Genomics enhance beef cattle breeding

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Photo by Laura Mushrush Selecting breeding animals on how they look, by phenotype, worked for centuries. Progress in improving cattle was made just on appearance.

Now genotype pushes phenotype back to horse-and-buggy days. It’s data and what’s inside that counts.
Arrival of huge computers and sequencing of the bovine genome changed all. “There’s a better way of selecting,” said Jared Decker, University of Missouri geneticist, at a Cattlemen’s Boot Camp, July 14 in Columbia.
Training by MU scientists was sponsored by the American Angus Association with MU. The Cattlemen’s Boot Camp is a national program.
Things changed in the 1970s with statistical models that predicted EPDs (expected progeny differences). Then software was developed to combine many EPDs into a single economic index number.
Indexes help herd owners search a sire catalog to match a bull’s traits needed to improve a farmer’s cow herd profits.
“We must still look at bulls and cows,” Decker assured his audience of mostly Angus breeders. “Phenotype still counts, as there’s no EPD for feet and legs in beef cattle.”
Genomics tells a lot about calving ease, weaning weight, carcass weight or carcass grade. But there is no index for feet and legs.
The eye of the stockman still plays a role in breeding. However, on traits of economic value, there are genetic tools.
Plain EPDs will fade away as breeders learn more from the DNA of individual animals. A calf’s genes at birth predict much of what that animal will do in a lifetime.
New tools provide genomic-enhanced EPDs. A GE-EPD cuts time spent waiting for EPDs from data collection.
EPDs are based on production records of offspring from a sire, for example. Those require recording weights at various stages of life. A growing calf is weighed and data collected. Not on just one offspring, but hundreds.
If a thousand calves are tested, accuracy goes up for EPD predictions for a sire. A thousand tests are better than a hundred.
Proven EPDs enhance breeding selections, but take time and money.
A bull might be 20 years old before it gains high-accuracy proof, Decker said.
Some EPDs—meat tenderness, marbling of rib-eye or carcass grade and yield—can only be collected after harvest. “Some data collection is very invasive,” Decker said. “You can’t collect and use semen to breed from that slaughtered steer.
“You buy a young sire, with few records, expecting high growth rate, but find after a year of use that actually it’s a low-growth bull.”
EPDs on young animals have low accuracy. There are no or few progeny to test. However, genomics improve accuracy on the young. Such a DNA test is like having 20 offspring to start.
Available tests range in price from $17 to $75, depending on depth of data.
Genomic tests five years ago tested one gene on one trait. Those were misleading, but new tests are useful, Decker said. “One trait, such as weaning weight, may be influenced by tens of thousands of genes.”
With today’s genomics, DNA can be collected and tested at birth for new herd replacements. DNA in a drop of blood can be tested with a chip called a “snip” or SNP (single nucleotide polymorphism). That gives more accurate answers from the whole genome.
A new University of Missouri SNP chip has 50,000 genetic markers.
Researchers at the MU College of Agriculture, Food and Natural Resources study three areas in cattle: embryonic death, feed efficiency and resistance to bovine respiratory disease.
Decker told producers: “It’s not all genetics. Environment and management still count. Genomics offer much for herd improvement to meet consumer demands.”


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Rod    
Texas  |  July, 22, 2014 at 05:15 PM

A geneticist would know that phenotype is more than visual assessment.

steve    
MT  |  July, 23, 2014 at 10:33 AM

Some good points, but the basic premise most often forgotten is " First, you have to get 'em on the truck!"


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