Depending on how you look at it, a bull-sale catalog is either packed with useful information or as confusing as a poorly translated instruction manual for a made-in-China entertainment center.
Development and application of expected progeny differences (EPDs) over the past 30 years, and more recently the incorporation of genomic predictions, have enabled dramatic progress in genetic selection.
However, the complexity of sorting through the growing list of EPDs can be daunting for many bull-sale customers. Also, a list of EPDs offers a temptation for ranchers to focus too much on one or two traits, gradually shifting the genetic makeup of their cow herds into undesirable territory.
That is where the selection index comes in. Virtually all the major breed associations now use at least one selection index, which combines a weighted list of EPDs for economically important traits to calculate a single rating, based on revenue potential, for comparing bulls.
Seedstock producer Willie Altenburg, of Altenburg Super Baldy Ranch in northern Colorado, believes strongly in the use of indexes. Producers often do not have the time or inclination to evaluate all the EPDs available on bulls or AI sires, he says.
Altenburg, who also serves as associate vice president of beef marketing for Genex cooperative, adds that an index, by definition, encourages multitrait selection. Indexes can help ranchers work toward specific genetic goals based on their production and marketing systems. He stresses, however, that bull buyers need to understand the index and know its limitations.
University of Nebraska animal scientist and geneticist Matt Spangler, PhD, says using an index helps mitigate the cumbersome nature of multi-trait selection and allows selection of bulls based on projected revenue or profit, at least to some extent. They do so by combining multiple EPDs, each weighted by an economic value, into one numeric value often expressed in dollars per animal. Along with “output” measures such as growth and carcass traits, an index also can include EPDs related to “inputs,” such as feed intake, that play a major role in profitability.
Applied properly, economic indexes are powerful tools for selecting cattle based on their potential to generate revenue, Spangler says. Ranchers need, however, to understand the underlying assumptions within an index before applying it toward their genetic selection.
Breed toward a goal
Spangler stresses that different indexes include different traits and associate different economic values with them. So, you must evaluate indexes based on traits you intend to emphasize in your herd. He adds that economic indexes allow for superiority in one trait to offset average or below-average performance in other traits. A sire with an above-average index value may not be above average for all its component EPDs but is superior in one that is weighted heavily. Also, the accuracy values associated with EPDs in an index influence how accurate the index will be.
Spangler advises ranchers to know the breed-average values for particular indexes and to use percentile ranks to determine how far above or below average a particular animal is compared to the rest of the breed.
Altenburg stresses the importance of matching any index to a ranch’s production system and marketing goals, and to look at the big picture. We’ve seen trends in the past in which the industry goes too far in one direction in genetic selection, he says. People assumed if milk production is good, maximum milk production is better. But we learned that single-trait selection leads to problems eventually.
Although indexes are designed to avoid single-trait selection, Altenburg says using an inappropriate index can lead to similar results, either within a herd or within a breed. Focusing selection pressure on carcass traits, for example, can result in a decline in maternal traits over time if a rancher retains heifers from those matings.
Indexes built primarily on EPDs for growth and carcass merit are good for terminal crosses, Altenburg says, but most ranchers want to produce replacement females from their own herds. They need to evaluate and select the appropriate index based on factors such as whether they plan to keep replacement heifers, sell all their calves at weaning or retain ownership beyond weaning.
Spangler agrees, saying some breed associations have developed multiple indexes for specific goals. For Angus cattle, for example, the $Beef index is a terminal index combining traits affecting feedyard value and grid value for finished cattle. It does not include maternal traits. If a rancher retains all calves through finishing, including heifers, or sells them all to a buyer who recognizes and pays for genetic merit, selecting based on $Beef can add value. But in a cow herd from which a rancher retains heifers for breeding, the Angus $W index, based on weaned calf value, is more appropriate.
Within his seedstock herd, Altenburg uses his own selection indexes along with individual EPDs. He has a separate “Willie index” for bulls used to breed heifers, focused on calving ease and light birthweights but possibly giving up some growth potential. His index for bulls mated to mature cows focuses more on growth traits, possibly giving up some calving ease.
Spangler says selection indexes are, and should be, dynamic and subject to change as breed associations incorporate more data, new EPDs and genomic or molecular breeding values (MBVs) for new traits. Researchers and breed associations, he says, are working to refine MBVs for traits associated with feed efficiency, which, as they are added to indexes, will help producers more accurately evaluate the production- cost side of the profit equation in their genetic selection, along with traits related to output such as weaning or yearling weights, feedyard gain and carcass values.
The potential for using genomic information to improve EPD and index accuracy continues to grow as the tests improve. Several breeds including Angus, Gelbvieh, Hereford, Limousin, Red Angus and Simmental currently incorporate MBVs into their EPDs for some traits. Over time, genomic technology will allow development of MBVs for additional economic traits relating to reproduction, animal health, production costs and beef quality.
Over time, Altenburg would like to see indexes become more interactive, allowing customization based on a producer’s individual goals and needs. He also believes cattlemen should have input in the development of indexes at the breed level, rather than relying on “PhDs in an office” making all the decisions.
Spangler agrees, saying selection indexes will likely become more flexible in the future. He cites the Charolais terminal index as one that allows input and customization from the producer. Ranchers using this index provide economic and herd-based assumptions through the American International Charolais Association’s web-based sire search. Users enter historical information about their herd such as average cow weight, length of the backgrounding phase, calf price, fed-cattle price and other performance information. The association’s database returns a list of sires that best suit the needs of the commercial producer.
Altenburg believes there could be an opportunity for university Extension specialists and perhaps students to work with individual ranchers to develop customized indexes for their herds, based on the production environment, genetic makeup of the cow herd, the rancher’s marketing plan, long-term goals and other factors. “One size does not fit all,” he says.
“Economic indexes are a valuable tool from which producers can make genetic change,” Spangler concludes. “Understanding the components of an index and the production scenario it is designed for is critical to avoid unwanted or unexpected results.”
Sidebar: Target your market
Several of the available economic indexes focus on terminal traits, but, Spangler says, relatively few producers capitalize on the opportunity to use terminal- cross systems. Ranchers tend to expect bulls to be good at everything, producing high-value feeder steers that excel at every stage and replacement heifers with excellent maternal traits. Some bulls do well in that regard, but generally speaking, the “all-around” bull gives up some potential for either maternal, growth or carcass traits.
A bull that produces moderate, easy-maintenance replacement heifers, for example, probably gives up growth potential in steer progeny. A bull that produces steers that gain quickly on the ranch and in the feedyard and produce heavy, high-value carcasses probably will sire females that grow too big and cost too much to maintain on the ranch.
Ranchers can avoid that dilemma by selecting terminal bulls based on growth and carcass traits, and purchasing all their replacement heifers. On some large ranches, another option is to maintain separate cow herds for maternal and terminal crosses. Some ranchers use maternal-calving-ease bulls on first-calf heifers and terminal bulls on older cows.
As genetic and reproductive technologies continue to advance, ranchers have additional opportunity to combine available tools for targeted breeding programs. Use of AI and sexed semen, for example, could increase returns from a terminal-cross or maternal-cross program.
In either case, Spangler points out, calves of the wrong sex drag down the value of a calf crop. For every high-value replacement heifer produced in a conventional maternal cross, there is one lower-value steer that falls short in growth and carcass traits compared with steers from a terminal cross. On the other hand, heifer calves from a terminal cross have lower value as feeder cattle compared with steers due to lower gains and lighter finished weights. Using sexed semen, ranchers could produce about 90 percent of the desired sex in either system.