BOVA Global Logo
BOVA Global Logo
global icon
Change region
GLOBAL UK AUS
Login
Change region
GLOBAL UK AUS

Laminitis in Horses (2023)

Last updated: 05/2023

If you are a horse owner, please watch our webinars on horses.

If you have an equine caseload, you are likely to be well-versed in managing laminitis. It is a debilitating condition, affecting up to 34% [1] of horses, has considerable welfare implications, and is a leading cause of euthanasia [2]. In this article, we will recap some of the basics of laminitis and signpost you to our other educational content on this topic.

What is laminitis in horses?

Equine laminitis is a complex, multifactorial and extremely painful condition which occurs when the lamellar structures within the foot change. It can affect any pony or horse and the associated degenerative changes often result in ongoing issues with pain and lameness.

The degenerative changes occur within the lamellar structures of the suspensory apparatus of the distal phalanx (SADP). In the normal equine foot these lamellar structures (epidermal and dermal laminae) are interlocked to form the interlaminar bond and connect the pedal bone to the hoof capsule. Destruction of this bond, through cellular and mechanical processes, results in rotation or sinking of the pedal bone within the hoof capsule.

What causes laminitis in horses?

Once a horse or pony has suffered from laminitis, they are more susceptible to future episodes, which is why a clear understanding of the underlying disease is required so management can be adapted to prevent recurrence. It is now thought that laminitis is a clinical syndrome, linked with systemic disease or mechanical overload, with three forms:

Endocrinopathic laminitis

– occurs in equids with an underlying endocrine disorder – equine metabolic syndrome (EMS) and pituitary pars intermedia dysfunction (blog on PPID; formerly equine Cushing’s disease). Both endocrine disorders can result in insulin dysregulation (ID), with hyperinsulinemia and insulin resistance being key in the pathogenesis of this form of laminitis. Lamellar inflammation does not seem to be a key feature in these cases, and it is instead thought the pathogenesis is linked to stretching of the secondary epidermal lamellae and cellular proliferation which weakens the lamellar structures. [3] Research has shown there is a correlation between the severity of laminitis and the levels of plasma in [4] sulin, and this form accounts for up to 90% [5] of cases of laminitis, so is by far the most common.

Sepsis-associated laminitis

– occurs in equids with sepsis or systemic inflammatory response syndrome (SIRS), resulting in a cascade of cellular changes which cause lamellar inflammation and separation. This form of laminitis can be a risk in cases of severe gastrointestinal disease, pleuropneumonia or septic metritis following retained foetal membranes (RFM). Ingestion of toxic plants can also lead to endotoxemia and this form of laminitis.

Supporting limb laminitis (SLL)

– uncommon but occurs when there is mechanical overload due to abnormal weight-bearing, for example in fracture or synovial sepsis cases. It is thought that the reduced weight unloading of a limb, combined with increased load bearing, results in lamellar ischaemia [6]. The development of this form of laminitis is unpredictable [7], but the severity and duration [8] of altered weight-bearing are thought to be risk factors.

Which horses are at risk of laminitis?

Any horse or pony can be at risk of laminitis, however, given the high prevalence of endocrinopathic laminitis, equids with EMS or PPID are especially vulnerable. Obesity and weight gain are both features of EMS, and PPID is an ageing-related disease [9]. So, these factors can also be seen as risk factors for laminitis.

Repeat cases of laminitis are common, so horses with a previous history of laminitis are also more at risk.

What are the clinical signs of laminitis in horses?

The clinical signs of laminitis can vary in severity, and in presentation depending on the stage. There are four main stages of laminitis:

Acute laminitis

Clinical signs are seen, the horse will either recover or enter the sub-acute or chronic phase, usually after 72 hours.

Sub-acute laminitis

This stage begins if the clinical signs persist for longer than 72 hours and there are no structural changes to the foot. Horses can remain in this phase for a prolonged period until the laminitis resolves or progresses into the chronic phase.

Chronic laminitis

This phase begins when there are structural changes are present within the foot – these cases are often hard to manage with a prolonged recovery period and episodes of recurrence.

Clinical signs include: [10] 

  • Lameness – usually affecting two or more limbs, although it is possible to only see lameness in one limb
    • Short, stilted gait – 93.1% [11] of animals with this clinical sign had laminitisReluctance to walkDifficulty turning
    • Recumbency
    • Recumbency
    • Recumbency
    • Recumbency
    • Recumbency
  • Stance changes
    • Weight shifting when standing – 98.1% [12] of animals with this clinical sign had laminitisCharacteristic ‘laminitic stance’ – leaning back to take weight off the toes
    • Reluctance to lift foot
    • Reluctance to lift foot
  • Acute clinical signs
    • Increased digital pulses – 91% [13]  of animals with this clinical sign had laminitisIncreased hoof wall temperaturePain on hoof testers at the point of the frog
    • Systemic signs of pain – increased heart rate and respiratory weight, sweating
    • Systemic signs of pain – increased heart rate and respiratory weight, sweating
  • Chronic clinical signs
    • Depression or swelling at the coronary band
    • Changes to the hoof wall – divergent hoof growth rings
    • Change in hoof wall angle
    • Flat/convex sole
    • Widened white line
    • Pink crescent dorsal to frog
    • Sole prolapse

It is vital that horse owners are educated in the clinical signs of laminitis to allow for rapid identification and veterinary intervention. Some cases can be subtle and therefore missed by owners. A recent study found that owners only suspected laminitis in 54.8% [14] of veterinary-diagnosed active laminitis cases.

How is laminitis in horses diagnosed?

Although there are no truly pathognomonic clinical signs associated with laminitis, diagnosis is usually based on a combination of the clinical signs above and history. Radiography is useful and allows the degree of structural changes to be assessed, namely sinking and rotation of the pedal bone. Although no changes will usually be evident initially in acute laminitis, a set of radiographs can be useful to provide a baseline. In chronic cases repeat radiography is recommended.

What is the treatment for laminitis in horses?

As laminitis is now considered to be a syndrome, rather than a discrete entity, diagnosis and treatment of the inciting cause are vital, and needs to be considered in any laminitis case.  The management of laminitis will depend on the stage:

Acute laminitis management

  • Analgesia – NSAIDs are the first choice, and no evidence exists [15] to suggest one is superior to the other. Further, off-license, analgesics may be required if the pain is unmanaged with NSAIDs alone.
  • Foot support – this is essential and can be achieved with deep bedding or applied directly to the foot itself. Supporting the caudal two-thirds of the foot provides pain-relief and minimises mechanical forces on the laminae.
  • Vasodilators – digital hypoperfusion is now known not to be a factor in endocrinopathic or sepsis-associated laminitis, but the sedative effect of acepromazine may be beneficial.
  • Cryotherapy – shown to be useful in sepsis-associated laminitis as discussed in our podcast on PPID [16]. No studies exist for its use in endocrinopathic or supporting limb laminitis cases.
  • Diet – cases of acute endocrinopathic laminitis should be removed from pasture and box rested.
  • Rest – during the acute phase to minimise further mechanical stress and damage to the lamellar structures.

Long-term management of laminitis

  • Management of underlying cause – in cases of endocrinopathic laminitis there are lots of options available for the management of EMS and PPID. For PPID, pergolide is the first-choice treatment. For EMS cases, weight reduction, primarily through diet and exercise is important, this can be supported with medical treatment if required.
  • Remedial farriery – regular corrective foot trimming and supportive shoes based on radiography.

Prevention of laminitis

Recognition, diagnosis and management of the underlying conditions before an episode of laminitis occurs should be the goal, and is key for preventing laminitis. For endocrinopathic laminitis, the underlying endocrinopathy needs to be appropriately managed and steps taken to prevent exacerbation of ID – as detailed in our webinar on PPID. This means an optimum weight needs to be maintained and intake of non-structural carbohydrate (NSC) limited, together with an exercise regime. Listen to our podcast on equine obesity to understand how it can be managed and laminitis prevented.

References

[1] Wylie, Claire E et al. “Frequency of equine laminitis: a systematic review with quality appraisal of published evidence.” Veterinary journal (London, England : 1997) vol. 189,3 (2011): 248-56. doi:10.1016/j.tvjl.2011.04.014-

[2] Pollard, D et al. “Factors associated with euthanasia in horses and ponies enrolled in a laminitis cohort study in Great Britain.” Preventive veterinary medicine vol. 174 (2020): 104833. doi:10.1016/j.prevetmed.2019.104833

[3] de Laat MA et al (2013). Histological and morphometric lesions in the pre-clinical, developmental phase of insulin-induced laminitis in Standardbred horses, Vet J 195(3): 305-312.

Karikoski NP et al (2016). Lamellar pathology in horses with pituitary pars intermedia dysfunction, Equine Vet J 48(4): 472-478.

Karikoski NP et al (2014). Morphological and cellular changes in secondary epidermal laminae of horses with insulin-induced laminitis, Am J Vet Res 75(2): 161-168.

de Laat MA et al (2013). A potential role for lamellar insulin‑like growth factor-1 receptor in the pathogenesis of hyperinsulinaemic laminitis, Vet J 197(2): 302-306.

[4] Walsh DM, McGowan CM, McGowan T et al (2009). Correlation of plasma insulin

concentration with laminitis score in a field study of equine Cushing’s disease and equine

metabolic syndrome, Journal of Equine Veterinary Science 29(2): 87-94.

[5] Karikoski NP, Horn I and McGowan TW (2011). The prevalence of endocrinopathic laminitis among horses presented for laminitis at a first-opinion/referral equine hospital, Domest Anim Endocrinol 41(3): 111-117.

[6] Medina-Torres CE et al (2016). The effect of weightbearing and limb load cycling on equine lamellar perfusion and energy metabolism measured using tissue microdialysis, Equine Vet J 48(1): 114-119.

[7] van Eps A et al (2010). Supporting limb laminitis, Vet Clin North Am Equine Pract 26(2): 287-302

[8] Peloso JG et al (1996). Case-control study of risk factors for the development of laminitis in the contralateral limb in Equidae with unilateral lameness, J Am Vet Med Assoc 209(10): 1,746-1,749.

[9] McGowan T W, Pinchbeck G P and McGowan C M (2013). Prevalence, risk factors and clinical signs predictive for equine pituitary pars intermedia dysfunction in aged horses, Equine Vet J 45(1): 74-79.

[10] Wylie, C. E., Shaw, D. J., Verheyen, K. L. P., & Newton, J. R. (2016). Decision-tree analysis of clinical data to aid diagnostic reasoning for equine laminitis: a cross-sectional study. Veterinary Record, 178(17), 420. https://doi.org/10.1136/vr.103588

[11] Wylie, C. E., Shaw, D. J., Verheyen, K. L. P., & Newton, J. R. (2016). Decision-tree analysis of clinical data to aid diagnostic reasoning for equine laminitis: a cross-sectional study. Veterinary Record, 178(17), 420. https://doi.org/10.1136/vr.103588

[12] Wylie, C. E., Shaw, D. J., Verheyen, K. L. P., & Newton, J. R. (2016). Decision-tree analysis of clinical data to aid diagnostic reasoning for equine laminitis: a cross-sectional study. Veterinary Record, 178(17), 420. https://doi.org/10.1136/vr.103588

[13] Wylie, C. E., Shaw, D. J., Verheyen, K. L. P., & Newton, J. R. (2016). Decision-tree analysis of clinical data to aid diagnostic reasoning for equine laminitis: a cross-sectional study. Veterinary Record, 178(17), 420. https://doi.org/10.1136/vr.103588

[14] Pollard D, Wylie CE, Verheyen KLP and Newton JR (2017). Assessment of horse owners’ ability to recognise equine laminitis: a cross-sectional study of 93 veterinary diagnosed cases in Great Britain, Equine Vet J 49(6): 759-766.

[15] Menzies-Gow NJ, Stevens K, Barr A et al (2010). Severity and outcome of equine pasture-associated laminitis managed in first opinion practice in the UK, Vet Rec 167(10): 364-369.

[16] van Eps AW, Pollitt CC, Underwood C et al (2014). Continuous digital hypothermia initiated after the onset of lameness prevents lamellar failure in the oligofructose laminitis model, Equine Vet J 46(5): 625-630.