As the beef industry strives for improvements in quality and predictability, some cite the diversity of beef-cattle breeds as a problem. “Seventy-some breeds,” the argument goes. “How can we compete with the genetic uniformity in the pork, poultry and dairy industries?”
This genetic melting pot can present challenges, but the depth of the gene pool also provides benefits. One of these, of course, is the availability of breeds or breed combinations that work in different environments. Another is the productivity offered by heterosis, or hybrid vigor.
Properly designed beef-cattle crossbreeding programs have the potential to substantially improve production efficiency, says Texas A&M University beef-cattle geneticist Andy Herring.
The value of heterosis
For a pair of breeds evaluated in the same environment, Dr. Herring explains, the heterosis or hybrid vigor for a characteristic is the amount the average of the F1 offspring exceeds the
average of the two pure breeds. Say, for example, the average weaning weight for purebred Brahman is 500 pounds, and the purebred Hereford average is 460 pounds. Then assume a Brahman-Hereford cross results in weaning weights averaging 516 pounds and a Hereford-Brahman cross averages 540 pounds. The average weaning weight for the two types of F1 crossbred calves would be 528 pounds, while the average for straight-bred calves from the two breeds is 480 pounds. The difference is 48 pounds, or a 10 percent improvement.
Heterosis is most important for female productivity, says Wayne Vanderwert, executive director of the American Gelbvieh Association. He also points out the inverse relationship between heterosis and heritability. “For moderately heritable traits such as growth and milk production, we might find a 10 percent advantage when the parents are from two different breeds,” he says. “The big difference is in less-heritable traits such as calf survivability, weaning weights, fertility and longevity, where heterosis can provide a 25 to 30 percent advantage.”
More than half of the effect, Dr. Herring adds, is dependent on the use of crossbred cows. Data from USDA’s Meat Animal Research Center indicates that breeding straight-bred cows to produce crossbred calves provides an 8.5 percent improvement over straight-bred calves, in terms of pounds of weaned calf per cow exposed. Crossbred cows producing crossbred calves, however, provide a 23.3 percent improvement. Heterosis also tends to be higher in breeds that are more genetically different from each other. So, heterosis can increase production per cow by 20 to 25 percent in Bos taurus x Bos taurus crosses, but the advantage can reach 50 percent in Bos indicus x Bos taurus crosses.
The cow-calf dilemma
Seedstock breeder Lee Leachman, manager of Leachman of Colorado, says that in beef-cattle production, breeding decisions affect the end product but also affect the future design of the factory. “Ranchers sometimes pay a premium for bulls to produce high-value feeder calves, but they mess up their factory by making their cows too big and giving up heterosis.” As they set goals for a breeding strategy, producers typically make some kind of compromise:
Use terminal crosses only, sell the calves as feeder cattle and purchase replacement females. Mr. Leachman stresses that heifers coming from a true terminal cross will be too big and high-maintenance for use in the breeding herd.
Breed for and sell top-quality replacement females. Steers will lack some of the growth and muscling traits that make efficient feeder cattle, Mr. Leachman points out.
Use a middle-of-the-road approach breeding for maternal traits, calf performance and carcass quality in the same herd. Mr. Leachman says this strategy gives up a little at both ends — heifers that are bigger than ideal and feeders that are less than ideal.
Dr. Vanderwert notes that Cattle-Fax data shows the industry as a whole has not made significant improvements in the percentage of cattle grading Choice, and yet the incidence of Yield Grade 3 and 4 carcasses is increasing. “We need to be smart about crossbreeding,” he says. He believes producers should use heterosis for efficiency in the breeding herd and use breed complementarity to build performance and carcass quality in the calf crop.
Composites bulls, Dr. Vanderwert says, make crossbreeding easy and can provide more consistency in the calf crop compared with rotating between different breeds of bulls. Mr. Leachman agrees. “Crossbreeding using straight-bred cattle is complicated, and composites simplify the process.”
Having your cake and eating it, too
Leachman of Colorado owner Dallas Horton encourages commercial customers to seek the best of both worlds by using maternal and terminal sires. He says maternal crosses should take full advantage of heterosis, producing efficient, moderate-sized crossbred replacements. Too often producers breed too much size into their cows by trying to produce bigger, heavier feeder calves, he says.
“Bigger cows are tough to breed back and require more feed,” Dr. Horton says. “Even in a good environment, a 1,200-pound cow is about 16 percent more productive than a 1,400-pound cow. The bigger cows will have up to a 10 percent higher open rate, unless it is hidden with supplemental feeding.” Heterosis in moderate-sized cows provides heavier weaning weights, higher weaning rates and better longevity, all with the same or less feed, he says.
Terminal crosses, on the other hand, should capitalize on heterosis in the cow herd and breed complementarity, producing calves that grow quickly, gain efficiently and produce a high-value carcass. “This is the way the pork industry does it,” Dr. Horton says. “They have boars that make gilts and other boars to make bacon and ham.”
On the terminal side, Dr. Horton says, “we want to mate a moderate, crossbred cow to a big, heavily muscled bull. Using a true terminal-cross bull will give you 25 to 40 pounds of extra weaning weight. At slaughter, a terminal-cross bull can provide 200 pounds more live weight to sell, compared with a middle-of-the-road bull.”
Dr. Horton practices what he preaches on his own ranch in central Wyoming. His 2,500-head cow herd is all black and all crossbred. On one part of the ranch, he breeds about 1,500 Angus-cross cows to the biggest black composite or Charolais bulls he can find. These terminal crosses produce steers and heifers that perform well in the feedyard and offer a high value to the packer.
On another part of the ranch, he breeds about 1,000 cows to black composite bulls selected for moderate size and maternal traits. He selects composite replacement heifers from that calf crop. Their steer mates are good quality but lack some of the growth and feed efficiency of the terminal-cross calves, he says. They’ll grade well but finish at lighter weights. Improvements in the cow herd easily compensate for the lesser-value feeder steers, he says.
Using color as a genetic marker can simplify this system for producers, Dr. Horton says. With a black Angus-based cow herd, he suggests using Charolais terminal-cross bulls and black maternal-cross bulls. The smoky-colored feeder calves are easily distinguished from the black calves bred as potential replacements. Producers who can maintain separate breeding herds and calf crops can use black or red terminal-cross bulls on their black or red cows.
The key point, Mr. Leachman stresses, is to use bulls for specific purposes. “If you are keeping replacements, use a bull that will build the right size, crossbred cow. Remember, no bull can do everything.”