Deciphering Genetic Data for Better Beef Cattle Management
By Gilda V. Bryant
Some ranchers may find expected progeny differences (EPDs) confusing and may have little experience in translating genetic data into useful management decisions. With a little help from DNA companies, beef cattle breed associations and seedstock producers, commercial and seedstock ranchers can tackle EPD reports.
John Ford, executive director of Santa Gertrudis Breeders International (SGBI), reports his organization was the first beef breed association to use a single-step methodology for calculating genomic-enhanced expected progeny differences (GE-EPDs). The single-step approach incorporates all available pedigree, genotype and phenotypic information into a single evaluation with accurate, reliable statistics.
“EPDs provide cattle producers with tools to evaluate breeding animals,” Ford explains. “They predict the performance of each offspring from individual animals and the genetic transmitting ability of an animal as a parent. I like to tell people that the calculation of EPDs is rocket science. They’re complex, statistical calculations based on [many] performance records of individual parents, progeny and relatives. They include calculations that incorporate genetic relationships between traits. It is a very difficult, complex statistical analysis. It is rocket science, but it isn’t rocket science to use an EPD.”
EPDs appear on an animal’s pedigree along with its tag or tattoo registration number, date of birth and owner’s name, for identification purposes. SGBI measures maternal, growth and carcass traits. For example, growth traits may include birth weight (BW), weaning weight (WW) and yearling weight (YW). Maternal traits include maternal milk (MAT) and maternal weaning weight (TMAT). Carcass traits include carcass weight (HCW), marbling (MARB) and ribeye area (REA).
Examples of EPD data can be found online at santagertrudis.com/epds.html. EPDs are always reported in the same unit of measurement as the trait. For instance, the birth weight EPD is expressed in pounds and yearling height EPD (YH) is reported in inches. Each bull is ranked as a percentage comparable to every other bull in the SGBI database.
Once a rancher determines his or her cattle breeding goals, EPDs allow the rancher to focus on the qualities most important to that operation. If the priority is weaning weight (WW), he or she can decide between two bulls by looking at their weaning weight EPDs.
Here is a simple example. Bull A has a WW EPD of 10 pounds. Bull B has a WW EPD of 5 pounds.
On average, Bull A will sire calves weighing 5 pounds heavier than offspring sired by Bull B. Testing gives the commercial producer improved accuracy and trust in genetic data.
Consider the environment when looking at EPDs
For the best results, cattle must fit their environment before producers use EPDs to meet production goals. For example, Ford says using EPD data can help producers avoid mistakes with the maternal trait of milking.
“A producer in West Texas, where forage is very limited, will want to select an animal with a lower value for the EPD that determines milk,” Ford reports. “Yet, a producer in East Texas, with higher rainfall and abundant grass, may select animals with a higher value for maternal milk. Utilizing this information can not only help producers reach their breeding objectives, but also avoid mistakes, including selecting an animal that doesn’t fit their program or environment. They can simply make sound selections and breeding decisions based on EPDs and/or other information generated by genetic evaluation.”
Evaluating the expensive or difficult-to-measure traits
Thanks to EPDs, ranchers are now able to assess traits such as carcass traits, which normally would be expensive or difficult to measure.
By using EPD information generated by a beef cattle breed association’s genetic evaluation, a rancher can place selection pressure on carcass traits. Improved carcass characteristics enhance marketing opportunities, which in turn increase profitability. Santa Gertrudis breeders have been able to boost carcass quality by choosing positive marbling EPDs.
“As seedstock producers, we need to utilize all these tools in the SGBI toolbox, making sure we’re producing the type of cattle that are profitable for our bull-buying customers, a profitable product for everyone else in the industry chain and a product that pleases consumers. I also encourage commercial cattlemen who are looking at the Santa Gertrudis genetic package to let seedstock providers know what your needs are. Ask them for help in utilizing all these new tools we have in the industry toolbox.”
The R.A. Brown Ranch is a family-owned ranch near Throckmorton, which has been in the seedstock business since 1895. Fifth-generation rancher Donnell Brown raises three commercial and seedstock cattle breeds — Angus, Red Angus and SimAngus™. As the president of the Beef Improvement Federation, an industry leader in applied beef cattle genetics, Brown is in a unique position to understand and utilize DNA testing and EPDs. He says EPDs are like the invoice pricing sheet on a new vehicle.
“Both tell you what to expect when you buy it,” Brown explains. “A window sticker tells you what is under the hood and inside the cab. It tells you what to expect from the vehicle in terms of power, efficiency, convenience and entertainment. A bull’s EPDs are similar in that they tell us what we can expect in his offspring. Like the long list of features on a window sticker, there are many EPDs. They can all be summarized into five economically relevant traits for beef cattle: calving ease, growth, carcass, maternal and efficiency traits.”
Historically, most EPDs have measured production or revenue traits, such as weaning weight or yearling weight, which is when most producers sell their calves. However, new traits focus on the cost side of the profit equation.
EPDs for heifer pregnancy and stayability indicate whether a bull will produce fertile daughters that are more likely to stay longer in the herd as producing females.
By selecting for females with enhanced fertility and longevity, Brown does not have to replace cows as frequently. He believes all cattlemen should consider buying bulls that have been DNA tested, and therefore have genomically enhanced EPDs.
“Let’s say you need to breed heifers and you have two bulls with the same EPDs,” Brown explains.
“One of the bulls has never had a calf; however, you used the other bull the previous year and all the calves were born easily. The bull with the full calf crop of proof is the obvious choice because we have a higher level of trust in his ability to produce calves that are born without assistance.”
DNA testing helps increase the accuracy of EPDs by about the same amount as one full calf crop. DNA testing is especially helpful for traits that are the most difficult and expensive to measure. Brown tests every animal on his operation for feed efficiency traits at a cost of $100 per head.
“We are finding animals that grow fast but eat half as much feed as those on the other end of the spectrum,” Brown explains. “It’s an expensive trait to measure and, as a result, few people are measuring it. DNA is a tool to help us identify the genetics of cattle that are more efficient. I think the next great frontier of cattle production is the measurement and selection for improved efficiency.”
By utilizing genomically enhanced EPDs along with the DNA testing of heifers for strategic selection and management, Brown produces more profitable cattle. Tests supply measurements to help him select commercial replacement females in his herd. He predicts this test will continue to improve and be more cost-effective. Brown encourages producers to use DNA tests after they have selected cattle that meet their needs for age, size, docility, structural soundness and conformation.
Brown sorts replacement heifers that fit his criteria. Keeping about 30 percent more than he needs, he then breeds them but keeps only the heifers that conceive in the first 30 to 45 days. This management strategy ensures that all his heifers calve early in their first calving season, and therefore have more time to be re-bred during the hardest year of their lives — while raising their first calf. As a result, they are more likely to stay in the herd long-term, consistently producing older calves that weigh more at market time. By matching his heifers to the environment, and selecting the phenotype he prefers, these management steps enhance the animals’ profitability. Brown also applies additional female testing strategies.
“To qualify for premium marketing programs, such as Top Dollar Angus, sires of your calf crop must meet certain EPD criteria for growth and carcass traits,” Brown explains. “Or you can DNA test a percentage of the calves to qualify. There’s no need to test steers that are going to harvest… just test the heifers you selected as keepers. If they qualify for the market premiums, their brothers will, too. I can tell more than just the carcass value and possible feedability with the commercial DNA test. I can also tell the maternal traits in the same test. Using DNA testing in this manner helps cattlemen decide if they should feed their steers and cull heifers or let someone else take that risk, while simultaneously finding females that should make more profitable mothers. It also gives producers a baseline for where their current herd ranks for all economically relevant traits and therefore gives them an idea of what kinds of bulls need to be purchased in the future to enhance the profitability of the entire herd.”
Translating EPDs into workable knowledge
Commercial cattle raisers have several options for finding assistance to interpret EPD data. Ranchers may visit with DNA- testing company representatives who are eager to explain how their testing works, and breed associations are equipped to assist producers. Bull providers also give customers accurate genetic information.
Brown says the value of a bull is not in the registration papers but in the ability to accurately predict the genetic merit of the animal through the DNA testing and registration process. He encourages commercial beef producers to test their current bulls to determine where their genetics stand while helping them become more comfortable with DNA technology. In fact, Brown recommends that ranchers, who might think they are saving money by purchasing or keeping unregistered bulls, DNA test the bulls to learn more about their genetics.
Although each bull is an investment, some producers choose to pay for it by investing in better genetics to produce more valuable offspring. Others may pay for it by using lower-quality bulls with the opportunity costs of less weight to sell and less valuable cattle.
“The mating decisions on our ranch are extremely important to us for the future of our business,” Brown concludes. “Many people believe DNA testing is a silver bullet. I wouldn’t go that far, but we can test our commercial or registered animals and know their genetics to a high degree of accuracy. But we still need to provide smart management. Management on the female side is a big factor. On the bull side, genetics come first.”
Deciphering Genetic Data is excerpted from the June 2018 issue of The Cattleman magazine.