Incidence of laminitis and survey of dietary and management practices in pleasure horses and ponies in south-eastern Australia

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).

Prevalence and risk factors for laminitis within the Norwegian pony breed Nordlandshest/Lyngshest

BACKGROUND

Laminitis is a systemic condition resulting in debilitating pain and structural changes within the feet, and hence has major welfare implications. Causes include endocrine and systemic inflammatory conditions. Ponies are frequently affected, and observations in the field suggest that occurrence of laminitis is also common in Norwegian breeds. The aim of this study was to estimate the prevalence and risk factors for laminitis within the Norwegian pony breed Nordlandshest/Lyngshest.

RESULTS

The study was a cross-sectional study based on questionnaires sent to members of the Norwegian Nordlandshest/Lyngshest breed association. Questionnaires were received for 504 animals, of which 464 records were eligible and included in analyses. The population comprised 71 stallions, 156 geldings, and 237 mares, with an age between 1 and 40 years (median and interquartile ranges: 12 (6-18) years). The estimated 3-year period prevalence of laminitis was 8.4% (95% confidence interval (CI₉₅): 6.0-11.3%), whereas lifetime prevalence was 12.5% (CI₉₅: 9.6-15.9%). Mares had a significantly higher period- and lifetime prevalence of laminitis than male horses, and horses 10 years and older had a significantly higher prevalence than younger horses. The lifetime prevalence of laminitis was 3.2% in horses 9 years and younger, whereas from 17.3-20.5% in older horses. Multivariable logistic regression analysis identified age, sex, and regional adiposity as significantly (P < 0.05) associated with the 3-year period outcome of laminitis: Horses older than 9 years had a three-fold increase in the likelihood of having laminitis compared to the younger horses (Odds Ratio (OR)_10-14 years = 3.37 (CI₉₅ = 1.19-9.50), OR_15-19 years = 3.06 (CI₉₅ = 1.04-9.05), and OR_>20 years = 2.70 (CI₉₅ = 0.90-8.02). Mares were more than twice as likely (OR = 2.44 (CI₉₅ = 1.17-5.12) to have laminitis compared to male horses, and horses with regional adiposity had increased odds (OR = 2.35 (CI₉₅ = 1.15-4.82) of laminitis compared to horses without regional adiposity.

CONCLUSIONS

Laminitis appears to be a considerable welfare issue in the Norwegian pony breed Nordlandshest/Lyngshest. The identified risk factors age, sex, and regional adiposity highlight the need for improved owner education and awareness of strategies to reduce laminitis risk.

The Fibre Requirements of Horses and the Consequences and Causes of Failure to Meet Them

Failure to meet the minimum forage requirement of 1.5% of the horse's bodyweight and the opportunity for foraging for a minimum of 8 h a day (not going without this opportunity longer than four to five consecutive hours) can have both physiological and behavioural consequences. To provide an energy source for horses, rations often include starch rather than fibre. This can result in health issues related to the gastrointestinal tract (GIT) in the horse. In the stomach, the main concern is equine gastric ulcer syndrome (EGUS) and, more specifically, equine squamous gastric disease (ESGD). Ulcerations are caused either by increasing acidity in the stomach (from starch ingestion and reduced saliva production) or splashing of acidic juices caused by a lack of a forage barrier prior to exercise or prolonged periods without fibrous feed intake, which allows the stomach to collapse and spread acidic gastric fluids into the upper squamous regions of the stomach. In the hindgut, starch that has escaped digestion in the small intestine causes microbial instability and increased production of volatile fatty acids (VFA) and lactic acid. This puts horses at great risk for acidosis and subsequent laminitis. Shifts in the hindgut microbiota will also affect a horse's behaviour via the gut-brain axis, as well as potentially compromise immune function. Reduced fluid intake caused by reduced saliva production can result in colic. Choosing a fibrous alternative for starch in a high-energy diet greatly reduces the risk of EGUS and acidosis and improves digestion, GIT pH, body condition, behaviour, immune functions, and performance. Providing hay can reduce crib-biting, wood-chewing, coprophagia, the consumption of bedding, aggression, and stress, and subsequently increase social bonding and affiliation with conspecifics. Adequate fibre intake is related to reduced clinical signs of EGUS, reduced reactivity, and better adaptation to weaning. Lignophagia (wood chewing) has also been observed in horses that are foraging, and this is thought to reflect low fibre content in the available forage (for example, early vegetative, lush pasture).

A Survey of Pennsylvania Horse Management: Part One-Nutrition

Various aspects of nutritional management can impact both a horse's gastrointestinal (GI) health and caretaker costs. The objective of this study was to characterize the feeding management and GI issues of horses in Pennsylvania (PA). An online survey was distributed from February 27th to August 31st, 2020. Kruskal-Wallis and Mann-Whitney tests were used to analyze the data. Nonparametric statistics were used when data were not normally distributed. From 470 responses collected, the average horse age was 15.7 ± 7.5 years, and the most common breeds were the Quarter Horse and Thoroughbred. Of the 345 horses who received premixed feed, 81% were fed on a volume basis. Most horses (95%) received hay on a volume basis, and 57% of horses were fed hay on the ground rather than in a feeder. No difference was detected in the number of scoops of premixed feed (median = 2; P = .284) or the flakes of hay per day (median = 5.7; P = .765) between horses in different exercise categories. The frequency of reported GI issues was 10% (46/470). Owner perceived, veterinary perceived, and veterinary diagnosed ulcers were found in 2.3%, 4%, and 2.3% of horses, respectively. No statistical difference was detected in the number of scoops of premixed feed fed per day between horses with or without GI issues (P = .536). Horses were provided the same amount of premixed feed and forage regardless of reported exercise category. Most equine caretakers fed concentrates on volume rather than weight, a common practice despite most feeding requirements being based on feed weights.

Validating owner-reporting of feather condition of pet Psittaciformes using photographs

Reporting of outcome variables by caregivers in welfare studies is commonplace but is open to subjective bias and so requires validation. Biases can occur in either direction: familiarity with an animal allows a deeper insight into welfare problems, but also can lead to reticence in admitting that an animal in one's care is experiencing problems. Here, we aim to validate owner-reporting of plumage condition of pet parrots, including those with self-inflicted feather-damaging behaviour (FDB), by comparing owners' scores of feather condition with those of two independent raters, blind to the owners' and each other's assessments. We surveyed pet parrot owners to collect data on basic demographics and feather condition, and requested four standardised photographs of birds. We received 259 responses (17% of the 1,521 people contacted); 78 sets of images of appropriate quality for assessment by raters were provided. Mean percentage agreement between owners' and raters' scores was mostly fair to substantial using Cohen's kappa; however, raters scored a greater proportion of feather damage than did owners. Overall, our results indicate owner-reporting of feather condition, including FDB, to be generally reliable and consistent with independent assessment of photographs. As the use of photographs can be limited by image quality, a failure to represent the long-term state of a parrot, and the potential for incorrect recording if assessed without relevant information (eg on moulting), this evidence that owner-reports can be reliable opens the door for larger-scale surveys of the extent of welfare-relevant problems.

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.

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.

Translating research into practice: Adoption of endocrine diagnostic testing in cases of equine laminitis

Research demonstrating insulin's causal role in endocrinopathic laminitis has greatly advanced understanding of equine laminitis. However, the degree to which this knowledge has been translated into clinical practice has not been assessed. This two-part study aimed to investigate veterinary surgeons' current diagnostic approach to laminitis, whether this had changed over time, and the impact of diagnosing an endocrinopathy on laminitis case management and outcome. Two cross-sectional online surveys of equine veterinary surgeons working within the UK were undertaken. The first study population comprised 141 veterinary surgeons, who had graduated a median of 8 years previously. Overall, 83.6% of respondents (n = 117/140) had changed their diagnostic approach to laminitis since graduating, primarily through increasing use of endocrine testing (88.7%; n = 86/97). Ninety-nine percent (n = 140/141) performed endocrine diagnostic test(s) for some or all laminitis cases at initial and/or subsequent examinations. The second study had 120 participating veterinary surgeons, ≥76% of whom considered diagnosing underlying endocrine diseases greatly influenced their laminitis case management. Where an endocrinopathy was identified, 75.0% (n = 90/120) considered that client communication regarding laminitis was facilitated, and ≥67% considered that treating the endocrinopathy was effective in reducing laminitis recurrence. This study demonstrates successful translation of research knowledge into equine practice, with the vast majority of veterinary surgeons adopting endocrine diagnostic testing within their routine approach to laminitis cases. Respondents perceived that this change in diagnostic approach has resulted in improvements in several non-clinical and clinical healthcare outcomes, including client communication and reduction in recurrent laminitis episodes.

Effect of body condition on intestinal permeability in horses

OBJECTIVE

To investigate effects of body condition on permeability of intestinal mucosa in horses.

ANIMALS

13 horses (7 obese and 6 lean) from 8 to 15 years of age.

PROCEDURES

Body condition score was assessed, and an oral sugar test (OST) was performed to evaluate glucose and insulin dynamics. Horses were allowed a 2-week diet acclimation period and were then euthanized. Tissue samples were collected from the jejunum, ileum, cecum, pelvic flexure, right dorsal colon, and rectum. Mucosal permeability was assessed by measuring transepithelial resistance and lipopolysaccharide (LPS) flux across tissue samples mounted in Ussing chambers.

RESULTS

5 obese horses and 1 lean horse had evidence of insulin dysregulation, whereas 1 obese and 5 lean horses had no abnormalities in results of the OST. Results for the OST were not available for 1 obese horse. Mucosal transepithelial resistance did not differ in any intestinal segment between obese and lean horses. Obese horses had a significantly higher LPS flux across jejunal mucosa, compared with results for lean horses, but there were no significant differences between obese and lean horses for other intestinal segments.

CONCLUSIONS AND CLINICAL RELEVANCE

Obese horses may have had greater paracellular mucosal permeability of jejunal mucosa to LPS, compared with that for lean horses. This finding was consistent with data for the gastrointestinal mucosa of humans and mice and supported the hypothesis that obese horses may be at higher risk from chronic exposure to increased amounts of LPS, compared with the risk for lean horses.

Incidence and risk factors for recurrence of endocrinopathic laminitis in horses

Background

Endocrinopathic laminitis is common in horses and ponies, but the recurrence rate of the disease is poorly defined.

Objectives

To determine the incidence of, and risk factors for, the recurrence of endocrinopathic laminitis.

Animals

Privately owned horses and ponies with acute laminitis (n = 317, of which 276 cases with endocrinopathic laminitis were followed up to study completion).

Methods

This prospective cohort study collected data on veterinary‐diagnosed cases of acute laminitis for 2 years. Each case was classified on acceptance to the study as endocrinopathic or non‐endocrinopathic using data collected in a questionnaire completed by the animal's veterinarian. Follow‐up data were collected at regular intervals to determine whether the laminitis recurred in the 2‐year period after diagnosis.

Results

The recurrence rate for endocrinopathic laminitis was 34.1%. The risk of recurrence during the 2‐year study period increased with basal, fasted serum insulin concentration (P ≤ .05), with the probability of recurrence increasing markedly as the insulin concentration increased beyond the normal range (0‐20 μIU/mL) to over the threshold for normal (up to approximately 45 μIU/mL). Being previously diagnosed with laminitis (before the study; P = .05) was also a risk factor for recurrent laminitis. Cases with a higher Obel grade of laminitis were likely (P = .05) to recur sooner.

Conclusions and clinical importance

Knowing that hyperinsulinemia and being previously diagnosed with laminitis are significant risk factors for recurrence will enable clinicians to proactively address these factors, thereby potentially reducing the risk of recurrence of laminitis.

Identification of modifiable factors associated with owner-reported equine laminitis in Britain using a web-based cohort study approach

Background

Equine laminitis is a complex disease that manifests as pain and lameness in the feet, often with debilitating consequences. There is a paucity of data that accounts for the multifactorial nature of laminitis and considers time-varying covariates that may be associated with disease development; particularly those that are modifiable and present potential interventions. A previous case-control study identified a number of novel, modifiable factors associated with laminitis which warranted further investigation and corroboration. The aim of this study was to identify factors associated with equine laminitis in horses/ponies in Great Britain (GB) using a prospective, web-based cohort study design, with particular interest in evaluating modifiable factors previously identified in the case-control study.

Results

Self-selected horse/pony owners in GB submitted initial baseline and follow-up health and management questionnaires for 1070 horses/ponies between August 2014 and December 2016. The enrolled horses/ponies contributed 1068 horse-years at risk with a median of 38 days between questionnaire submissions. Owners reported 123 owner-recognised and/or veterinary-diagnosed episodes of active laminitis using a previously-validated laminitis reporting form. Multivariable Cox regression modelling identified 16 risk/protective factors associated with laminitis development. In keeping with the previous case-control study, a prior history of laminitis (particularly non-veterinary-diagnosed episodes), soreness after shoeing/trimming and weight gain were associated with higher rates of laminitis. There is now strong evidence that these risk factors should be used to guide future recommendations in disease prevention. Factors with some prior evidence of association included breed, steroidal anti-inflammatory administration, transport and worming. The modifiable factors amongst these should be the focus of future laminitis studies. The remainder of the identified factors relating to health, turnout and grazing management and feeding are novel, and require further investigation to explore their relationship with laminitis and their applicability as potential interventions.

Conclusions

This study has demonstrated a temporal relationship between a number of horse- and management-level factors and laminitis, identifying potential interventions and important risk groups for which these interventions would be of particular importance. These results serve as a sound evidence-base towards the development of strategic recommendations for the horse/pony-owning population to reduce the rate of laminitis in GB.

Electronic supplementary material

The online version of this article (10.1186/s12917-019-1798-8) contains supplementary material, which is available to authorized users.

Phenotypic, hormonal, and clinical characteristics of equine endocrinopathic laminitis

Background

Equine endocrinopathic laminitis is common and can be associated with an underlying endocrinopathy, such as equine metabolic syndrome (EMS), pituitary pars intermedia dysfunction (PPID), pasture consumption, or any combination of these factors.

Objectives

The aim of the study was to improve the risk assessment capabilities of clinicians, and to inform management strategies, for acute endocrinopathic laminitis by prospectively examining the phenotypic, hormonal, and clinical characteristics of the disease in a large cohort.

Animals

Privately owned horses and ponies (n = 301) of any age, sex, or breed diagnosed with laminitis by a veterinarian. A history of laminitis was acceptable.

Methods

This was a prospective cohort study. Veterinarians provided information on each case via an online questionnaire after informed consent from the animal's owner, and all data were de‐identified before analysis. Serum insulin and plasma adrenocorticotrophic hormone concentrations were measured in each case.

Results

Most cases were recruited in spring (109/301; 36.2%). Concurrent EMS and PPID resulted in higher basal insulin concentrations (49 [21.5‐141]; P < .02) than if an animal had a single underlying cause for their laminitis. The insulin concentration was negatively correlated (r² = −0.38; P < .001) with the animal's height, being higher in ponies (33[10‐14]; P < .001) than horses (9.5 [3‐25.7]) and was positively correlated (r² = 0.12; P = .05) with their grade (severity) of laminitis.

Conclusions and Clinical Importance

Horses and ponies with concurrent endocrinopathies have more marked hyperinsulinemia. Higher basal insulin concentrations were associated with more severe lameness.

Incidence and clinical signs of owner-reported equine laminitis in a cohort of horses and ponies in Great Britain

BACKGROUND

Previous robust epidemiological studies of equine laminitis have utilised only veterinary-diagnosed episodes of disease, potentially underestimating true disease frequency.

OBJECTIVES

To estimate the incidence of, and describe clinical signs associated with, owner-reported active laminitis in horses/ponies, using both veterinary-diagnosed and nonveterinary-diagnosed episodes.

STUDY DESIGN

Prospective cohort.

METHODS

Data were collected from horse/pony owners in Great Britain between August 2014 and December 2016 using a web-based application. The incidence of owner-reported laminitis was estimated using both first incident and repeat episodes reported during the study period via a previously validated laminitis reporting form. Owner-reported clinical signs present in these episodes were recorded.

RESULTS

A total of 1070 horses/ponies contributed 1068 horse-years at risk (HYAR) and 123 active laminitis episodes were reported in 97 animals. Sixty-two of these episodes (50.4%, 95% confidence interval [CI] 41.6, 59.2%) were veterinary-diagnosed and 75.3% (CI 66.7, 83.8%; n = 73) of horses/ponies reported to have laminitis during the study had a previous laminitis history. Overall owner-reported first episode incidence was 9.6 episodes (CI 7.8, 11.7)/100 HYAR, whereas incidence including repeat episodes was 11.5 episodes (CI 9.7, 13.7)/100 HYAR. Laminitis occurred throughout the year with no significant differences between seasonal incidence estimates. Incidence was highest in Connemara and New Forest and lowest in Draught and Cob breed categories. The most prevalent owner-reported clinical signs (≥70%) were difficulty turning and a short/stilted or lame walk. Laminitis was reported in all limbs, however; both forelimbs were most commonly affected (62.9%, CI 54.1, 71.7%; n = 73/116).

MAIN LIMITATIONS

Self-selection enrolment of participants may limit generalisability of the findings.

CONCLUSIONS

Laminitis remains a considerable year-round welfare issue of horses and ponies, with frequency estimates utilising owner-reported data more representative of the true impact of the disease. The clinical signs reported by horse/pony owners were reflective of those previously described by veterinary surgeons.