By Larry Dreiling
Research into new types of cattle expected progeny differences (EPDs) was a highlight of the 5th annual open house at the University of Nebraska-Lincoln's Gudmundsen Sandhills Laboratory, near Whitman, Neb.
Dr. Jim Gosey, UNL professor of animal science and Extension beef specialist, explained that an evolution is taking place in the use of EPDs, those estimates of genetic merit based on performance versus like animals, trait heritability, and correlation with other traits.
Gosey noted how the use of EPDs has changed growth traits in cattle, particularly in the last 15 years, as cattle producers have become better at using them for breed selection.
"The evolution of EPDs has led us from obvious production traits to more sophisticated carcass EPDs, which are many of the traits we use today," Gosey said. "We've got things like product percents and so on. That even includes the use of ultrasound data on live cattle to estimate intramuscular fat, ribeye size, backfat and ultimately retail product size."
Among the seven major cattle breeds, there are 24 EPDs. For some people, Gosey said, that number might prove intimidating. Other producers, meanwhile, are demanding even more data.
"It's awful tough sometimes, to know how to use the darned things and you need to have some sort of simplicity to them," Gosey said.
He particularly noted that use of EPDs determined via ultrasound on live cattle is so vast that it outstrips the amount of actual carcass data by a 4:1 ratio.
Measure of carcass merit
"Everyone's going to have their own interpretation as to what kind of data is most important," Gosey said. "The ultrasound data is a large dataset. It actually does an excellent job of estimating the percent of fat in the ribeye, perhaps even a more accurate job than what's done by federal graders."
One of the newest carcass EPD has recently been developed by the American Simmental Association, Gosey said, which measured 102 bulls for tenderness based on the shear force of their progeny.
"This was developed over the course of about four years in measuring these bulls and their steer progeny," Gosey said.
Measure of fertility
In the last few years, breed groups such as the American Red Angus Association have developed EPDs for fertility and maintenance energy.
"The only way the Red Angus people have been able to do this is because they are the only breed that does whole herd reporting," said Gosey, who added that it wouldn't surprise him if all major breed associations develop fertility EPDs.
"Every female in the breed is accounted for in one way or another. Whether she's open or culled for a specific reason, there is a position mark for every female in the breed. It's the only way they can deal with fertility traits."
Among these new fertility trait EPDs are heifer pregnancy percentage and "stayability" percentage. The former is the probability that a bull's daughters will conceive to calve as a two-year old. The latter is the probability that after a bull's daughters enter a herd, they will remain productive until six years of age.
"Stayability is a measure of longevity," Gosey said. "The reason cows fail to achieve maximum longevity is generally because they're open, but it's also because of poor calf production. They produce reject calves. There are also conformation problems, like udders, bad feet, temperament and body condition.
"It may not be a perfect measure and we can quibble about the ways we can improve it, but at least it's some measure of longevity and that's important stuff. At least it's in the right area of not only determining the growth rate of cattle, but to take the next step and evaluate the complex of fertility traits."
Culling older cows maybe nothing new to the cattle producer, but a stayability EPD could prove valuable because it could reduce replacement rates. Red Angus breeders, Gosey said, have already seen some reduction in replacement rates through use of this newer EPD.
"Anytime you reduce replacement rates, you turn over the number of higher value cattle you have to sell, since you have more younger cattle to sell and fewer old culls that sell at old cull prices," Gosey said.
While the heritability of heifer pregnancy and stayability EPDs by Red Angus cattle is low, there still is much to be gained by the hybrid vigor selection by these EPDs can offer, Gosey said.
"We all know that hybrid vigor has its greatest impact on low heritability traits, because they all tend to be influenced by environment," Gosey said. "If we can restir the hybrid pot, if you will, we can help ourselves with these traits."
Measure of maintenance
Another new EPD is maintenance energy (ME), or the metabolizable energy required for maintenance of cow body weight. It is expressed in megacalories per month for a mature cow.
"Again the Red Angus breed is the only one that is doing this," Gosey said. "The idea is to look at bull groups of daughters, of which some bulls daughters will be more costly to maintain."
ME, Gosey explained, is measured from the prediction of mature cow size and the prediction of that cow's milk production. It is a measure of feed input, not of feed efficiency.
"We can easily visualize mature cow size as having an impact on feed requirements," Gosey said. "More importantly, it brings milk production into focus."
All breeds have a milk production EPD, Gosey explained, that offers a good estimate about the milk production of bull's group of daughters. Using these two ME predictors can determine feed requirements that tend to be proportional to body surface area in cattle.
"In other words, the weight of that cow is taken to the three-quarter power," Gosey said. "If we have to put weight on our cattle, we can estimate feed needs base on that and using milk production, we can adjust that amount based on maintenance energy."
Using all these EPDs as a group can net good cows, but it takes observation to make it work, Gosey said.
"We as commercial cattlemen have to put a hard pencil to efficiency," he said. "We cannot just look at outputs, which we've done for the last 40 years, but also look at the combination of output and input to really get at efficiency."
Measure of profit
The daunting numbers of new EPDs have led three breed associations to develop profit indices that merge economics with genetics and uses correlations between traits. That in turn reduces the number of EPDs producers need to glean through to get to a suitable animal.
"One way toward simplification is that American Angus Association has published what are selection indices. So has the American Gelbvieh Association and the American-International Charolais Association," Gosey said.
Angus breeders recently developed three trait indices: the $ Feedlot Index, the $ Grid Index and the $ Beef Index.
"The $ Feedlot trait is a combination of the growth trait and the prediction of feed intake that would relate to performance in the feedlot coupled with an economic weighting of the Choice:Select spread," Gosey said. "What are the discounts on Grade 4s, or on low weights and high weights, or dark Cutters?
"Taking a rolling average of the last three years of carcass prices and putting together the economic weighting with its estimate of growth and producer value gives you the $ Feedlot index. This way you can go into that sire evaluation and see that estimate and compare every bull in the Angus breed to every other bull based on that calculation."
The $ Grid refers to a combination of quality grade and yield grade.
"It's a combination of things like retail product, yield and ribeye size on the quantity side and things like marbling scores on the quality side," Gosey said. "It's weighted by the economics of the particular grid. The combination of those two indices produce the $ Beef Index."
Gosey warned that this index only is good for examining post-weaning traits.
"There is a real need for the Angus association to take the next step and look at what you might call a $ Cow-Calf Merit or $ Fertility Index. There needs to be an index of all the things that take place before that calf is weaned. The loop will not be complete until we get back in front of weaning time," Gosey said.
The American Gelbvieh Association has a similar program as their Angus friends with their Feedlot Merit and Grid Merit Indices, Gosey said.
"The idea is to evaluate Gelbvieh and Gelbvieh Balancer or composite Gelbvieh-Angus bulls and based upon their feedlot and grid merits," Gosey said. "The Charolais people have introduced a Terminal Sire Profitability Index that is combination economic weighting to genetic estimates."
Gosey offered two cautions in using these types of indices. First, some traits work against each other and second, extreme EPDs work together to compensate to make attractive cattle.
"Make sure we don't get wrapped up in a $ Feedlot Index and forget about not making a profit on the cow side. We need better estimates from these breeds about cow-calf merit and fertility EPDs," Gosey said.
"Also you can have cattle that marble poorly but are very lean and have very high retail product. You can put those two together and come up with fairly appealing index. That's dangerous. You need to have independent culling levels before calculating the index level."
The newest EPDs being tested, but not yet released, are genetic marker EPDs using DNA sampling as an enhancement, though not a complete replacement for progeny testing.
"Eventually there will be a way to incorporate individual gene tests into EPDs enhance value," Gosey said. "If you could identify genes that predict marbling and find steer progeny out that bull, then you could increase the value of that marbling EPD."
Currently, tests are available for marbling, tenderness and fat metabolism.
"A high fat metabolism marker can reduce the way those cattle need to be fed in order to reach a certain level of marbling."