So Why Are We Still Talking About Crossbreeding?
Research documenting the value of crossbreeding in production systems spans well over 30 years in many different species. The value of using breed differences to capture hybrid vigor (heterosis) has been well established. We frequently find ourselves compared to poultry or pork. How many straight-bred chickens are marketed in retail stores? How about zero! The same trend has been evident in the pork industry. All commercial swine enterprises are based on crossbred females and a large percentage use crossbred or hybrid boars. I remember going to my first extension meeting over 30 years ago (I was about six years old!!) and hearing reports about the value of crossbreeding. The importance of heterosis was inarguable-the data was clear and consistent-not that I understood at that age. Not long after that, I remember my dad introducing Angus bulls for the first time in a predominately straight- bred Hereford and Shorthorn herd.
So why are we still talking about the value of crossbreeding?
It is rare that I go to a meeting where someone doesn’t blame crossbreeding for the “mongrelization” of the nation’s cow herd. You can find the negatives of crossbreeding in the popular press on a regular basis. Are we sure we should blame crossbreeding for the variation we see in cattle, or should we blame the crossbreeder? If crossbreeding causes variation, why are broilers (all hybrids) so uniform? Broilers are consistent in age, weight, feed efficiency and carcass merit at slaughter.
One of the major advantages poultry has in the competition with beef for the animal protein dollar is consistency. Perhaps we should review some simple concepts. Crossing of two pure breeds results in a calf superior to the average of the two parental breeds. The superiority of this calf is called “individual heterosis” or hybrid vigor. This does imply that crossing a Charolais and a Hereford will result in a weaned calf that is bigger than the Charolais, but the calf should be somewhat above the average of the sire and dam is the “percent heterosis”.
Second, and more importantly, if that calf is a heifer that you keep as a replacement, you capture “maternal heterosis” -the incredible value of the crossbred cow! Recently, I have heard several ranchers comment that they don’t see the value in crossbreeding, saying there is “too much inconsistency and you don’t really get that much more growth.”
Once again, let’s look at how heterosis works. Heterosis does not have a large effect on many of the easily measured traits-like weaning weight or carcass traits. It’s about 4%. However heterosis has a small, but positive effect on many traits that are critical to profitability. Deceased age at puberty, increased conception rate, greater calf livability and vigor, disease resistance and increased longevity result in a substantial cumulative effect-much of it realized from “maternal heterosis”. If you look at any economic analysis of ranch data, these less obvious traits are dramatically important to the bottom line. It is a lot harder to brag at the coffee shop about lower culling rates and more cows in production at 10 years of age than it is about the heaviest sale weights! Generally speaking, we get our largest “kick” from hybrid vigor on traits that are not highly heritable-primarily production traits. Traits that are relatively highly heritable (growth and carcass) will still exhibit heterosis, although to a lesser degree. So, what is the value of a planned crossbreeding system? Most studies like to measure the value of heterosis in “the increase in pounds of calf weaned per cow exposed.” Think about the measurement-it is extremely powerful, encompassing fertility, mothering ability, calf livability, milk production, growth rate, longevity, etc. The data suggest an 8.5% increase in pounds of calf weaned per cow exposed by simply crossing two pure breeds. If you retain that crossbred heifer and put her into a two-breed rotational system, you increase that advantage to 14.8%. If you enter into a three-breed rotation, the potential advantage becomes almost 23%! In these challenging economic times, it would seem rather difficult for a rancher to ignore a potential 15 to 20% in pounds at weaning-the combined effect of 4% weaning weight plus all of the advantages in the lowly heritable traits.
Remember my earlier reference to crossbreeding, where I suggested the crossbreeder could be the problem? The problem with crossbreeding is what I call the “Breed of the Month Club” where the producer tries one breed for two years, switches to another based on his neighbor’s advice, tries a different one because they are cheap at the bull sale and switches again because of an order buyers suggestion. What a way to plan a breeding program! We end up with the classic “Heinz 57” herd and blame crossbreeding! Cattle breeding is a very slow process-to turn over a generation takes five to eight years. Sometimes we switch breeds before we know if the one we had was working. To make the process more complicated, we often mix breeds of widely varying biological type. “Biological type” basically refers to the mature size, milk production and muscling of a particular breed. Just picture running bulls from a large breed in the same field as bulls of a small breed. The daughters of these sires will be highly variable, requiring extremely different feed, management and marketing. We have complicated our management and destroyed our consistency, not by crossbreeding, but as the result of poor planning.
The other often overlooked advantage of crossbreeding is the importance of breed complementarily. The data is clear that different breeds are noted for superiority in certain traits, whether it be growth, carcass or reproductive fitness. The perfect example is the general advantage that the Continental breeds have in growth rate, muscling and leanness, while the British breeds are noted for their adaptability to the range, fleshing ability and maternal contribution. The cross results in a hybrid that is intermediate for many traits, providing the right “dose of genes” to produce an animal that fits our entire industry from the cow/calf operator to the packer. Using breed complementarity to improve a herd can be just as important as the heterosis that is obtained. The final piece of the puzzle that we call crossbreeding is based on the ability to match your cow herd to your environmental conditions and feed resources. The genetic diversity between breeds allows you to identify breeds best suited for your particular environment. If we just remember that crossbreeding is a way to capture individual and maternal heterosis, utilized breed complementarity and match cattle to specific environments, then the value to our industry is unquestionable. Crossbreeding does not result in increased variability! Clay Center, Nebraska has 20 plus years of data indicating no more variability in the crossbreed progeny than in the purebred parents. Remember the variability is the result of poor planning and life membership in “Breed of the Month Club”!
WRITTEN BY DAVID A. DALEY, PH.D. CALIFORNIA