Evidence for dopamine production and distribution of dopamine D2 receptors in the equine gastrointestinal mucosa and pancreas.

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, ß 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 ß 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.

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.

Factors associated with insulin responses to oral sugars in a mixed-breed cohort of ponies.

BACKGROUND: Serum insulin concentration at 60 min (InsulinT60) during an oral sugar test (OST) indicates future laminitis risk and insulin dysregulation (ID). Associations between InsulinT60 and physical and owner-reported variables may help clinicians select individuals for ID testing. Associations between InsulinT60 and other metabolic markers may help elucidate ID pathophysiology. OBJECTIVES: To describe associations between (A) season, physically-apparent and owner-reported factors and binary InsulinT60 interpretation (initial models) and (B) variables included in the initial models, other metabolic markers and continuous InsulinT60 (full models). STUDY DESIGN: Prospective longitudinal. METHODS: Non-laminitic ponies were examined and OSTs (0.3 mL/kg Karo syrup) performed every 6 months (autumn and spring) for ≤4 years. Factors associated with InsulinT60 were determined using mixed-effects models with physical, owner-reported, season and serum/plasma markers as fixed effects and pony and premises identifiers as random effects. Autumn and spring data were analysed separately for full models. RESULTS: One thousand seven hundred and sixty-three OSTs from 367 ponies were included. High-risk InsulinT60 (>153 µIU/mL) was independently associated with (odds ratio, 95% confidence interval [CI]): age (1.36, 1.16-1.60), body condition score (BCS) (2.38, 1.21-4.69), and bulging supraorbital fatpads (7.25, 2.1-24.98). However, the initial models provided little explanatory power (Nakagawa R2 = 0.1-0.27). LoginsulinT60 was independently associated with (effect estimate, 95% CI): age (0.02, 0.01-0.04), Welsh/Welsh X breed (0.22, 0.05, 0.39), sex (gelding = -0.2, -0.34 to 0.06), BCS (0.16, 0.08-0.23), plasma adiponectin (-0.02, -0.02 to 0.01) and basal insulin (0.01, 0.01-0.01) in spring, and: age (0.03, 0.02-0.04), BCS (0.17, 0.08-0.26), bulging supraorbital fatpads (0.37, 0.2-0.54), turnout score (0.05, 0.02-0.09), plasma adiponectin (-0.01, -0.02 to 0.01), ACTH (per 10 pg/mL) (0.01, 0.00-0.01), triglycerides (0.28, 0.07-0.49) and InsulinT0 (0.01, 0.01-0.01) in autumn. MAIN LIMITATIONS: Only non-laminitic ponies in one region were included. CONCLUSIONS: Owner-reported and physically-apparent data were limited InsulinT60 predictors. InsulinT60 is a complex trait, independently associated with numerous variables, some with seasonal interactions.

Development of a body condition index to estimate adiposity in ponies and horses from morphometric measurements.

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.

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.

A glucagon-like peptide-1 receptor antagonist reduces the insulin response to a glycemic meal in ponies.

High plasma concentrations of insulin can cause acute laminitis. Ponies and horses with insulin dysregulation (ID) exhibit marked hyperinsulinemia in response to dietary hydrolyzable carbohydrates. Glucagon-like peptide-1 (GLP-1), an incretin hormone released from the gastrointestinal tract, enhances insulin release, and is increased postprandially in ponies with ID. The aim of this study was to determine whether blocking the GLP-1 receptor reduces the insulin response to a high glycemic meal. Five adult ponies were adapted to a cereal meal and then given two feed challenges 24 h apart of a meal containing 3 g/kg BW micronized maize. Using a randomized cross-over design all ponies received both treatments, where one of the feeds was preceded by the IV administration of a GLP-1 receptor blocking peptide, Exendin-3 (9-39) amide (80 µg/kg), and the other feed by a sham treatment of peptide diluent only. Blood samples were taken before feeding and peptide administration, and then at 30-min intervals via a jugular catheter for 6 h for the measurement of insulin, glucose, and active GLP-1. The peptide and meal challenge caused no adverse effects, and the change in plasma glucose in response to the meal was not affected (P = 0.36) by treatment: peak concentration 9.24 ±â€…1.22 and 9.14 ±â€…1.08 mmol/L without and with the antagonist, respectively. Similarly, there was no effect (P = 0.35) on plasma active GLP-1 concentrations: peak concentration 14.3 ±â€…1.36 pM and 13.7 ±â€…1.97 pM without and with the antagonist, respectively. However, the antagonist caused a significant decrease in the area under the curve for insulin (P = 0.04), and weak evidence (P = 0.06) of a reduction in peak insulin concentration (456 ±â€…147 µIU/mL and 370 ±â€…146 µIU/mL without and with the antagonist, respectively). The lower overall insulin response to the maize meal after treatment with the antagonist demonstrates that blocking the GLP-1 receptor partially reduced insulin production in response to a high starch, high glycemic index, diet. Using a different methodological approach to published studies, this study also confirmed that GLP-1 does contribute to the excessive insulin production in ponies with ID.

Horses and ponies are prone to suffer from laminitis if they produce too much insulin after eating a high-sugar/starch meal. Laminitis associated with high insulin is very painful and can result in the affected animals having to be put down. The reason why some ponies over-produce insulin is not known. However, we do know that small molecules produced in the upper intestine contribute to the problem. In this study we blocked the action of these molecules, to see if we could reduce the insulin released after a meal that was high in soluble carbohydrate (starch and sugar) content, in ponies. Using a specially designed drug, we were able to reduce insulin responses to the meal by over 20%. None of the ponies had any clinical problems in this study. This study helped us to explain why some animals produce excessive insulin; this compound may even have potential as a future therapy. However, whilst a promising finding, this effect was not as strong as it needs to be to help prevent laminitis in all animals. The next step is to test the drug at different doses, and under varying conditions, to see whether we can improve its performance.

Risk Factors for Equine Gastric Ulcer Syndrome Incidence in Adult Icelandic Riding Horses.

A high prevalence of both squamous (ESGD) and glandular (EGGD) ulcers was previously found in, mainly young, Icelandic horses coming into training for the first time. This study evaluated risk factors for gastric ulcers in Icelandic riding horses at various ages and stages of training. The horses (n = 211) were gastroscoped from 21 equine establishments across Iceland. A variety of morphometric, clinical, behavioural and management factors were evaluated as potential risk factors for gastroscopically significant (grade ≥ 2/4: found in 27% of horses) or gastroscopically severe (grade 3 or 4/4: found in ~10% of horses) ESGD or gastroscopically significant EGGD (grade ≥ 1/2: found in 46.4%). Body condition score (BCS), cresty neck score (CNS), stable/turnout behaviour, exercise intensity/frequency and age were not significantly associated with ESGD or EGGD ulcer score. However, having come off the pasture into training for 4 weeks or less was a significant risk factor for gastroscopically significant and severe ESGD compared to 5 weeks or more. For both EGGD and ESGD, "region" was important. Gastroscopically significant EGGD and gastroscopically severe ESGD were more prevalent in those showing clinical signs often associated with ulcers. Geldings were more likely to have gastroscopically significant ESGD than both mares and stallions and more EGGD than stallions. Being stabled, but spending >2 h/day out in the paddock, compared with <2 h paddock time or full-time turnout, was protective for gastroscopically significant ESGD as was being fed complementary feed (all fed <1 g non-structural carbohydrate (NSC)/kg/BW/meal). Being at a training establishment for >4 weeks was protective for gastroscopically significant and gastroscopically severe ESGD but not EGGD. This study confirms the relatively low prevalence of ESGD in Icelandic horses being kept in training establishments and fed low NSC diets but highlights the high prevalence of EGGD.

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.

Homemade Nucleic Acid Preservation Buffer Proves Effective in Preserving the Equine Faecal Microbiota over Time at Ambient Temperatures.

The equine faecal microbiota is often assessed as a proxy of the microbial community in the distal colon, where the microbiome has been linked to states of health and disease in the horse. However, the microbial community structure may change over time if samples are not adequately preserved. This study stored equine faecal samples from n = 10 horses in four preservation treatments at room temperature for up to 150 h and assessed the resulting impact on microbial diversity and the differential abundance of taxa. Treatments included "COLD" (samples packaged with a cool pack), "CLX" (2% chlorhexidine digluconate solution), "NAP" (nucleic acid preservation buffer), and "FTA" (Whatman FTA™ cards). The samples were assessed using 16S rRNA gene sequencing after storage for 0, 24, 72, and 150 h at room temperature under the different treatments. The results showed effective preservation of diversity and community structure with NAP buffer but lower diversity (p = 0.001) and the under-representation of Fibrobacterota in the FTA card samples. The NAP treatment inhibited the overgrowth of bloom taxa that occurred by 72 h at room temperature. The COLD, CLX, and NAP treatments were effective in preserving the faecal microbiota for up to 24 h at room temperature, and the CLX and NAP treatments improved the yield of Patescibacteria and Fibrobacterota in some cases. The cold and CLX treatments were ineffective in preventing community shifts that occurred by 72 h at room temperature. These findings demonstrate the suitability of the COLD, NAP, and CLX treatments for the room temperature storage of equine faeces for up to 24 h and of NAP buffer for up to 150 h prior to processing.

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.

Age-Related Differences in Short-Term Transportation Stress Responses of Horses.

Transportation of horses on short journeys can lead to an increase in stress. There are known age-associated changes in immune and metabolic responses in horses; however, no research exists evaluating how age may influence these responses to transportation stress. Eleven mares within two age groups, aged (n = 5, 22 ± 1 year) or young (n = 6, 2 ± 1 year), were transported 1 hour and 20 minutes. Peripheral blood and saliva were collected before and after transportation at baseline (2 to 3 weeks prior to transportation), 24 hours pre-transport, 1 hour before loading, 15 minutes, 30 minutes, 1 to 3 hours, 24 hours and 8 days post-transport. Heart rates, rectal temperatures, under the tail temperatures, serum cortisol, plasma ACTH, serum insulin, salivary cortisol and salivary IL-6 were measured. Whole blood gene expression of the cytokines IL-1b, IL-2, IL-6, IL-10, IFNγ, and TNFα were determined through qPCR, and peripheral blood mononuclear cells were isolated, stimulated, and stained to determine IFNγ and TNFα production. Serum cortisol (P < .0001), salivary cortisol (P < .0001) and heart rate (P = .0002) increased in response to transportation with no age differences. Rectal (P = .03) and under the tail temperatures (P = .02) were increased in young versus aged horses. ACTH was higher in aged horses (P = .007) and post-transportation (P = .0001). Aged horses showed a greater increase in insulin compared with young horses (P < .0001). While age does not seem to impact cortisol responses to short-term transportation in horses, it did influence the post transportation insulin response to stress in aged horses.

Initiating Virtual Nursing in General Inpatient Care.

ABSTRACT: With increased demands for inpatient care and limited nursing resources, bedside RNs at one health care system were challenged to find experienced nurse colleagues to provide mentorship when they needed assistance in executing best practices. A virtual RN (ViRN) role was created to support bedside RNs and patients on designated general care inpatient units. The ViRN provided real-time virtual clinical guidance to bedside RNs and actively surveilled patients. Bedside RNs were surveyed by email to gauge the utility and their perceptions of integrating ViRNs into the nursing care team. RNs reported that they valued the consistent availability of having the ViRNs' expert nursing knowledge and virtual assistance with nursing tasks.

Association between insulin dysregulation and adrenocorticotropic hormone in aged horses and ponies with no clinical signs of pituitary pars intermedia dysfunction.

BACKGROUND: High concentrations of adrenocorticotropic hormone (ACTH) are used as an indicator of pituitary pars intermedia dysfunction (PPID), but other factors that may influence ACTH need to be understood, if diagnostic reference ranges for ACTH are to be used with confidence. Insulin dysregulation (ID) could be one such factor, as insulin affects pituitary hormones in other species. OBJECTIVES: To test the hypothesis that a relationship exists between high insulin and high ACTH in aged (>15-year-old) animals with no clinical signs of PPID. STUDY DESIGN: A cohort study. METHODS: Thirteen horses and eleven ponies (17-25 years-old; mares and geldings) were clinically examined for signs of PPID in the spring (November 2020) and autumn (April 2021). On the same day, blood samples were taken before and 2 h after an oral glucose test (OGT). Concentrations of insulin, glucose, ACTH and cortisol were measured. RESULTS: There was no association between ACTH and cortisol. However, there was a positive linear correlation between ACTH and post-OGT (insulin in the autumn (r = 0.427, p = 0.04). Two horses and six ponies had ACTH above the cut-off value for PPID diagnosis, and of these eight animals, six also had insulin concentrations above the cut-off value for ID. MAIN LIMITATIONS: The cohort was small and thyrotropin-releasing hormone (TRH) stimulation tests were not performed. CONCLUSIONS: In autumn, high ACTH was associated with ID, when no clinical signs of PPID were present. Because ACTH is used in PPID diagnosis, further work is required to understand this interaction.

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.

Effect of moving from being extensively managed out in pasture into training on the incidence of equine gastric ulcer syndrome in Icelandic horses.

OBJECTIVE: To investigate equine squamous gastric disease (ESGD) and equine glandular gastric disease (EGGD) in Icelandic horses moving from pasture into training. ANIMALS: 81 horses (median age, 3 years; interquartile range, 1 year) from 10 farms representing 4 different Icelandic regions. PROCEDURES: Initial gastroscopy was undertaken within 2 weeks of moving from pasture into a training establishment. A total of 71 horses underwent endoscopic examination again 8 weeks later. Various management and behavioral factors were assessed through face-to-face questionnaires with the owners or trainers. Multivariable logistic regression was used to determine factors contributing to any change in ESGD and EGGD severity score during the 8-week training period. RESULTS: Incidence of EGGD and ESGD in this feral population was similar to that found in domesticated horses. ESGD incidence (severity score, ≥ 2; score range, 0 to 4) reduced from an initial 71.6% (58/81) to 25.4% (18/71). On multivariable analysis, sex (ie, being a stallion or a female vs gelding) increased the likelihood of ulcer grade reduction. Being fed preserved forage 3 or more times a day also improved the likelihood of ESGD reduction (odds ratio, 17.95; 95% CI, 1.67 to 193.40; P = .017). Overall, the farm explained 35% of the variance, confirming the importance of management factors. Incidence of EGGD (severity score, ≥ 1; score range, 0 to 2) reduced from 47% (38/81) to 40.8% (29/71) during the same period. No measured variables were associated significantly with EGGD incidence or reduction. CLINICAL RELEVANCE: Pasture provision (without supplementary feed or forage) does not result automatically in a low incidence of gastric ulcers. Regular provision of preserved forage is a key factor in reducing ESGD incidence.

Nitric oxide synthase inhibition reveals differences in the nitric oxide pathway in previously laminitic ponies.

Previously laminitic (PL) ponies are reported to have higher blood pressure than non laminitic (NL) ponies. This relative hypertension may be related to endothelial cell dysfunction, similar to humans with metabolic syndrome. To investigate the relationship between laminitis predisposition and endothelial dysfunction, the effect of nitric oxide synthase (NOS) inhibition on the change in circulating nitric oxide (NO) concentrations and systemic blood pressure (BP) was determined. An intravenous NO sensor was used to measure changes in blood NO concentration during and after intravenous infusion of the NOS inhibitor L-nitroarginine methyl ester (L-NAME; 4 mg/kg IV) in PL and NL ponies. NO concentrations decreased and BP increased in response to L-NAME infusion, with a significantly (p = 0.02) greater rate of increase in systolic BP in PL (14.62 ± 1.88 mmHg/h) compared to NL (8.54 ± 1.88 mmHg/h) ponies. This greater effect on BP in PL compared to NL ponies is consistent with higher basal NO production in PL ponies, suggesting that the relative hypertension previously seen in PL ponies results in increased basal NO production, rather than being caused by reduced NO production as hypothesised. Up-regulation of the NO system may be a compensatory mechanism stimulated by the higher resting BP in PL ponies. Further investigation of the mechanism underlying the relative hypertension seen in PL ponies is required.

Development and Evaluation of a Muscle Atrophy Scoring System (MASS) for Horses.

Loss of skeletal muscle mass likely compromises performance and welfare in horses and thus routine monitoring would be valuable. Currently available methods to assess muscle mass require expert knowledge and are often expensive. To provide a simple method, a muscle atrophy scoring system (MASS) was created and tested by three evaluators (raters) in 38 horses of varying age, breed, and health status. Inter-rater agreement on atrophy scores was in the good-to-excellent range for ratings of the neck (ICC = 0.62), back (ICC = 0.62) and hind (ICC = 0.76) regions but was poor for the abdominal region (ICC = 0.29). Due to this low agreement, the abdominal region was excluded from further analysis. Associations between muscle atrophy scores and age, pituitary pars intermedia dysfunction (PPID) status, and body composition indicators, including weight and estimated fat-free mass (FFM), were examined. Weight was inversely associated with neck, back and hind muscle atrophy scores (ß = -0.008, ß = -0.008, ß = -0.009, respectively; all P <0.001), but estimated FFM was not associated with muscle atrophy scores at any region (P >0.05). Age was positively related to neck (ß = 0.030, P <0.01), back (ß = 0.037, P <0.001) and hind (ß = 0.040, P <0.001) muscle atrophy scores. PPID-positive horses (n = 4) had higher muscle atrophy scores than PPID-negative horses (n = 23), even after adjusting for age (P <0.05). This data suggests that neck, back and hind region evaluations by individual raters likely have acceptable reliability. In addition, these findings support further evaluation of the potential benefits of the MASS to identify and monitor muscle atrophy in horses.

The Effect of Strip Grazing on Physical Activity and Behavior in Ponies.

This work aimed to determine the effect of strip grazing on physical activity in ponies using behavioral observations alongside accelerometers positioned at the poll. In study one, ten British native breed ponies were randomly assigned to paddock A (50 × 110 m) or B (50 × 110 m divided into seven equal strips with access to one additional strip per day) for seven days (n = 5/paddock). In study two, ten different British native breed ponies were randomly assigned for 14 days individually to (1) a control field where the animal was allowed complete access to their allotted area (n = 4); (2) a field that increased in size daily by moving a lead fence (n = 2); and (3) a field that was strip grazed using lead and back fences moved the same distance daily (n = 4). Accelerometer data were sorted into twenty-four-hour periods; each 10-second epoch was categorized as standing, grazing or locomoting using previously validated cut-off points; and time spent in each category for each day calculated. Behavioral monitoring was undertaken by direct observation on days 12-14 (study two only). Accelerometer and behavioral data were compared between grazing methods within each study. Strip grazing had no significant effect on the time spent in each physical activity category in either study. Behavioral observation revealed all ponies spent most time grazing ≤4 hours after fence moving and strip grazed ponies spent significantly more time grazing the newly available grass than elsewhere. Thus, strip grazing did not alter physical activity in ponies, but did result in preferential grazing of new grass.

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.