Show me a horse carer who isn't obsessed with our UK weather.

Us humans are lucky. We can add another layer, turn the heating up, peel off when the sun finally appears, or head for the shade (or a pool) when it's roasting.

Our horses, meanwhile, rely largely on their own brilliant, self-regulating thermoregulatory system instead – and twice a year, that includes changing an entire coat.

And while that in-built system is pretty amazing, our weather certainly likes testing it. One minute we're wondering whether summer is ever going to arrive; the next we're melting in 30+°C and our horses are already beginning to look suspiciously... hairy.

Because here's the interesting bit. Coat growth doesn't simply wait for the weather to change. Shortening daylight is one of the major signals controlling the seasonal hair cycle, which is why that winter coat can already be secretly underway while we're still melting in August.

And although coat change is completely normal physiology, that doesn't mean it asks nothing of the body. In fact, underneath all that apparently innocent fluff, there's a whole lot going on.

But first... I need to revisit one little word: detox

If you’ve read my previous Coat Change posts, you'll no doubt have heard me describe coat change as a "metabolic and detox event".

And there was good reason for that thinking. Growing a coat requires active metabolism - protein and amino-acid handling and turnover produces metabolic by-products - which means the liver, kidneys and lymphatic system all have important everyday jobs in processing, excretion and tissue-fluid balance. None of this has changed.

What has changed is how I'd now describe the bigger picture - because I've been revisiting the biology, and these days I don't think “coat change = detox event” is quite the right way to frame what's happening.

Your horse isn't suddenly filling up with old-hair “toxins” that their liver has to frantically clear. The old hair shaft we're grooming onto ourselves, the yard, our car seats and into our underwear is already dead, keratinised tissue. 😂

But – and this bit really matters – correcting this thinking also doesn't mean thinking back to hair grows, it's normal, so nothing much to see here.

Because… normal physiology can still ask quite a lot from the body – and the coat change is a perfect example.

So what IS actually going on?

Twice a year – spring and autumn – the hair follicles shift through their seasonal cycle of growth and rest.

And those follicles aren't passive little holes that hairs happen to fall out of. They're metabolically active little factories, supplied by living tissue underneath the skin and busy producing an entirely new covering of protein-rich hair. Which means…

They need raw materials.

Hair is predominantly keratin, a structural protein. So to manufacture a new coat, the horse needs an adequate supply of good-quality dietary protein and the right amino acids.

Then we have the supporting cast:

1.      Sulphur-containing amino acids, particularly cysteine, are important to keratin's structure and strength.

2.      Zinc and copper are among the trace minerals involved in healthy skin and hair production.

3.      Essential fatty acids, i.e. micronized linseed, help support healthy skin and normal inflammatory balance.

4.      And meanwhile, amino acids and proteins are continually being used, recycled and broken down throughout the body.

This protein metabolism naturally creates nitrogenous waste, including urea, which needs to be processed and excreted.

So yes... the liver and kidneys are still very much in this story. Just perhaps not for quite the reason I've historically described.

Normal physiology – but metabolically active physiology

This is the distinction I think matters.

Growing a new coat isn't a pathological process that needs fixing or "cleansing". But it’s also not metabolically insignificant.

The horse is changing hair-follicle activity, synthesising substantial amounts of new keratinised tissue, supplying amino acids and micronutrients to that process, and carrying on with all the normal metabolic housekeeping that goes alongside nutrient use and protein turnover.

And they're not doing any of this in a lab - they're doing it while February or September is happening to them.

Daylight is changing, temperatures shift, grass quality and availability may change. Meanwhile hay supply either reduces or increases in the diet, and activity levels may increase as temperatures fall – or decrease as fields become wetter and turnout changes.

And there's another important seasonal shift happening too: ACTH naturally rises, particularly relevant to our older and PPID horses.

So no, coat change isn't just hair. It's happening within a much wider seasonal adjustment involving nutrition, metabolism, skin, gut health, thermoregulation, and the individual horse's own ability to adapt.

And that's where some horses may begin to show us that they have rather less nutritional wriggle-room than others.

Why does one horse sail through while another really struggles?

You know the horse.

One minute sleek summer pony; seemingly three minutes later, fabulous winter woollies. No drama, no noticeable dip, barely a brush required.

Meanwhile, the horse next door looks as though several different coats have been glued onto them at random.

They're dull, they're itchy or scurfy, they're taking forever to shed, they may be a little flat or grumpy – and their coat just doesn't have its normal healthy bloom that we’re used to seeing.

That doesn't necessarily mean the coat change itself is the problem - sometimes the seasonal transition simply makes an existing nutritional or metabolic weak spot easier to see. An older horse may have less resilience than they once did, a horse with compromised gut health may not be getting the same nutritional value from their diet, or the metabolically challenged horse has other seasonal changes going on.

Meanwhile, another may simply be sitting close to the margins for quality protein, amino acids or essential micronutrients – and growing an entirely new coat makes those margins more apparent.

That's why, rather than previously asking, “How do I detox my horse through coat change?” iIt’s more about:

“What does the body need to do this well – and where might my horse need some extra support?”

What if my older horse isn't shedding properly?

A slightly slower coat change in an older horse can reflect age, nutrition, changing metabolic resilience or individual variation.

But if an older horse is retaining an unusually long, thick or curly coat, shedding very late, or showing other changes such as increased drinking/urination, muscle loss or altered fat distribution, it's worth speaking to your vet about PPID rather than assuming it's simply a difficult coat change.

So where DO the liver, kidneys & lymph fit in?

Ahhh, my beloved 3-Amigos.

Don't worry - they're not getting their P45s; we just need to give them their correct job descriptions.

• Protein and amino acids are continually being used, recycled and broken down.
• Nitrogen from amino-acid metabolism has to be handled safely, with the liver playing a central role in that metabolism, and nitrogen ultimately converted into forms including urea that can be eliminated.
• The kidneys continually filter the blood and excrete urea and other metabolic waste products.
• Meanwhile, the lymphatic system calmly goes about its everyday business, helping maintain tissue-fluid balance and transporting fluid, proteins and immune cells around the body.

Normal metabolism never happens without normal metabolic housekeeping alongside it. But - does growing a winter coat automatically mean the liver becomes flooded with old-hair toxins, or the kidneys face a huge excretion crisis, or the lymph fills up with residual protein waste?

That's the part I'd describe a bit differently now.

For most healthy horses with good nutritional foundations, the body is perfectly well  equipped to manage normal coat turnover all by itself. This is an important distinction from the older “toxin overload” framing.

Where I become more interested in additional support is the horse who doesn't sail through the transition so happily – particularly where their coat is only one part of a wider picture.

Before supplements - give the body something to build with

This bit hasn't changed at all - foundations first, always.

No supplement can manufacture a fabulous new coat from building blocks that simply aren't there. Hair is mostly keratin, and keratin is protein. So look at the whole diet:

• Is your horse receiving enough good-quality protein?
• Do they have an appropriate amino-acid supply?
• Is their mineral balancer providing properly balanced zinc and copper?
• Are they receiving a useful source of omega-3 fatty acids?
• And what’s their gut health like?

This is particularly worth thinking about because at both coat change times the grass quality and availability are changing, and hay is either leaving – or coming back into – the diet.

In short?

Sometimes the most useful "coat supplement" isn't a coat supplement at all. It's fixing the nutritional gap underneath it.

And then there's sulphur...

Sulphur doesn't tend to get the same attention as zinc, copper, or protein, but when we're talking about hair, skin and hooves, it’s more than relevant.

Keratin is rich in the sulphur-containing amino acid cysteine, and the bonds formed between those sulphur groups contribute to keratin's strength and structure. Which is why sulphur nutrition is important when we're looking at healthy hair, coat, skin, connective tissue, and hoof horn.

But another little caution here. A poor coat doesn’t automatically mean your horse is sulphur deficient. Protein quality, amino-acid balance, zinc, copper, essential fatty acids (linseed), overall diet, age and underlying health – all can influence what eventually appears on the outside.

Again, we're back to the whole horse.

If it was me?

Once I'm happy with the foundations, this is where I'd start thinking about the individual horse.

And interestingly, when we pull the biology apart properly, the three products we've historically used around coat change suddenly become much easier to explain – because they aren't all trying to do the same job.

• MSM  provides a bioavailable source of organic sulphur, supporting the wider nutritional picture around healthy hair, skin, connective tissue and hoof structure.
• L-Glutamine is heavily used by rapidly renewing tissues, as well as its important role in supporting normal gut-barrier integrity. For the horse where coat quality may be reflecting a wider nutritional or digestive picture, that's where it becomes particularly useful.
• And LKLCARE? Still the core blend for the coat change, if the horse is older, metabolically challenged, struggles through seasonal transitions, or their coat hints at needing wider support for normal liver, kidney and lymphatic function.

Three products. Three different jobs. Which coincidentally is precisely why we've now put the three together as our CoatCOMBO, with our usual 5% SmartShopping COMBO saving.

(Yes, you guessed right - I accidentally invented a new product while writing this! But actually, that's the way round I like it. Understand the biology first – then let the biology earn the product.)

And don't forget the fats

Essential fatty acids (EFAs) are another part of the healthy skin-and-coat picture, so if your horse isn't already receiving a useful omega-3 source, micronised linseed is one of the simplest additions to make.

You don't need anything fancy here. A straightforward bag of micronised linseed added to the daily feed at around 20g per 100kg BW does the job nicely – and is considerably more economical than us putting enough of it into CoatCOMBO to make a meaningful difference!

Bottom line?

Your horse's seasonal coat change is normal, it's clever, and most horses manage it beautifully.

• A coat change requires active follicles, protein synthesis, amino acids, micronutrients, and normal metabolic processing.
• The liver matters, the kidneys matter, lymphatic circulation matters.
• Nutrition absolutely matters.

But - normal physiology can still be nutritionally and metabolically demanding - and all of this happens against the backdrop of changing daylight, forage, activity and temperatures.

So rather than thinking "coat change = detox", these days I'm more about "support the biology".

Get the protein right, balance the minerals, support the gut, add sulphur and omega-3s. And if your horse is older, metabolically challenged, or simply doesn't sail through seasonal transitions as easily as they once did, that's where some thoughtful, targeted support for the wider picture can make sense with wider liver, kidney and lymphatic support.

Sometimes it’s not the coat itself that’s the problem - it's simply where the wider picture becomes visible.