The Paw Print Genetics Blog

Tissue Management Prior to Genetic Testing

Tissue Management Prior to Genetic Testing

Nothing brightens the schedule like seeing an 11:20am slot given to Mrs. Doe who is bringing in a three-day old litter for assessment, tails and dewclaws.  The whole clinic reminds you all morning that puppies are coming in.  Then the magic hour arrives and in comes Mrs. Doe with a laundry basket covered in a towel that is making a surprising level of grunts and squeals.  Wow! Thirteen little fuzzballs in varied states of activity from litter-surfing to dreamless slumber that makes you a little jealous.  You go through the exam; each one is fully formed with no gross congenital defects.  While prepping your tools for dewclaw removal and tail docking, Mrs. Doe asks that you save the remnants so she can have the litter tested with Paw Print Genetics for known disease-causing mutations in this breed.  Hmmm, what does this entail?

Typically, we recommend to clients who choose to submit cheek swabs to wait until they begin weening the pups off mom. This allows them to separate the puppies from their mother to reduce possible contamination by the mother’s milk that may remain in the puppies’ mouths.  Given that testing takes 14 days from the time a sample is received by the laboratory, adding in shipping time of kits both to and from the breeder, sometimes availability of testing results comes very close to their ‘go home’ date.  A simple solution to this is to submit tissue for testing.  We can use one dewclaw, a quarter inch of a docked tail, or a half inch of an umbilical cord (from the side still attached to the placenta) for genetic testing.

This option is becoming popular with breeders, as not only do tissue samples like docked tails and dewclaws provide an ample supply of DNA for testing, but testing can begin right away.  Breeders want their results before they determine the outcome of each puppy in a litter. Is this a keeper for their own breeding program? Is this one they want to market to another breeder? Or, is this little critter a carrier of a mutation that warrants removal from the gene pool and sold as a pet only? 

There are a few things to keep in mind when accommodating Mrs. Doe’s request.  Nothing changes in your protocol for the procedure, whether you like to make a “V” incision and demonstrate your micro-suturing technique, or you clamp, cut and glue.  That is your call.  First, keep in mind that just like mother’s milk can contaminate a cheek swab sample, blood from one puppy can confound the sample of another.  Ideally, a fresh blade or tool should be used for each puppy.  However, a quick cleaning with alcohol or other sterilization of the instruments is sufficient between puppies.  Second, each puppy’s tissue sample must be identified and kept separate from the others.  It has happened where a client requested the tissue be saved and the vet happily complied, handing a container of all the tails and dewclaws jumbled together back to the owner.  DNA is precious and valuable, while sample bags are inexpensive and convenient to keep the individual samples separated. 

Before beginning, ask the owner how they want each sample identified, so that each sample corresponds to one pup. Depending on the breed, many breeders will use collar colors or coat color, or other markings, to uniquely identify each pup. After each puppy is processed, place the tissue in the sample bag with a unique identifying label that corresponds to that pup.  This way, the owner can match each sample to the puppy that donated it and make the appropriate submission to our lab.  If the sample bag is made of plastic (most are) the bag should not be completely sealed as that prevents the tissue from appropriately dehydrating and leads to necrosis. 

Many vets will recruit the aide of the owner in the process.  I have always found it is better to let the owner decide how much tail to dock and mark each puppy rather have them criticize me a few months down the road when they are unhappy with the results. Therefore, a useful technique is to have the owner collect the sample into a correctly labeled container.  This continues for every puppy in the litter.  When all the puppies have been processed, Mrs. Doe has all the samples identified and separated.  Remind the client that samples must be dried for at least a week before shipping to our lab, and some of the tissue should be saved for each puppy in case the samples are lost in transit.  A suggestion from one of our clients is to use a muffin tin to help keep samples organized.  When the samples are dehydrated and ready for shipping, they can be sealed into separate, labeled plastic bags. Remove the air from the bags to reduce space.  Then place all the samples in a heavy padded mailer, review and include the requisition form provided by our lab when the order is placed and seal it up securely. 

When you are assisting with the birth of a litter, whether helping a dam through natural parturition or performing a C-section, keep in mind umbilical cords can also provide a convenient sample for genetic testing.  These should be collected immediately after the puppy is born or passed out of the surgical suite, during the C-section. If the mother chews on the cord the sample should be considered contaminated and cannot be used for genetic testing.  After the cord is clamped and cut, remove about a half inch section from the portion of the cord still attached to the placenta.  Label each segment of cord with a unique puppy identifier.  Any tools used for collection, including gloves, should be exchanged for new ones, or cleaned with alcohol between samples to prevent contamination. Like the tails and dewclaws, these also must be dehydrated prior to mailing to our laboratory.

Puppies are always a boon to a stressful day in the clinic.  With a little preparation and assistance from the owner, tissue samples can be a great way to get earlier genetic results.  Given that the client is making the effort to reduce disease in their program through genetic testing, take the time to provide samples that can be submitted for genetic analysis. 


  • John Jess on 11/07/2020 5:26 a.m. #

    Thank you for all the tips and ideas you have given us in this article. While highlighting the importance to make sure that any tooling is kept clean and blood free when collecting DNA from the next puppy.
    Thanks again for writing this article it very helpful.

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