By: Joan S. Bowen, DVM
Updated by ADGA Staff, 2007

Since January 1998, the American Dairy Goat Association has been using DNA typing for identification and parentage verification of dairy goats. Between 1990 and 1998, serological markers were used to blood type dairy goats. Due to the limited number of antisera available, occasional parentage cases could not be resolved due to lack of differences between individuals. Dr. Jerry Caldwell, director of ImmGen, recommended that ADGA make the switch to DNA typing to allow greater discrimination between individuals.

Use of DNA technology makes it easier for the producer to submit samples for identification or verification. Thawed semen or tufts of hair follicles can be mailed in an envelope with no special handling. Blood samples that in the past have deteriorated due to heat or time can still be tested using DNA methods.  ADGA coordinates the identification, submission and verification program.

Buccal epithelial cells from the inside of the cheeks have been used in some species for DNA typing.  Unfortunately, this cell sample cannot be used for DNA typing ruminants due to sample contamination with rumen bacteria.  While nucleated cells can be harvested from goat cheeks, rumen bacteria present in the mouth overgrow the sample during shipment and destroy the cells.

DNA typing can be performed on any nucleated tissue such as hair, bone, semen or blood.  Each nucleated cell contains a complete copy of all that animal's chromosomes.  All chromosomes are made up of the four deoxyribonucleic acids adenine, thymine, guanine, and cytosine. The orders in which these acids are present determine the function of that chromosome.  The method of DNA typing most frequently used for identification of livestock and parentage verification uses the microsatellite portion of the chromosomes.  This section of each chromosome has no known biologic function, but seems to demonstrate maximum variation between individuals.  Microsatellites are short paired repeats of gene sequences that consist of two, three or four nucleotide units repeated in multiple tandem copies. The repeats that contain two nucleotides, such as AA AA AA AA OR CA CA CA, are the most common, have the most variation, and occur throughout the genome.

To start the process, DNA is extracted from the sample, and then millions of copies of the microsatellites are made using Polymerase Chain Reaction (PCR).  During the copying process, both genes that the animal inherited from it's parents are multiplied.  The genes from each parent may have a different number of repeats, so the copies must be sorted into groups of similar length by running the sample through gel under electric current.  Shorter length chains move faster in a specific period of time, and analysis of the gel yields bands of different length copies. A variety of fluorescent dyes are used in the replication process, so even if two separated based on the difference in color of the dye.  Each microsatellite used has a specific name and data is recorded as the integer number of base pairs for each paired allele. The DNA type is recorded for each sample tested, and types can be compared to verify parentage.

ADGA members that would like to use the DNA typing program should contact the ADGA office to schedule the testing and to request paperwork. All paperwork and sampling materials are provided.

The member must supply the office with a list of the registered/recorded name and number for each animal to be sampled and the reason the sampling is being done.

For example, the samples might be submitted to determine the sire on an as yet unregistered kid.  For identification of that kid, list the tentative name and tattoo, the possible sires' names and registration number for the dam.  Samples must be submitted for each possible parent and kid.  The office then sends the owner a sampling kit containing the necessary materials.

The cost for testing is $30/animal and should be sent to the office with your request.  The results are sent to the ADGA office and the results are mailed to the member.   Questions should be directed to Lisa Shepard at performanceprograms@adga.org