Severity and outcome of equine pasture-associated laminitis managed in first opinion practice in the UK

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.

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.

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.

Nutritional Considerations When Dealing with an Obese Adult Equine

Equine obesity is common, reducing quality of life and requiring dietary energy restriction. Equine obesity is identified using subjective body condition scoring. Considerations are given for life stage and health status when managing obese equines. Every effort should be made to maximize feeding duration, and minimize time spent without feed while meeting all essential nutrient requirements. Limiting total daily dry matter intake to 2% of current bodyweight per day of a low caloric, forage-based diet may result in adequate body weight loss. Weight loss and weight management plans should be monitored for success and potential gastrointestinal, metabolic, and/or behavioral complications.

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.

COVID-19: Impact on United Kingdom Horse Owners

COVID-19 was declared a global pandemic on 11 March 2020; the United Kingdom (UK) implemented quarantine measures shortly afterward, resulting in rapid changes in how owners managed and interacted with their horses. This study provides a rapid analysis of the initial impact of the COVID-19 outbreak on the management of UK leisure and competition horses. A 17 question online survey was distributed via equestrian social media sites to ascertain the impact of COVID-19 on horse and yard management and on human-horse interactions. Frequency analysis combined with Chi-squared and thematic analyses identified the impact of COVID-19 on UK horse owners. Major changes within horse management and horse-human interactions were reported for the majority of horse owners (>65%), regardless of the establishment type or region. Social distancing and visiting restrictions were implemented at most yards, but nearly half were not providing hand sanitization or disinfection protocols for the shared areas/equipment to prevent cross-contamination between users. The financial impact of the pandemic combined with restricted access to veterinary professionals resulted in owners expressing concerns that horse health and welfare may be compromised as a result. Horse owners also felt that the reduced opportunities for horse-human interactions were negatively affecting their mental health and wellbeing.

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.

Factors associated with euthanasia in horses and ponies enrolled in a laminitis cohort study in Great Britain

Euthanasia is a complex topic, with animal owners using multiple factors to shape their decision-making process. Previous epidemiological studies have described causes of equine mortality in specific populations, but there is limited evidence regarding factors contributing specifically to equine euthanasia in Great Britain (GB). This observational study used a prospective cohort design: the objectives were to describe owner-reported reasons for euthanasia, estimate the rate of euthanasia and identify associated factors in horses/ponies enrolled in a web-based epidemiological study of laminitis in GB. Self-selected horse/pony owners submitted regular management and health data over 29 months and reported dates and reasons for euthanasia during this period. The overall incidence of euthanasia was estimated and associated factors were identified using multivariable Cox regression modelling, adjusted for age, with variables retained in the final model if P ≤ 0.05. Data were available for 1070 horses/ponies contributing 1093 horse-years at risk (HYAR), with 80 owner-reported euthanasias. The incidence of euthanasia was 7.3 euthanasias per 100 HYAR (95 % confidence interval [CI] 5.9, 9.1). The most frequently reported health reasons contributing to euthanasia were laminitis-related consequences (25.0 % ; CI 16.8, 35.5 %), colic (21.3 % ; CI 13.7, 31.4 %), non-laminitic lameness (20.0 % ; CI 12.7, 30.1 %) and age-related deterioration, including owner-perceived compromised quality of life (20.0 % ; CI 12.7, 30.1 %). Health-related factors associated with significantly higher rates of euthanasia were colic (hazard ratio [HR] 26.4; CI 12.5, 55.8), pituitary pars intermedia dysfunction (HR 3.0; CI 1.7, 5.4) and lameness due to navicular syndrome (HR 5.9; CI 1.8, 20.0), soft tissue injury (HR 6.5; CI 2.7, 15.6) or laminitis (HR 2.7; CI 1.3, 5.7). Further factors included being pure bred (HR 1.7; CI 1.0, 2.8), female (HR 1.7; CI 1.0, 2.9), having poor owner-perceived hoof quality (HR 2.4; CI 1.1, 5.2), being entirely stabled (HR 5.0; HR 2.1, 12.0), being on loan or under temporary care of the study participant (HR 2.3; CI 1.2, 4.4) and participating in affiliated or professional competitions (HR 5.9; CI 2.4, 14.8). Euthanasia rates were significantly higher in the first two study years compared to the third (P < 0.001). Animals whose owners used the study's custom-designed weight tracker tool had significantly lower rates of euthanasia (HR 0.6; CI 0.3, 0.95). This study has identified a number of, arguably preventable, health-related factors associated with higher rates of euthanasia. Data on owners' decision-making process regarding euthanasia, including emotive and financial impacts, were not recorded but are important contributors to euthanasia that require better understanding.

Insulin Resistance as a Result of Body Condition Categorized as Thin, Moderate, and Obese in Domesticated U.S. Donkeys (Equus asinus)

Donkeys are often kept, especially in industrialized countries, as companion animals. Donkeys have greater digestive efficiency and tend to expend less energy than horses or ponies, which contributes to obesity in nonworking donkeys. Obesity in all equine species increases risk of chronic health conditions such as laminitis and insulin resistance. Previous studies in horses and ponies have documented obesity's potential effects on glucose-insulin dynamics with lower insulin sensitivity and higher insulin responses to glucose. However, limited studies on obesity and its health impacts in donkeys exist, so these effects on glucose-insulin dynamics have not been fully studied. Twenty-four donkeys were selected according to initial body condition score (BCS) and divided into three categories with eight donkeys in each: thin, moderate, and obese. A frequently sampled glucose-insulin tolerance test was performed with subsequent MINMOD analysis to determine the effects of BCS on glucose-insulin dynamics. Basal insulin was highest in obese donkeys when compared with moderate and thin donkeys (P = .02 and P = .01, respectively). There was an overall trend across groups for BCS to lower insulin sensitivity (P = .06). No other effect was found. Body condition score seems to affect donkeys in a similar manner to horses and ponies as higher BCS was associated with higher basal insulin and may lower insulin sensitivity. Higher basal insulin concentrations in obese donkeys could negatively influence health and contribute to serious, chronic conditions.

Maternal obesity increases insulin resistance, low-grade inflammation and osteochondrosis lesions in foals and yearlings until 18 months of age

INTRODUCTION

Obesity is a growing concern in horses. The effects of maternal obesity on maternal metabolism and low-grade inflammation during pregnancy, as well as offspring growth, metabolism, low-grade inflammation, testicular maturation and osteochondrotic lesions until 18 months of age were investigated.

MATERIAL AND METHODS

Twenty-four mares were used and separated into two groups at insemination according to body condition score (BCS): Normal (N, n = 10, BCS ≤4) and Obese (O, n = 14, BCS ≥4.25). BCS and plasma glucose, insulin, triglyceride, urea, non-esterified fatty acid, serum amyloid A (SAA), leptin and adiponectin concentrations were monitored throughout gestation. At 300 days of gestation, a Frequently Sampled Intravenous Glucose Tolerance Test (FSIGT) was performed. After parturition, foals' weight and size were monitored until 18 months of age with plasma SAA, leptin, adiponectin, triiodothyronine (T3), thyroxine (T4) and cortisol concentrations measured at regular intervals. At 6, 12 and 18 months of age, FSIGT and osteoarticular examinations were performed. Males were gelded at one year and expression of genes involved in testicular maturation analysed by RT-qPCR.

RESULTS

Throughout the experiment, maternal BCS was higher in O versus N mares. During gestation, plasma urea and adiponectin were decreased and SAA and leptin increased in O versus N mares. O mares were also more insulin resistant than N mares with a higher glucose effectiveness. Postnatally, there was no difference in offspring growth between groups. Nevertheless, plasma SAA concentrations were increased in O versus N foals until 6 months, with O foals being consistently more insulin resistant with a higher glucose effectiveness. At 12 months of age, O foals were significantly more affected by osteochondrosis than N foals. All other parameters were not different between groups.

CONCLUSION

In conclusion, maternal obesity altered metabolism and increased low-grade inflammation in both dams and foals. The risk of developing osteochondrosis at 12 months of age was also higher in foals born to obese dams.

Decision-tree analysis of clinical data to aid diagnostic reasoning for equine laminitis: a cross-sectional study

The objective of this cross-sectional study was to compare the prevalence of selected clinical signs in laminitis cases and non-laminitic but lame controls to evaluate their capability to discriminate laminitis from other causes of lameness. Participating veterinary practitioners completed a checklist of laminitis-associated clinical signs identified by literature review. Cases were defined as horses/ponies with veterinary-diagnosed, clinically apparent laminitis; controls were horses/ponies with any lameness other than laminitis. Associations were tested by logistic regression with adjusted odds ratios (ORs) and 95% confidence intervals, with veterinary practice as an a priori fixed effect. Multivariable analysis using graphical classification tree-based statistical models linked laminitis prevalence with specific combinations of clinical signs. Data were collected for 588 cases and 201 controls. Five clinical signs had a difference in prevalence of greater than +50 per cent: 'reluctance to walk' (OR 4.4), 'short, stilted gait at walk' (OR 9.4), 'difficulty turning' (OR 16.9), 'shifting weight' (OR 17.7) and 'increased digital pulse' (OR 13.2) (all P<0.001). 'Bilateral forelimb lameness' was the best discriminator; 92 per cent of animals with this clinical sign had laminitis (OR 40.5, P<0.001). If, in addition, horses/ponies had an 'increased digital pulse', 99 per cent were identified as laminitis. 'Presence of a flat/convex sole' also significantly enhanced clinical diagnosis discrimination (OR 15.5, P<0.001). This is the first epidemiological laminitis study to use decision-tree analysis, providing the first evidence base for evaluating clinical signs to differentially diagnose laminitis from other causes of lameness. Improved evaluation of the clinical signs displayed by laminitic animals examined by first-opinion practitioners will lead to equine welfare improvements.

Does oral prednisolone treatment increase the incidence of acute laminitis?

REASONS FOR PERFORMING STUDY

It is accepted among equine practitioners that glucocorticoid treatment is a risk factor for the development of laminitis. However, there is little published evidence of a link between glucocorticoids and laminitis.

OBJECTIVES

To determine whether horses receiving oral prednisolone are at increased risk of laminitis.

STUDY DESIGN

Retrospective case-control study.

METHODS

Clinical records of horses registered with the ambulatory service at Liphook Equine Hospital between January 2001 and November 2014 were reviewed retrospectively to identify horses that had received treatment with oral prednisolone. For each treated horse, 2 time-matched controls that received veterinary attention but were not treated with prednisolone were selected. Incidence of laminitis was compared between the 2 groups and factors associated with laminitis were assessed using Cox regression analysis.

RESULTS

Of the 416 horses treated with prednisolone, 16 (3.8%) were diagnosed with laminitis subsequent to the initiation of prednisolone treatment with an overall incidence of 2.60 (95% CI 1.49-4.22) cases per 100 horse-years at risk. A total of 7 horses (1.7%) developed laminitis during the course of their treatment and 3 (0.7%) of the horses treated with prednisolone were ultimately subjected to euthanasia as a result of laminitis. A total of 46 (5.7%), of the 814 time-matched control horses were diagnosed with laminitis during the study period with an overall incidence of 3.46 (95% CI 2.54-4.62) cases per 100 horse-years at risk. Of these, 12 (1.5%) were subjected to euthanasia as a result of laminitis. There were no significant differences in the overall laminitis incidence rate (P = 0.8), incidence rate during prednisolone treatment (P = 0.09), or probability of laminitis (P = 0.3) between the 2 groups. Mean survival time was greater in the prednisolone than the control group. Equine metabolic syndrome and increasing age were associated with increased risk of laminitis.

CONCLUSIONS

Administration of oral prednisolone did not increase the risk of laminitis.

Risk factors for equine laminitis: a case-control study conducted in veterinary-registered horses and ponies in Great Britain between 2009 and 2011

Laminitis is a highly debilitating disease of the foot known to have a complex and multifactorial aetiology of metabolic, inflammatory, traumatic or vascular origin. The disease has major welfare implications due to unrelenting pain associated with degenerative changes, which often necessitate euthanasia on welfare grounds. Despite this, there have been few high-quality studies investigating risk factors for equine laminitis, and only a limited number of risk factors have been previously investigated. The aim of this study was to conduct a case-control study of risk factors for active episodes of veterinary-diagnosed laminitis in horses and ponies attended by veterinary practitioners in Great Britain, based on multivariable statistical analyses. Questionnaires were received for 1010 animals, comprising 191 laminitis cases and 819 controls. Factors associated with an increased risk of laminitis were weight gain in the previous 3 months, summer and winter months compared to spring, new access to grass in the previous 4 weeks, box rest in the previous week, owner-reported history of laminitis, lameness or foot-soreness after shoeing/trimming, existing endocrinopathic (pituitary pars intermedia dysfunction and equine metabolic syndrome) disease and increasing time since the last anthelmintic treatment. Factors associated with a decreased risk of laminitis were increasing height (cm), feeding of additional supplements in the previous week and transportation in the previous week. Novel associated factors were identified that may aid in the management and prevention of the disease in the veterinary-registered equine population.