A Winter Wisdom Feature - with a nod to Dr Eleanor Kellon, VMD

Winter often feels like the “safe season” for our laminitis-prone horses. The grass looks sparse, brown, and harmless, and it’s easy to assume the danger has passed for another year.

But winter grass – especially following an autumn drought, sudden rainfall, or sharp temperature swings – can be one of the most deceptive laminitis triggers of the year.

And to complicate things further, some horses experience a second, entirely different syndrome: cold-induced hoof pain, a circulatory issue that looks very much like laminitis but isn’t inflammatory at all.

This blog looks at both patterns to help you understand what’s really happening, and how to protect your horse through the cold months.

Part 1 – Why winter grass can trigger laminitis

- Drought Stress, Sugar Storage & the Post-Rain Spike

When grass dries out in late summer or early autumn, it goes into survival mode. Growth slows, but photosynthesis continues, creating a mismatch:

• Sugars keep being made
• Growth stops using them
• NSC (sugars, starch, fructan) accumulate in the stems, crowns, and leaf bases

Cool-season grasses – ryegrass, fescue, timothy, orchard – rely heavily on fructan as their storage carbohydrate, but under drought conditions, fructan levels can rise dramatically. Some varieties have been recorded with up to 60% NSC under prolonged stress.

Then the autumn rain arrives… and we’ve certainly seen that this year!

- After rain - a surge of sugary new growth

The moment drought-stressed grass receives moisture:

• Stored fructans break down into short-chain sugars
• New shoots appear rapidly, often extremely high in sugar
• Ryegrass is an exception – for those of us on former dairy farms, be aware that it can create even more fructan after rainfall

To the eye, it looks like harmless tiny green tips. To the metabolism of a sensitive horse, it can be dynamite.

- Why this matters for hindgut laminitis

Shorter-chain carbohydrates ferment much faster in the hindgut. When the bacterial population shifts suddenly:

• Lactic-acid–producing bacteria bloom
• pH drops
• Endotoxins/exotoxins are released
• The laminae become vulnerable

This is the classic hindgut-driven laminitis pathway – the one we see every year in spring, and again in early winter, right after the rains break drought.

- Weeds - the winter wildcard

Sparse winter pasture encourages horses to graze weeds they normally ignore.

Some – such as chicory, thistles, and dandelion roots – contain inulin, a form of fructan used experimentally to induce laminitis in research models.

Others concentrate toxins under drought:

• nitrates
• oxalates
• alkaloids
• cyanogenic glycosides
• prussic acid

These compounds can disrupt digestion, metabolism or liver pathways depending on the plant, adding another layer of risk during sparse grazing.

Endophyte-infected fescue may accumulate ergovaline, a vasoconstrictive alkaloid associated with laminitis and pregnancy risk in mares.

- Practical winter prevention

• Limit grazing after drought-breaking rain.
• Use strip grazing, dry-lot time, or muzzles until grass has grown to 2–3" tall. Why?
• Because those first tiny green shoots are the most sugar-dense stage of growth. When grass is short, it has almost no leaf area for photosynthesis, so it relies heavily on stored fructans and sugars pulled up from the crown and roots. This makes the earliest regrowth after drought or cold snaps unusually high in NSC. Once the plant reaches around 2–3 inches, it starts using those sugars for actual growth instead of simply hoarding them – meaning NSC begins to stabilise and the metabolic risk drops.
• Offer plenty of hay so horses aren’t driven to eat weeds.
• Watch for early signs of hindgut unrest (gas, loose droppings).
• Test NSC if your pasture is unpredictable. How?
• Take small “scissor snips” from multiple spots in the field (mimicking what your horse grazes), mix them together, and freeze the sample immediately to lock in the sugars. Then send it to a forage lab that offers NSC testing (look for WSC + starch). Most UK labs provide a clear NSC percentage so you can compare it with hay your horse does well on. This gives you a realistic picture of the pasture’s sugar load during risky weather patterns.
• Support the hindgut and biome during transitional weather. How?
• Seasonal shifts can unsettle the hindgut, especially when grass sugars swing around. Offering steady biome support helps keep things balanced. SiboCARE is ideal for horses needing deeper digestive support during unsettled periods, while BiomeTonic provides everyday microbial nourishment to help maintain a resilient, well-functioning gut environment.

❄️ Part 2 – Cold-induced hoof pain

- A second winter syndrome – brilliantly described by Dr Eleanor Kellon, VMD (26 December 2024)

Not all winter hoof pain is metabolic or inflammatory. Dr Kellon describes a distinct syndrome often mislabelled as laminitis but rooted in circulatory dysfunction, not inflammation.

- When hooves react badly to cold

Most horses feel bright and energised in cold weather. But some – particularly EMS horses – experience:

• sudden, severe hoof pain
• reluctance to move
• a stance that resembles laminitis
• no heat, no pulse, no radiographic change

For some, the threshold is surprisingly mild – as warm as 4°C.

- What’s actually happening?

Cold weather naturally reduces blood flow to the limbs – it’s the body’s way of conserving heat. The hoof manages this using tiny 'bypass channels' called arteriovenous shunts, which divert blood away from the tissues and straight back toward the core when temperatures drop.

In most horses, these shunts don’t stay open for long. The body periodically sends warm, oxygenated blood back into the hoof to keep the tissues healthy.

But in susceptible horses – typically those with EMS, insulin resistance, a past history of laminitis, or generally sensitive circulation – this re-warming process doesn’t happen as it should. Their blood vessels simply don’t respond efficiently to cold. The shunts stay open for too long, the hoof tissues miss out on oxygen and nutrients, and circulation falls below their personal tolerance level.

When that happens, the feet become painful very quickly. Movement slows or stops altogether until the horse warms up again and blood flow returns to normal.

- Support strategies (Dr Kellon’s recommendations)

These focus on supporting circulation:

• Jiaogulan → stimulates nitric oxide, a potent vasodilator *We're currently not able to supply the J-herb – our three suppliers are no longer able to source it, but shop around – it’ll be out there somewhere.
• Arginine, citrulline & folate → support endogenous nitric oxide production
• Rugging → reduces the need for shunting blood away from the limbs
• Leg wraps → lined shipping boots work especially well
• Wool socks inside hoof boots → keep coronary bands & heels warm

With warmth and circulation support, the pain usually resolves quickly and completely.

Bringing it all together – a safer winter for sensitive horses

Winter laminitis is not a myth – it’s a physiological reality, driven by:

• drought-stressed grasses
• sudden rainfall
• cold, clear days with bright sun
• low-growth pastures rich in stored NSC
• weed foraging
• microbial disruption
• and, in some horses, circulatory dysfunction once temperatures drop

Understanding these mechanisms means you can plan ahead, rather than react later.

A huge thank-you to Dr Eleanor Kellon, VMD, whose decades of work on metabolic horses have transformed how we recognise winter hoof syndromes and protect the most vulnerable.