From the Fall 2010 issue of the Isa Informer

Lorenzo currently serves as President of Beefmaster Breeders United. In this capacity, he has written many articles for the Beefmaster Cowman magazine.

Harnessing the Power of Heterosis

Note: I have borrowed a lot of the following information from a great presentation by Dr. Bob Weaber of The University of Missouri at our recent Beefmaster Symposium in Springfield, Missouri. Thanks to Bob for loaning me his slides and letting me share his excellent info with you. (Extra note: the anti-Angus flavor is purely mine.)

Once upon a time the U.S. Beef industry understood and practiced the value of heterosis. Ranchers crossed different breeds of cattle in order to harness the unbelievable (and inexpensive!) power of heterosis in their production systems.

Heterosis, also known as hybrid vigor or outbreeding enhancement, is the increased function of any biological quality in a hybrid offspring. It is the occurrence of a genetically superior offspring from mixing the genes of its parents. Heterosis is obviously introduced through cross-breeding, and it comes at a very low cost since you have to buy or raise two parents anyway.

Today, much of the U.S. beef herd has become a homogenized, largely Angus herd. This was done in hopes of capturing a price advantage. But many ranchers we talk to are now realizing that, while they may have gained a few more cents per pound, what they gave up in reduced weights, decreased efficiency, decreased adaptability and increased costs ate that “premium” up and then some! The real shock came, though, after keeping several generations of replacement heifers, their cow herd began experiencing big changes in production efficiency and profitability.

The chart below shows us what happens when a single breed is bred back repeatedly; heterosis goes from a high of 100% in the F1, to a mere 6.25%—in just five generations!

Impact of Straight-Breeding on Heterosis

Generation Breed A Fraction Breed B Fraction Individual Heterosis
1 1/2 1/2 100%
2 3/4 1/4 50%
3 7/8 1/8 25%
4 15/16 1/16 12.5%
5 31/32 1/32 6.25%

Why does this matter? The power of heterosis has the greatest impact on the traits with the lowest heritability, like fertility. Things like carcass traits are highly heritable and can be fixed in one generation using a breed with the desired characteristics. But to move the needle for things like fertility and production efficiency is much more difficult.

What does it mean in terms of production? You can see from the list below that heterosis improves production efficiency at the herd level.

Heterosis:

  • Improves calving rate—6% a
  • Improves calf survival to weaning—4% a
  • Improves WW—8% a
  • Improves YW—4% a
  • Improves carcass traits—0–2% a
  • Significantly improves traits with low heritability
  • Improves weaning weight per cow exposed—23% b
  • Improves animal disease resistance to BRD and Pinkeye c
  • PLUS: Breed Complementarity

It is obvious that heterosis is an important tool in the rancher’s toolbox, but one many in the industry have gotten away from. The second chart shows the various effects of different types of crossbreeding systems on weaning weights. You can see quickly that breeding the same breed year after year eliminates any advantage from heterosis.

Impact of Cross-breeding on Weaning Weights

System % Max Heterosis % Increase in Calf Wt per Exposed Cow
Pure Breeds 0 0
2 breed rotation 67 16
3 breed rotation 86 20
2 breed composite 50 12
3 breed composite 63 15
Term Sire x F1 100 23-28

If you don’t need replacement heifers, you maximize heterosis in a terminal system, like breeding Isa Charolais bulls. There is no more sought-after feeder calf than the Charolais-cross, and this simple system yields the maximum pounds of calf with the fewest inputs.

If you do need to keep replacement heifers, consider using Isa Beefmaster bulls. A three-breed composite offers 63% retained heterosis, while delivering excellent feeder steers (see results in “It’s No Accident …” on the following page) and the best quality replacement females available.

One important thing to keep in mind about Beefmaster is that the three-breed composites, like Beefmasters, retain that heterosis even when rebred, generation after generation. This means you can come back generation after generation with Beefmasters, and the jump from hybrid vigor remains in the cattle at 63%—generation after generation. This is a huge advantage over a straight-bred system.

We understand there is market pressure to raise a single type of calf. But beware where those pressures come from and what their motivation may be. Sure the order buyer and feedyard owner want them all the same, because it makes their lives easier. But does raising them all the same actually make a difference where it matters—in your ranch’s bottom line?

a Kress and Nelsen (1998), b Gregory and Cundiff (1980) , c Snowder et al. (2005a, 2005b)


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