Beef Improvement Federation
The Next Generation
of Genetic Tools
By Troy Smith
Before he became technical services director
for genomics service provider Neogen, John
Genho spent his growing-up years on Florida’s
Deseret Ranch. That large beef cattle operation’s
breeding program employed a three-breed
rotational cross. According to Genho, the
purpose was to exploit the effects of heterosis.
Also called hybrid vigor, heterosis refers to
the performance advantage of crossbred
animals, over the average of their genetically
dissimilar parents. Of particular advantage is
heterosis enhancement of traits that are lowly
heritable and difficult to advance through
genetic selection — such as fertility.
Speaking at the 2019 Beef Improvement
Federation Symposium, hosted June 18-21 in
Brookings, S.D., Genho said the reason many other
commercial cow-calf operations do not crossbreed
is that doing so can get complicated, especially if
the goal is to retain the most heterosis possible.
It’s challenging for producers running a single
herd of relatively small numbers. Most U.S. herds
are small, according to Genho, averaging 40 brood
cows. In many cases, they are straightbred cows.
Genho acknowledged the question of
whether heterosis exists within a breed, but
suggested consideration of heterozygosity
within a breed. That’s the term applied when
gene pairs associated with a certain trait
are different from each other. When gene
12 | AUGUST / SEPTEMBER 2019
pairs are identical, they are homozygous.
Heterozygosity represents greater diversity.
“Is there heterozygosity within a breed? Yes,
that’s absolutely the case,” stated Genho,
explaining that a measure of heterozygosity
(RHET) can be performed easily when DNA-
testing any animal. This heterozygosity
score is a genomic indicator of heterosis.
“It’s not true heterosis; its’ an indicator,” emphasized
Genho, also explaining that while genetic in
nature, these values are not passed on to the
next generation, so they are not valuable in a
selection program for offspring. However, Genho
thinks these “H-scores” could be beneficial to
commercial replacement heifer program to
identify candidates more or less likely to remain
productive members of the herd for a longer time.
“I think there’s a ton of value in knowing that a
heifer is 15% more likely, for example, to stay in
the herd, based on heterozygosity,” Genho stated
noting how the concept can also be applied to
predicting birth-to-weaning survivability among
calves. While he can’t prove it yet, he suspects it will
work for predicting feedlot health by identifying
calves more at risk for health problems. LT
This article is reprinted with permission from www.
BIFconference.com, Angus Media’s online coverage
site of the 2019 Beef Improvement Federation
Research Symposium and Annual Meeting.