Written by Ron Metz, President, PDCA
As we move forward with developing genetic tests for measuring quality traits in Dexter Beef and Milk, I would like to discuss the different acceptable options for collecting DNA samples. Many of us are most familiar with the method of collecting hair samples. There are two other DNA sampling options that you may not be aware of. One uses a blood card, the other takes a tissue sample. For the benefit of Dexter owners new to genetic testing, I will give a detailed explanation of each method.
Collecting hairs from the poll, neck or tail switch are acceptable. I find hair collection from the switch to be the easiest. Although it is not a requirement, I find it is better to wait until the animal is a bit older and the root bulb of the hair is better developed. Cells from the root bulb are used in the tests. To be effective, a minimum of 20-30 hairs with bulbs need to be collected. You will need the following items on hand to do the collection: disposable rubber gloves, small envelopes or Ziploc bags, scotch tape, scissors, clean pair of pliers and a sharpie. First restrain the animal. It is important to wear disposable rubber gloves while collecting tail hairs so as not to contaminate the sample with your DNA. The hairs are collected from the switch portion of the tail. The tail and switch should be clean, dry and free from manure and other contaminants. With a pair of pliers, grab a group of hairs in the switch close to the skin and with a quick pull remove them from the switch. Be careful to not let the root bulbs touch anything.
Examine the hairs to make sure they all have bulbs intact. If you do not have 20-30 hairs with bulbs present, you will have to pull another group of hairs. When you have at least 20-30 hairs with bulbs, carefully take a piece of scotch tape and wrap it around the bundle of hairs at least 2 inches above the root bulbs. Take a pair of scissors and cut off the excess hair above the scotch tape. Do not cut off the bulb end of the hairs. Carefully place the bundle in an envelope and label with the animal’s ID. Repeat the steps for each animal sampled.
Some testing facilities such as Neogen accept the blood card method. Obtain the necessary number of blood cards (and a few extra) from the testing facility for the animals you are testing. Items you need to have on hand include: disposable rubber gloves, clean needle/syringe for each animal being tested, sharpie. First, write the animal’s name and ID in the appropriate places on the blood card. Restrain the animal. Locate a blood vessel in the ear visually or by feel. Make sure the area is clean, dry and free from dirt, manure and other contaminants. Using a clean needle/syringe draw blood. Be sure and us a clean needle/syringe for each animal. Blood can also be drawn from the vein on the underside of the tail which may be easier than the ear. Deposit drops of blood until the inside of the circle on the blood card is full. Do not wipe the needle, ear or tail on the card. Let the card(s) sit open and air dry before closing the cover flap. If blood is sticky and gets on the top of the card, the sample is not usable.
This method requires taking a tiny tissue sample from the animal’s ear. It does require a special sampling gun and tissue sample vials. The vials are available in boxes of ten or individually. This method was developed by the AllFlex tag company. The necessary items for taking tissue samples are available through AllFlex distributors or several online veterinary or farm and ranch supply companies. The process is similar to installing an ear tag in the animal’s ear. First restrain the animal. Make sure the ear is clean, dry and free from dirt, manure and other contaminants. Insert a tissue sample vial in the tissue sample gun. Cock the gun. Apply the gun over an appropriate place on the animal’s ear and quickly squeeze the handles. The plunger pushes a small tissue sample from the ear into the vial containing a special fluid while simultaneously sealing the vial. Many people use the same small piercing in the ear to then install an ear tag.
Once the sample has been collected, indicate the animal’s ID on the corresponding space on the box or on the vial. I have included a video link so you can see the process.
The DNA collection method preferred by the genetics company we are working with to develop specific genetic testing for the DexStar program is the tissue sample. The sample collected in the vial is good for up to one year. In addition to using cells from the actual tissue sample, the fluid used to preserve the sample can also be used for testing. Between the tissue sample and the fluid, hundreds of tests can be run. The next DNA sample method preferred is the blood card. Samples are punched out of the material containing blood within the circle on the card. However only a finite number of blood samples can be punched to run tests. The least favored DNA collection method is the hair sample. Hair root bulbs provides the least amount of available genetic material for testing.