Merle Breeding Record Keeping: Building a Genetic Database for Your Programme

In 2017, I was asked to consult on a case that should never have happened. A respected Australian Shepherd breeder produced a double merle puppy in what she believed was a merle-to-non-merle breeding. The "non-merle" sire had been tested seven years earlier, when he was a young dog, and the results showed him as non-merle. What the breeder did not know - because she had not recorded the specific allele length from that original test - was that the laboratory had reported him as "merle negative" based on a threshold that has since been revised. His actual allele length, when retested, placed him in the cryptic merle range.

Had she kept detailed records of the original test - the specific base pair count, the laboratory used, the methodology employed - she would have known to retest when industry standards changed. Instead, she relied on a seven-year-old "negative" result and a puppy paid the price. This case crystallised for me the absolute necessity of comprehensive, meticulous record keeping in any breeding programme involving the merle gene.

Why Standard Pedigree Records Are Not Enough

Traditional pedigree records tell you who a dog's parents, grandparents, and great-grandparents are. They may note coat colour, show titles, and health certifications. What they typically do not record is the molecular detail that makes the difference between a safe merle breeding and a catastrophic one.

A pedigree that lists a dog as "blue merle" tells you nothing about the specific allele length. It does not distinguish between a dog carrying a 265 base pair allele and one carrying a 255 base pair allele - a difference that may determine whether offspring carry classic merle or atypical merle alleles. It does not record which laboratory performed the testing, what methodology was used, or when the test was conducted. And it certainly does not flag dogs in the pedigree that were never tested at all.

For breeders working with merle, the standard pedigree is a starting point. It is not a safety tool. Building a proper genetic database requires documenting information that goes far beyond what any kennel club registration system provides.

Recording Allele Lengths: The Critical Detail

I cannot overstate the importance of recording exact allele lengths rather than relying on category designations alone. The merle allele spectrum is continuous, not discrete. The categories we use - cryptic, atypical, classic - are convenient labels imposed on a continuous range of poly-A tail lengths. The boundaries between categories are somewhat arbitrary and have been revised as research has progressed.

A dog with a 228 base pair allele is categorised as cryptic merle (Mc). A dog with a 231 base pair allele is categorised as atypical merle (Ma). The three base pair difference between them is biologically trivial - far less than the natural variation that can occur through allele instability during inheritance. Yet the category labels suggest a meaningful distinction.

By recording the actual number, you preserve information that category labels discard. You can assess how close a dog's allele length is to a category boundary, which helps predict the likelihood of offspring shifting categories. You can track allele length changes across generations in your own lines, building a picture of how stable or unstable the allele is in your specific population. And you have data that remains valid even if category definitions are revised in the future.

Structuring Your Database

The format of your database matters less than its completeness and accessibility. I have seen effective databases maintained in spreadsheets, dedicated software programmes, and even carefully organised paper filing systems. What matters is that the information is recorded consistently, stored securely, and accessible when breeding decisions are being made.

The Individual Dog Record

Each dog in your programme - whether owned by you, used at stud, or the offspring of your breeding - should have a complete individual record that includes all genetic test results with full documentation, a detailed phenotype description (ideally with photographs in natural lighting), and a complete breeding history including all partners and resulting offspring.

The Breeding Record

For each breeding, record the complete genetic profiles of both parents, the predicted outcomes based on parental genotypes, the actual outcomes for each puppy (tested individually), any discrepancies between predicted and actual results, and the destination of each puppy (pet, show, breeding programme, etc.).

The Generational Tracker

Track allele lengths across generations to identify patterns of instability in your lines. If you notice that a particular line consistently produces offspring with alleles that differ from their parents by more than a few base pairs, this information should influence your breeding decisions and your advice to puppy buyers who may breed from your dogs.

Sharing Records: The Collaborative Imperative

A genetic database has value beyond your own programme. When breeders share their data, the entire breed benefits. Patterns that are invisible within a single kennel become clear across a population. A line that shows high allele instability in your programme may show the same pattern in another breeder's dogs, confirming a heritable tendency rather than a random occurrence.

I advocate for open sharing of merle test results within breed communities. This does not mean publishing every detail of your breeding programme publicly. It means being willing to share specific genetic test results with other breeders who are considering using your dogs or their offspring, with breed health committees tracking merle in the population, with testing laboratories conducting research on allele instability, and with veterinary geneticists studying merle inheritance patterns.

Some breeders resist sharing because they view genetic information as proprietary - a competitive advantage. I understand this perspective, but I reject it. The purpose of genetic testing is to prevent suffering. Withholding information that could prevent another breeder from producing a double merle puppy is, in my view, ethically indefensible regardless of commercial considerations. This is especially critical in breeds where merle has been recently introduced, where the absence of any shared data infrastructure means the gene can spread unchecked through entire populations.

Organisations focused on shepherd breed genetics have demonstrated how collaborative data sharing can dramatically improve breeding outcomes across an entire breed population. The merle breeding community would benefit enormously from similar cooperative approaches.

When Records Reveal Problems

Good records sometimes reveal uncomfortable truths. You may discover that a dog you have been breeding from carries a merle allele you did not know about - perhaps masked by a sable or recessive red coat that rendered the pattern invisible. You may find that your line shows higher allele instability than average. You may realise that a dog you sold as a pet three years ago should have been tested before being placed in a breeding programme.

The temptation to ignore or suppress inconvenient data is human and understandable. I urge you to resist it. Every piece of information in your database exists to protect future dogs. A record showing that a popular stud dog carries a cryptic merle allele is not a problem to be hidden - it is a warning that could prevent double merle puppies in every future breeding involving that dog or his descendants.

Practical Templates

Based on my work with breeding programmes across Europe and North America, I recommend structuring your records around three core documents:

Document One: The Individual Genetic Profile

A single-page summary for each dog containing registration details, complete merle genotype with allele lengths, all other colour gene test results, the laboratory report reference number, and a photograph. This document should be immediately accessible whenever you are discussing a potential breeding or answering queries from puppy buyers. It is the document you share with other breeders and with your veterinarian.

Document Two: The Breeding Plan Assessment

Before any breeding takes place, complete a written assessment that pairs the genetic profiles of both prospective parents, calculates the possible outcomes for each gene, identifies any risk factors (including boundary allele lengths that might shift through instability), and documents your decision and reasoning. This assessment serves both as a planning tool and as a record that demonstrates due diligence if questions arise later. Following a structured responsible breeding protocol should be standard practice.

Document Three: The Litter Record

For each litter, record the date of birth, the number and sex of puppies, a phenotype description of each puppy, individual genetic test results for each puppy (obtained before placement), the destination of each puppy, and any follow-up information received from buyers. This litter record, when combined with the breeding plan assessment, creates a complete history of each breeding that can be reviewed and learned from.

Technology and Tools

Several software tools and online platforms exist for canine breeding record management. When evaluating options for merle-specific record keeping, look for the ability to record custom genetic test fields (not just standard health clearances), flexible pedigree display that includes genetic data, export functionality so your data is never locked into a single platform, and the ability to attach document scans (laboratory reports, photographs).

I personally use a combination of a spreadsheet for the genetic database and a dedicated pedigree programme for visual pedigree analysis. The spreadsheet allows me to sort and filter by allele length, identify dogs near category boundaries, and track changes across generations. The pedigree programme provides the visual representation that helps identify patterns of inheritance.

Whatever tools you choose, ensure they are backed up regularly and that you can access your data independently of any single platform. Online services can close, software companies can cease trading, and proprietary formats can become unreadable. Your data must outlast any particular technology.

Record Keeping as Ethical Practice

I began this article with a case where inadequate records led to a preventable tragedy. I want to close by framing record keeping not as an administrative burden but as an ethical practice - a concrete expression of the commitment every responsible breeder makes to the welfare of the dogs they produce.

When you record a test result, you are creating a permanent resource that will inform every future breeding decision involving that dog and its descendants. When you share that record with another breeder, you are extending that protection to dogs you will never meet, in programmes you may never know about. When you maintain your database meticulously, updating it with every new test and every new litter, you are building something of genuine value - a tool that prevents suffering.

The merle gene is beautiful and dangerous. It demands respect, knowledge, and discipline from every breeder who works with it. Comprehensive record keeping is not the most glamorous aspect of that discipline, but it may be the most important. The test result you record today could prevent a double merle puppy five generations from now. That is not an exaggeration. That is how genetics works, and that is why every number, every date, every laboratory reference matters.

Build your database. Maintain it. Share it. The dogs of tomorrow depend on the records you keep today.