Photo By Sam Wirza

Photo by Sam Wirzba

Whether you’re talking cattle, corn or hogs, heterosis (hybrid vigor) has proven its value. There are three kinds of heterosis in cattle – individual (the calf), maternal and paternal. Of the trio, paternal heterosis has received the least attention.

Research trials report up to a 25% increase in pounds of calf weaned per cow exposed to a bull when crossbred cows produce crossbred calves. Crossbred calves demonstrate increased weaning weights and yearling weights when compared with the average of parent breeds.

Maternal heterosis in a cow increases her performance and that of her calves. She reaches puberty earlier, rebreeds more quickly, her calves have greater survivability, she stays in the herd longer, and  she produces more pounds of calf during her lifetime. Now some producers are looking at possible advantages of utilizing paternal heterosis, and improving reproductive characteristics of the bull. 

Simplifying crossbreeding

Wade Shafer, American Simmental Association (ASA) director of performance programs, has worked with ASA’s multi-breed genetic evaluation, comparing seedstock of all breeds and breed combinations.

“Crossbred sires simplify crossbreeding. After you’ve settled on an optimal proportion for your herd, you can keep it that way by using crossbred bulls,” Shafer says.

“If you want a half-Simmental, half-Angus cowherd, and start with Angus cows, you can use a Simmental bull and produce heifers of the desired mix. The next step is to use a SimAngus bull on those heifers to maintain the desired proportion of each breed. This results in higher uniformity than if you rotate back and forth between purebred sires,” he explains.

Shafer says the beef industry has long encouraged use of purebred sires in rotational crossbreeding systems. Academics point out that rotational systems using purebred bulls produce slightly more heterosis. For example, a two-breed rotation using purebred sires will settle at 68% of maximum heterosis. Meanwhile, two-breed, half-blood sires on a herd with the same breed composition will result in 50% of maximum heterosis.

“But it’s very cumbersome to maintain a rotational crossbreeding system, as it requires sorting bulls and females into multiple breeding pastures. With crossbred seedstock, you can maintain nearly as much heterosis and it’s as simple as a straightbred system – you just turn out the bulls,” Shafer says.

Jack Whittier, Colorado State University Extension beef specialist, says one of the driving factors behind increased use of hybrid bulls is the fact that many cowherds have become less crossbred. “Using a crossbred or composite bull can restore heterosis – in a much more simple way than using elaborate rotational crossbreeding systems,” he says.

Scott Greiner, Virginia Tech Extension beef cattle specialist, says hybrid bulls allow for practical crossbreeding, especially in small herds. “The traditional rotational or terminal sire systems are not applicable,” he says. The producer may have only one breeding pasture and one bull.

“By using a hybrid bull, heterosis can be introduced. By keeping the heifers, maternal heterosis can be added, in a simple and practical fashion, without having wide fluctuations in breed composition from one generation to the next,” he says.

Mark Thallman, a research geneticist at the U.S. Meat Animal Research Center (MARC) in Clay Center, NE, says more heterosis is possible with an F1 bull than with a composite bull.

“However, if you want to maximize heterosis throughout the herd or system, you’re better off with a four-breed composite, or to use more than two breeds in a crossbreeding program. With a four-breed composite, you get a little less heterosis from the bull himself, but more heterosis across the whole system,” he explains.

Another option is to use a crossbred bull that incorporates two breeds not found in the crossbred cows – creating a calf with genetics of four breeds, for maximum heterosis.

“One caution about composites or hybrids is that you have to be just as careful about inbreeding with them as you do with straightbreds,” Whittier says. “As inbreeding increases, heterosis decreases. If you’re using hybrid bulls to get heterosis back into your cows, be careful to not keep using the same lines, or you’ll lose that advantage.”