Using Genomic Tests to Detect Genetic Abnormalities in Beef Cattle

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:

  1. Cull the carriers.
  2. Make sure not to mate two known carriers.
  3. 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.

References
Van Eenennaam, A. 2015. Managing Genetic Defects. http://articles.extension.org/pages/72662/managing-genetic-defects

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.

Comments

Post a Comment

Popular posts from this blog

ARSBC 2018: EPDs and Reasonable Expectations in Commercial Crossbred Operations

Image
Jared Decker, PhD
University of Missouri
One point must be clear from the very beginning: EPDs work. When we select parents based on EPDs the genetic merit for that trait increases in our herd. When we select the parents using EPDs the performance of the next generation improves. EPDs Defined EPD stands for Expected Progeny Difference. These three words are loaded with meaning, thus the need to define them here. The most loaded word is Expected. Here we use Expected the way a statistician would use the word. Expected means we are making a prediction of a future value. But, in this context, Expected also means we are describing the average of a group. What is the group for which we are predicting the average? We are predicting the average performance of the Progeny or calves out of an animal. An animal’s own performance and its EPD can be quite different, because that is not the purpose of an EPD. The EPD is predicting the average performance of that animal’s calf crop. Finally, EPDs are u…
Read more

Neogen launches upgraded Igenity® Beef Profile

Commercial beef producers will get more traits and selection index tools in the upgraded Igenity® Beef profile.
The Igenity Beef Profile will offer 16 traits for $29, replacing Neogen’s 13-trait Igenity Gold ($40) and 6-trait Igenity Silver ($25) tests. The upgrade includes new predictions for weaning weight, yearling weight and hot carcass weight for a total of 16 traits scored on a 1–10 scale, plus two new selection indexes.
“Our customers will be getting a powerful new profile at even greater value,” said Dr. Stewart Bauck, vice president of agrigenomics at Neogen. “The Igenity profile was designed and validated for crossbred or straightbred cattle with backgrounds of Angus, Red Angus, Simmental, Hereford, Limousin and Gelbvieh.
“Most DNA profiles are breed-specific,” Bauck continued. “The novel design of Igenity Beef allows for the accurate prediction of performance in both crossbred or straightbred cattle among the target breeds. This lets cow-calf producers use a DNA profile to …
Read more

EPDs 101: Use Information to Improve Your Herd

Image
Jared E. Decker
Associate Professor, Division of Animal Sciences, University of Missouri

Reprinted with permission from The Cattlemen and Santa Gertrudis Breeders International.

Can we be frank for a minute? It is quite simple: EPDs work. When we use EPDs to make selection decisions (which bulls to buy, which females to keep and cull), the performance of our herd improves. Let’s discuss why EPDs work, how they can be used, and pitfalls to avoid. Defining EPDEPD stands for Expected Progeny Difference. “Expected” in this context is a loaded word. We use it here the way a statistician would use it. Expected means we are describing a prediction of the future. Expected also means we are discussing an average, not a single observation. What is the average that we are predicting with EPDs? We are predicting the average progeny, or the average of an animal’s calf crop. Finally, when we are discussing EPDs we are discussing differences. Either the difference between two animals or the difference b…
Read more