Genomics Enhance Beef Cattle Selection
Improved genetic testing options offer cattlemen means to make more accurate selection at an earlier age.
Selecting breeding animals on how they look, by phenotype, worked for centuries. But now, says Jared Decker, University of Missouri (MU) geneticist, “There’s a better way of selecting.” Now genotype pushes phenotype back to horse-and-buggy days.
Arrival of huge computers and sequencing of the bovine genome changed all. It’s data and what’s inside that counts, he told cattlemen at a Cattlemen’s Boot Camp July 14 in Columbia, Mo. The special training session by MU scientists was sponsored by the American Angus Association with MU.
Things changed in the 1970s with availability of statistical models that predicted expected progeny differences (EPDs). Then software was developed to combine many EPDs into economic indexes, which the Association calls dollar value indexes, or $Values. These indexes can help commercial cattlemen evaluate bulls on multiple traits simultaneously to advance their herd toward greater weaned calf value ($W), feedlot value ($F), grid value ($G) or beef value ($B, which combines $F and $G into one postweaning growth and carcass value assesment).
“We must still look at bulls and cows,” Decker assured his audience of mostly Angus breeders. Genomics tells a lot about calving ease, weaning weight, carcass weight and 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 importance, Decker encouraged cattlemen to take advantage of genetic tools when they are available. Those tools are improving, especially in evaluating younger animals, with the incorporation of genomics.
Traditional EPDs are calculated on available information including the animal’s pedigree, its own performance and the performance of its progeny. When a calf is born, the only information available is the pedigree, so the accuracy of that EPD is very low. As the animal’s own performance — its birth weight, weaning weight, yearling weight, etc. — is added, the accuracies of its EPDs increase. When progeny performance is included, the accuracy of an EPD increases further, but that takes time.
Progeny-proven EPDs enhance breeding selections, but take time and money. You may buy a young sire with a high-growth but low-accuracy weaning or yearling EPD, only to find a couple years later that his progeny proved him to actually be a low-growth bull.
That makes a good case for using high-accuracy sires, but a bull might be 20 years old before he gains a high-accuracy proof, Decker said.
Incorporating DNA typing into genomic-enhanced EPDs (GE-EPDs) cuts time spent waiting for EPD accuracy from data collection. A DNA test on a newborn calf can offer equivalent predictive information as 8-20 offspring, depending on the trait.
It also allows for measurement of traits that otherwise might be impossible to directly measure on a live animal — meat tenderness, marbling, carcass grade and yield, for example.
“Some data collection is very invasive,” Decker said. “You can’t collect and use semen to breed from that slaughtered steer.”
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. DNA in a drop of blood can be tested for as many as 78,000 SNPs (single nucleotide polymorphisms) to give more accurate answers from the whole genome. Available tests range in price from $17 to $75, depending on depth of data.
A new University of Missouri SNP chip has 50,000 genetic markers. Researchers at the MU College of Agriculture, Food and Natural Resources are looking for genomic markers associated with 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.”
For more information on DNA typing, visit http://www.angus.org/AGI/default.aspx.
