Making Sense of Feed
Efficiency
High-Tech DNA Tests Take Productivity to Next Level
By Boyd Kidwell
Contributing Editor
DTN/The Progressive Farmer
Mon Mar 1, 2010 08:42 AM CST
Feed efficiency is the Holy Grail of the cattle business.
Feed accounts for 70% of the cost of running a cow/calf operation, so even a
small improvement in feed efficiency goes straight to the bottom line.
Perhaps the most important thing we know about feed
efficiency is it's a trait that's moderately heritable. A bull passes the
genetics for feed efficiency to his progeny, leading to improved feed
conversion for calves in feedlots and more efficiency for daughters saved as
replacement heifers. Stacking efficient bulls on efficient cows
speeds up the development of feed efficiency in a herd.
The trouble starts when you try to measure feed efficiency.
Special equipment is needed to track how much feed each animal consumes, and
the tests are expensive. Lee Leachman knows that
firsthand.
Leachman, of Leachman
Cattle of Colorado, has measured actual feed intake on 500 young bulls. He
pooled his data with other sources to create records on 8,000 animals. The data
compares how much feed each animal consumes along with its average daily gain. Leachman found that feed conversion varies greatly, with
some animals requiring 10 pounds of feed per pound of gain while others need
just 4 pounds of feed to 1 pound of gain.
"At this point, I believe feed efficiency offers more
economic gain than does selection for any other
trait," says the cattle breeder from
Whatever he's doing, it's working. Leachman
is part owner of an emerging Angus sire called Protege,
co-owned by ABS Global. Protege was in the first
generation of bulls evaluated for feed conversion. He earned one of Leachman's highest feed efficiency EPDs.
ABS tested the bull through the Angus Sire Alliance where Protege
proved to be the No. 1 sire for profitability based in part on feed efficiency.
"Finding gene markers for feed efficiency is increasing
our accuracy of selection for that trait. Commercial producers soon will be
able to buy young bulls with higher-accuracy EPDs for
feed efficiency. And producers can also use DNA tests to choose more efficient
replacement heifers."
That said, Leachman adds a caveat:
"I wouldn't select a bull or a heifer based on a DNA test for a single
trait. Too many traits affect profit and that's what we're really after."
"The DNA information helps us know which heifers to
keep and gives our bull customers more information on the bulls we sell. We
want to sell only our best bulls, and I want to keep only our best heifers as
replacement females," says the veteran Angus breeder.
Lane takes DNA samples through tiny notches of ear tissue
and sends the samples to Igenity for tests on a panel
of 12 traits. Igenity returns the results in two
weeks. If a young bull from Lane's herd rates below average for the Angus breed
in four or more of the 12 traits tested, the bull becomes a steer. In 2009,
Lane tested 40 bulls and 42 heifers. He culled 10 bulls, and three of those
decisions were based on DNA results.
"I culled one heifer and two bulls based on DNA for
feed efficiency. If I can run 10 efficient cows on the same feed as eight less
efficient cows, my operation will be more profitable. Commercial customers also
will benefit from improved genetics for feed efficiency as they purchase my seedstock," says Lane.
Kris Luoma, of
"We still rely heavily on our eyes in deciding which
heifers we keep as replacements. DNA tests are tools that help us make
decisions early before we make costly mistakes by keeping heifers that
ultimately won't work out in our herd."
Validating Feed Efficiency Tests
Feed efficiency often is measured as residual feed intake
(RFI). RFI is the difference between the animal's actual feed intake and its
expected requirement for maintenance and growth.
Efficient animals eat less than expected; inefficient
animals eat more than expected for the level of production. Unfortunately, DNA
tests for feed efficiency on the market today aren't always reliable for
measuring RFI, according to independent evaluations by the National Beef Cattle
Education Consortium (NBCEC).
NBCEC has undertaken a validation process to verify
associations independently between genetic tests and traits as claimed by
commercial genotyping companies. Based on the NBCEC evaluation, Igenity Taurus feed efficiency molecular breeding values (MBVs) were inconsistently associated with RFI in the
validation populations.
In two populations there was a significant positive
association of the trait, but in four populations there was no significant
effect. In two Angus populations the estimated association was negative,
meaning the results were associated in the opposite direction.
"What the NBCEC results show is that RFI is a very
difficult trait to measure," says Stewart Bauck,
director of research and development for Igenity.
"What the validation results don't show is all of the development work on
large populations of cattle that went into this product. We are quite confident
in using this marker panel as a tool to identify feed efficiency, but we accept
the NBCEC results at face value and encourage customers to use all available
information to make the most appropriate decisions."
Bauck goes on to say that Igenity is committed to strengthening its profiles and
important updates are scheduled for coming months. The Igenity
MBVs for average daily gain and carcass
characteristics all showed significant positive associations in NBCEC
validations.
The Igenity feed efficiency (indicus) MBVs were significantly
and positively associated with Bos indicus-influenced cattle but there were no significant
associations for the MBVs found in purebred Brahman
cattle.
The GeneSTAR feed efficiency
molecular value prediction (MVP) was significantly and positively associated
with RFI in 671 Bos taurus cattle in the NBCEC validation. But no
significant association was found between this MVP and feed efficiency in 395
Brahman-influenced cattle.
Pfizer purchased GeneSTAR in 2008
and the company has improved its DNA products. "We'll have even more
powerful GeneSTAR tests based on a larger panel of
markers entering the market soon. A lot of this new DNA technology is geared
toward improving feed efficiency," says Ronnie Green, of Pfizer Animal
Genetics.
As GeneSTAR becomes more powerful,
less expensive tests will be available for commercial producers. "We
really think that 2010 is the year DNA technology becomes a tool for commercial
cow/calf and feedlot producers," says Green.
The NBCEC web site (www.nbcec.org) shows the validation
results on DNA tests, but some tests on the market haven't been evaluated
independently.
"Lack of validation doesn't mean there's anything wrong
with a particular test, but we'd like to validate all of the tests if possible.
At this time, NBCEC just doesn't have the resources to validate some of the
tests," explains John Pollak, a professor at
Cornell and director of NBCEC.
New Feedlot Tool
Realizing that genetic improvement for feed efficiency in
feeder calves will take years, Cargill Inc. has started a large-scale program
using DNA to sort incoming animals by expected outcome. Cargill has taken DNA
samples on 700,000 head upon arrival at its feedlots. The data is used to sort
animals into groups fed to make high-quality grades, or into groups fed to
produce a high yield of red meat at the least cost.
"We gain efficiency by minimizing fallouts of
individual animals from groups—animals that will be too heavy, too fat, too light or a lower grade as the group reaches the end of
the feeding period," says Ben Brophy, genomics
commercialization manager for Cargill.
While there's potential to increase feedlot efficiency, Brophy points out management and environment as well as
genomics influence outcome.
"We're still in a trial-and-error period with genomics.
We're working to make DNA tests more accurate and hope eventually to use
genomics in procurement of cattle for our feedlots," says Brophy.
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