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The goal of this effort is  to produce dogs with the sweet personality and ability to adapt to modern pet life typical of the Cavalier King Charles Spaniel,  without the heartbreaking and longevity limiting health concerns so prevalent in the CKCS population, such as: 

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Improving the health of CKCS type dogs will require more than a simple outcross. It will require the infusion of genetics from several other sources, and careful selection over many generations. 

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Companion Dog Project is committed to working with breeders interested in participating at any level in this effort. We encourage all breeders of both purebred CKCS, and mixes to register dogs in CDR, regardless of their current health status or level of inbreeding.

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Guidelines for Breeding Cavalier King Charles Spaniel Mixes

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When producing Cavalier King Charles Spaniel mix litters, it is essential to account for the breed’s wide range of inherited health issues, such as:

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• Mitral Valve Disease (MVD)

• Chiari-like Malformation/Syringomyelia (CM/SM)

• Chondrodystrophy (CDDY) and related spinal disorders

• Eye disorders (cataracts, retinal dysplasia, dry eye/curly coat syndrome)

• Episodic Falling Syndrome (EFS)

• Hip and patella issues

• PSOM (Ear canal stenosis) and chronic ear infections

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In most cases, when Cavaliers are bred to healthy, unrelated dogs of other breeds, the risk of the most severe genetic diseases is significantly reduced or eliminated—particularly those caused by recessive genes or those linked to extreme brachycephaly. However, ethical health screening is still critical.

 

Breeding Age Information

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Breeding later in a dog’s life—particularly for males—offers the advantage of knowing whether age-related or inherited health issues will emerge, allowing breeders to make more informed, responsible choices. Males can remain fertile well into their senior years, so waiting until 4–5 years old before first breeding helps screen for late-onset conditions like heart disease, neurological issues, or orthopedic problems.

 

Females, however, are a different case: while it’s still important to ensure they are fully mature before breeding (no earlier than 18 months), starting too late can increase health risks. Studies show that females bred for the first time at advanced age (discrepancy exists) are significantly more likely to require a C-section, as pregnancy and whelping become more taxing with age. For optimal balance, many breeders aim to use males later in life for genetic clarity and breed females between 2–4 years old, when they are physically mature but still young enough for an easier pregnancy and delivery.

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Even though breeding males later in life is helpful for spotting late-onset health problems, there are valid reasons not to require advanced age when breeding mixed-breed dogs—especially in carefully planned outcross programs.

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Key reasons:

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• Genetic diversity goals – In outcross programs, the priority is often to bring in new genes quickly to lower COI (coefficient of inbreeding) and dilute breed-specific health risks. Waiting too long before using a valuable male could shorten his reproductive window and limit his genetic contribution.

• Fertility decline with age – While many males can sire litters well into old age, sperm count, motility, and viability can drop after 6–7 years, which may make breeding less successful.

• Health screening timelines – If both parents have already had thorough health testing (echocardiogram, genetic panel, orthopedic exams), many major concerns can be addressed without waiting years for age-related issues to appear.

• Program efficiency – In projects where each generation is planned toward a specific goal (e.g., lowering CDDY risk, improving heart health, widening gene pool), delaying sires to advanced age could slow progress by several years.

• Reduced breeding opportunity – If the male belongs to another breeder, his availability may be limited, and waiting could mean losing the chance to use him altogether.

 

Practical interpretation

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• Don’t rely on a single age cutoff for all dogs. Instead:

  • Treat age as something that needs to be evaluated case-by-case.

  • Be especially cautious with brachycephalic and small-breed dams; consider earlier first breeding.

  • Use breed-specific data where possible (look for papers or club statistics for that breed).

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Recommended guidelines for breeding age

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• Males (Sires): Minimum 2–3 years old (ensures health conditions have time to appear before breeding).
   

• Females (Dams): Minimum 18 months old; should be physically mature and in optimal health.

 

Required Health Testing (Both Sire and Dam)

 

Cardiac Health

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• Echocardiogram performed by a board-certified veterinary cardiologist:

• • Before the first litter

  • Every 2 years thereafter​

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When breeding Cavaliers to non-Cavaliers, echocardiogram (echo) screening for both sire and dam is very important — even more so than simple auscultation — because of the nature of mitral valve disease (MVD) in the breed and the limitations of listening alone.

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1. MVD is highly prevalent and can be early-onset in Cavaliers

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• Cavaliers have the highest known rate of early-onset degenerative mitral valve disease of any breed.

• It is polygenic, and even though the risk is greatly reduced when crossed with a non-Cavalier, the risk does not disappear. 

• Both parents can carry genetic risk factors for MVD, even if one is from a breed not commonly associated with it.

• If the non-Cavalier parent also has undetected heart issues, those risks compound.

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2. Auscultation misses early disease

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• Auscultation (listening with a stethoscope) detects murmurs caused by valve leakage — but murmurs often appear after structural damage has begun.

• An echo can detect thickened valve leaflets, prolapse, or regurgitation years before a murmur is audible.

• Early-stage disease without an audible murmur could still be passed genetically to puppies.

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3. Echocardiography gives a baseline and clears “silent carriers”

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• An echo performed by a board-certified veterinary cardiologist shows valve structure, chamber size, and blood flow.

• This allows breeders to avoid pairing two dogs with even mild early changes, significantly lowering the chance of producing puppies that develop early, severe MVD.

4. Health in the litter depends on both parents

• If the Cavalier parent has an early-stage, subclinical MVD, and the non-Cavalier parent also has hidden valve changes, the puppies’ genetic “load” for heart disease remains high.

• By clearing both sire and dam with an echo, you ensure that the combination of genetics going into the litter has the lowest possible MVD risk.

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5. Better long-term breeding strategy

• Keeping detailed echo records over generations allows breeders to track improvement and avoid “reintroducing” MVD risk through outside crosses.

• Auscultation alone can give a false sense of security and slow progress toward healthier hearts.

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Neurological Health

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MRI screening when breeding Cavaliers with normal-skulled mesocephalic breeds can be useful, but it’s not always strictly necessary, because the risk dynamics of Chiari-like malformation (CM) and syringomyelia (SM) change significantly when you alter skull shape through crossbreeding.

Why it can still be useful:

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• CM/SM is highly prevalent in Cavaliers.

• Even though skull shape plays a major role, CM/SM also has a heritable, polygenic component that isn’t entirely tied to head type.

• Some mesacephalic breeds can still have CM/SM (though far less common), so an MRI can confirm whether either parent is affected.

• Screening gives you a baseline for future generations if you keep any puppies for breeding.

Why it’s not always essential in a cross bred or mixed breed litter:

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Cavaliers are brachycephalic-to-moderately brachycephalic, which increases risk by reducing caudal fossa volume in the skull. When crossed with a normal-skulled mesocephalic breed, most puppies inherit a longer skull and larger caudal fossa, which tends to reduce or eliminate the physical compression that causes CM/SM symptoms.

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In first-generation (F1) mixes, many puppies will not express CM/SM to a clinically significant degree, especially if the non-Cavalier parent comes from a breed with no history of the condition

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• Recommendations for MRI screening for Cavalier crossed F1 litters:
   

  • Optional when breeding Cavaliers to normal-skulled mesocephalic breed breeds, with low CM/SM incidence.

  • Required when breeding Cavaliers to brachycephalic breeds (e.g., English Toy Spaniel, French Bulldog, Shih Tzu) or breeds with high CM/SM occurrence (e.g., Papillon, Chihuahua, Havanese, Yorkshire Terriers).

  • Reason: Non-brachycephalic crosses often produce offspring without the skull shape predisposing them to CM/SM.

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Genetic Testing

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• MMVD Genetic Test (NEBL3 gene) for both sire and dam.

• Full genetic panel from Embark, UC Davis, or another reputable provider to identify

• • Carrier status for breed-relevant diseases in both the sire and dam

  • Diversity metrics (COI)

  • Risk factors for orthopedic, neurological, and cardiac disease

 

Orthopedic Health

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• PennHIP evaluation for hips (CDP accepts either Penn  Hip or OFAs scoring Excellent or Good  over 1 year of age for CDR verified litters. PennHip is strongly preferred)

• OFA patella certification

• OFA elbow certification

 

CDDY Risk Management

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Each generation should maintain or reduce the likelihood of producing puppies with CDDY. Track genetic results to ensure progress over time. See the CDP guideline for all dog types here. 

 

Best Practices

• Keep detailed health and pedigree records for all breeding dogs and their offspring.

• Aim to lower COI (Coefficient of Inbreeding) with each generation—ideally keeping it under 10%, and preferably under 5%.

• Choose breeding partners with complementary temperaments and physical traits, focusing on improving health and preserving the Cavalier’s hallmark affectionate personality.

• Look closely at the non-Cavalier breeding partner’s health risk and history. Test for those heritable diseases. Be conscientious about what a pairing would produce in terms of health and temperament.

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