The Next Generation of Genetic Tools

Knowing heterozygosity can help identify candidates that will be more productive members of the herd for a longer time.

by Troy Smith, field editor

BROOKINGS, S.D. (June 20, 2019) — 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 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.

The 2019 BIF Annual Convention was hosted by South Dakota State University and the South Dakota Beef Breeds Council June 18-21 at the University Comfort Suites and Convention Center in Bookings. ANGUS MEDIA® provides comprehensive online coverage of the event at www.BIFconference.com. Visit the Newsroom for summaries, proceedings, PowerPoints, video and/or audio of the sessions and the Awards page for announcements and photos of award winners.

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