Equine Conditions: Laminitis

We’re back with the equine conditions series, and this time, we dive into laminitis. 

What is laminitis? 

Laminitis is a condition of the hoof, and occurs when the connection between the horse’s inner hoof wall and distal phalanx is impaired, which can cause serious injury to the structure of the hoof. Laminitis is scary, because once we see clinical signs, other things are happening below the surface: inflammation and physical trauma to the lamellae (Harris et al., 2006). Due to its severity, laminitis always counts as a veterinary emergency, so if you believe your horse could be experiencing a laminitic episode, call your vet immediately.

What causes laminitis? 

Laminitis is commonly considered a syndrome instead of a single disease due to the multiple contributory causes and pathophysiological pathways that can lead to the development of laminitis. These include: 

Endocrine/Metabolic origins - the most common cause of laminitis. This is associated with insulin resistance, obesity, IR, EMS, and/or PPID, prolonged elevated insulin levels, high cresty neck score (CNS >2) or body condition (BCS >7).

Ingestion: Grain/starch overload (carbohydrate overload, especially when starch intake is over 2-4g/kg BW per meal); Pasture grazing (pasture-associated laminitis). Note that individual risk may vary depending on the horse’s unique metabolism, and may relate back to that horse’s endocrine/metabolic function (above).

Sepsis or systemic inflammatory origin: This can include retained placenta in broodmares, gastrointestinal disease, septic metritis, pneumonia, carbohydrate overload, diseases such as strangulating small or large intestinal obstructions, duodenitis-proximal jejunitis; Potomac Horse Fever.

Miscellaneous: Mechanical overload (supporting limb laminitis), road founder, ingestion of black walnut shavings, etc.

While diet can play a role, diet alone is not sufficient to manage laminitis. An individualized care team with your horse’s vet, farrier and nutritionist is crucial. Work with this team to identify the main primary cause of your horse’s laminitic flare up, as this will make the most significant impact on their treatment and prognosis. 

What influences laminitis risk?

Research is still working to better understand what contributes to laminitis, but based on the existing data, some key pieces seem to underpin a lot of laminitic cases. These include:

Factors that impact endocrine & metabolic function, even if not diagnosed with PPID, IR, EMS.

• Body condition (Pratt-Phillips and Munjizun, 2023): All horses should be kept under a BCS of 7. Horses with BCS 7+ are more likely to develop laminitis, and have a reduced survival rate in laminitis. Horses at higher BCS have higher levels of adipose tissue, which can impair insulin signalling and glucose regulation, while also increasing inflammation. Insulin concentrations and systemic inflammation levels are correlated to body condition score, so it is crucial to maintain a healthy body condition. Grab my free BCS guide here.

• Cresty neck score: Cresty neck scoring is used to determine regional fat accumulation on the neck. The proportion of fat in this area is disproportionate to the amount of total body fat, and can be used to assess adiposity (Carter et al, 2009; Busechian et al, 2022). Neck crest fat in horses has been suggested to be associated with IR and increased laminitis risk, and better predicts ID than obesity or BCS, as a high CNS group had greater insulin response to the oral glucose test than those in the normal/fleshy BCS group (Fitzgerald et al., 2019). Learn how to assess CNS here.

• Insulin: Elevated insulin for 2-3 days has been reported to contribute to laminitis in susceptible horses, suggesting even short-term changes can increase risk (Geor, 2008). This may be the contributing primary cause in situations such as: 

  • Laminitis flare up with no recent diet change, due to fluctuating non-structural carb (NSC) levels in pasture. Remember, spring and fall temperature fluctuations, summer drought, rainfall and time of day will all impact NSC levels in pasture.

  • Consumption of other feeds that elevate insulin such as elevated NSC content in a new hay, swap to a higher NSC feed or feeding sugary grain-based treats. Learn more about treats here.

  • A recent weight gain can be the difference in tipping the horse into an increased risk. If your horse’s caloric needs change without an appropriate diet change to account for the reduction, whether due to reduced workload or inaccurate feeding (always feed by weight!), weight gain will result.

  • Stress: Cortisol increases insulin (Pratt-Phillips et al, 2014). A new horse in the barn, an environment change, trailering, unmet species appropriate needs such as turnout & social opportunities with other horses, environment stress due to extreme weather conditions, etc. 

Factors that impact gut health: Microbes that break down forage prefer a higher pH environment (less acidic), so when the hindgut pH drops, they will die. Microbes that break down starch are the opposite, and contribute to a further reduction of hindgut pH (Hart, Farmer and Duberstein, 2023). When this environment is disrupted, pH drops. The now acidic environment is upsetting - and killer - to the good bacteria, and as these die off, proinflammatory molecules such as LPS, histamine and others are released. These molecules can cause damage, and may trigger laminitis due to their vasoconstrictive nature (reduce blood flow). Gut health is compromised by: 

• High exposure of starch or oligofructose, which alter the microbiome. Control excess starch by feeding smaller meals of lower-starch items.

• Insufficient fiber intake, which impair digestive health. Weigh your forages/fiber sources and ensure you are providing enough hay to meet their fiber requirement. 

• Feed changes without sufficient time to adjust. While colic risk is higher for 7-14 days after a diet change, especially a hay change, new feedstuffs such as a new batch of hay, rapid transition to a new feed or exposure to free-choice pasture without gradual introduction can all contribute to hindgut dysfunction.

Genetic predisposition & individual variation: A genetically predisposed horse who is overweight will have a higher risk of laminitis than a genetically predisposed horse at a BCS 5. Studies assessing hindgut challenges reported large individual differences in response to the same stressor. Horses who are predisposed may suffer flare ups even in ideal set ups due to factors outside of our control.

Laminitis Diet Checklist 

• Ensure you are meeting your horse’s minimum fiber requirement. Use hay testing to guide feeding rate and hay suitability based on calorie and sugar content. For most horses, ensure you are feeding 1.5% BW (DM basis) of appropriate hay per day. Do not feed below this amount unless you are working under the close supervision of a vet and nutrition professional.

• Feed a balanced diet that controls calories without limiting crucial nutrients required for healing and optimal body functions. Studies have consistently reported that horse owners overfeed their horses due to overestimating their requirements, and only 33% of horses receive the correct amount of forage in the diet (Venable et al., 2017). Feeding by weight - both your horse’s weight AND the weight of your feed - is crucial. Feeding a handful? Here's why that probably isn't cutting it.

Keep the diet at <10-12% NSC on a DM basis by testing your hay, controlling pasture access, and feeding a low-NSC source of essential nutrients.

• Limit starch intake per meal according to your horse’s insulin sensitivity. For insulin dysregulated horses, limit NSC/meal below 0.1g/kg BW. Work with a nutritionist to ensure your math is right on this.

• Feed to achieve and maintain a healthy BCS of 5.

Laminitis Management Checklist 

• Work closely with your horse’s vet and farrier team, and consider radiographs that will help evaluate severity, track response to treatment and aid in monitoring long-term.

• Identify the primary trigger for your individual horse to allow for an individualized, strategic program to control future risk. Testing your horse’s insulin and ACTH levels after the resolution of the acute laminitic episode to gain insight on your horse’s metabolic function. Laminitis-associated pain and stress will confound test results so work with your vet to identify the optimal time for testing.

• Careful pasture restriction is necessary. Ponies can ingest up to 1% of their BW in DM of grass within 3 hours (Longland et al, 2011a). Another study showed that ponies can consume from 22-49% of their daily DM intake within a 3 hour turnout period and that they adapt to short turnout periods by increasing DM intake (Ince et al, 2011). Restricted grazing may not adequately limit daily intake of NSC and rapidly fermentable carbs, particularly in times of year where pasture forage sugar and/or fructan content is high. Learn more about pasture and your horse here.

• For horses with an increased risk due to weight loss, work with a nutrition professional to ensure that weight loss is safe and gradual, so not to exceed 1% BW change per week to avoid hyperlipemia.

• Keep it cool: Cryotherapy use continuously for 48 hours has been reported to reduce severity (Moore, 2008).

• Increase insulin sensitivity by increasing exercise, achieving an ideal body condition score, and moderating NSC content per meal (Moore, 2008). We have more evidence that insulin sensitivity is better improved by exercise than by any supplement, so maximize the amount of safe, low-impact exercise that your horse can do, even if that’s just turnout on a dry lot or track system. 

• Monitor body condition and crest score: Keep your horse at a healthy body condition score. If you notice changes in body condition or in the size of your horse’s crest, adjustments in diet and management are likely required.

Note that this is not a complete list of recommendations, and that this article is for educational purposes only. Need a hand formulating a balanced diet that fits these recommendations for your horse? As an independent equine nutritionist, I can work collaboratively with your horse's care team to ensure we are supporting recovery with adequate, individualized nutrition for your horse's situation.

References

Ayoub et al., 2023. Fecal microbiota of horses with colitis and its association with laminitis and survival during hospitalization. JVIM 36(6): 2213-2223. DOI: https://doi.org/10.1111/jvim.16562

Busechian, S., Turini, L., Sgorbini, M., Pieramti, C., Pisello, L., Orvieto, S., Rueca, F. 2022. Are Horse Owners Able to Estimate Their Animals’ Body Condition Score and Cresty Neck Score? Vet Sci 9(10): 544. 

Carter, RA., Geor, RJ., Burton Staniar, W., Cubitt, TA., Harris, PA. 2009.Apparent adiposity assessed by standardised scoring systems and morphometric measurements in horses and ponies. The Veterinary Journal 179(2): 204-210.

Divers, TJ. 2010. Update on Metabolic Diseases Associated With Laminitis in Horses and Ponies. Journal of Equine Veterinary Science 30(9): 504-505. 

Fitzgerald, DM., Anderson, ST., Sillence, MN., de Laat, MA. 2019. The cresty neck score is an independent predictor of insulin dysregulation in ponies. PLoS One 14(7): e0220203. https://doi.org/10.1371/journal.pone.0220203

^*Firouzabadi, M.S., A.P. Ardakani. 2024. Plasma concentration of serum amyloid A and lipopolysaccharide binding protein in horses with laminitis resulted from hindgut acidosis. Veterinary Journal: doi: 10.1016/j.tvjl.2024.106190. 

Hart, R., Farmer, J., Duberstein, K. 2023.Chew frequency and duration in horses consuming bermudagrass hay in slow feeders as compared to loose hay. Journal of Equine Veterinary Science 124: 104405. DOI: https://doi.org/10.1016/j.jevs.2023.104405

Johnathan, E., Simon, RB. 2006. Gastrointestinal Derived Factors Are Potential Triggers for the Development of Acute Equine Laminitis. The Journal of Nutrition 136(7): 2103S-2107S. DOI: https://doi.org/10.1093/jn/136.7.2103S

Lynden, J., Hollands, T., Ogden, J. 2020. A Farrier Making Every Contact Count: A Microlevel Analysis of Farrier-Client Interaction for Partnership Working in Managing a Horse With Laminitis. Journal of Equine Veterinary Science 87(2020). DOI: https://doi.org/10.1016/j.jevs.2020.102924

Macon, EL., Harris, P., McClendon, M., Perron, B., Adams, A. 2024. Insulin dysregulated horses metabolic responses to forage pellets. Journal of Equine Veterinary Science 133: 104991. DOI: https://doi.org/10.1016/j.jevs.2023.104991

Moore, RM. 2008. Evidence-Based Treatment for Laminitis—What Works?. Journal of Equine Veterinary Science 28(3): 176-179. DOI: https://doi.org/10.1016/j.jevs.2008.01.015

Pratt-Phillips, S., Gill, J.,  Mansmann, R., Tillotson. K. 2014. Effect of transport on serum insulin concentrations in normal and equine metabolic syndrome-affected horses. In: Macro and trace elements in equine nutrition: An update. Proc. 7th European Workshop on Equine Nutrition, Leipzig, Germany, p. 112-113.  

Pratt-Phillips, S., Munjizun, A. 2023. Impacts of Adiposity on Exercise Performance in Horses. Animals (Basel) 13(4):666

Sheridan, L., Hutton, P., Noble, G., Nobari, B. 2026. An in vitro investigation into the effects of postbiotic supplementation on stabilising equine hindgut pH. Journal of Equine Veterinary Science 156: 105746.

Steelman, SM., Hood, DM., Fan, YY., Chapkin, RS., Chowdhary, BP. 2013. Fish oil is a modulator of neutrophil function in chronic laminitis. Journal of Equine Veterinary Science 33(10): 855.

Tuniyazi et al., 2021. Changes of microbial and metabolome of the equine hindgut during oligofructose-induced laminitis. BMC Veterinary Research 17(2021).