Laminitis in horses: recognise the emergency, adjust feeding

How do you recognise a laminitis emergency?

Acute laminitis is a medical emergency because the pedal bone can shift quickly. If you suspect it, you should call your vet immediately ¹. A typical sign is a stance in which the horse shifts its weight onto the hindquarters and places its front legs forward. This is often accompanied by a bounding digital pulse at the fetlock and warm hooves ³.

Laminitis can also develop gradually, without lameness being noticeable straight away. The guideline therefore recommends radiographs to detect changes in the hoof, even if the horse is not lame ².

• The horse is reluctant to move or tries to take weight off the affected hooves ¹.
• It shifts its weight onto the hindquarters and places its front legs forward ³.
• The hooves are warm and the pulse at the fetlock is clearly palpable ³.
• The horse seems dull or eats less ¹.
• The signs appear after colic, intestinal inflammation, an infection or, in a mare, after retained placenta. These are also known triggers ¹.

Why does insulin play such a big role in laminitis?

According to the expert group, insulin-associated laminitis is the most common form in horses and ponies, accounting for over 90% of cases. The term replaces the older names pasture-associated laminitis and endocrinopathic laminitis. It can begin unnoticed and often becomes chronic with recurring episodes ². The veterinary reference overview also names endocrine disorders as the probably most common underlying cause ³.

Non-structural carbohydrates (NSC), i.e. sugar, fructan and starch, are the most important trigger of insulin release. A ration rich in NSC is considered a risk factor for insulin dysregulation and insulin-associated laminitis regardless of predisposition ². Overweight increases the risk but is absent in some affected horses; testing is therefore not limited to fat horses ².

Other forms have other triggers, such as too much cereal, severe infections or overloading of one leg when the other is injured ³. PPID is also one of the risk factors: about 30% of PPID horses have insulin dysregulation, and horses over ten years of age should be tested for both ².

• Cushing's (PPID) and feeding
• EMS, laminitis and PPID at a glance

What do sugar, fructan and starch in hay mean for a laminitic horse?

For horses with insulin dysregulation, the guidelines recommend hay with less than 10% NSC ²⁴. NSC is the sum of water-soluble carbohydrates and starch. An NFC value calculated by difference is not a substitute ². In the laboratory order form reviewed, the hay nutrient package includes sugar and fructan; starch is ordered as an extra ⁵.

Even suitable hay is no guarantee: some severely affected horses show an excessive insulin response even at less than 10% NSC ². Whether the ration suits your horse is therefore shown by veterinary follow-up checks, not by the lab value alone.

Further points from the guideline: offer forage via slow feeders such as a small-mesh hay net or in several small portions so that there are no long gaps between meals. High-quality straw can replace part of the hay but must be introduced over at least two weeks, while watching droppings and signs of colic ².

• Understanding sugar and fructan in hay
• Planning and reading a hay analysis
• Sample hay analysis report

What does soaking hay achieve – and where are its limits?

The guideline recommends soaking hay for at least 60 minutes in cold water if it contains more than 10% NSC or has not been analysed ². How much sugar is actually lost varies widely: in a study with soaking times of up to 16 hours at about 8 °C, water-soluble carbohydrates fell by an average of 27%, within a range of 6 to 54%. Seven of the hays tested were still above 100 g per kg dry matter afterwards ⁶.

Soaking has side effects on the ration. With longer soaking, phosphorus, potassium and magnesium fell considerably; after twelve hours, phosphorus needed to be balanced, whereas 15 to 60 minutes did not lead to a calculated deficiency for a 500 kg horse in light work in the study ⁷. Long soaking in warm surroundings also raises concerns about microbial growth; under warm conditions, the EMS consensus advises 1 to 2 hours ⁴. Steaming does not change the sugar content to any meaningful extent ⁸.

How do you deal with overweight without starving the horse?

Overweight is not the same as EMS, but it is considered an aggravating factor for insulin dysregulation ⁴². For overweight horses with insulin dysregulation, the guideline names as the starting point for weight loss low-NSC hay in an amount of 1.5% of current body weight as dry matter. Weight is checked every 30 days and the amount is only reduced gradually, down to a lower limit, if no weight is lost. Stress should be avoided as far as possible because of the risk of hyperlipaemia ².

A freely chosen worked example of the reference basis, not a recommendation for your horse: 1.5% of 500 kg is 7.5 kg dry matter. If the hay has 85% dry matter, this corresponds to just under 8.8 kg of hay as fed ⁹. Rules of thumb that give a percentage of body weight without a reference basis are therefore imprecise. Have your vet determine the amount and pace.

Exercise helps with overweight and insulin sensitivity, but only without acute laminitis. After laminitis, workload is only built up again once the hoof is stable and while watching for lameness ². As insulin values can be higher in winter, the guideline advises avoiding overfeeding and NSC-rich supplements especially then ².

• Understanding overweight in horses
• Measuring or estimating your horse's weight
• Understanding the body condition score

When can a horse go back out on pasture after laminitis?

At first, the guideline recommends severely restricting grazing, for example on a small paddock with little grass and with companions, or doing without it entirely in cases of severe insulin dysregulation ². Whether and how much grazing is possible again is only decided once the signs of laminitis have subsided, on the basis of an insulin test after about two hours of grazing. This is followed by gradual reintroduction with a grazing muzzle, paddock track or similar systems. If laminitis recurs, grazing is stopped ².

Grass is not a constant: its sugar and protein content varies with temperature, sunlight, rainfall and fertilisation ². Horses eat faster when grazing time is short ¹⁰, and the effect of a grazing muzzle differed greatly between two studies ¹¹¹². Short grazing times are therefore not reliable protection.

• Accounting for pasture grass in the ration

How do you keep the mineral supply covered with restrictive feeding?

If you limit the amount of hay or soak hay, you also change nutrient intake. Forage can be low in protein, and soaking washes out minerals and vitamins. These nutrients should be balanced in a targeted way ⁴. The guideline names a low-sugar mineral, vitamin and protein supplement for this ².

More is not automatically better. For magnesium and chromium, the EMS consensus describes isolated indications of improved insulin regulation that other studies have not confirmed ⁴. So calculate the total ration from hay analysis, hay amount and all supplements against requirements instead of adding another product across the board ⁹.

• Note the hay analysis of the batch being fed and the daily hay amount.
• State whether and for how long hay is soaked.
• Record all supplements with their declaration and daily amount.
• Discuss calculated gaps and possible double supply with a specialist.

• Choosing a mineral feed based on the total ration
• Understanding magnesium in horses
• Avoiding oversupply of trace elements

Key takeaways

• Acute laminitis is a veterinary emergency; do not wait to see whether it gets better on its own ¹.
• Soaking lowers the sugar in hay unreliably and washes out minerals; a hay analysis is the better basis ⁶⁷.
• A restricted ration needs targeted balancing of protein, minerals and vitamins ⁴.

Frequently asked questions