For Breeders

Core principle

Recommendations below are graded by evidence.[Documented] marks claims supported by findings in the peer-reviewed literature.[Precautionary] marks guidance based on biological mechanism and responsible-breeding principle, where direct outcome data is not yet available.

Breed a DBE-positive cat to a genetically test-negative partner.

A cat carrying a DBE variant is best bred only to a partner genetically confirmed as free of all known DBE variants. The specific risk to avoid is pairing a carrier of one DBE variant with a carrier of a different DBE variant: such a mating can produce a kitten that inherits two different DBE variants in a single body — one from each parent (a compound heterozygote). The principal risk is producing offspring that are homozygous for one DBE variant or compound heterozygous for two different DBE variants. A DBE-CEL/DBE-ALT litter containing two deaf compound-heterozygous kittens has been documented. The authors proposed that the combined effect of two PAX3-associated alleles may compromise normal PAX3 function, but the precise functional mechanism was not measured experimentally. For this reason, combining known DBE variants is not currently recommended.
[Documented for DBE-CEL/DBE-ALT combination² — Precautionary for other variant combinations⁴ — supported by Abitbol et al. 2025]

Test both parents before breeding.

Responsible practice is to base breeding decisions on confirmed genotype rather than eye colour, white spotting, pedigree assumption or photographs.

Test every kitten from a DBE litter.

Each kitten from a DBE breeding is best given its own individual genetic test, whether it stays in the programme or is placed as a companion animal. Individual testing supports:

- confirming the kitten's genotype;

- identifying the specific DBE variant present;

- documenting inheritance within the breeding line;

- informing future breeding decisions;

- monitoring the long-term stability and safety of the line.

Even where a particular DBE variant currently appears safe in the heterozygous state, genetic monitoring is best continued. Responsible breeding rests on continuous data collection rather than assumption: every genetically confirmed kitten adds information that improves understanding of inheritance, penetrance, phenotype and long-term health outcomes. Maintaining complete genetic records benefits the individual programme, supports future scientific research, and helps preserve confidence in responsible DBE breeding.

Collect BAER hearing data.

Even where a specific DBE variant has not been associated with hearing loss in the heterozygous cats studied to date, hearing data remain valuable. BAER results build evidence for your own line and support responsible long-term breeding decisions. [Precautionary]

Document the differences between variants.

DBE-CEL has not been associated with deafness¹ ⁴, whereas the DBE-RE variant has been directly linked to congenital hearing loss, although its penetrance appears to vary between studies.³ ⁴ [Documented]

Phenotype is not proof

A blue-eyed, odd-eyed, white, bicolour, van or harlequin cat cannot be reliably classified as DBE by appearance alone. The only reliable way to confirm whether a cat carries a known DBE variant is genetic testing.

Why Combining DBE With KIT Raises Ethical Concerns

Intentional combinations of PAX3-associated DBE with KIT-associated white raise both welfare and transparency concerns.

The KIT dominant-white allele is independently associated with an incompletely penetrant risk of sensorineural deafness.⁵ ⁶ ⁷ Hearing impairment has also been documented in particular PAX3-associated DBE variants and genotypes, including heterozygous DBE-RE cats and DBE-CEL/DBE-ALT compound heterozygotes.

No peer-reviewed study has yet measured the hearing outcome of cats inheriting both a PAX3-associated DBE variant and KIT dominant white. It is therefore not possible to quantify whether the combination creates an additive or interacting risk of deafness.

However, the absence of direct outcome data is not evidence that the combination is safe. Because both genetic mechanisms affect melanocyte biology and because melanocytes are required for normal inner-ear function, an additional hearing risk cannot currently be excluded.

From an ethical breeding perspective, deliberately creating an unstudied combination in order to increase the likelihood of blue eyes, odd eyes or commercially desirable white patterns is difficult to justify when safer and genetically clearer mating options are available.

For this reason, intentional DBE × KIT dominant-white matings are not recommended unless future evidence demonstrates that the combination is safe.

[Documented hearing risk for KIT dominant white and for particular PAX3-associated DBE genotypes — Precautionary regarding the additional risk created by their combination]

KIT White Spotting

KIT-associated white spotting should be considered separately from KIT dominant white.

Current peer-reviewed evidence does not demonstrate that KIT white spotting alone carries the same hearing risk as dominant white, nor that combining white spotting with a PAX3-associated DBE variant increases the risk of deafness.

Nevertheless, intentional DBE × KIT white-spotting combinations raise significant ethical concerns because they can obscure the genetic origin of blue eyes and white markings.

Such combinations may allow:

• a KIT-associated blue-eye phenotype to be advertised as genetically confirmed DBE;

• a genuine DBE variant to be concealed behind a white, bicolour, harlequin or van phenotype;

• kittens to be priced or represented as DBE without individual genetic confirmation;

• pedigree and show classifications to be interpreted incorrectly;

• and long-term health and inheritance data to become unreliable.

Avoiding DBE × KIT white-spotting combinations is therefore recommended as a precautionary policy for genetic clarity, transparent breeding records and honest representation of kittens.

Every kitten advertised, sold or retained as DBE should have an individual genetic test confirming the specific variant. Parentage, eye colour, pedigree and photographs are not substitutes for the kitten’s own result.

All kittens from any DBE × KIT combination should also undergo BAER testing, because visual behaviour cannot reliably exclude unilateral hearing loss.

[Documented hearing risk for KIT dominant white and for particular PAX3-associated DBE genotypes — Precautionary regarding the additional risk created by their combination]

Recommended breeder standard

A robust DBE breeding programme is expected to maintain:

- genetic test results for all breeding cats;

- DBE variant identification;

- confirmation that DBE cats are heterozygous where applicable;

- BAER hearing results for breeding cats;

- BAER hearing results for kittens;

- kitten-specific DBE test results;

- clear records of which variants were tested;

- transparent documentation provided to buyers.

Position statement

Responsible DBE breeding prioritises evidence over visual outcome. The goal is not to produce the highest number of blue-eyed or odd-eyed kittens, but to preserve health, transparency and genetic clarity. DBE can be bred responsibly only when breeders recognise that different DBE variants are not interchangeable and that phenotype alone is not enough.

Why combining DBE with KIT is not recommended —>

References

1. Abitbol M, Couronné A, Dufaure de Citres C, Gache V. A PAX3 insertion in the Celestial breed and certain feline breeding lines with dominant blue eyes. Animal Genetics. 2024;55(4):670–675. doi:10.1111/age.13433

2. Abitbol M, Dufaure de Citres C, Rudd Garces G, Lühken G, Lyons LA, Gache V. Different Founding Effects Underlie Dominant Blue Eyes (DBE) in the Domestic Cat. Animals. 2024;14(13):1845. doi:10.3390/ani14131845

3. Rudd Garces G, Farke D, Schmidt MJ, Letko A, Schirl K, Abitbol M, Leeb T, Lyons LA, Lühken G. PAX3 haploinsufficiency in Maine Coon cats with dominant blue eyes and hearing loss resembling the human Waardenburg syndrome. G3 Genes|Genomes|Genetics. 2024;14(9):jkae131. doi:10.1093/g3journal/jkae131

4. Abitbol M, Cloquell A, Kaczmarska A, Holmes K, Lühken G, Macaulay K. Dominant blue eyes in Maine Coon cats: New PAX3 variant and updated phenotypic data. Animal Genetics. 2025;56(3):e70020. doi:10.1111/age.70020

5. David VA, Menotti-Raymond M, Wallace AC, Roelke M, Kehler J, Leighty R, et al. Endogenous retrovirus insertion in the KIT oncogene determines white and white spotting in domestic cats. G3: Genes|Genomes|Genetics. 2014;4(10):1881–1891. doi:10.1534/g3.114.013425.

6. Cvejic D, Steinberg TA, Kent MS, Fischer A. Unilateral and bilateral congenital sensorineural deafness in client-owned pure-breed white cats. Journal of Veterinary Internal Medicine. 2009;23(2):392–395. doi:10.1111/j.1939-1676.2008.0262.x

7. Mari L, Freeman J, Van Dijk J, De Risio L. Prevalence of congenital sensorineural deafness in a population of client-owned purebred kittens in the United Kingdom. Journal of Veterinary Internal Medicine. 2019;33(4):1707–1713. doi:10.1111/jvim.15515