Looks can tell in beef cattle

Why some apples fall farther from the tree

By Miranda Reiman

“Boy, if he isn’t a spitting image of his grandpa!”

You’ve likely heard similar references before and they make this concept easy to grasp: Just like people,cattle don’t inherit genes equally.“

Because of random assortment and recombination, or crossover events during the sperm or egg cell formation, they can get an unequal proportion of genetic material from their grandparents,” says Bob Weaber, Kansas State University animal scientists.

Thus, an animal might favor its maternal grandfather and look nothing like the paternal one—which matters in cattle herds where sires vary greatly for economically important traits.

That’s just Mother Nature’s mechanism for maintaining genetic diversity in the population. “But from a geneticist’s perspective,” Weaber says, “we’re trying to figure out: Did they get a good assortment of genes or a bad assortment of genes from their parents?”

The question is especially relevant in explaining variation in composite cattle breeds and herds. More than a decade ago, Colorado State University professor Daryl Tatum noticed that variability when looking over the King Ranch’s Santa Gertrud is bulls.

“They all were the same percentage of Brahman and Shorthorn breeding, but there was everything from what looked like straight Shorthorn to ones that looked like a big, old red-colored Brahman,” he says. “If the genes segregated so differently in these populations to where they looked so much different, does it mean their meat quality was different as well?”

So, the curious meat scientist studied it.

Steers of known genotype, either a quarter Braham and three-quarters Hereford or half-and-half, were scored based on appearance to estimate their percentages of each breed.

“We had some all over the spectrum based on phenotype,” Tatum says. The breed estimates for quarter-blood Brahmans came in anywhere from no Brahman influence to 9/16. Looking at the half-bloods,estimates ranged from a quarter to 13/16 Brahman.

“They were highly variable in appearance and we found it was correlated with tenderness,” he says. “At the end of the day, cattle that looked more Brahman produced tougher steaks than the ones that looked like they had less Brahman in them, even though they might have been the same actual percentage.”

In steaks from cattle that appeared to have 1/8 or less Brahman breeding, the Warner-Bratzler shear-force value (the standard mechanical measure of tenderness) was 3.88. That’s compared to a less desirable 4.91 rating for those with more than 50% Brahman influence.

“We don’t have conclusive proof, but perhaps the cattle that looked less Brahman in phenotype actually have genes that are more like the other breed,” Tatum says.

Scientists are anxious to use DNA technology for additional research.

Weaber says variation in the progeny (F2) from two first-cross (F1) animals is more noticeable.

“Where it becomes more complicated is when you breed a hybrid to a hybrid,” he says. “Even though the F2s have half of their genetic material from each breed on average, some re-pairing of chromosomes from the same breed occurs.”

That explains why the heterosis advantage is diminished the second time around, though some will have more and others less than average. Using DNA to identify which ones were truly half-bloods with each chromosome in the pair coming from different breeds would help.

“You could do some pretty interesting things if you had those genotypes,” Weaber says. “You could optimize heterosis through different breeding structures.

”Of course, making sure the genes from both sides of the pedigree are superior is an insurance policy.

“You don’t dig yourself out of the hole just by crossbreeding,” he says. “The merits of the parents going into those systems are important,” especially for traits with moderate to high heritability where heterosis is low. “If you’ve got two parents that you put together, one excels and one does not, the rules of additive genetics suggest you’re likely going to produce an animal that’s somewhere near the middle.”

DNA: an arriving tool for beef cattle

by Miranda Reiman

Right now, it’s hard to imagine how future tools will change the beef cowherd.

Today, heifer development costs are high and getting higher as ranch profit goals demand efficiency while consumers want quality.

DNA technology is one of the emerging solutions for beef production, in line with the role it has played in agronomy.

“It takes so much time to develop a herd of cattle—a lifetime, honestly—that’s designed to be feed-efficient or have high reproduction,” says Cody Jorgensen, of Jorgensen Land and Cattle, Ideal, So. Dak. “The more knowledge you have about DNA to help you make the right decision, the better.”

His family has DNA-tested standout Angus bulls and donor cows for years, but he plans to step it up a notch this fall.

“It’s going to be a tremendous tool to add, along with the quantitative genetic research that we do,” Jorgensen says. And although the registered cattle world will be quicker to use the tool, he says the new lower-density, lower-cost tests “could impact commercial cattle heavily.”

“Data is a power,” he says. “You get a lot of cost and time and energy stuck into a bred female, and every day that it maybe in the wrong group, it’s very expensive. If a guy knew early in a calf’s life if it had the abilities we want, it would definitely improve the costs of raising replacement heifers.”

“Just a few percentage changes in fertility would have a much higher impact in whole-system profitability than most of these carcass measures we’re talking about,” he says.

The Angus breed is working on measuring longevity and survivability currently.

“Once you get data and ways to measure traits like that, then a DNA test is soon to follow,” Bowman says.

Jorgensen dreams of a system similar to what has shaped the crop side of their business.

“If we could genetically select for all the things that challenge us—if that’s the fescue grass or the elevation—if we could understand DNA that could handle that type of environment or that was resistant to respiratory disease—just imagine that. It would be a game changer.”

E. coliresistance. Fertility. Ability to handle “hot” rations. Tests for these traits are all on the horizon.

“Any places we can increase efficiency by selling one more calf, because we have one more fertile female,” Kuehn says, “or have one more calf sold for slaughter because he made it through the feedlot without respiratory disease, or fewer food-borne pathogens are advantageous—those sorts of changes are a boon for the industry in terms of perception and environmental footprint.”

Jorgensen has been pulling DNA samples for their files, “just in case” they want to analyze them.

“It’s not like the poultry or swine business where they can do 2.4 turns per year,” he says.“You just can’t make that much progress in a year’s time. It’s critical to know whether those cattle will do it or not.”

It matters to individual ranchers and to those further down the beef production chain.

“Meat demand is not going down, especially worldwide, Kuehn says. “It’ll take focus if we’re going to keep beef competitive to other protein sources.”

Tag: breeding

Looks can tell in beef cattle

By Miranda Reiman

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