Extension Communications
3614 Administrative Services Building
Ames, Iowa 50011-3614
(515) 294-9915
8/16/00
Contacts:
Daryl Strohbehn, Iowa Beef Center, (515) 294-0847, stroh@iastate.edu
Darrell Busby, Iowa Beef Center, (712) 769-2600, dbusby@iastate.edu
Elaine Edwards, Extension Communications Systems, (515)
294-5168, eedwards@iastate.edu
Tenderness Test Results Show Potential Genetic Differences
AMES, Iowa -- Tenderness evaluations on 119 steers entered in the Iowa Beef Tenderness and Carcass Evaluation Project were completed the first week of August, according to Daryl Strohbehn, Extension beef specialist with the Iowa Beef Center at Iowa State University.
"We are elated with the results from this year's project," Strohbehn said. "The main objective of this project is to assist Iowa producers in evaluating seedstock and finding out which sires do the best job of producing calves highly desirable in tenderness."
All cattle in the project were brought to a central test location in December for feeding and management. "This is done to equalize the differences due to feed and environment and make the genetic evaluation more exact. Then, as near as practical, the cattle are harvested at similar fat thickness, thus minimizing the influence of this variable on tenderness," Strohbehn said.
The day following harvest, one ribeye steak is obtained from each carcass. The steaks are trimmed of fat and bone, cut to one-inch thickness, sealed and allowed to age for a total of 14 days. Because the cattle were harvested on two different dates all steaks were frozen following the aging process.
To evaluate tenderness all steaks were thawed and cooked to an internal temperature of 160 degrees F, which is equal to a chef's equivalence of medium doneness. Following cool down, the steaks were cored in six places and evaluated for tenderness using the Warner-Bratzler shear force technique.
"We certainly believe this project is succeeding in showing differences between sires," Strohbehn said. "Our best sire had five progeny tested and they averaged .82 lb. less shear force than the average. That's a 14 percent advantage in tenderness," he continued. "A lower shear value is better. A lower force value means that it takes less biting power to cut through the muscle fibers, resulting in an easier to chew and more tender product for the consumer."
The lowest sire for tenderness had four progeny that averaged 1.65 lb. more shear force or a product that is 28 percent less tender than the average.
"The important question is how much of the differences seen here are genetic," Strohbhen said. Recent reviews of research studies concluded that approximately 20 to 25 percent of this difference is genetic and the rest is due to management and environment.
"If you look at other economically important traits like calving ease, growth rate or carcass quality grade, you will see similar heritabilities," Strohbehn said. "Our challenge with tenderness improvement is the difficulty of measurement. That's why our scientific community is seeking out gene markers and chemical assays which will allow for easier, faster and less expensive methods of evaluation."
The Iowa Beef Center has plans to continue this tenderness evaluation project and invites Iowa producers to consign progeny by known sires in the 2000-2001 project.
Results of this year's test and information on next year's test can be obtained by visiting the Iowa Beef Center Web page at www.iowabeefcenter.org or contact the Iowa Beef Center at (515) 294-BEEF.
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