Why Fibre Is Not Just Nutrition, It Is Thermoregulation

One of the most overlooked truths in horse care is that fibre is not simply food.

Fibre is not filler.

Fibre is not “roughage.”

Fibre is warmth.

In the horse, fibre is part of thermoregulation, the horse’s ability to stay warm from the inside out.

The Horse Has an Internal Heater

Horses are hindgut fermenters.

The caecum and large colon are not just digestive chambers, they are fermentation engines.

Microbial fermentation breaks down fibrous plant material, extracting usable energy.

But fermentation also produces heat.

That heat is not incidental.

It is part of the horse’s intelligent design.

The horse is warmed internally, through the steady work of fibre fermentation.

Summer and Winter Forage Are Not the Same

Nature is extraordinarily precise.

In summer, grasses are often more nutrient-dense and easier to digest.

Less bulky fibre needs to be retained for long fermentation.

Energy is extracted efficiently, and internal heat loading is naturally lower.

In winter, pasture quality declines.

Fibre becomes tougher, less concentrated, more weathered.

The horse compensates by holding more fibrous material in the hindgut for longer fermentation.

The result is more internal heat production.

This is one of nature’s ways of warming the horse from within.

The Winter Hay Mistake

I have had countless calls from northern states, Minnesota, Pennsylvania, the Dakotas, New York, where people say:

“My horses are cold and shivering in winter, even though they are well fed.”

And my first question is almost always:

“I bet you are feeding them beautiful spring-cutting hay, aren’t you?”

And the owners respond with pride:

“Nothing but the best. Highest quality. Rich, soft, premium hay.”

Here is the problem.

In winter, horses do not naturally eat spring pasture.

They eat weathered forage.

They eat tougher, more fibrous material.

Material that stays in the hindgut longer.

Material that ferments longer.

Material that produces warmth.

Weathered Hay Can Be a Gift

In cold climates, feeding some more weathered, stemmy hay can actually support the horse’s natural internal heating rhythm.

It is often cheaper.

It is often more seasonally appropriate.

And owners are consistently amazed when, within a week or two, they say:

“I cannot believe it. My horses are not shivering anymore.”

This is not magic.

It is fermentation biology.

Fibre is heat.

Fibre Supports the Whole Horse

This is why fibre-first feeding is not just nutrition.

It supports:

Digestive stability

Behavioural steadiness

Natural metabolic rhythm

Internal warmth in winter

The horse was designed to be heated from within by fermentation.

Final Thought

Fibre is not just nutrition.

Fibre is thermoregulation.

The hindgut is the horse’s internal heater, adjusting naturally with the seasons.

When we feed in alignment with that design, the horse becomes more resilient, more comfortable, and more settled.

Because horses have not changed.

Nature built them brilliantly.

Our job is simply to stop fighting that design.