October 6, 2022
A crossbred animal has several advantages over the purebred, especially in traits important to commercial cattlemen: increased fertility, longevity, feed efficiency and disease resistance—due to the phenomenon of hybrid vigor (heterosis). It also generally provides an increase in growth and carcass yield over what the parents produce.
The more unrelated the parents, the more “kick” you get from hybrid vigor. Zebu (Bos indicus) cattle, such as the Brahman, are the least closely related to most of the other domestic breeds; crossing them results in the most hybrid vigor. Also, European cattle brought to North America during the 1960’s were unrelated to the British breeds already here, and there were many benefits gained by crossing them.
In recent years, however, breeders have infused Angus into these breeds to make them black, so these animals are not as unrelated to the British breeds as they once were. They won’t give as much hybrid vigor if you use the ‘black’ versions for crossing with British breeds.
Composites (a stabilized mix of 2 or more breeds) already have their “kick” from crossing, and pass along a lower percentage of hybrid vigor to their offspring. They are not as unrelated as crossing an animal of one breed with an animal of a different breed. With composite cattle you get desirable traits from 2 or more breeds, but you don’t get as much hybrid vigor when you breed animals within that composite group. If you want to maximize hybrid vigor, you need a complete outcross.
Darrh Bullock, a University of Kentucky Extension Professor specializing in beef cattle genetics, says there are many genetic tools available, but the two most important are crossbreeding and selection. “In terms of crossbreeding, heterosis (hybrid vigor) is something we all know about but not enough folks are utilizing,” said Bullock. In recent decades most commercial herds have lost the hybrid vigor they once had.
“The beauty of crossbreeding is that the offspring perform better than the average of the parent breeds, but not necessarily above the best trait of each breed. The reason that crossbreeding is beneficial is that we are dealing with multiple traits. If we are only looking at a single trait, a straightbred might be better.”
This is evidenced in the milking ability of the dairy cow or the marbling of the Wagyu. A breed that has been selected for maximizing a single trait can usually be the best in that one trait.
“But in the beef industry we have many traits to focus on. We also have to deal with the environment, and heterosis gives us a benefit there. The cumulative effect we get with heterosis is always beneficial. There is also breed complementarity. We can look at how well certain breeds fit the environment, our management, and each other. We used to talk about complementarity just from the standpoint of maternal and paternal breeds,” said Bullock.
Genetic trends for the beef industry have changed over the years.
“Back in the 1970’s there was more spread for most traits than there is today. Now we are putting them all together. The cattle that had lots of milk back then are no longer producing as much, and the ones that had just a little milk back then have increased in milk production. Growth has also changed. Back in the 1960’s Angus cattle were one of the smallest beef animals and are now one of the largest in terms of yearling and mature weight. We have different breed philosophies. That’s fine, but breeds today no longer fall as neatly into those maternal/paternal breed classification as they used to,” he said.
“If you are in an environment that can provide for lots of milk, growth and production, choose breeds that fit that scenario. If you are in a more limited, harsh environment, think about that. This is why we should focus on crossbreeding and heterosis.” The two traits it has the biggest impact on are traits that have some of the biggest impact on your operation--reproduction and longevity. Improving reproduction of your herd and keeping cows longer in the herd provides a huge financial benefit for most commercial operations. Health is another important factor that improves with crossbreeding.
“The end product—carcass weights, marbling, etc.—is where we see the least impact. It doesn’t hurt those traits, to crossbreed; we just don’t see a big increase.”
He gives some economic examples to show why crossbreeding is beneficial. One example is a 100-cow herd in which weaned calf per cow exposed to a bull is 85%. “Let’s say weaning weights average 525 pounds, and we’ll say $1.50 on the price.” The economic impact of heterosis in that scenario can be substantial, improving number of calves weaned and/or weaning weight of the calves.
In a two-breed composite you maintain about 50% of maximum heterosis. “In that situation, your additional return on a yearly basis is around $7000 on that 100-head herd. Another scenario that’s similar is the most simple rotational breeding system—a two-breed rotation. You select two breeds and rotate between those two breeds (with change of breed for the bulls) every 4 years. If you go 4 years with Angus, 4 years Hereford, 4 years Angus, etc. it’s about the same level of heterosis,” he said. That simple rotation has a fairly significant return.
A more sophisticated two-breed rotation can be accomplished with a crisscross system. This can add another $2000 per year in return.
“You still have two breeds, but whatever the sire breed of the female is, you breed that female to the opposite breed. If she was sired by a Hereford you would breed her to an Angus and vice versa,” he explained.
“A 4-breed composite is probably where you get the most benefit for a sustainable system, adding about $11,000 to the herd’s annual income. There is also a roto-terminal cross, which many folks feel is more efficient (two breeds in the rotation, with a third breed as a terminal cross), but because of the heterosis that you miss on the female side, it’s not quite as good. The females only have about 2/3 retained heterosis on a rotational cross. The majority of the calves have full heterosis (being a 3-breed cross) but the maternal heterosis is where we get the biggest bang for our buck (an F1 cow that’s half and half—two breeds) because she has the most increase in fertility and longevity.”
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