Could castration could be a thing of the past?

Imagine not having to castrate calves every year. A gene editing project with pigs is in early stages that might make that a possibility in the future.

Imagine animal agriculture without the need to castrate livestock. Wouldn’t that be nice? A gene-editing project involving pigs is working to create just that.

Recombinetics, together with DNA Genetics, are in the early stage of a project to produce castration-free hogs for the U.S. pork industry. The effort is using gene editing technology to “knock out” a gene in pigs to produce a condition that keeps them in a pre-pubertal state. In humans, the syndrome is called hypogonadotropic hypogonadism.

“We thought, ‘why can’t we mimic that mutation in pigs?’” Dr. Tad Sonstegard, chief scientific officer of Acceligen, Recombinetics’ agriculture division, explained to WLJ.

A first effort was funded through a grant from USDA National Institute of Farm and Agriculture (NIFA).

“The goal was to prove we could make a phenocopy of the human syndrome in pigs, and it worked,” explained Sonstegard. The first effort produced 19 piglets. “They got pigs that were castration-free. There was no testicular development beyond what happened in utero.”

With this proof of concept in place, Sonstegard sought another grant through the Foundation for Food and Agriculture Research, a funding group set up by the 2014 Farm Bill.

“They’re very interested in filling the gaps in research where there’s not a lot of effort being placed either by ag research services or by NIFA. Animal wellbeing is one of those gaps,” said Sonstegard.

No castration-free pigs have been created yet using the new grant.

Dr. Tom Rathje, Chief Technical Officer at DNA Genetics, explained to WLJ that this current project has three parts; create more castration-free pigs using a different gene editing process, try to recover fertility in the affected pigs, and then test them for commercial traits like feed efficiency and carcass quality.

Though they are focused on the science, both Sonstegard and Rathje kept commercial applications in mind.

“The edit we’re creating prevents puberty, so obviously—for this to be effectively used in a production situation—you have to be able to recover puberty and the animals have to be able to reproduce normally,” Rathje said.

He explained that if fertility is recovered, they would then continue to a large-scale study of commercial performance. He noted that extremely early castration of male piglets—usually from day 4 to 10 of age—is the norm for the swine industry.

“We're comfortable with their growth, their feed efficiency, their meat quality, and all of those aspects. So, the question would be in this castration-free model, can we expect a similar phenotype or performance level from those pigs, whether they be male or female. That would be the last step of the project once we get through those first goals.”

When asked what a timeline to even considering these production considerations might be, Sonstegard said it won’t be before the end of 2020.

Cattle and reception

When asked if this project might be applied to cattle, Sonstegard said there was no reason why not.

“There’s no reason why it shouldn’t be easily translatable to cattle, because the gene pathway that we’re inhibiting should be exactly the same in cattle.”

He also said that the project could be stacked with University of California, Davis’ Dr. Alison Van Eenennaam’s “boys only” cattle project, covered in the Feb. 5 issue of WLJ.

“Ours is just a gene knockout and hers is a transgene.”

He speculated however that the “boys only” cattle will likely be considered genetically-modified organisms. Citing the ongoing uncertainty over how gene-edited livestock will be regulated, he stressed the value of gene editing applications that address consumer concerns.

“We can show them that the technology is being used not only for the wellbeing of the animal, but also for the producer and the consumer.”

“Castration is a widespread practice in the swine industry and if we can use genetics to eliminate that practice—just from a practical standpoint—it’s one less handling of a pig,” Rathje explained. “You can save the cost of implementing that practice, and it can promote the wellbeing of the animal.”

“At the end of the day, the consumer has the ultimate decision,” he added. “Anything that we do, whether it’s this technology or really anything else we do in the production of food animals, the consumer has a large sway.” — Kerry Halladay, WLJ editor

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