The Fast Track to Polled Genetics

Transitioning the entire population of the U.S. dairy herd to polled genetics is a lofty yet admirable goal to improve animal welfare.

Concerned consumer groups cite dehorning pain as a primary welfare concern. While much progress has been made in using pain management techniques to lessen dehorning stress, creating a completely polled population would eliminate the procedure altogether.

In addition to improved animal welfare, erasing dehorning also would reduce labor and medication costs for producers.

But simply choosing polled sires doesn’t appear to be happening at a rate to significantly shift the population to date, according to University of California-Davis researcher Alison Van Eenennaam. She and her team with the UC-Davis Animal Genomics and Biotechnology Project have studied the issue of polled animal development extensively.

Van Eenennaam told the audience of the virtual 2021 University of California Golden State Dairy Management Conference that homozygous polled animals in both the Holstein and Jersey breeds typically fall about $150 less in genetic merit compared to horned animals.

“Producers don’t like to use polled animals because you have this big drag on genetic merit,” she shared.” Additionally, she said genetic change comes more slowly in cattle than other animals because they are a relatively large species with a generation interval of about two years. Compared to mice or rabbits, that’s a much longer period to wait for genetic changes.

That rate of progress could change with the introduction of genome editing. Technology, like the  CRISPR/Cas9 technique, now exists to splice in DNA to “instruct” genes to express certain traits. This would allow breeders to introduce useful variations into livestock breeding programs for traits like disease resistance, milk production, adaptability, and appearance.

Proponents of the technology say it could improve animal welfare and resilience; reduce the need for antibiotic use; and lower the carbon footprint of food animal production via improved production.

In the case of polled genetics, gene editing would allow the polled trait to be introduced into the next generation of high genetic merit sires, creating polled offspring from the most elite dairy genetic lines.

Currently, there is a regulatory patchwork of oversight of the technology worldwide. In countries like Brazil and Argentina, no additional regulation of the technology is required, as long as the trait being modified is one that could be produced through conventional breeding – albeit at a slower pace.

In the U.S., law-making efforts are underway to transfer regulatory oversight of livestock gene editing from the FDA to the USDA.  At present, the FDA is regulating the technology as a “New Animal Drug Application,” which Van Eenennaam says is an awkward fit, costly, and excessively time-consuming.

The USDA, on the other hand, already has a review process in place for gene editing in plants, which could serve as a framework for food animals.

Van Eenennaam is hopeful the regulatory tug-of-war in the U.S. can be resolved sooner versus later, so gene editing research can progress, and its benefits can be realized. “We have the ability to precisely knock out undesirable traits and knock in desirable traits like polled,” she stated. “This technology has the potential to dramatically impact global agriculture for the better.”