Freestyle SportHorse Stud

23/10/2026

28/09/2026

Part 2 on genetics 

🧬🐴 GENETICS 101 — PART 2

7 GENETIC CONDITIONS EVERY QUARTER HORSE BREEDER SHOULD KNOW ABOUT

Last time we talked about what N/N, N/Variant and Variant/Variant actually mean.

Now let's get into the diseases themselves.

Because here's the truth:

“7 Panel Negative” sounds great… but if you don't know WHAT was tested, you don't really know what you're looking at.

So let's break it down. 👇

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🧬 1. GBED

Glycogen Branching Enzyme Deficiency

GBED is a fatal inherited disorder involving glycogen storage.

Glycogen is how the body stores energy.

With GBED, the horse cannot properly form glycogen because of a mutation affecting the glycogen branching enzyme.

The result can be catastrophic.

Affected foals may be aborted, stillborn, or born with severe problems including weakness, low blood sugar and muscle abnormalities.

THE GENETICS:

N/N
✅ No GBED variant detected
✅ Cannot pass the variant to offspring

N/GBED
🧬 Carrier
✅ Generally not affected
⚠️ Can pass the variant to approximately 50% of offspring

GBED/GBED
❌ Affected
❌ Fatal condition

Two carriers bred together have approximately:

25% N/N
50% carriers
25% affected

That 25% affected number is why knowing the genetics of BOTH parents matters.

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🧬 2. HERDA

Hereditary Equine Regional Dermal Asthenia

HERDA is a connective-tissue/skin disorder primarily associated with Quarter Horses.

Affected horses can develop:

❌ Extremely fragile skin
❌ Hyperextensible skin
❌ Severe lesions
❌ Scarring
❌ Skin separation, particularly along the back

The underlying mutation affects a protein involved in collagen formation.

And here's something important:

A CARRIER DOES NOT HAVE TO LOOK SICK.

N/N
✅ Not affected
✅ Cannot transmit the tested variant

N/HRD
🧬 Carrier
✅ Generally unaffected
⚠️ Can transmit the variant to approximately 50% of offspring

HRD/HRD
❌ Affected

Two carriers:

25% affected
50% carriers
25% N/N

That is classic recessive inheritance.

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🧬 3. HYPP

Hyperkalemic Periodic Paralysis

HYPP is different.

It is a muscle disorder associated with the well-known Impressive bloodline.

Horses carrying the HYPP variant can experience episodes involving:

⚠️ Muscle tremors
⚠️ Weakness
⚠️ Sweating
⚠️ Muscle spasms
⚠️ Collapse or paralysis

The frequency and severity of episodes can vary, and diet and exercise can influence clinical signs.

THE GENETICS:

N/N
✅ Not affected by the HYPP variant
✅ Cannot transmit it

N/H
⚠️ Can have episodes
⚠️ Can transmit the variant to approximately 50% of offspring

H/H
⚠️ Can be more severely affected
⚠️ Passes the variant to 100% of offspring

And this is an important distinction:

HYPP is NOT a simple “carrier” situation like HERDA or GBED.

A horse with one copy can potentially show disease.

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🧬 4. MH

Malignant Hyperthermia

This one deserves serious attention because MH can be triggered by certain situations, including certain anesthetics, and can cause a dangerous hypermetabolic reaction.

Clinical problems can include:

🔥 Dramatically increased body temperature
💪 Muscle contracture
❤️ Abnormal heart rhythm
⚠️ Potentially life-threatening complications

And here's the important genetic difference:

A horse with ONE copy of the MH variant can be susceptible.

So:

N/N
✅ No tested MH variant

N/MH
⚠️ Susceptible to malignant hyperthermia

MH/MH
⚠️ Also affected/susceptible

Breeding an N/MH horse to an N/N horse produces approximately:

50% N/N
50% N/MH

That's why knowing the actual genotype matters.

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🧬 5. PSSM1

Polysaccharide Storage Myopathy Type 1

Now we're getting into one a LOT of horse people have heard about.

PSSM1 is a muscle disorder involving abnormal glycogen accumulation.

Possible clinical signs can include:

💥 Muscle soreness
💥 Stiffness
💥 Weakness
💥 Sweating
💥 Muscle twitching
💥 Reluctance to move
💥 Muscle damage/rhabdomyolysis

And here's where PSSM1 gets interesting:

PSSM1 is considered an autosomal dominant condition.

That means one copy can be associated with disease.

RESULTS:

N/N
✅ No PSSM1 variant
✅ Cannot transmit it

N/PSSM1
⚠️ May develop signs
⚠️ Can pass the variant to approximately 50% of offspring

PSSM1/PSSM1
⚠️ May have more severe disease
⚠️ Passes the variant to 100% of offspring

AND…

PSSM1 is NOT the explanation for every horse with abnormal muscle glycogen.

There are horses with muscle disease that do not have the PSSM1 variant.

So:

PSSM1 testing is useful… but it isn't a magic “muscle disease detector.”

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🧬 6. MYHM

Myosin-Heavy Chain Myopathy

MYHM is particularly interesting because it can involve two different clinical presentations:

🔹 Immune-mediated myositis
🔹 Non-exertional rhabdomyolysis

One can involve significant muscle loss, while the other can involve muscle damage.

The genetic situation is also different from a classic recessive disease.

UC Davis describes MYHM as autosomal codominant with variable penetrance.

In plain English?

Having the variant doesn't mean every horse will develop the exact same clinical disease.

RESULTS:

N/N
✅ No increased susceptibility from the tested MYHM variant
✅ Cannot transmit it

N/My
⚠️ May develop MYHM
⚠️ Can transmit the variant to approximately 50% of offspring

My/My
⚠️ May develop a more severe form
⚠️ Passes the variant to 100% of offspring

Researchers have also found that environmental triggers can play a role in horses that develop clinical signs.

So this isn't simply:

“Positive = sick.”

Genetics and environment can interact.

---

🧬 7. EJSCA

Equine Juvenile Spinocerebellar Ataxia

This one is particularly important because it's newer to the genetic-testing conversation.

EJSCA is an inherited neurologic disease identified in American Quarter Horse foals.

Affected foals develop:

⚠️ Ataxia/incoordination
⚠️ Severe hind-limb involvement
⚠️ Progressive difficulty standing
⚠️ Eventually inability to stand without assistance

The typical onset is extremely young:

Approximately 1–4 weeks of age.

EJSCA is inherited as an autosomal recessive condition.

RESULTS:

N/N
✅ Not affected
✅ Cannot transmit the tested variant

N/JSA
🧬 Carrier
✅ Not affected
⚠️ Can transmit the variant to approximately 50% of offspring

JSA/JSA
❌ Affected

Two carriers:

25% N/N
50% carriers
25% affected

This is one reason genetic testing continues to evolve.

New diseases and new genetic variants are still being identified.

---

🚨 HERE'S THE PART I REALLY WANT HORSE PEOPLE TO UNDERSTAND:

“NEGATIVE” DOESN'T MEAN “NOTHING CAN EVER GO WRONG.”

Genetic testing is incredibly useful.

But it only answers the questions the test was designed to answer.

A horse can test negative for every tested genetic disease and STILL develop:

❌ Arthritis
❌ Lameness
❌ Colic
❌ Injury
❌ Ulcers
❌ Respiratory disease
❌ Training problems
❌ Conformational problems
❌ Other diseases that aren't part of that genetic panel

Genetic testing is one piece of the puzzle.

It does NOT replace:

🩺 Veterinary care
🩻 Radiographs when appropriate
🩺 Pre-purchase examinations
🐴 Good breeding decisions
📋 Accurate pedigree information
👀 Evaluation of conformation
🏆 Performance history

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🤯 AND HERE'S SOMETHING THAT SHOULD MAKE EVERY BREEDER PAY ATTENTION:

THE WORD “CARRIER” DOES NOT AUTOMATICALLY MEAN “BAD HORSE.”

For recessive diseases, a carrier can be completely healthy.

The problem comes when breeders don't know what the horse carries and accidentally breed two carriers of the same recessive disease together.

A carrier may still have:

🏆 Excellent performance
🧬 Exceptional pedigree
🦵 Good conformation
🧠 Great mind
🐴 Outstanding athletic ability

The answer isn't necessarily:

“Never breed a carrier.”

The answer is:

KNOW WHAT YOU HAVE AND MAKE THE BREEDING DECISION WITH THE GENETICS IN MIND.

That's responsible breeding.

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🧬 AND ONE MORE VERY IMPORTANT POINT:

“7 PANEL NEGATIVE” IS NOT A UNIVERSAL MAGIC PHRASE.

Ask:

“Which seven tests?”

Because panels can differ.

For example, UC Davis currently offers a Quarter Horse & Related Breeds panel containing:

GBED
HERDA
HYPP
MH
PSSM1
MYHM

And EJSCA is available as an additional test.

So don't just look at:

🚨 “7 PANEL NEGATIVE!”

Ask to see the actual laboratory report.

Know exactly what was tested.

Know exactly what the genotype means.

And know how those results affect the potential breeding.

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🐴 SPINNING B EQUINE BELIEVES:

GOOD BREEDING ISN'T JUST ABOUT MAKING A PRETTY BABY.

It's about making informed decisions.

Pedigree.

Conformation.

Temperament.

Athletic ability.

Soundness.

Performance.

Health.

AND GENETICS.

Because every breeding decision is putting together two sets of DNA…

and hoping to create something better than what you started with.

That's the responsibility that comes with breeding.

👇👇👇

NOW LET'S HEAR FROM THE BREEDERS:

Which genetic condition do you think horse owners misunderstand the MOST?

And be honest…

Did you know that PSSM1, HYPP and MYHM don't follow the same simple recessive “carrier = unaffected” pattern as diseases like HERDA, GBED and EJSCA?

Drop your answer below. 👇

SHARE THIS POST.

The more horse owners understand genetics, the better decisions they can make for the next generation.

🐴🧬 SPINNING B EQUINE

28/09/2026

A good read on genetics and what you really should be considering 

🧬🐴 GENETICS 101: “7 PANEL NEGATIVE” DOES NOT MEAN WHAT A LOT OF PEOPLE THINK IT MEANS.

Let’s talk about something that gets thrown around in horse ads all the time:

GENETIC TESTING.

We see “5 Panel N/N,” “7 Panel Negative,” “DNA tested,” and “clear” constantly.

But do you actually know what those results mean?

Because there is a HUGE difference between understanding a genetic test and simply looking at the word NEGATIVE.

👇 Here’s the crash course from Spinning B Equine.

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🧬 FIRST: WHAT IS A GENETIC TEST?

A genetic test looks for specific DNA variants that scientists have identified and associated with a particular inherited disease or trait.

Your horse's DNA doesn't change because the horse gets older.

A horse can be tested as a foal, yearling, adult or senior. DNA testing can be performed from samples such as hair with intact roots, blood or tissue, depending on the laboratory's requirements.

So no…

A 2-year-old doesn't need to be retested at 10 years old because its genetics “changed.”

They didn't. 😂

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🧬 WHAT DOES “N/N” MEAN?

For many recessive genetic diseases, a horse receives one copy of a gene variant from each parent.

Think of it like this:

N/N = no tested variant detected

N/Variant = carrier

Variant/Variant = affected

But here's where things get REALLY important…

A carrier isn't necessarily a sick horse.

For an autosomal recessive condition, a carrier typically has one copy of the variant and one normal copy and may appear completely healthy.

That carrier can still pass the variant to its offspring.

That's why testing BOTH parents can be incredibly important when breeding.

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🚨 HERE'S THE 25% FACT THAT EVERY BREEDER SHOULD KNOW:

If you breed:

N/N × N/N

➡️ 0% affected
➡️ 0% carriers for that variant

If you breed:

N/N × N/Variant

➡️ 0% affected
➡️ approximately 50% N/N
➡️ approximately 50% carriers

If you breed:

N/Variant × N/Variant

➡️ approximately 25% N/N
➡️ approximately 50% carriers
➡️ approximately 25% affected

THAT LAST ONE IS WHY GENETIC TESTING MATTERS.

A perfectly healthy-looking mare and a perfectly healthy-looking stallion can both carry the same recessive mutation.

Put them together…

…and genetics doesn't care how pretty the parents are. 😳

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🧬 SO WHAT IS THE “5 PANEL”?

The traditional AQHA five-panel testing program evaluates five inherited conditions:

🔬 GBED — Glycogen Branching Enzyme Deficiency
🔬 HERDA — Hereditary Equine Regional Dermal Asthenia
🔬 HYPP — Hyperkalemic Periodic Paralysis
🔬 MH — Malignant Hyperthermia
🔬 PSSM1 — Polysaccharide Storage Myopathy Type 1

These conditions aren't all inherited in exactly the same way, and they don't all behave the same clinically.

That's important.

“5 Panel” isn't one disease.

It's a group of separate genetic tests.

And modern testing has expanded beyond the original five-panel concept.

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🧬 WHAT ABOUT “7 PANEL”?

This is where you need to READ THE ACTUAL RESULTS.

Different laboratories and registries may offer different panels containing different tests.

For example, additional testing may include conditions such as:

➡️ MYHM
➡️ EJSCA
➡️ additional breed-specific genetic diseases
➡️ coat-color genes
➡️ white-pattern genes
➡️ other inherited conditions

So when somebody says:

“7 Panel Negative.”

Don't automatically assume you know which seven tests they mean.

ASK TO SEE THE ACTUAL RESULTS.

That's not being difficult.

That's being an educated horse buyer.

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🧬 GENETICS ≠ A VETERINARY PRE-PURCHASE EXAM

THIS ONE IS HUGE.

A horse can be:

✅ N/N on every test performed

…and still have:

❌ a bad leg
❌ arthritis
❌ ulcers
❌ a breathing problem
❌ poor conformation
❌ an old injury
❌ a training issue
❌ a lameness problem
❌ behavioral problems

Genetic testing tells you about the specific genetic variants being tested.

It does NOT replace a veterinarian.

It does NOT replace a pre-purchase examination.

And it certainly doesn't guarantee a horse will never develop a medical problem.

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🧬 DNA TESTING ALSO ISN'T JUST ABOUT DISEASE.

Genetics can help determine things like:

🎨 Coat color
🧬 Parentage
🐴 Certain coat patterns
🧬 Certain performance-associated traits
🧬 Specific inherited disorders

For example, coat color itself is influenced by multiple genes.

A chestnut, bay, black, palomino, buckskin, dun or other color isn't simply a matter of “what the parents look like.”

You're looking at combinations of genetic variants.

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🤯 HERE'S ANOTHER FACT:

A HORSE CAN CARRY A GENETIC VARIANT WITHOUT LOOKING LIKE IT.

That's one of the biggest reasons genetic testing has become such an important tool for responsible breeding.

You can't always look at a horse and determine what it carries.

You need the DNA.

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🧬 AND HERE'S SOMETHING ELSE PEOPLE DON'T REALIZE:

A genetic test is only testing for WHAT IT WAS DESIGNED TO TEST FOR.

If a horse tests N/N for a particular disease…

that does NOT mean:

“This horse has no genetic mutations whatsoever.”

It means the horse tested negative for the specific variant(s) included in that particular test.

There are thousands upon thousands of genetic variants in a horse.

Science hasn't identified every genetic cause of every disease.

So…

“Genetically tested” ≠ “genetically perfect.”

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🐴 AT SPINNING B EQUINE, WE BELIEVE BREEDERS SHOULD KNOW WHAT THEY'RE BREEDING.

We're not interested in hiding behind fancy pedigrees, pretty pictures or the phrase:

“He's a great breeding horse.”

If you're breeding, you should know:

🧬 Who the parents are
🧬 What genetic tests have been performed
🧬 What the results actually mean
🧬 What your mare carries
🧬 What your stallion carries
🧬 What combinations could produce an affected foal
🧬 And what additional testing may be appropriate for your particular breeding program

Because breeding isn't just:

“That horse is pretty. Let's breed it.”

It's genetics, conformation, health, temperament, athletic ability, pedigree, performance, and responsible decision-making.

And sometimes…

the best breeding decision is NOT making a particular cross.

That's part of responsible breeding.

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👇 NOW WE WANT TO HEAR FROM YOU:

Be honest…

Did you know what “N/N,” “carrier,” and “affected” actually meant before reading this?

And breeders:

What genetic test do you think EVERYONE breeding Quarter Horses should understand better?

Drop it below. 👇

And SHARE this post.

There are a LOT of horse buyers and breeders out there who see:

“7 PANEL NEGATIVE”

and have absolutely no idea what they're actually looking at.

Let's make educated horse people instead of just people who know how to read a sales ad. 😂🐴

— Spinning B Equine

23/09/2026

This is what not to do, if you feel uneasy foaling, have a vet present, for both the mare and foal.

A textbook foaling can turn into a complete nightmare the instant h...

12/09/2026

22/08/2026

With breeding season starting this month, now is the perfect time to refresh yourself about diseases that can affect broodmares🐴 🦠

Today we are going to focus on Equine Herpesvirus Type 1 (EHV-1) and Strangles (Streptococcus equi, subspecies equi).

EHV-1 is a serious threat to broodmares, known for causing late-term abortions, neonatal foal death, and neurological disease. Prevention is key, and that starts with vaccination, supported by on farm biosecurity.
EHV-1 can linger silently in horses and re-emerge under stress. Staying ahead with proactive care keeps your mares - and foals - safe.
While EHV-1 is particularly serious in broodmares due to the risk of late-term abortion, any horse under stress: whether from travel, illness, social stressors, or environmental changes, can shed the virus. This shedding can occur even in horses that appear healthy, making them silent carriers and a potential source of infection for others in the herd. That’s why biosecurity and vaccination protocols are essential not just for pregnant mares, but for all horses on the property.

Vaccination Matters - Broodmares should be vaccinated at 5, 7, and 9 months of gestation using a vaccine specifically labelled for abortion protection. Annual boosters for all horses on the property help reduce viral shedding and protect the herd.

Strangles is one of the most contagious bacterial diseases of horses and can spread quickly through breeding farms, agistment properties, sales complexes, and youngstock operations. Foals, weanlings, and yearlings are particularly susceptible, and outbreaks can lead to illness, disrupted training and sales preparation, and can have significant management costs.
Strangles spreads easily through direct horse-to-horse contact, as well as contaminated equipment, water sources, vehicles, clothing, and handlers. Good biosecurity practices, including quarantine of new arrivals, monitoring horses for fever, and prompt isolation of sick horses, are essential for reducing the risk of an outbreak.

While young horses are often most affected, any horse can become infected and some may continue to carry the bacteria after they appear clinically recovered. These silent carriers can unknowingly introduce infection into a herd, making veterinary testing and strong biosecurity protocols important for all horses on the property.

Vaccination can help reduce the severity of disease and decrease bacterial shedding, making it a useful tool for properties with a higher risk of exposure. Broodmares should have a strangles (and tetanus) booster four to six weeks before foaling.

06/08/2026

🥶❄ Frosty mornings = higher laminitis risk? Here's why...

As we're sure you've all been feeling, the cold snaps and frosts have well and truly arrived across New Zealand!

Not only does this mean digging out five layers of clothing ... it also means it's time to pay extra attention to your horse's grazing. 🌱

When we get frosty mornings followed by bright, sunny days, grass can accumulate higher levels of sugars (non-structural carbohydrates). During the day, grass produces sugars through photosynthesis. Normally, it uses these sugars overnight to grow. However, when overnight temperatures drop below around 5°C, grass growth slows dramatically, meaning those sugars remain stored in the plant.

The result? Grass can contain significantly higher sugar levels, particularly during the morning after a frost.

For horses and ponies that are overweight, have a history of laminitis, are insulin resistant, or are considered "good doers," this sudden increase in sugar intake can significantly increase the risk of a laminitic episode.

How can you help reduce the risk?

✅ Limit grazing for at-risk horses, especially following frosty nights.
✅Consider using a well-fitted grazing muzzle.
✅ Provide low-sugar hay to reduce the urge to gorge on pasture.
✅ Maintain a healthy body condition and regular exercise where appropriate.
✅ Keep a close eye out for early signs of laminitis, including:
- Reluctance to move
- Increased heat in the feet
- Strong digital pulses
- Shifting weight between feet or standing rocked back

If you're concerned your horse may be at risk, or you'd like advice on managing pasture during winter, get in touch with our team. A few simple management changes now could help prevent a very painful condition later.

Stay warm out there and give those frosty paddocks a little extra respect this winter! ❄💙

08/07/2026

Oh yes

08/07/2026

Hi everyone. As some of you may be aware, I have recently taken on a part-time role as Head of Equine Services for the NZVA, and as part of that role, I have been involved in communications with both our veterinary members and horse owners across NZ. I just want to reassure you that we are not concerned about a widespread outbreak, but vigilance is still needed around Thoroughbred horses moving from the Waikato. This little flowchart our team has put together should be very helpful. Thank you to all my Worm-Ed clients for your understanding regarding the postponements of my regular appointments this week. A hot tip is to jump onto the New Zealand Equine Health Association's page for the most up-to-date resources and a tally of properties affected.