Genetic Testing Used to Improve Predictability of Young Cattle
Wednesday, August 17th, 2011
Genomics is the study of the genome and how it relates to traits.
"We are looking at how genes cattle have relate to traits we see and can measure," explained Barney Gehl, with Pfizer Animal Health.
Cattlemen have been evaluating their cattle for more than 100 years.
"In 1883, the American Angus Association was formed to get breeders together because they realized the value of pedigrees," Gehl said. "In the 1950s, cattlemen started using A.I., and in 1961, herd records were developed."
By 1977, cattlemen were utilizing embryo transfer techniques, with EPDs initiated in 1985.
"In 2001, the first DNA markers were available, and in 2005 Index EPDs were published," Gehl said during a presentation at the Illinois Beef Association's Summer Conference.
The first marker was identified in 1989.
"It has progressed from there to seven markers and two traits in 2004," Gehl reported. "In 2007, the first cow genome was sequenced at the USDA research center in Montana."
A sample of hair, semen or blood is required for a genetic test.
"You can take a sample from a calf the day it is born," the Pfizer spokesman said. "We prefer blood on a young calf up to seven months old, then we can use hair and for A.I. sires we can use semen."
When a sample is sent to a company such as Pfizer for a genetic test, the DNA from the sample is compared to the mapped genome and the markers that have been identified.
"We're finding where the pairs differ on the chromosomes," Gehl said. "We put the DNA on very sensitive cards which go into a machine the illuminates the DNA based on enzymes and proteins. Then we can see if the animal has the markers or not."
Gehl highlighted several opportunities for utilizing genomic testing
"Over the last couple of years, producers have been using testing to detect recessive carriers of traits that aren't very good for the industry," he said. "This is a simple test; either the animal has it or it doesn't."
Using a genomic test can reduce the time required to identify the carrier animals.
For example, Gehl said, before the tests were available a cattleman would need to mate 10 cows to a bull to make sure none of the calves were born with the trait to determine the bull was not a carrier.
"That would take three years from the time the bull starts breeding cows to determine if he is a carrier," he explained. "Now we have a simple DNA test when the calves are born."
The tests also can assist cattlemen with sire selection.
By using traditional evaluation, it will take several years to gather information on the progeny of a bull. Calves from a bull purchased in 2011 will be born in 2012. Then it will be two more years before those daughters calve.
"With genomic testing we have the opportunity on a female born in the spring to pull her blood and do a high density panel genomic marker test," Gehl said.
EPDs will remain an important tool for cattlemen, according to Gehl.
"Once a bull is over 80 percent accurate, we can pretty much count on that," he said. "We won't gain whole lot by doing a genetic marker test on a bull with high accuracy."
However, genomic testing can help cattlemen gain predictability on young sires.
"We use pedigree information, individual data and progeny performance data to come up with EPDs and accuracies," Gehl said. "But it takes a lot of time, money and opportunity costs to get that progeny data."
Genomic testing can be utilized for parent verification.
"If you have multiple sires in a pasture or if the breed association wants parent verification, a genomic test can help you with that," Gehl said. "Or you can use a test to figure out who sired those outlier calves in the feedyard."
A sire dominance study included five groups that each had two bulls and 50 cows in a pasture.
"With the sire verification test they found out the number of calves sired ranged from three to 32," Gehl reported. "Some bulls out there were just eating grass and others we doing the work."
As more data from DNA samples is acquired by companies, the accuracy of the tests will increase and more correlations will be identified.
"With more data and live animal tests, maybe we will find that some cattle have certain enzymes in their lungs that can take care of some of the toxins that bacteria produce so they may react better to vaccines," Gehl said.
"There is also work being done on BRD susceptibility which is a tough trait to narrow down. Just think of all the factors that affect BRD."
Pinkeye susceptibility may also be identified by a trait.
"There may be genetic lines that don't have the depth of cornea that allows them to be more susceptible to infections in their eyes," Gehl said. "This is emerging technology, so we have a lot more to be learned."