By Jared E. Decker Many of you have probably noticed that things have been a lot less active on the A Steak in Genomics™ blog, but you probably haven't known why. In January 2021, I was named the Wurdack Chair in Animal Genomics at Mizzou, and I now focus on research, with a little bit of teaching. I no longer have an extension appointment. But, with exciting news, the blog is about to become a lot more active! Jamie Courter began as the new MU Extension state beef genetics specialist in the Division of Animal Sciences on September 1, 2023. I have known Jamie for several years, meeting her at BIF when she was a Masters student. I have been impressed by Jamie in my interactions with her since that time. Dr. Courter and I have been working closely together the last 6 weeks, and I am excited to work together to serve the beef industry for years to come! Jamie holds a bachelor’s degree in animal science from North Carolina State University and earned a master's degree in animal
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Using Genomic Tests to Detect Genetic Abnormalities in Beef Cattle
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Christian P. Lewis
South Dakota State University undergraduate student
Rapid advances in science and technology are appearing
throughout agriculture. One of the newest technologies that has worked its way
into the cattle industry is DNA testing and the use of genomic data.
Practical Uses of Genomic Data
Genetic abnormalities are not a common problem in beef
cattle production, but they do appear if precautions are not taken. Most
frequently, a genetic abnormality appeared because both the cow and bull were
carriers of a recessive allele that causes the abnormality. An animal is termed
a “carrier” when they have a dominant allele that is masking the recessive allele.
Figure 1 illustrates how an abnormality can appear by mating two carriers.
Genetic abnormalities will appear when a calf has two copies of the recessive
allele that it got from its sire and dam.
A
a
A
AA
Aa
50% chance the calf will be a carrier
a
Aa
aa
25% chance the calf will have the abnormality
Figure 1: Mating two carriers (Aa) of a recessive allele (a) that is completely masked by the dominant allele (A)
Without a DNA test for an abnormality, the only way you will know an animal is a carrier or not is when you mate the suspected carrier to a known carrier and offspring with the abnormality are born. If you want to test for a genetic abnormality, the first thing that you should do is contact your breed association to see how they want DNA collected for a test and where to send DNA samples.
DNA Collecting Basics
There are three common ways to obtain DNA samples from
cattle: blood samples on FTA cards, tissue samples, and hair samples. If
testing young calves, a blood sample is often preferred. There are several
videos online that demonstrate how to collect DNA samples if you are new to DNA
testing.
Collecting blood samples
Collecting tissue samples
Collecting hair samples
Managing Known Defects
After you receive the results, there are three
possible ways to keep the tested abnormality from appearing again:
Cull the
carriers.
Make sure not to mate two known carriers.
Utilize
crossbreeding.
Culling the known carriers and not using carrier bulls will eliminate
the abnormality from appearing in your herd again. By always using non-carrier
bulls, none of your calves will ever present the abnormality. If the genetics from the known carriers are
too valuable to cull, you must plan your mating decisions so that two carriers
are not allowed to mate. If you use a carrier bull, all calves sired by this
bull should either be sold after weaning or tested for carrier status before
they are bred. Crossbreeding may be the easiest way to avoid genetic
abnormalities. It’s very rare for one abnormality to segregate within two
breeds, but it’s not unheard of. For example, Tibial Hemimelia (TH) segregates
in both Shorthorn and Maine Anjou, as some of the same sires were used in both
breeds. So, mating Shorthorn with Maine Anjou presents a risk of the TH
abnormality appearing in calves.
Further, if both the sire and dam share a breed (e.g., both sire and dam
are Angus-influenced), mating these individuals could still result in the
appearance of a genetic abnormality.
DNA Test Available
Producers can often order tests for genetic
abnormalities along with other DNA tests. These DNA tests are priced based on
how many tests you want them to perform. Most DNA tests for genetic
abnormalities cost approximately $25 per head, but the cost per head may be
lower if you test for more than one genetic abnormality or purchase another DNA
testing product (e.g., Igenity Profile, PredicGEN). If you wish to learn more about genetic
abnormalities and available DNA tests for these abnormalities, you can visit
websites maintained by Zoetis Animal Genetics https://www.zoetisus.com/animal-genetics/beef/index.aspx
or Neogen Corporation http://genomics.neogen.com/en/genetic-health-and-conditions. Both of these companies provide DNA testing
services for the beef industry. A more
comprehensive list of DNA test providers can be found in the article titled
“Managing Genetic Defects” authored by Dr. Alison Van Eenennaam (see references
list).
Conclusion
In today’s production environment, it is often easier
to take precautionary steps than fix something after it becomes a problem. Genetic
abnormalities may not appear in your calf crop this year, but they could down
the road. If your cowherd is at risk (e.g. you know you have used carrier bulls
in the past), testing your cowherd for abnormalities will at the very least
give you peace of mind. It might even save a calf from developing an
abnormality, which in turn, will lead to more pounds to sell at weaning time.
As part of our USDA-NIFA local adaptation grant, Michael G. Gonda at South Dakota State University has developed a course titled "Applied Beef Cattle Breeding." Christian wrote this article while participating in that course.
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All bulls purchased after February 1st, 2019 for use as natural service sires in the Show-Me-Select Replacement Heifer Program ™ must be DNA tested to have genomic-enhanced EPDs. All bulls used as natural service sires after February 1st, 2020 must have genomic-enhanced EPDs, regardless of when they were purchased. Seedstock producers classifying bulls as Show-Me-Select qualified in sale books must have genomic-enhanced EPDs on those lots. Bulls purchased prior to February 1st, 2019 will be grandfathered into the program, as is the common practice with all natural service sires. However, this grandfather grace period will end February 1st, 2020. At that time for a bull to qualify for use in the program, it must have genomic-enhanced EPDs. Why the change? The Show-Me-Select Replacement Heifer Program has the goal of producing premium heifers that perform predictably as 2 year olds. The program has a history of requiring Show-Me-Select producers to go beyond typical cat
At the January 4th Show-Me-Select Board of Directors meeting, new service sire EPD requirements were approved. All sires, artificial insemination and natural service, must meet minimum Calving Ease Direct (CED) EPD requirements. In addition to yearly updates, two changes were made. First, no Birth Weight EPD requirement will be published. All commonly used breeds now have CED EPDs available. Second, all breeds in the International Genetic Solutions (IGS) genetic evaluation are now set to a common requirement. In the summer of 2018, breeds within the International Genetic Solutions switched to a single-step BOLT multi-breed genetic evaluation. The EPDs for animals in the IGS genetic evaluation are directly comparable across breeds. In 2017, the Red Angus requirement for CED was a CED of 8, which represents the 30th percentile. Less than 5% percent of heifers breed to a bull with a CED EPD of 8 or larger had calving difficulty. We feel that this require is meeting the need to re
Bob Hough recently posted the following comment on Facebook (posted with his permission): Early in my career at a breed association, the much beloved American Angus breed executive told me that the secret to success running a breed association was to have a top junior program, keep the books straight, and make sure the numbers (EPDs) don't change. This philosophy meant Angus valued stability in their genetic predictions over keeping them up-to-date with the latest science. The Angus Association also marketed extremely effectively the infallibility of their EPDs because of the size of their database. I will start with the later. Yes, a database needs certain critical mass to make sure the animals are tied, but that can be achieved in a modest size database. After that, data quality far and away outweighs data quantity in assuring the most precise and reliable EPDs possible. On the former point, Angus breeders are simply not use to change. This is not the case in most breed associ
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