Genetic defects, specifically simple recessive genetic defects, have been a part of cattle breeding since the discovery of snorter dwarfism in Angus and Herefords in the 1950s. As we have moved into the 21st century, genomic tests and full genome sequences have helped producers identify a number of genetic defects in various breeds. Limousin encountered its own genetic defect in Protoporphyria in the 1990s, and genetic defect testing and breeder selection has all but eradicated this defect from the population.
In the last eight years, the cattle industry has been challenged with a number of genetic defects in the Angus population that have become an issue for a number of breeds with open registries and hybrid programs. This, coupled with defects from Red Angus, Maine-Anjou and Shorthorn, the largest challenge comes in the sheer number of deleterious genetic defects identified (Angus: 5, Red Angus: 1, Maine-Anjou: 1 and Shorthorn: 1). These discoveries have led to a number of questions for breeders and breed associations alike as how to best handle these genetic defect carriers.
In order to protect the integrity of the herd book, the NALF Board of Directors voted to require testing of all potential carriers of Arthrogryposis Multiplex (AM), Neuropathic Hydrocephalus (NH), Contractural Arachnodactyly (CA), Osteopetrosis (OS), Tibial Hemimelia (TH) and Pulmonary Hypoplasia with Anasarca (PHA) born January 1, 2012, or later. Animals that test free of these genetic defects will be registered. Carrier females will be registered; however they will be designated as carriers on their registration papers and in the NALF system. These females will also not be allowed to register embryo offspring. Carrier bulls will not be registered, but their performance information can be recorded in order to accurately represent contemporary groups.
In order to identify potential carriers of these defects, NALF has traced the descendents of the oldest known carriers of each defect in its herd book. There are more than 25,000 animals in the NALF herd book that trace to these original carriers. Testing that has been done by Limousin breeders and in other registries has lowered the number of potential carriers to approximately 2,500 currently in the herd book.
Identification is an ongoing process while staff continues to search for test results currently on file with other breed associations in order to fully quantify the number of potential carriers in the herd book. As a staff, we have worked toward identifying all animals that are potential carriers and move through process of elimination to the true number of animals that require testing in order to insure we test all animals that potentially need testing.
As members reading this, by now you have likely received a letter stating the animals within your herd that have a possible or carrier status for a genetic defect. Be aware that just because an animal is identified as a potential carrier doesn’t mean that testing the animal is the most cost effective or plan of action. If you can obtain a sample on either the sire or dam that is the root of the animal’s potential status, it is best to test that animal first in order to clear as many animals as possible with a single test. For example if there are 12 animals on your list that are potential carriers, look at their pedigrees first and look for common ancestors. In most situations NALF has encountered thus far, it’s normally a potential carrier bull that a member has purchased that is the potential carrier and cause of the problem. If the bull tests clean, the breeder can save dozens of potential tests through one single test.
Breeders also need to remember that the original carriers of the Angus defects were born in the late 1970s to early 1990s, so the actual tested carrier in the pedigree could be as many as 10 generations back. This means the chances of the animal being a carrier is very low, however in order truly account for the potential we must require a test.
Also realize that the NALF system only tracks historical Angus animals through three generations so there might be a few more potential carriers that show up once we have obtained a complete defect status listing from the American Angus Association. Once this list has been obtained and the NALF system has been updated, an animal’s defect status will be available on the animal search page of the NALF website.
The NALF Board of Directors and staff are committed to helping the membership overcome this obstacle and come out stronger on the other side. If you have any questions concerning defects, you can find links to information on the NALF website, or you can contact the NALF office if you have a question regarding a particular animal.