Genetic Editing Emerges

March 21, 2015 03:02 PM
Genetic Editing Emerges

Selecting for individual traits is often discouraged, but an emerging genetic technology could change your mind

Producers have many genetic tools to advance the productivity and profitability of their cowherds. AI, genomic enhanced EPDs, timed estrus synchronization, embryo transfer and sexed semen are just a few tools producers have to choose from. The newest tool is gene editing.

Gene editing allows producers to select traits they like from a particular breed and add it to their breed of cattle. It means single trait selection can be done without sacrificing production goals. For example, researchers at Climate Adaptive Genetics are breeding Angus cattle that will be white-haired instead of black for improved heat tolerance.

Climate Adaptive Genetics has 40 embryos ready to be placed in recipient cows this April. The 40 embryos have all been edited to contain the white hair gene from Silver Galloway cattle and the short hair gene from the Senepol breed.

The idea of using genetic technology to breed a more heat-tolerant Angus calf came to Warren Gill while he was attending a conference where conventional breeding methods for the task were being discussed. Gill, manager of Climate Adaptive Genetics, is also the director of the School of Agribusiness and Agriscience at Middle Tennessee State University. 

Returning from the conference, Gill asked his colleague James West, associate professor of medicine at Vanderbilt University and CEO of Climate Adaptive Genetics, if it was possible to speed up the process through gene editing. 

There are a variety of methods you can use to do the editing. The first step in Climate Adaptive Genetics’ process is to pull skin fibroblasts from the animal’s ear. Cells from the ear are grown in a petri dish, and the genes with fibroblasts in-culture are edited. Cloning produces the live calves.

“It is relatively straightforward,” West explains. “The tools for doing this have gotten much better over time.”

Photo: Recombinetics

In a Recombinetics and Texas A&M University collaboration, a Nellore bull, right, was genetically edited with a myostatin gene from Belgian Blue. The increase in muscle mass is evident, compared to the paternal twin heifer, left.

Climate Adaptive Genetics selected Silver Galloway as the source for the white hair gene because the breed also has a black hide underneath, which will help reduce sunburns. The short hair gene from Senepol cattle will further increase heat tolerance, according to their research.

“Our strong impression is that the world would love to see superior Angus genetics get into a lot more places,” Gill says.

Interest in the project has come from warmer regions around the globe, such as Brazil and northern Australia, where introduction of Angus genetics could help increase the carcass merit of the predominantly Brahman-type cattle. Until now, heat absorption from black hair color and a longer hair coat has prevented it.

“They really are having trouble with heat tolerance,” West says. “Improving heat tolerance in Angus is going to do wonderful things for production in hot climates.”

In the U.S., feedlots could benefit from the improvement in heat tolerance as well.

“The performance they get in the summertime, certainly in Texas but even in Nebraska and Colorado, could be improved,” Gill says.

However, the debate on genetically modified organisms (GMOs) could make widespread use of gene editing more difficult.

“A lot of the concern is a very  vocal minority of people that aren’t really plugged in to how we’re going to feed the world,” Gill says.

GMOs are classified as having genes from other species. The process of gene editing by Climate Adaptive Genetics focuses on just using cattle DNA for improvement.

When work on the project began, a white gene from Leghorn chickens was used because of its dominance. White hair color in cattle is typically recessive. “If you wanted to pick a really strong gene, you go to a Leghorn, but all of sudden, that raises that GMO question. It is one thing when you start moving from one species to another; we wanted to avoid that,” Gill says.

Gene editing helps decrease the amount of time spent trying to breed for a single trait. In a conventional breeding system it might take at least 15 to 20 years to achieve the change being sought. This technology allows producers to select the trait desired and have it in a single generation rather than spending decades.

Other technologically savvy “green” investment groups have expressed interest in the work because they understand these breeding methods are an alternative to cutting down the rest of the rainforest for herd expansion. 

“Brazil needs to increase their beef production,” West says. “They’ve got two ways of doing that: producing more efficient cattle or cutting down the rest of the rainforest. If you want to produce more efficient cattle, this is the way to do it.” 

The addition of Angus genetics might help increase rate of gains for Nellore (Brahman) cattle in Brazil. 
Angus cattle can gain on average 35 lb. to 45 lb. per month versus Nellore cattle at 15 lb. to 17 lb. “This is how cattle are going to be bred in the future,” West adds.

There are many other organizations working on gene editing in cattle to achieve production goals. Since 2008, Recombinetics based in St. Paul, Minn., has been working in multiple areas, including beef and dairy cattle, swine, sheep, goats and other species.

One particular project is to remove horns from cattle, which has caught a lot of attention because it could eliminate the practice of dehorning—which animal rights activists have been against for years.

The application of genetic dehorning would be relevant across the cattle industry, says Scott Fahrenkrug, CEO, Recombinetics and former molecular geneticist for the University of Minnesota and USDA Meat Animal Research Center.

“We’re really trying to optimize genetic dehorning, so we can move as quickly as possible for those who want to get polled at a high enough frequency that we make dehorning go away,” Fahrenkrug adds.

The dairy industry has expressed the most interest for breeding horns out of Holsteins. Hereford breeders also see the value in turning horned animals into genetic polls without crossing to a polled animal.

“It is really an important moment for this accelerated breeding technology,” Fahrenkrug says. “Its impact 
will be on the scale of AI—but it will be even faster 
and more precise.”

Gene editing does not create new genes or alleles, and it is also not a transgenic animal. 

“The result we get is identical to cross breeding, except you don’t have to put the back crossing into the program,” Fahrenkrug says.

Proof of concept with any new technology is important, and Recombinetics has produced several different types of gene-edited animals, including dehorned cattle, disease resilient pigs and swine for the biomedical market.

Additionally, the company worked with reproductive biologists at Texas A&M University to produce a Nellore bull with increased muscle production. The myostatin gene in Nellore was edited to produce a protein identical to that produced by Belgian Blue cattle, corresponding to a natural variant which results in dramatic improvements in retail product yield. The result was a Nellore with much larger muscle mass.

The segregation of this trait in breeding is being analyzed through AI, using semen from the Nellore bull to determine what the impact might be in a Nellore population. 

Not only can gene editing help increase productivity of cattle, but there is also the potential to fix genetic defects that occur from line breeding in purebreds.
“It is genetic repair, but all we’re really doing is restoring the sequence to what is normal,” Fahrenkrug says.

For instance, tibia hemimelia, or TH, a defect in Shorthorn and Maine Anjou breeds could be eliminated through gene repair. It could even help salvage the popular genetics of the Angus bull Precision 1680 that was linked to arthrogryposis multiplex defect, also known as Curly Calf.

“You can rescue a genetic line by getting rid of those recessive lethals that are segregating in the population,” Fahrenkrug says.

The timeline for when gene edited cattle will be available for breeding is yet to be determined. Regulators from the Food and Drug Administration (FDA) and USDA will have the final say.

Thus far, USDA has ruled several gene-edited plant products don’t need to be regulated because they are not GMOs. However, as for transgenic animals, there is a danger that the FDA might consider gene-edited animals a drug. Fahrenkrug finds the reasoning for this hard to comprehend, especially when you consider a similar technique called gene therapy can be used to cure disease in people—who are not then themselves considered to be a drug and are sent home to their families. 

If agriculture producers are going to feed 9 billion people by 2050, there is no way producers can rely solely on traditional breeding techniques, he adds.

“We can do it the old fashion way and take generations to improve performance, quality, welfare and 
sustainability—or we can rapidly breed with editing while maintaining the integrity of our best genetics,” Fahrenkrug says.

“Gene editing is simply a breeding and genetics technique,” Fahrenkrug adds. “It is not transgenesis, it is not Frankenfood. The outcomes of our precise and accelerated breeding are identical to those you would get traditionally, but without investing lots of money and decades of work before delivering.”

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Spell Check

Jared Lloyd
Collbran, CO
4/4/2015 09:06 PM

  Yeah, because we have to "one-up" the Brits for BSE, then don't we?


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