The foot disease equine laminitis remains a significant challenge for horse owners and carers. Despite being acutely aware of its clinical features and profound welfare impact for many decades, we are still struggling to understand and manage the condition.
Equine laminitis is a painful and common disease that affects all Equidae, from elite sporting animals to donkeys and retired ponies. Preventing disease onset should be our primary aim.
Recent improvements in our understanding of the causative factors, and their relative likelihood in each case, has helped us to prevent laminitis more actively.
Insulin Dysregulation and Equine Laminitis
The metabolic disease insulin dysregulation (ID) is the most common cause of laminitis.1 Abnormally increased insulin concentrations occur in animals with ID.2
In some animals, high insulin concentrations occur only after eating. However, in other animals, the increases are more persistent and can last for many hours or be perpetual.
Insulin drives elongation and weakening of the structures in the hoof that hold the foot bone firmly against the inner hoof wall.3 This results in movement of the foot bone toward the ground, tearing, and further damaging the sensitive structures within the hoof capsule. All this causes pain and lameness.
Preventing Equine Laminitis
To prevent insulin triggering structural damage of the lamellae in the foot, it is essential to reduce the insulin concentrations that are circulating in the animal. This can be achieved with dietary modification, weight loss (particularly in certain areas such as the neck crest), and exercise in many cases.
Close consultation with an experienced veterinarian and equine nutritionist can help owners effectively manage their horses or ponies with insulin dysregulation. Management should begin ideally as soon as it is recognised that an animal has ID. This is in an effort to prevent laminitis from ever occurring, or at least from recurring.4
Managing Insulin Dysregulation
The key management goal should be to reduce the stimulation of insulin release. This is most effectively achieved by avoiding sudden rises in blood glucose concentration. Rises are caused by eating sugar and/or starch-rich meals or treats.5
Formulating a diet that minimises changes in blood glucose concentrations in animals with ID will reduce the risk that insulin will increase to a point where lamellar damage occurs.
Currently, the exact concentration at which insulin starts to damage the lamellae is not known. It is very likely to be different in each animal. Current advice suggests that keeping insulin responses to a meal in the normal post-meal range (i.e., below 60-80 µIU/mL) is likely to be beneficial.6
In some animals, reducing insulin concentrations below thresholds at which laminitis can occur is challenging. These cases might be able to be managed with some off-label, experimental medications that reduce insulin release by pharmacological mechanisms. However, this should be carefully managed by a veterinarian.
It is important to know that any reduction in insulin concentration will reduce the risk of laminitis, and/or the amount of damage to the lamellae. It has also been shown that the lamellae can repair to some extent,7 so efforts to reduce high insulin concentrations will always be beneficial.
Final Words
In summary, it is now well known that high insulin concentrations damage the lamellar structure and can cause laminitis.
The best approaches to reducing the risk of laminitis in an animal with insulin dysregulation includes managing diet. For some animals, reducing body fat is critical. These are aimed at minimising the release of insulin into the circulation, particularly after eating.
References
- The prevalence of endocrinopathic laminitis among horses presented for laminitis at a first-opinion/referral equine hospital. Karikoski, N.P.; Horn, I.; McGowan, T.W.; et al. Domest Anim Endocrinol 2011;41:111-117.
- Insulin dysregulation. Frank, N., Tadros, E.M. Equine Veterinary Journal 2014;46:103-112.
- Histological and morphometric lesions in the pre-clinical, developmental phase of insulin-induced laminitis in Standardbred horses. de Laat, M.A.; Patterson-Kane, J.C.; Pollitt, C.C.; et al. Veterinary Journal 2013;195:305-312.
- Incidence and risk factors for recurrence of endocrinopathic laminitis in horses. de Laat, M.A.; Reiche, D.B.; Sillence, M.N.; et al. Journal of Veterinary Internal Medicine 2019;33:1473-1482.
- Equine hyperinsulinemia: investigation of the enteroinsular axis during insulin dysregulation. de Laat, M.A.; McGree, J.M.; Sillence, M.N. American Journal of Physiology – Endocrinology and Metabolism 2016;310:E61-E72.
- ECEIM consensus statement on equine metabolic syndrome. Durham, A.E.; Frank, N.; McGowan, C.M.; et al. Journal of Veterinary Internal Medicine 2019;33:335-349.
- Hoof wall wound repair. Pollitt, C.C.; Daradka, M. Equine Veterinary Journal 2004;36:210-215.
Further Reading
- Assessing Your Animal’s Risk of Laminitis. Dr. Ed Knowles. MySeniorHorse.com
- Possible New Insulin Dysregulation Treatments. Kimberly S. Brown. MySeniorHorse.com
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Associate Professor Melody de Laat, BVSc(Hons), PhD, MANZCVS(Pharm), SFHEA GradCertAcadPrac, is a clinical and research veterinarian with. more than 15 years of experience on equine endocrine diseases, pharmacology, and laminitis. She works at the Queensland University of Technology in Australia.View all posts