category of laminitis. Furthermore, in naturally occurring pasture-associated laminitis, pathways that predominate in each type of laminitis contribute to laminar lamellar pathology to varying extents. Based on the molecular mechanisms determined in experimental models, interactions between these pathways are identified.

Impacts of Adiposity on Exercise Performance in Horses

There is ample research describing the increased risk of health concerns associated with equine obesity, including insulin dysregulation and laminitis. For athletes, the negative effect of weight carriage is well documented in racing thoroughbreds (i.e., handicapping with weight) and rider weight has been shown to impact the workload of ridden horses and to some degree their gait and movement. In many groups of competitive and athletic horses and ponies, obesity is still relatively common. Therefore, these animals not only are at risk of metabolic disease, but also must perform at a higher workload due to the weight of their adipose tissue. Excess body weight has been documented to affect gait quality, cause heat stress and is expected to hasten the incidence of arthritis development. Meanwhile, many equine event judges appear to favor the look of adiposity in competitive animals. This potentially rewards horses and ponies that are at higher risk of disease and reinforces the owner's decisions to keep their animals fat. This is a welfare concern for these animals and is of grave concern for the equine industry.

Palatability, glycemic, and insulinemic responses to various carbohydrate formulations: Alternatives for the diagnosis of insulin dysregulation in horses?

BACKGROUND

Oral glycemic challenge (GC) tests are recommended for diagnosis of insulin dysregulation (ID). Various protocols are used, but all have limitations in terms of palatability, ease of use, variable composition, geographic availability, or some combination of these.

HYPOTHESIS/OBJECTIVE

To evaluate newly developed formulations with defined carbohydrate composition for use as oral GCs.

ANIMALS

Thirty-four horses and ponies in various metabolic states.

METHODS

Our objectives were carried out in 2 separate cross-over experiments. First, the palatability and acceptance of various GCs (2 syrups, 1 granulate) offered for free intake were compared to glucose mixed in a chaff-based diet. Subsequently, syrups were administered by syringe and compared to an oral glucose test using naso-gastric tubing (tube OGT) to investigate the glycemic and insulinemic responses. Second, these variables were compared in the best performing GC-formulations (granulate further optimized to pelleted formulation and 1 syrup) and a tube OGT. All GCs were administered with equivalent amounts of 0.5 g glycemic carbohydrates per kg body weight.

RESULTS

Only the GC pellets were consumed completely by all horses (consumption time 5 ± 2 min). When administered by syringe, the GC syrup also was well accepted. The insulin concentrations at 120 min correlated significantly between tube OGT and GC pellets (r = .717; P < .001) or GC syrup (r = .913; P < .001). The new GC syrup and GC pellets discriminate between healthy and ID horses.

CONCLUSIONS AND CLINICAL SIGNIFICANCE

The GC pellets (DysChEq)™ and GC syrup can be used as palatable and well-accepted oral GC tests for assessment of ID in horses.

Predictors of laminitis development in a cohort of nonlaminitic ponies

BACKGROUND

Quantifying risk factors for laminitis development requires improvement.

OBJECTIVES

To identify the most useful physical examination, metabolic and management factors to predict laminitis development in client-owned, nonlaminitic ponies.

STUDY DESIGN

Prospective cohort study.

METHODS

Physical examination, metabolic and management data were collected from a pony cohort 6 monthly for up to 4 years. Ponies were monitored for the development of laminitis. Metabolic data included basal plasma concentrations of ACTH ([ACTH]), adiponectin ([adiponectin]), triglycerides and glucose. Serum insulin concentrations ([insulin]) were measured in the unfasted basal state ([insulin]T0) and 60 minutes ([insulin]T60) after administration of corn syrup (0.3ml/kg). Separate multivariable Cox proportional-hazards models were developed for physical, management/signalment and metabolic data and later combined into two final models. Low-, medium- and high-laminitis risk categories were defined based on basal or T60 [insulin].

RESULTS

Overall, 374 ponies (age 5-32 years) and 891 pony-years were included in the main analysis. Laminitis incidence (95% confidence interval (CI)) was 4.8 (3.5-6.5) cases/100 pony-years. Laminitis development was associated with numerous univariable factors. Significant (P < .05) factors retained in the final multivariable models included [insulin]T0, [insulin]T60, [adiponectin] and divergent hoof growth. [ACTH] was not independently associated with laminitis. Based on [Insulin]T0, low- (<21.6 µIU/ml), medium- (21.6-45.2 µIU/ml) and high-risk (>45.2 µIU/ml) categories encompassed 70, 20 and 10% of the population and had estimated 4-year laminitis incidences (95%CI) of 6 (2-9)%, 22 (10-33)% and 69 (48-82)% respectively. Based on [Insulin]T60 the low- (<53.4 µIU/ml), medium- (53.4-153 µIU/ml) and high-risk (≥153 µIU/ml) categories comprised 60, 30 and 10% of the population and had estimated 4-year laminitis incidences (95%CI) of 3 (0-6)%, 20 (10-29)% and 73 (52-84)% respectively.

MAIN LIMITATIONS

Results may not apply to different insulin assays, geographical regions, breeds or management types.

CONCLUSIONS

[Insulin]T0 or [insulin]T60 best quantify the risk of future laminitis development in nonlaminitic ponies.

A one-health approach to identifying and mitigating the impact of endocrine disorders on human and equine athletes

Endocrinopathies affect multiple species in ever-increasing percentages of their populations, creating an opportunity to apply one-health approaches to determining creative preventative measures and therapies in athletes. Obesity and alterations in insulin and glucose dynamics are medical concerns that play a role in whole-body health and homeostasis in both horses and humans. The role and impact of endocrine disorders on the musculoskeletal, cardiovascular, and reproductive systems are of particular interest to the athlete. Elucidation of both physiologic and pathophysiologic mechanisms involved in disease processes, starting in utero, is important for development of prevention and treatment strategies for the health and well-being of all species. This review focuses on the unrecognized effects of endocrine disorders associated with the origins of metabolic disease; inflammation at the intersection of endocrine disease and related diseases in the musculoskeletal, cardiovascular, and reproductive systems; novel interventions; and diagnostics that are informed via multiomic and one-health approaches. Readers interested in further details on specific equine performance conditions associated with endocrine disease are invited to read the companion Currents in One Health by Manfredi et al, JAVMA, February 2023.

The Welfare of Traveller and Gypsy Owned Horses in the UK and Ireland

Travellers and Gypsies are recognised ethnic groups in the UK and Ireland. Horse ownership is an important cultural tradition, however, practices associated with poor welfare are often perceived to be linked to these horse owning communities. Despite this, empirical studies on the welfare status of Traveller and Gypsy owned horses are lacking. To determine the welfare status of Traveller and Gypsy owned horses, 104 horses were assessed using a bespoke horse welfare protocol. This protocol assessed animal, resource and management-based measures. In addition, Qualitative Behaviour Assessment (QBA) identified horses’ emotional state. Results indicated that 81% of horses had an optimal body condition score, with no horse recorded as very thin/fat. The absence of limb conditions (95%), ocular (98%) and nasal (93%) discharges were evident in most horses, and 81% of horses responded positively to the voluntary animal approach test. The most commonly observed welfare issues were hoof neglect (27%), with hoof cracks/breakages (19%) being the most prevalent. QBA indicated that positive emotional states were more commonplace than negative. A relationship between QBA and other horse welfare measures was observed, e.g., improved mood was associated with better water availability. This research provides novel data in the under-researched area of the welfare of Traveller and Gypsy owned horses and counters perceptions of a poor welfare state in this group of horses.

Demographic, morphologic, hormonal and metabolic factors associated with the rate of improvement from equine hyperinsulinaemia-associated laminitis

Background

Although several studies have investigated factors associated with the onset and occurrence of hyperinsulinaemia-associated laminitis (HAL), few have examined the factors associated with the rate of improvement during recovery from an acute bout of the disease. This observational study sought to discover if a range of demographic, morphologic, hormonal and metabolic variables are associated with the improvement rate from HAL in 37 naturally-occurring cases identified by 16 clinics across Germany. Each case was evaluated for laminitis severity on the day of inclusion in the trial (d 0), then after 4, 9, 14, 25 and 42 d. The horses were managed according to best clinical practice including restricting exercise and prescribing a diet of hay-only, for a minimum of 9 d. Blood samples were also collected during each evaluation, except on d 9, and analysed for glucose, insulin, ACTH and leptin.

Results

Based on individual clinical laminitis scores plotted against time, most horses improved markedly within 2 weeks, with a ‘fast group’ (n = 27) having a median (interquartile range) score on a 12-point scale of 0 (0–2) by d 14. However, there was a clear disparity within the total cohort, as ~ 1 in 4 horses demonstrated much slower improvement, with a median score of 5 (4–7) by d 14, or a marked relapse thereafter (‘slow group’, n = 10). Horses in the slow improvement group were younger (12.5 (8.8–16.3) vs 17 (14–24) yr; P = 0.008), but were not more likely to be heavier, male, very fat, to have presented with a previous history of laminitis or elevated ACTH concentrations, or to be receiving pergolide treatment. Of the hormonal and metabolic parameters measured, glucose and insulin concentrations were within the normal range following transition to the hay-only diet, but were higher in the group that failed to improve quickly, with a small but significant difference being evident on d 4, 14 and 25 for glucose (11 to 16%; P < 0.05), and a larger difference for insulin on d 14 and 25 (51 to 55%; P < 0.05). There was no difference between the groups in ACTH or leptin concentrations throughout the study. The main limitations of this study were the small number of slow-improvement horses and an inability to control or measure certain variables, such as feed quality.

Conclusions

Young age and a modest increase in blood glucose and insulin concentrations are associated with delayed laminitis improvement.

Obesity-Related Metabolic Dysfunction in Dairy Cows and Horses: Comparison to Human Metabolic Syndrome

Obesity has become a serious health problem with frequent occurrence both in human and animal populations. It is estimated that it may affect over 85% of the human population and 70–80% of horses and cows by 2030. Fat cow syndrome (FCS) is a combination of metabolic, digestive, infectious, and reproductive disorders that affects obese periparturient dairy cows, and occurs most frequently in loose-housing systems, where periparturient and dry cows are fed and managed in one group disregarding the lactation stages. Equine metabolic syndrome (EMS) was named after human metabolic syndrome (MetS) and has insulin dysregulation as a central and consistent feature. It is often associated with obesity, although EMS may occur in a lean phenotype as well. Other inconsistent features of EMS are cardiovascular changes and adipose dysregulation. Laminitis is the main clinical consequence of EMS. MetS holds a 30-years old lead in research and represents a clustering of risk factors that comprise abdominal obesity, dyslipidemia, hypertension, and hyperglycemia (impaired fasting glucose or type 2 diabetes mellitus—T2DM), which are associated with doubled atherosclerotic cardiovascular disease risk, and a 5-fold increased risk for T2DM. The main aim of this review is to provide critical information for better understanding of the underlying mechanisms of obesity-related metabolic dysfunction in animals, especially in cows and horses, in comparison with MetS. Human medicine studies can offer suitable candidate mechanisms to fill the existing gap in the literature, which might be indispensable for owners to tackle FCS, EMS, and their consequences.

Variation in insulin response to oral sugar test in a cohort of horses throughout the year and evaluation of risk factors for insulin dysregulation

BACKGROUND

The oral sugar test (OST) is commonly used to diagnose insulin dysregulation (ID) and equine metabolic syndrome; however, possible seasonal changes in OST results have not been evaluated.

OBJECTIVE

To determine the possible variation in insulin response to OST throughout the year and risk factors associated with maximum insulin concentration (InsMax) and ID.

STUDY DESIGN

Prospective, longitudinal cohort study.

METHODS

The OST was performed on 29 Finnhorses every other month six times. Serum total adiponectin concentration and phenotypic variables related to obesity were also measured. Changes in InsMax, adiponectin, scale weight, body condition score, cresty neck score (CNS), and fasting glucose concentration were assessed. Risk factor analyses were performed on InsMax and ID status, and ID groups were compared with each other.

RESULTS

Fourteen horses were categorised with non-ID each time and 15 as having ID at least once during the follow-up period. The ID status of 12 horses varied throughout the year, but neither the insulin variables measured during the OST nor adiponectin expressed significant seasonal variation. Increasing age and CNS, and decreasing adiponectin were observed as risk factors for a high InsMax after OST. The risk of ID was higher in horses with no exercise compared to horses with exercise (OR 7.6, 95% CI 1.2-49.3, P = .03). Horses with ID had lower serum adiponectin concentrations, longer neck circumference and larger height than horses in the non-ID group.

MAIN LIMITATIONS

The environmental conditions (feeding, exercise) were not constant for all horses throughout the study and only one breed was used.

CONCLUSIONS

Neither OST results nor adiponectin varies with season; however, there were a substantial number of horses with variable ID status throughout the year, in which repeated OSTs may be beneficial. Lack of exercise was a risk factor for ID.

Endocrinopathic Laminitis

Endocrinopathic laminitis (EL) primarily occurs because of insulin dysregulation (ID) mediated through downstream effects of insulin on IGF-1R in lamellar tissues. There is likely contributing vascular and metabolic dysfunction within the lamellae, but EL is relatively non-inflammatory. EL is associated with lamellar stretching, proliferation, and failure, ultimately causing failure of the suspensory apparatus of the distal phalanx. Proper education regarding mitigating risk factors makes this a largely preventable cause of laminitis. Annual hoof evaluation plus screening geriatric horses for pituitary pars intermedia dysfunction and ID, and younger horses for ID, can significantly decrease the incidence of this devastating condition.

Understanding rider:horse bodyweight ratio trends, weight management practices and rider weight perceptions within leisure and amateur riders in the UK

Horse riders in the UK have a legal responsibility for the welfare of the horses in their care, outlined by the Animal Welfare Act (2006). Understanding weight management factors that influence rider: horse bodyweight (RHBW) ratio is key to safeguarding horse welfare as human obesity rates increase. Recent high-profile incidents have seen riders being asked to dismount for being too heavy, demonstrating an awareness of the possible impact of excessive rider weight, threatening the equestrian industry’s social licence to operate. This study investigated RHBW trends within the UK leisure and amateur rider population to understand rider perception of ‘ideal’ RHBW and factors influencing rider and horse weight management. An online survey (SurveyMonkey®) was distributed via UK equine-related Facebook™ groups and collected information on horse and rider demographics, rider weight management strategies and respondents’ views on the importance of rider weight on horse welfare. Kruskal-Wallis analyses with Mann Whitney U post-hoc tests identified whether differences in respondent views differed between RHBW groups. A total of 971 riders completed the survey; respondents were aged between 18-65+ years old and 88% (n=953) were experienced riders. RHBWs were calculated for 764 (79%) of respondents as 21.2% (n=206) did not know either their own and/or their horses’ weight. Weight tapes (44.5%; n=432) and weigh bridges (29.5%; n=286) were common horse weight estimation methods. RHBWs ranged from 4.9% to 21.88%, mean: 12.5%±2.7%. Riders with lower RHBW thought about their own weight less and measured their horses’ weight less often than those with higher ratios (P<0.005, P<0.0004, respectively). The majority of riders who participated were weight conscious and recognised potential detrimental impacts associated with increased rider weight. Development of RHBW guidelines supported by equestrian governing bodies would highlight the need for riders to consider the impact of weight and support them in choosing suitable horses.

Cross-sectional study to identify the prevalence of and factors associated with laminitis in UK donkeys

BACKGROUND

Laminitis causes lameness in donkeys, but its prevalence and factors associated with disease remain uncertain.

OBJECTIVES

To determine the prevalence of and identify factors associated with laminitis in donkeys.

STUDY DESIGN

Retrospective cross-sectional study.

METHODS

All donkeys at the Donkey Sanctuary, UK, October 2015 to March 2019 were included. For animals that had laminitis during this period, age, sex, weight, body condition score, and the onset date and type of each episode (first or recurrent, acute or chronic) were recorded. Additionally, management data, foot lesion score, endocrine data, other medical conditions, occurrence of foot trimming, surgical procedures, diagnostic imaging, behavioural modification therapy or movement between farms within the month prior were noted. Controls were animals that did not experience laminitis during this period and similar data were recorded. Multivariable logistic regression modelling assessed the differences between the control group and laminitis outcome groups (first, all laminitis, acute and chronic episodes).

RESULTS

Altogether, 707 animals were included; 364 were control animals; 343 had a first episode of laminitis during the study period, of which 200/343 had no further episodes and 143/343 had recurrent episodes resulting in a total of 512 laminitis episodes and the period prevalence was 48.5% over 42 months. Overall, 180/512 (35%) laminitis episodes were acute and 332/512 (65%) were chronic. Compared with control animals, the laminitic outcome groups were significantly (P < .05) more likely to be younger (first episode), less likely to get extra feed (all four groups) or have an additional medical problem (first episode), and less likely to have undergone dental work, movement, imaging (all four groups) or surgery (first; all laminitis, chronic episodes) in the month preceding the episode.

MAIN LIMITATIONS

These results may not be applicable to the wider donkey population.

CONCLUSIONS

Laminitis commonly affects donkeys, but factors associated with donkey laminitis differ from those reported in horses.

UK Horse Carers' Experiences of Restricting Grazing When Aiming to Prevent Health Issues in Their Horses

Laminitis and obesity are leading welfare issues for UK leisure horses. Limiting grass intake is a common preventative measure but may result in other aspects of welfare being compromised. This study aimed to determine how commonly different restricted grazing methods are used in the UK, barriers limiting their accessibility, and the potential benefits and welfare issues associated with each. A cross-sectional online survey was distributed with questions relating to horse carers' opinions of different restricted grazing practices, which methods they used, and how they implemented these. Closed questions were analyzed using descriptive statistics and non-parametric tests. Free text questions underwent content analysis. 503 respondents completed the questionnaire, 468 (93.0%) had practiced restricted grazing. Strip grazing was the most commonly tried method (67.7% of restricted grazers), followed by grazing muzzles (61.3%), starvation paddocks (57.4%), stabling (49.9%), crew yards (27.5%) and track systems (15.3%). Perception of welfare impact differed significantly between methods for both those who had (P < .001) and had not (P < .001) restricted grazing. Both groups considered strip grazing best for welfare and stabling worst. Barriers (including ease of implementation [52.0%], yard restrictions [24.0%], cost/affordability [23.7%]) prevented some from using their preferred methods. Respondents had similar priorities when choosing a restricted grazing method but did not agree which methods met these criteria. Strip grazing was favored by the greatest proportion of respondents whilst grazing muzzles and stabling polarized opinion. This study has provided initial insights into the challenges faced by horse carers when aiming to restrict grazing to combat equine health issues.

Associations of plasma sphingolipid profiles with insulin response during oral glucose testing in Icelandic horses

BACKGROUND

Sphingolipids modulate insulin sensitivity in mammals. Increased synthesis of ceramides is linked to decreased insulin sensitivity of tissues. Conversely, activation of the insulin signaling pathway can downregulate ceramide synthesis. Elucidating the association between sphingolipid metabolism and insulin response during oral glucose testing may help explain the pathophysiology of insulin dysregulation in horses.

HYPOTHESES

Horses with insulin dysregulation will have a plasma sphingolipid profile characterized by increased ceramide concentrations. The plasma sphingolipid profile will have decreased ceramide concentrations after acute activation of the insulin signaling pathway by oral glucose testing.

ANIMALS

Twelve Icelandic horses.

METHODS

Horses were subjected to an oral glucose test (0.5 g/kg body weight glucose), with plasma insulin concentrations measured at 0, 30, 60, 120, 180, and 240 minutes postglucose administration. Plasma samples were collected at 0 and 120 minutes for sphingolipid profiling using a liquid chromatography-mass spectrometry-based metabolomics analysis. Eighty-three species of sphingolipids were detected, including 3-ketosphinganines, dihydroceramides, ceramides, dihydrosphingomyelins, sphingomyelins, galatosylceramides, glucosylceramides, lactosylceramides, and ceramide-1-phosphates.

RESULTS

Glucose administration did not significantly alter plasma sphingolipid profiles. C22:0-ceramide, C24:1-ceramide, C23:0-ceramide, C16:1-sphingomyelin, C22:0-dihydroceramide, and C24:0-ceramide were positively correlated with the insulin response (area under the curve).

CONCLUSION AND CLINICAL IMPORTANCE

Positive correlation between the insulin response and sphingolipid concentrations implies upregulated sphingolipid metabolism in insulin dysregulated horses. A high plasma ceramide concentration can indicate insulin dysregulation in horses.

COVID-19 impacts equine welfare: Policy implications for laminitis and obesity

The COVID-19 pandemic continues to impact human health and welfare on a global level. In March 2020, stringent national restrictions were enforced in the UK to protect public health and slow the spread of the SARS-CoV-2 virus. Restrictions were likely to have resulted in collateral consequences for the health and welfare of horses and ponies, especially those at risk of obesity and laminitis and this issue warranted more detailed exploration. The current study utilised qualitative methodology to investigate the implications of COVID-19 related policies upon equine management and welfare with a focus on horses and ponies at risk of laminitis and obesity. Twenty-four interviews with five sub-groups of key equestrian welfare stakeholders in the UK were conducted between May and July of 2020 to understand the challenges facing equine welfare in the context of laminitis and obesity susceptible animals. Thematic analysis revealed lockdown-associated factors with the potential to compromise welfare of horses and ponies at risk of obesity and laminitis. These included: disparate information and guidance, difficulties enacting public health measures in yard environments, and horses having reduced exercise during the pandemic. Positive examples of clear and consistent information sharing by farriers were reported to have improved horse owner understanding of routine hoof care during lockdown. Analysis suggested that the recommendations for supporting the management-based needs of horses under reduced supervision were not clearly defined, or were not sufficiently disseminated, across the equine industry. These findings support the development of guidelines specific to the care of horses and ponies at risk of obesity and laminitis through collaborative input from veterinary and welfare experts, to reduce the negative impacts of future lockdown events in the UK.

The application of a new laminitis scoring method to model the rate and pattern of improvement from equine endocrinopathic laminitis in a clinical setting

Background

Endocrinopathic, or hyperinsulinaemia-associated laminitis (HAL) is a common and debilitating equine foot disease, and although no pharmacological treatments are registered, several are under development. To evaluate the effect of such treatments, an accurate and consistent method is needed to track the clinical signs of laminitis over time, and the natural history of the disease, in terms of a ‘normal’ pattern of improvement, needs to be understood. This study examined the improvement pattern in clinical cases of naturally-occurring HAL subjected to a range of best-practice interventions, using two different scoring methods. Eighty horses and ponies with suspected HAL were enrolled in a study conducted at 16 veterinary practices across Germany. The severity of laminitis was assessed by independent veterinarians using both the traditional Obel method and a modified Obel method developed by Meier and colleagues. Assessments were made on the day of diagnosis (d 0), then on days 4, 9, 14, 25 and 42 during the intervention period. Pain medications were withheld for 24 h prior to clinical examination in all cases.

Results

Time to marked improvement from laminitis varied between individuals, but was difficult to monitor accurately using the Obel method, with the median grade being 2/4 on days 0 and 4, then 0/4 from d 9 onwards. More subtle changes could be identified using the Meier method, however, and the median scores were seen to follow the form of an exponential decay model in most horses, improving from 8/12 on d 0, to 0/12 on d 25. Within this composite scoring method, considerable variation was observed in the rate of improvement of individual clinical signs, with the average time taken for each sign to reach a median score of 0 ranging from 4 days (foot lift and weight shifting) to 25 days (gait when turned in a circle) across all 80 horses.

Conclusions

The Meier method provides a reliable and consistent method for monitoring the clinical status of horses with HAL, and despite the variability, the pattern of improvement described here should provide a useful benchmark against which individual cases and new treatments can be assessed.

Strip-grazing: Reduces pony dry matter intakes and changes in bodyweight and morphometrics

BACKGROUND

Obesity can negatively impact upon equine welfare and bodyweight (BW) of pastured equines is often difficult to manage.

OBJECTIVES

To compare the effects of three restricted grazing regimens on changes in pony BW and morphometric measurements.

STUDY DESIGN

Randomised study.

METHODS

Twelve mature ponies were individually grazed in 10m wide, rectangular, electric fenced paddocks. The dry matter (DM) herbage yield of each paddock was determined, and paddock length adjusted on Day 1 to provide 1.5% of individual pony BW as herbage DM daily, for 28 days. There were four ponies per treatment. Treatments were: total paddock area (TA) and strip grazing treatments, SG1 and SG2. SG1 had a 'lead' fence spanning the paddock width being moved a set distance along the paddock length daily to provide 1.5% of pony BW as fresh pasture DM (as determined on Day -1). SG2 also had a 'back fence' 7-12m behind the 'lead' fence which was moved the same distance as the lead fence daily. Calculated dry matter intakes, changes in cresty neck score (CNS), body condition score (BCS) and percentage changes in BW, heart girth (HG), belly girth (BG) and rump width (RW) were compared between treatments.

RESULTS

Mean (±SD) calculated pasture DM intakes (as % BW/d) by TA ponies were 2.33 ± 0.50, being significantly higher (P < 0.05) than 1.82 ± 0.43 (SG1) and 1.59 ± 0.42 (SG2). Mean percentage BW changes were higher (P < 0.05) for TA ponies at 4.82 ± 1.36 vs. 1.16 ± 0.39 (SG1) and 1.54 ± 1.35 (SG2). SG1 and SG2 pony BW changes were not significantly different. TA, but not SG1 or SG2 animals showed significant (P < 0.05) increases in BCS1/9 (+0.94 ± 0.32), CNS1/5 (+0.5 ± 0), RW (+2.11 ± 3.6) and BG (+4.15 ± 2.29). SG1 and SG2 ponies showed significant (P < 0.05) decreases in HG (-0.05 ± 2.12) and BG (-5.53 ± 4.89) respectively.

MAIN LIMITATIONS

Small sample size.

CONCLUSIONS

Strip grazing limited pony bodyweight gains and upward changes in morphometric parameters.

Equine metabolic syndrome in UK native ponies and cobs is highly prevalent with modifiable risk factors

BACKGROUND

The epidemiology of equine metabolic syndrome (EMS) is poorly described.

OBJECTIVES

To estimate the prevalence of EMS in native UK ponies and cobs in England and Wales and identify associated risk factors.

STUDY DESIGN

Cross-sectional study.

METHODS

Breeders registered with UK native pony breed societies and registered riding schools and livery yards within a set radius were invited to participate. All native UK ponies and cobs aged 3-14 years and not diagnosed or being treated for conditions likely to affect insulin regulation at participating premises were eligible. Animals underwent a clinical examination and an oral glucose test while their owner or keeper completed a questionnaire by face-to-face interview. Data were analysed by multilevel uni- and multivariable modelling using insulin concentration and EMS diagnosis as outcomes.

RESULTS

A total of 354 animals were examined at 64 properties (19 studs, 19 livery yards, 26 riding schools). The overall prevalence of EMS adjusted for clustering within yard was 23.3% (95%CI 17.9%-29.8%). Risk factors associated with a diagnosis of EMS included age, being female, more sedentary main activity, obesity, and shorter periods on pasture during the summer. Compared to the Welsh section A, the other Welsh, Connemara and cob breeds all had decreased odds of EMS. Clinical manifestations of hoof growth ring and supraorbital fat scores of 3/3 were more frequent in EMS ponies and animals with a history of laminitis within the last 5 years (9.7%) were 14.4 (95% CI 5.9-35.3) times more likely to be positive for EMS than those without.

MAIN LIMITATIONS

Results may not be transferable to other breeds or age groups.

CONCLUSIONS

Equine metabolic syndrome is highly prevalent in UK native ponies and cobs with modifiable risk factors including obesity and sedentary activities. Modifying risk factors could help reduce the risk of laminitis in susceptible animals.

Foraging efficiency, social status and body condition in group-living horses and ponies

Individual animals experience different costs and benefits associated with group living, which may impact on their foraging efficiency in ways not yet well specified. This study investigated associations between social dominance, body condition and interruptions to foraging behaviour in a cross-sectional study of 116 domestic horses and ponies, kept in 20 discrete herds. Social dominance was measured for each individual alongside observations of winter foraging behaviour. During bouts of foraging, the duration, frequency and category (vigilance, movement, social displacements given and received, scratching and startle responses) of interruptions were recorded, with total interruption time taken as a proxy measure of foraging efficiency. Total foraging time was not influenced by body condition or social dominance. Body condition was associated with social dominance, but more strongly associated with foraging efficiency. Specifically, lower body condition was associated with greater vigilance. This demonstrates that factors other than social dominance can result in stable differences in winter body condition.

Genetics and Signaling Pathways of Laminitis

Laminitis is a devastating disease with diverse etiologies and few, if any, effective treatments. Gene expression and hypothesis-generating genomic studies have provided a fresh look at the key molecular players at crucial timepoints in diverse experimental and naturally affected tissues. We summarize findings to date, and propose a unifying model of the laminitis disease process that includes several pathogenesis concepts shared with other diseases of epidermal and epithelial tissues. The value of these new pathways as potential therapeutic targets is exciting but will require careful future work to validate new methods and launch systematic clinical trials.

Metabogenomics reveals four candidate regions involved in the pathophysiology of Equine Metabolic Syndrome

An analogous condition to human metabolic syndrome, Equine Metabolic Syndrome (EMS) is defined by several clinical signs including obesity, hyperinsulinemia, and peripheral insulin dysregulation (ID). Affected horses may also exhibit hypertension, hyperlipemia and systemic inflammation. Measures of ID typically comprise the gold-standard for diagnosis in veterinary care. Yet, the dynamic nature of insulin homeostasis and complex procedures of typical assays make accurate quantification of ID and EMS challenging. This work aimed to investigate new strategies for identification of biochemical markers and correlated genes in EMS. To quantify EMS risk within this population, we utilized a composite score derived from nine common diagnostic variables. We applied a global liquid chromatography/mass spectroscopy approach (HPLC/MS) to whole plasma collected from 49 Arabian horses, resulting in 3392 high-confidence features and identification of putative metabolites in public databases. We performed a genome wide association analysis with genotypes from the 670k Affymetrix Equine SNP array utilizing EMS-correlated metabolites as phenotypes. We discovered four metabolite features significantly correlated with EMS score (P < 1.474 × 10^-5). GWAs for these features results (P = 6.787 × 10^-7, Bonferroni) identified four unique candidate regions (r² > 0.4) containing 63 genes. Significant genomic markers capture 43.52% of the variation in the original EMS score phenotype. The identified genomic loci provide insight into the pathways controlling variation in EMS and the origin of genetic predisposition to the condition. Rapid, feasible and accurate diagnostic tools derived from metabogenomics can be translated into measurable benefits in the timeline and quality of preventative management practices to preserve health in horses.

Preliminary analysis of the FAM174A gene suggests it lacks a strong association with equine metabolic syndrome in ponies

Equine metabolic syndrome (EMS) describes a group of risk factors, including obesity and insulin dysregulation (hyperinsulinemia and/or insulin resistance), that can lead to the development of the debilitating hoof disease laminitis. Although the underlying mechanisms of EMS are not fully understood, a genetic component has been reported, and an 11 guanine polymorphism located at the FAM174A gene has been identified as a risk locus for the syndrome in Arabian horses. To examine associations between the FAM174A risk allele and the clinical signs of EMS, the allele was examined in an Australian cohort of ponies (n = 20) with known metabolic status. The 11 guanine polymorphism was identified in only 3 of 13 ponies with EMS, and no significant association could be made between the risk loci and morphometric measurements associated with obesity (BCS [P = 0.21], cresty neck score [P = 0.58], basal triglyceride concentration [P = 0.85], and adiponectin concentration [P = 0.48]), or insulin dysregulation (insulin dysregulation status [P = 0.35] and serum insulin concentration during an oral glucose test [P = 0.44]). These results suggest that the FAM174A 11 guanine homopolymer allele is unlikely to be a singular key gene polymorphism associated with EMS in ponies. However, due to the small number of ponies identified with the polymorphism, further study of the FAM174A risk allele in a larger cohort of horses and ponies of uniform breed would be useful.

Insulin dysregulation in a population of Finnhorses and associated phenotypic markers of obesity

Background

Obesity and insulin dysregulation (ID) predispose horses to laminitis. Determination of management practices or phenotypic markers associated with ID may benefit animal welfare.

Objectives

Determine ID status of a population of Finnhorses using an oral sugar test (OST) and compare phenotypes and management factors between ID and non‐ID Finnhorses.

Animals

One hundred twenty‐eight purebred Finnhorses ≥3 years of age.

Methods

Owners were recruited using an online questionnaire regarding signalment, history, feeding, and exercise of their horses. Selected contributing stables within a predefined area were visited. Phenotypic markers of obesity and the weight of each horse were recorded. After fasting overnight, horses received 0.45 mL/kg corn syrup PO. Serum samples before and at 60 and 90 minutes after syrup administration were analyzed for insulin by chemiluminescent assay. Horses met ID criteria if insulin concentrations were ≥33 μIU/mL at T0, ≥66 μIU/mL at T60 or T90 or some combination thereof. Associations between phenotypic markers, feeding and exercise variables, and ID were examined using mixed effects logistic regression modeling.

Results

Several phenotypic markers of obesity were significant on univariable analysis but in the final multivariable model, only obesity (body condition score  ≥8) was associated with ID (P = .04). Over half of the horses (60% [95% confidence interval (CI), 51%‐68%]) were considered overweight or obese whereas 16% (95% CI, 10%‐23%) were classified as having ID.

Conclusions and Clinical Importance

Because obesity is associated with ID in cold‐blooded type horses, objective monitoring of phenotypic markers by owners may be beneficial for health outcomes.

Differential Proteomic Expression of Equine Cardiac and Lamellar Tissue During Insulin-Induced Laminitis

Endocrinopathic laminitis is pathologically similar to the multi-organ dysfunction and peripheral neuropathy found in human patients with metabolic syndrome. Similarly, endocrinopathic laminitis has been shown to partially result from vascular dysfunction. However, despite extensive research, the pathogenesis of this disease is not well elucidated and laminitis remains without an effective treatment. Here, we sought to identify novel proteins and pathways underlying the development of equine endocrinopathic laminitis. Healthy Standardbred horses (n = 4/group) were either given an electrolyte infusion, or a 48-h euglycemic-hyperinsulinemic clamp. Cardiac and lamellar tissues were analyzed by mass spectrometry (FDR = 0.05). All hyperinsulinemic horses developed laminitis despite being previously healthy. We identified 514 and 709 unique proteins in the cardiac and lamellar proteomes, respectively. In the lamellar tissue, we identified 14 proteins for which their abundance was significantly increased and 13 proteins which were significantly decreased in the hyperinsulinemic group as compared to controls. These results were confirmed via real-time reverse-transcriptase PCR. A STRING analysis of protein-protein interactions revealed that these increased proteins were primarily involved in coagulation and complement cascades, platelet activity, and ribosomal function, while decreased proteins were involved in focal adhesions, spliceosomes, and cell-cell matrices. Novel significant differentially expressed proteins associated with hyperinsulinemia-induced laminitis include talin−1, vinculin, cadherin-13, fibrinogen, alpha-2-macroglobulin, and heat shock protein 90. In contrast, no proteins were found to be significantly differentially expressed in the heart of hyperinsulinemic horses compared to controls. Together, these data indicate that while hyperinsulinemia induced, in part, microvascular damage, complement activation, and ribosomal dysfunction in the lamellae, a similar effect was not seen in the heart. In brief, this proteomic investigation of a unique equine model of hyperinsulinemia identified novel proteins and signaling pathways, which may lead to the discovery of molecular biomarkers and/or therapeutic targets for endocrinopathic laminitis.

Glucagon-like peptide-1, insulin-like growth factor-1, and adiponectin in insulin-dysregulated ponies: effects of feeding a high nonstructural carbohydrate diet and association with prospective laminitis

Endocrinopathic laminitis, related to equine metabolic syndrome and insulin dysregulation, causes marked pain and suffering in horses and represents a substantial cost to the horse industry. This study investigated the effect of feeding a diet high in nonstructural carbohydrates on concentrations of active glucagon-like peptide-1 (aGLP-1), total insulin-like growth factor-1 (IGF-1), and high-molecular-weight (HMW) adiponectin, in insulin-dysregulated ponies. Thirty-seven ponies were challenged with this diet for up to 18 d to induce hyperinsulinemia. Hormone concentrations were measured in selected samples on day 2 of the diet challenge period, over 4 h after feeding. Fourteen of the ponies developed mild laminitis induced by the diet challenge. Insulin and glucose responses to the diet have been reported previously. Feeding increased the concentrations of aGLP-1 (P < 0.05) and HMW adiponectin (P < 0.001), but there was no difference between the laminitic and nonlaminitic groups for either hormone. Concentrations of IGF-1 and insulin were inversely related, with IGF-1 being 32% lower in hyperinsulinemic/laminitic ponies compared with nonlaminitic ponies (P = < 0.05). These results indicate that unlike insulin and possibly IGF-1, concentrations of aGLP-1 and HMW adiponectin do not have a strong association with, or play a major role in, the pathogenesis of equine laminitis.

Comparison of Two Diagnostic Methods to Detect Insulin Dysregulation in Horses Under Field Conditions

Straightforward testing procedures to enable the diagnosis of insulin dysregulation (ID) in horses that are suitable for use in daily veterinary practice are needed because of the risk that ID could result in laminitis. In our study (that included 90 horses), we compared the proportion of horses classified as ID-positive, ID-suspect, and ID-not diagnosed according to the basal insulin concentration (BIC) with the proportion of horses classified as ID-positive or ID-negative according to a practical and feasible version of an oral sugar test (OST). Furthermore, BIC, basal glucose concentration, and insulin and glucose concentration after OST were analyzed and compared. In the total study population, the OST detected significantly more ID-positive cases than the BIC, with cutoffs at equivalent specificities. Receiver operating characteristics analysis showed that at a lower cutoff, the sensitivity of the BIC could be increased, but at the cost of a significantly lower specificity. Taking this into account, we found diagnostic performance of the OST to be considerably better than the BIC and therefore considered it more recommendable for use as a screening test for ID in ambulatory practice. Furthermore, we investigated the relationship between body condition score and breed type with glucose and insulin concentration as determined after our version of the OST. For that purpose, the study group was subdivided into lean, moderate, and obese horses and "easy keeper breeds" versus "non-easy keeper breeds". Results supported the general assumption that obese horses and "easy keeper breeds" are more prone to the development of ID.

Equine metabolic syndrome: evolution of understanding over two decades: a personal perspective

There has been a marked increase in the incidence of equine obesity globally, especially in countries where there has been a shift away from the horse having an economically essential working role. This change in its core role, plus the increasing numbers of individual horse owners without access to traditional knowledge of animal and land management, have helped fuel this equine obesity ‘epidemic’. Other important potential contributory factors include increased availability of good grazing and/or forage, as well as supplementary feeds. Obesity now presents a major welfare issue for horses and ponies, not only because of the direct weight-associated effects, but also due to the increased risk it poses for certain clinical conditions, in particular laminitis. For many owners and veterinarians, obesity and the equine metabolic syndrome are synonymous, but this is not necessarily the case. Furthermore, as we understand more about this syndrome and the causes of endocrinopathic laminitis, the emphasis has shifted from tissue or peripheral insulin resistance to insulin dysregulation. The present paper outlines how our knowledge of equine metabolic syndrome arose and continues to develop, as well as the authors’ personal involvement in some of these advances.

The effect of different grazing conditions on the insulin and incretin response to the oral glucose test in ponies

BACKGROUND

The oral glucose test (OGT) is a useful tool for diagnosing insulin dysregulation (ID) and is somewhat repeatable in ponies under consistent management. This study aimed to determine whether the insulin and incretin responses to an OGT in ponies differed after short-term access to fertilised pasture, compared to unfertilised pasture, by using a randomised, repeated measures study design. Sixteen mixed-breed ponies were classified as severely insulin-dysregulated (SD; post-prandial insulin ≥80 μIU/mL) or not severely insulin-dysregulated (NSD; post-prandial insulin < 80 μIU/mL) using an OGT prior to the study. The ponies accessed pasture that was fertilised, or unfertilised, for 5 days (4 h/day, with supplemental hay provided at 0.7% bodyweight), with a 10 day period between phases. An OGT was performed after each phase. Glucose, insulin, active glucagon-like peptide-1 (aGLP-1), and glucose-dependent insulinotropic polypeptide (GIP) were measured in post-prandial blood samples.

RESULTS

The volume of fertilised pasture was five-fold greater than unfertilised pasture, with % non-structural carbohydrates (NSC) similar between all forages. Consuming fertilised pasture increased (P = 0.018) the serum insulin response to an OGT, compared to grazing unfertilised pasture. A limitation of the study was that pasture intake was unable to be quantified. Insulin responses were greater in SD, compared to NSD, ponies (P < 0.001) and remained well above the test cut-off at all times. A subset of ponies, initially screened as NSD, became (more) insulin-dysregulated after pasture access. Further, aGLP-1 was a significant predictor of insulin concentration in this cohort.

CONCLUSIONS

Whereas some insulin-dysregulated ponies were comparatively resistant to dietary intervention, others showed markedly different OGT responses following subtle changes in their forage-based diet. This implies that mild/early ID might be unmasked by dietary change, and that dietary management is important in these ponies. However, dietary management alone may not be adequate for all cases of ID.

Pharmacodynamic Effects of Pioglitazone on High Molecular Weight Adiponectin Concentrations and Insulin Response After Oral Sugar in Equids

Chronic insulin dysregulation is challenging to manage with pharmaceuticals in horses. Pioglitazone improves insulin sensitivity in humans, and the pharmacokinetics of pioglitazone have been evaluated in horses. The objectives of this study were to assess the pharmacodynamic effects of oral pioglitazone on morphometric parameters, hepatic enzyme activity and function, adipokines, and enteroinsular response to oral sugar. A prospective pilot study was performed using fifteen adult equids (8 ponies, 7 horses) to evaluate the effects of short-term pioglitazone administration (2 mg/kg PO q 24 hours, 28 days). Oral sugar tests (OST) were performed before and after treatment. Adipokines were measured at day 0, 14, and 28 of administration. Plasma drug concentrations were measured at day 14 and 28 of administration. The subjects were grouped into horses, ponies, and insulin dysregulated (ID) animals. Baseline values for all parameters were compared with values obtained at day 14 and 28 using one-way or two-way analysis of variance. Mild changes were noted in morphometric parameters and hepatic enzymes. No differences were found in leptin concentrations or the blood glucose response to the OST. Significant decreases were found in the insulin response to OST at 90 and 120 minutes time points and the area under the curve after pioglitazone treatment in the pony and ID groups. High-molecular-weight (HMW) adiponectin concentrations were significantly increased in all groups after pioglitazone treatment. Decreased insulin concentrations in response to oral sugar and increased HMW adiponectin concentrations indicate positive effects of pioglitazone for treatment of metabolic derangements in equine metabolic syndrome, which warrant future clinical study.

Comparison of fasted basal insulin with the combined glucose-insulin test in horses and ponies with suspected insulin dysregulation

Fasting horses for measurement of basal serum insulin concentration (fasting insulin; FI) has been recommended to standardise testing for insulin dysregulation (ID), yet limited data exist comparing it to dynamic tests. This study aimed to compare FI with the combined glucose-insulin test (CGIT) in horses suspect for ID. We hypothesised that FI would have poor sensitivity for detecting ID compared to CGIT using conventional cut-offs. Records were retrieved from CGITs performed in horses fasted for approximately 8h. Serum insulin and glucose concentrations were measured before and for 150min following an IV bolus of glucose followed by insulin. Correlations between FI and CGIT values were assessed. Youden's index analysis was used to determine the optimal cut-off for FI. Logistic regression and Mann-Whitney U tests were used to determine factors affecting the results. CGITs (n=130) from 62 horses were evaluated. Compared to CGIT, sensitivity and specificity of FI for diagnosis of ID were 14.6% and 100% at a cut-off of 20μIU/mL and 63.4% and 87.2% at a cut-off of 5.2μIU/mL, respectively. FI was significantly correlated with insulin at 45min (r_s=0.66) and 75min (r_s=0.72); area under the curve for insulin (AUC_insulin; r_s=0.67); glucose at 45min (r_s=0.53); and AUC_glucose (r_s=0.50). Obesity was significantly associated with increased odds of a positive CGIT and horses with a positive CGIT were significantly older (P<0.05). In conclusion, FI correlated well with CGIT results and had adequate sensitivity and specificity at lower cut-offs, despite poor sensitivity at conventional cut-off values. Further research to derive cut-off values relevant to the fasting period is warranted.

From Table to Stable: A Comparative Review of Selected Aspects of Human and Equine Metabolic Syndrome

Obesity data in people and companion animals are depicting a future of increasing morbidity, cost for society, and significant health and welfare concerns. Between 25 and 50% of cats, dogs, and horses in developed countries are overweight or obese, which mirrors the situation in humans. Equine metabolic syndrome (EMS) was named after human metabolic syndrome (MetS), which has about 30 years of lead in research efforts. Even though the complications of the two syndromes seem to grossly differ (cardiac vs. laminitis risk), a number of similar disease mechanisms are worthy of investigation. Since the first EMS consensus statement by the American College of Veterinary Internal Medicine in 2010, numerous studies have confirmed the link between insulin dysregulation and laminitis, even though the mechanisms are not fully understood. After the discovery of the role of adipokines in MetS, evidence about inflammatory mechanisms related to adiposity in rodent models, companion animals, horses, and humans is constantly increasing. Oxidative and dicarbonyl stress have been correlated with insulin dysregulation, obesity, and recently with laminitis. Vascular actions of insulin through nitric oxide, endothelin-1, and other mechanisms are being studied in horses and can provide a better understanding of laminitis pathophysiology. More research is needed on neuropathic mechanisms in insulin-dysregulated horses, which could be important in the pathogenesis of laminitis and laminitic pain. Human literature can provide viable material for novel studies in areas that have received limited attention, in addition to being valuable information for clients about the consequences of unhealthy management of their horses.

Case-control study of risk factors for pasture-and endocrinopathy-associated laminitis in North American horses

OBJECTIVE To investigate risk factors for the development of pasture- and endocrinopathy-associated laminitis (PEAL) in horses and ponies in North America. DESIGN Case-control study. ANIMALS 199 horses with incident cases of PEAL and 351 horses from 2 control populations (healthy horses [n = 198] and horses with lameness not caused by laminitis [153]) that were evaluated in North America between January 2012 and December 2015 by veterinarian members of the American Association of Equine Practitioners. PROCEDURES North American members of the American Association of Equine Practitioners were contacted to participate in the study, and participating veterinarians provided historical data on incident cases of PEAL, each matched with a healthy control and a lameness control. Conditional logistic regression analysis was used to compare data on PEAL-affected horses with data on horses from each set of controls. RESULTS Horses with an obese body condition (ie, body condition score ≥ 7), generalized or regional adiposity (alone or in combination), preexisting endocrinopathy, or recent (within 30 days) glucocorticoid administration had increased odds of developing PEAL, compared with horses that did not have these findings. CONCLUSIONS AND CLINICAL RELEVANCE The present study identified several risk factors for PEAL that may assist not only in managing and preventing this form of laminitis, but also in guiding future research into its pathogenesis.