by: Heather Smith Thomas

Heterosis (hybrid vigor) has proven its value in many agricultural sectors—whether production of hybrid corn, hogs or beef. Research studies have reported up to 25 percent improvement 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 calves of a single breed.

Maternal heterosis, seen in the crossbred cow, increases her performance and that of her calves. She reaches puberty earlier, rebreeds quicker after calving, has greater survival rate in her calves, stays in the herd longer, and produces more pounds of calf during her lifetime. Now some producers are looking at the possible advantages of utilizing paternal heterosis (improvement in reproductive characteristics of the crossbred bull) and the benefits of using crossbred sires in a breeding program.

Simplifying Crossbreeding – Wade Shafer, Director of Performance Programs, American Simmental Association (ASA), has been working with ASA's multi-breed genetic evaluation, comparing seedstock of all breeds and breed combinations. “Crossbred sires simplify crossbreeding and also make it easier to tap into and fully utilize complementarity. After you've determined the optimal breed proportion you want in your herd, you can keep it that way by using crossbred bulls,” says Shafer.

“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 find a half Simmental-half Angus bull to use on those heifers to maintain the same proportion of each breed. This approach will generally result in greater uniformity in the calves than if you switch back and forth between purebred sires,” he explains.

“The beef industry has encouraged the use of purebred sires in a rotational crossbreeding system, rather than using crossbred seedstock. Purebreds have been promoted by breed associations as the only true seedstock. Academics have always been quick to point out that rotational systems using purebred bulls will return slightly more heterosis (15 to 25 percent). For example, a two breed rotation using purebred sires will settle at 68 percent of maximum heterosis, while using two-breed half-bloods on a herd with the same breed composition will result in 50 percent of maximum heterosis,” he says.

“One big hurdle in using a rotational crossbreeding system is that it's very cumbersome to maintain, as it requires sorting the bulls and females into multiple breeding pastures based on breed proportions. With crossbred seedstock, you can maintain heterosis and it's as simple as a straightbred system—you just turn out the bulls,” says Shafer.

Beef Industry Has Been Slow To Crossbreed - Historically, our beef industry has known for several decades that crossbreeding can improve profitability. “From a scientific standpoint, there's no question about it. We've known this for years. So we wonder why crossbreeding has not dominated our industry, like it has in other food production industries that have taken advantage of heterosis,” he says.

“One reason our industry is different is that breed associations have spent a lot of blood, sweat and tears promoting the concept that seedstock has to be purebred. This idea is deeply entrenched in seedstock breeders. We've spent lots of time, effort and money convincing the commercial industry that if it isn't purebred, it isn't seedstock, and you shouldn't be using it,” says Shafer.

“The chicken and swine industry figured out a long time ago that composites work very effectively as seedstock. There were also some beef cattle breeders that figured this out many years ago, but they were ostracized by other breeders and by the breed associations,” he says.

Some of the early composites in this country—Brangus, Santa Gertrudis, Beefmaster, Braford, etc—gained acceptability, but it was because their breeders promoted them as breeds. “They were not thought of as composites; in most people's minds they became breeds. A friend of mine in North Dakota developed a composite and he called them Continentals. He didn't want anybody calling them composites; he wanted them to be called a breed. That was the only way he could convince people to use them,” says Shafer

“Now in our breed we also have Simbrah. That's clearly a composite just like Brangus and Santa Gertrudis, etc. but those early ones were called breeds just to give them more legitimacy. Now that veil has lifted, and today it's ok to have composite seedstock. Yet there are still many people within the breed associations and in the commercial industry who feel that composites are inferior, and basically it's a dirty word. In their eyes, crossbred cattle should not be considered seedstock,” he says.

People forget that every “pure” breed began as a crossbred in earlier times. “When you talk about purity, looking at the traditional breeds in Europe or the British Isles, there were times these cattle were mixed or crossed. There were wars and other disruptions where the fences were torn down and there was plenty of crossbreeding going on.” In early times, some people crossed different strains of cattle from different regions, and then selectively bred these “crossbreds” to create a breed.

“There really aren't any pure breeds. It sounds good, and it's appealing, and it's something that breed associations have gone to great lengths to sell, but it's really a misnomer. There are populations of cattle that have been closed for long periods of time, however. They are probably much less genetically diverse than populations of cattle that have been open and have had some migration of new genetics into the group,” he says.

You get a lot of heterosis when you cross two breeds that have been deprived of open genetics for a long time, especially if the two groups are totally unrelated. “The more you inbreed, keeping a breed pure, the more bang you get when you outcross to something totally different,” says Shafer.

Utilizing Complementarity - “Besides making crossbreeding easier, using crossbred seedstock allows commercial producers to fully utilize complementarity, while maintaining consistency,” says Shafer. “Complementarity, the concept of matching strengths to weaknesses, is a very powerful tool. Though it is possible to match strengths to weaknesses within a breed, crossbreeding greatly accentuates complementarity. In straight breeding you are limited by the genetic boundaries of a breed when selecting sires to complement your cows. Crossbreeding can expand your selection pool dramatically,” he explains. You can add strengths from two or more breeds to create something better than one breed can produce.

If you use a rotational crossbreeding system to leverage complementarity, and want to maintain various traits like milk production, a certain mature size, marbling level, yield level and all the other traits that impact your bottom line, and still maintain uniformity, you must pick breeds that are similar in all those areas. With rotational crossbreeding systems using purebred sires, if the breeds are very different, offspring won't be uniform.

“Because complementarity is most thoroughly exploited by crossing diverse biological types, a rotational crossbreeding system using purebred bulls can pose challenges—creating great variation in breed proportion within the herd. If highly diverse breeds are used in the rotation, a lack of uniformity will result,” explains Shafer.

“To counteract that, a producer might select breeds of similar biological type to use in sire rotation. While this will deliver consistency, you don't obtain the power of complementarity,” he says. With a 3-breed rotational cross, if the breeds are virtually identical in their genetic levels for all those genetic traits you are concerned about, you can maintain uniformity and it won't a wild swing. But this doesn't allow you to tap into complementarity because you are not utilizing diverse genotypes and leveraging them.

“If you are just picking breeds that are already similar, you are not leveraging complemetarity,” says Shafer. “With use of crossbred sires, we can maintain a constant breed proportion. The crossbred bulls and the herd they are used in can be comprised of very diverse breeds, yet uniformity will be maintained.”

To explain complementarity, an example might be a herd that utilizes ¼ Jersey—since they marble well, milk well, calve easily, etc. A producer might feel that ¼ Jersey blood in the cowherd is appropriate. A three-breed cross containing ¼ Jersey can maximize cow heterosis, complementarity and calf production (and the calves will only be 1/8 Jersey). But if it's a rotational crossbreeding system, using purebred sires, it won't work. You'd have to use a purebred Jersey bull. Besides the fact that Jersey bulls are mean, you'd have females from that bull that are half Jersey—and that's not what you want. You only want a quarter. With a composite system, you can set your breed proportion and keep it that way, and still benefit from the traits you want from the diverse breeds.

“You have ease of implementation; it's as easy as straight breeding, but allows you to tap into complemetarity, and these are the two major plusses of using crossbred seedstock. When we look at other species and other industries (like swine and poultry) and see how long and how effectively they've utilized composites, I think the writing is on the wall,” he says.

Hybrid Bull Selection Is Easier Now - “In 1997 when we ran our first multi-breed genetic evaluation, we couldn't effectively evaluate crossbred seedstock. We really didn't have a good way to predict their EPDs. That was a short-coming, and the early adopters of crossbred seedstock had a struggle because they didn't have an infrastructure in place that allowed for accurate evaluation of their seedstock. In 1997 ASA calculated the first EPDs on crossbreds, and in the beginning there are things that weren't ideal or perfect. Over time we tweaked and changed and improved it, so we can now do a better job of evaluating crossbred seedstock,” says Shafer.

Paternal Heterosis – One thing that has been hard to evaluate or do studies on has been the breeding ability of crossbred bulls. Anecdotally, there is lots of information that says, on average, that the crossbred bull has a little more breeding ability and longevity. Studies have shown that young crossbred bulls reach puberty quicker than purebreds, have better than average scrotal circumference, increased survivability of sperm, improved sperm concentration, and increased pregnancy rates in cows they bred.

The crossbred bull may also have a little more drive to breed cows. He may be more athletic, with higher-than-average endurance, and might get around a little better in big pastures than most purebred bulls. In range situations where you want active, vigorous bulls with a lot of drive and endurance and fewer breakdowns, crossbred bulls may be the best choice for that job. We can't say this is always true, because there is some individual variation among bulls, depending on what they inherited, structurally, from their parents. But as a rule the crossbred bulls will be above average in fertility, longevity and breedability.

“We certainly expect this, because these kinds of traits tend to be highly impacted by hybrid vigor. We need more research in this area, to know how much is paternal heterosis. We know a lot more about individual and maternal heterosis. We have measured those, but we are still in the dark a little about paternal heterosis. Maybe someone will design studies to look at this. We do hear anecdotal evidence from producers that crossbred bulls seem to last a little longer, and maybe cover a few more cows,” says Shafer.

The Power Of Crossbreeding - Heterosis is an amazing thing, and very powerful. It helps if a person can select good individuals to begin with, for crossing, but even if the animals are not outstanding, some traits are improved in the offspring. “When it comes to fertility and longevity, at least in females, even if you start with mediocre purebred lines (the parents are sub-par for fertility and longevity) the heterosis effect on those traits is such that the resulting offspring are pretty darn good. If you can start out with better parents, of course, that's a plus, but even if you have mediocre parents you get a boost of improvement,” says Shafer.

“In early years when people first started crossbreeding, some of the cows that were bred to Angus bulls had bad udders, cancer eye, prolapses and other weaknesses. All you had to do was cross them, and the daughters didn't have those problems. Since most of them got crossed with Angus, people thought Angus must be wonderful, but we've since learned that it doesn't matter what you cross with. You can cross an inferior cow with any other breed and create a super cow, without her mother's problems. Heterosis is so powerful, when it comes to longevity and fertility. It covers up all those undesirable traits like bad bags and cancer eye, infertility, etc.”

Many producers who crossbred in the past have now been breeding to purebred bulls for several generations and have lost the hybrid vigor because their herds have become too straightbred again. Their calves are smaller at weaning, so now they think they need to start crossing again by using a different breed of bull. “This is one reason to cross, to have higher weaning weights, but if they still maintain a straightbred herd, they are still missing out on the best benefits of crossing. The crossbred female is what gives you the most bang for your buck,” says Shafer.

“The sad thing is that there are still a lot of commercial breeders and seedstock producers who are very leery about using crossbreeding. Perhaps if we can get more research on crossbred bulls, this will change. It's hard, however, to do the studies because you'd need large groups of similar cattle that could be bred to either purebreds or composite bulls,” he says.

“Years ago, when we first started doing research, we had to talk like used car salesmen to convince commercial ranchers to crossbreed, but that has changed. In the past decade many people have been using composite bulls or AI-ing to composite bulls and now they like those bulls so much that we can hardly get them to use straight bred bulls anymore. You'd have to find some herds that would be willing to use both straight bred bulls and composites, to compare the results,” says Shafer.

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