What is the difference between LP/LP and LP/lp horses?

LP/LP (homozygous) expresses stronger, more extensive patterning than LP/lp (heterozygous), and passes LP to 100% of offspring. LP/lp passes LP to approximately 50% of offspring from a non-LP mare. LP/lp horses range from subtle to boldly patterned depending on PATN1; LP/LP horses tend toward FewSpot or near-FewSpot with sufficient PATN1.

Does LP/LP cause night blindness in horses?

LP/LP horses have Congenital Stationary Night Blindness (CSNB), a stable, non-progressive condition affecting vision in dim or dark conditions. The same TRPM1 gene pathway disrupted by LP in the skin also affects retinal signal processing in LP/LP horses. Daytime vision is normal. LP/lp horses are not affected at the same level.

Is night blindness in LP/LP horses progressive?

No. CSNB in LP/LP horses is congenital and stationary — it is present from birth and does not worsen over time. It is not a degenerative condition. The horse does not progressively lose vision; the dim-light limitation is stable throughout its life.

Can LP/LP horses compete in sport?

Yes. LP/LP horses compete successfully across equestrian disciplines. CSNB affects dim-light vision only; in well-lit arenas and competition environments, LP/LP horses perform without measurable visual disadvantage. Appropriate management — avoiding sudden dark transitions, stable familiarisation — accommodates the condition effectively.

What is TRPM1 and how does it relate to LP?

TRPM1 (Transient Receptor Potential Melastatin 1) is the gene associated with the LP mutation. It is expressed in pigment-producing melanocytes, and when disrupted by LP, it alters normal pigmentation to produce Appaloosa patterns. The same gene is expressed in retinal ON bipolar cells, which is why LP/LP horses also have CSNB.

How is LP/LP inherited?

LP follows standard Mendelian inheritance. To produce a LP/LP foal, both parents must carry at least one LP allele. If both parents are LP/lp (heterozygous), the probability of LP/LP offspring is 25%. If one parent is LP/LP and the other LP/lp, the probability rises to 50%. If both parents are LP/LP, all offspring will be LP/LP.

Can a non-patterned horse carry LP?

No. A horse must carry at least one LP allele to show any Appaloosa characteristic. LP produces its effects even in a single copy (LP/lp); there is no hidden carrier state without visible Appaloosa traits in any form. If a horse shows no Appaloosa characteristics at all, it does not carry LP.

What breeds carry the LP gene?

The LP gene occurs naturally in Appaloosas, Knabstruppers, Norikers, and breeds derived from these or historically crossed with LP-carrying horses. Mainstream warmbloods, Thoroughbreds, and most other European sport horse breeds do not carry LP unless Appaloosa or Knabstrupper blood has been introduced.

Is there a commercial genetic test for LP genotype?

Yes. LP genotype testing is commercially available from accredited equine genetics laboratories, including the UC Davis Veterinary Genetics Laboratory. The test uses a hair or blood sample and produces definitive results — LP/LP, LP/lp, or lp/lp — typically within a few weeks.

Can a LP/LP horse have a non-patterned coat?

Not in the traditional sense. LP/LP horses always show some Appaloosa characteristics at minimum — mottled skin, striped hooves, visible white sclera. With very low PATN1 dosage, the visible coat pattern may be subtle (varnish roan or minimal blanket), but the physical Appaloosa markers remain detectable by examination.

Genetics

LP/LP Genetics

Q: What does LP/LP mean in horses?

LP/LP means a horse is homozygous for the Leopard Complex gene — it carries two copies of the LP allele, one from each parent. LP is the genetic switch that enables Appaloosa coat patterning. A LP/LP horse expresses the maximum possible patterning for its PATN1 genotype and passes LP to 100% of its offspring.

Q: Does LP/LP guarantee spotted offspring?

Yes. An LP/LP horse can only pass LP alleles to its foals — there is no lp allele to contribute. Every foal, regardless of the mare's colour or breed, will inherit one LP allele and will show at least some Appaloosa characteristic: spots, mottled skin, striped hooves, or visible white sclera.

Quick Answer

LP/LP is the homozygous form of the Leopard Complex gene. A horse with two LP alleles expresses maximum Appaloosa patterning (typically FewSpot with sufficient PATN1) and passes LP to 100% of offspring. LP/LP horses also carry Congenital Stationary Night Blindness — a stable, non-progressive condition affecting dim-light vision only.

LP/LP is the homozygous form of the Leopard Complex gene — the genetic foundation behind every spotted Appaloosa and Knabstrupper coat. A horse carrying two copies of LP passes the spotted gene to every single foal it produces, regardless of the mare's colour or breed. For breeders who want spotted offspring with certainty, LP/LP genetics is the starting point. It also comes with a known health consideration — Congenital Stationary Night Blindness — that every LP/LP owner and breeder should understand.

What Is the Leopard Complex (LP) Gene?

The Leopard Complex gene — locus symbol LP — is located on chromosome 1 of the horse genome. It is the primary genetic switch that enables Appaloosa patterning. Without at least one copy of LP, no horse — regardless of breed or parentage — can display Appaloosa characteristics: no spots, no mottled skin, no striped hooves, no white sclera.

LP is associated with the TRPM1 gene (Transient Receptor Potential Melastatin 1), which is expressed in pigment-producing melanocytes. When LP is present, TRPM1 expression is altered in a way that disrupts normal pigmentation across the body, allowing the characteristic Appaloosa patterns to emerge. This molecular mechanism, identified through equine genetics research, also has consequences in retinal tissue — which is the basis of CSNB in LP/LP horses.

LP/lp vs LP/LP: The Critical Difference

LP follows an incomplete dominance pattern of inheritance. A horse with a single copy of LP (LP/lp, heterozygous) will show Appaloosa characteristics — but the degree of patterning is variable and depends heavily on modifier genes, particularly PATN1. The same LP/lp horse might present as a bold leopard or a subtle snowflake.

A horse with two copies (LP/LP, homozygous) shows significantly stronger and more consistent patterning. With sufficient modifier genes, LP/LP horses typically present as FewSpot or near-FewSpot — bodies predominantly white with residual colour only on the face and lower legs. The patterning is more extreme because both alleles are driving the disruption of normal pigmentation.

The breeding consequence of this distinction is decisive. An LP/lp horse, when crossed with a non-LP mare, will produce approximately 50% LP foals and 50% non-LP (plain) foals. An LP/LP horse produces 100% LP foals — regardless of the mare's genetics. This is the core advantage of LP/LP in a breeding programme.

Feature	LP/LP	LP/lp
Typical pattern	FewSpot or near-FewSpot (with PATN1)	Blanket, leopard, near-leopard, or snowflake
LP passed to foals	100%	~50% (from non-LP mare)
CSNB	Yes — all LP/LP horses	Not at same severity
Appaloosa markers	Always present (mottled skin, striped hooves, white sclera)	Present, but may be subtle
Pattern intensity	Maximum for given PATN1 dosage	Intermediate for given PATN1 dosage

Offspring Probabilities at a Glance

Stallion	Mare	LP Foals
LP/LP	Any (lp/lp)	100%
LP/LP	LP/lp	100% (50% LP/LP)
LP/lp	Any (lp/lp)	~50%
LP/lp	LP/lp	~75% (25% LP/LP)
lp/lp	Any	0%

The top row is the key figure: an LP/LP stallion crossed with any non-patterned mare produces 100% LP-carrying foals. All will have some Appaloosa characteristic. None will be plain.

LP/LP and Congenital Stationary Night Blindness

One finding all LP/LP breeders and owners should understand is the established association between LP/LP homozygosity and Congenital Stationary Night Blindness (CSNB). Research has confirmed that LP/LP horses have a structural difference in the retina's ON bipolar cells — the same TRPM1 pathway affected by LP in the skin also plays a role in how the retina processes signals in low-light conditions.

CSNB is stationary and non-progressive. LP/LP horses see normally in daylight and ordinary artificial lighting. They do not experience worsening vision over time. The limitation is specifically in dim or dark conditions: objects that a horse with normal night vision would detect become harder to see. This can manifest as increased reactivity or uncertainty when moved into unfamiliar dark environments.

LP/lp (heterozygous) horses are not affected to the same extent — the CSNB association is specifically linked to LP/LP homozygosity. This does not prevent LP/LP horses from competing or breeding at high levels. Many LP/LP horses have distinguished careers in eventing, dressage, and showjumping. The practical management approach is straightforward:

Allow adequate time for adaptation when moving into darker areas
Keep stable environments consistently and adequately lit
Familiarise the horse with competition venues — particularly tunnels, covered arenas, and dark loading areas — during daylight before working in low-light conditions
Inform handlers, riders, and farriers that the horse may react more to dim-light objects

Responsible disclosure of LP/LP status to buyers is an important part of transparent equine commerce. The condition is well-characterised, manageable, and stable — but buyers have the right to know it is present.

LP and Pattern Modifiers

LP alone does not fully determine what a horse looks like. The extent of pattern — how much of the body is covered, how bold the spots are, whether the horse presents as blanket, leopard, or FewSpot — is substantially influenced by modifier genes, the most studied of which is PATN1.

A LP/LP horse with low PATN1 may still have a blanket or varnish roan appearance. A LP/LP horse with PATN1/PATN1 is far more likely to be FewSpot. Understanding LP/LP in isolation is only part of the picture — the modifier genes determine the practical outcome. For a full explanation, see PATN1 Genetics.

LP/LP in a Breeding Programme

The strategic value of LP/LP in a breeding programme depends on the goal. If the objective is consistent, guaranteed LP transmission across every mating — regardless of the mare chosen — then an LP/LP sire is the only reliable way to achieve that. Not a probability. A certainty.

For breeders crossing warmbloods with spotted genetics to produce sport horses with distinctive coats, LP/LP is the necessary starting point. The final pattern in each foal will vary, but the presence of Appaloosa characteristics will not.

Donatello is LP/LP and PATN1/PATN1 — doubly homozygous for both genes. His offspring record to date confirms the LP guarantee: every foal born has presented with a spotted coat pattern. For the full picture of what this means in practice, see 100% Spotted Offspring.

Common Misconceptions

"LP/LP horses are always FewSpot"

LP/LP sets the maximum potential for pattern coverage, but the actual appearance also depends on PATN1 dosage. An LP/LP horse with very low PATN1 may present as a varnish roan or subtle blanket — not FewSpot. FewSpot expression reliably requires LP/LP combined with high PATN1.

"LP/LP horses are blind"

LP/LP horses have CSNB — a specific limitation in dim-light vision. They are not blind. Daytime vision and performance in well-lit environments are normal. The condition is stable and non-progressive. Many LP/LP horses compete at high levels in well-lit competition environments without measurable disadvantage.

"A horse with no visible spots can still be LP/LP"

With very low PATN1, an LP/LP horse's coat may appear minimally patterned. However, the physical Appaloosa markers — mottled skin, striped hooves, and visible white sclera — are always present in LP/LP horses. A horse with none of these markers does not carry LP.

"LP/lp stallions are 'almost as good' as LP/LP for producing spotted foals"

In terms of LP transmission, LP/lp produces approximately 50% spotted foals from a non-LP mare — meaning roughly half the foal crop will show no Appaloosa characteristics at all. LP/LP produces 100%. For breeders targeting consistent spotted offspring, this is not a minor difference; it is the fundamental distinction between certainty and probability.

Frequently Asked Questions

What does LP/LP mean in horses?

LP/LP means the horse is homozygous for the Leopard Complex gene — it carries two LP alleles, one from each parent. This is the genetic foundation of Appaloosa patterning and means the horse expresses maximum pattern intensity for its PATN1 genotype, passing LP to 100% of offspring.

Does LP/LP guarantee spotted offspring?

Yes. An LP/LP horse has only LP alleles to pass — there is no lp allele. Every foal, from any mare, inherits one LP allele and will show Appaloosa characteristics. The pattern type varies by PATN1, but LP presence is certain.

What is the difference between LP/LP and LP/lp?

LP/LP passes LP to 100% of foals and expresses stronger patterning than LP/lp. LP/lp passes LP to ~50% of foals from a non-LP mare. LP/LP horses also carry CSNB; LP/lp horses are not affected at the same level.

Does LP/LP cause night blindness?

Yes. All LP/LP horses have Congenital Stationary Night Blindness (CSNB) — a stable, non-progressive condition affecting vision in dim or dark conditions due to the TRPM1 pathway affecting retinal ON bipolar cells. Daytime vision is unaffected.

Is CSNB in LP/LP horses progressive?

No. CSNB is congenital (present from birth) and stationary (does not worsen over time). The horse is not losing vision — the condition simply represents a stable structural difference in the retina's low-light signal processing.