Breeding cattle without horns

For generations dairy farmers and cattle breeders have sought ways to breed a hornless cow. Up next, Science Friday looks at how geneticists at the university of California Davis are partnering with biotech researchers to edit genes and breed cattle without horns.


For generations, dairy farmers and cattle breeders have sought ways to breed a hornless cow.

Up next, 'Science Friday' looks at how geneticists at the University of California, Davis, are partnering with biotech researchers to edit genes and breed cattle without horns.

How are you?

Nice to see you.

Nice to see you, my friend.

How are you? You good?

Yeah, I know.

So this is Spotty Guy.

Yeah, he's very friendly.

So normally, his horns would be growing up here and here.

But you can see that -- that they're not growing.

This is -- this guy's called Barry.

He has a slightly different spotting pattern but also no horns.

And so these are the stars of the show, yes, the two bulls that have been, um, genome edited.

So we tweaked that gene so that they no longer grow horns.

As a geneticist and animal breeder, Dr. Alison Van Eenennaam doesn't see a cow the way that most people do.

Things like the -- the health of the animal, the reproductive capability of the animal, what its form is like, and then also the amount of -- of protein it produces.

It's a genetic basis underneath all of that.

And it's due to the random mutations that happen during evolution or selection, artificial selection.

And while much of her work has involved wrangling these random DNA changes, Dr. Van Eenennaam's motivations are hardly clinical.

Some of the work we're doing with them to try to select for animals that are less susceptible to disease and to try to minimize welfare issues, like dehorning, is really what interests me about animal breeding.

And I think that genetics is a really sustainable approach to dealing with some of the problems of -- of agriculture.

Some of these challenges popped up long after cattle were domesticated.

During the development of -- of dairy cattle breeds, um, the horned trait came along.

It wasn't necessarily something breeders were selecting for.

But it is now fixed in the dairy breeds, for example, Holstein and -- and -- and Jersey.

And it's not a trait that is optimally suited to modern production systems because the animals can hurt each other with the horns.

And they can also hurt the human handlers.

So to previous future harm, dairy farmers often burn the growing horn buds off of male and female calves.

It's done at a young age, when the animals are one or two months old.

And it's painful when it's done.

And so typically, a lidocaine block is given to the animal before the heat is applied to the -- to the horn bud.

And so that's unpleasant.

And it's not something that is enjoyed by either the farmer or the -- or the cow.

Thankfully, not all breeds of cattle are given this procedure.

As it happens, Angus have a naturally occurring mutation in their DNA that makes them not grow horns.

So they're what's called polled, which means that they don't grow horns.

It's a genetic defect, if you will.

And of course, this leads to the question, 'Why can't they get rid of the horn trait the old-fashioned way?'

You could cross an Angus over the top of a Holstein and get a polled, no-horned calf.

But you'd have this calf that was kind of half dairy and half beef.

And it wouldn't really be ideally to -- to either.

And then you'd have to cross it back to Holstein to Holstein to Holstein to get it back to the high productivity of a typical Holstein.

So by the time you did eight crosses, that's, you know, a 20-year process.

And that's assuming the random genetic changes that come with traditional breeding methods work out in your favor.

It's a process cattle breeders are not likely to adopt.

So how do we make the Holsteins hornless?

In the case of the bulls that we've been working with in collaboration with the company Recombinetics, the editing reagents were brought into cell culture.

And they went in and very precisely made a tweak in the DNA at the gene that grows horns to introduce exactly the same sequence as is found in Angus at that particular gene.

So we introduced, basically, a cow sequence into a cow genome.

And then those cells were cloned.

And that's the two bulls that we have here on campus that are Holsteins that no longer grow horns.

Dr. Van Eenennaam and her team at UC-Davis is currently working on editing embryos in a similar manner.

But it may be a while before bulls like these are ready for prime time.

They're prototype animals.

It wasn't done in an elite genetics line.

It was really done more as a -- as an experimental proof of concept.

So there's very elite animals that are at the top of the breeding pyramid.

So, for example, if you edited an elite Holstein, then all of the daughters that he produces would inherit that change.

And so you could make improvements quite rapidly in -- in a production system like that.

Um, but how soon this technology might be seen in agricultural breeding programs really is 90 percent dependent on regulations and 10 percent dependent on scientists.

Um, if there's an overly arduous, you know, 20-year time frame to bring it to market, then obviously, that's gonna make it cost-prohibitive.

Because the edit to the animals DNA is identical to a random mutation during sexual reproduction, Dr. Van Eenennaam doesn't believe this type of change merits legal oversight.

We don't regulate that now.

I mean, the reason that a Holstein looks different to an Angus is because of spontaneous mutations in evolution or selection, artificial selection.

And so what's the rationale for -- for regulating it if it's done by done by man versus if it occurs spontaneously?

To me, there's no scientific rationale for that.

It's just, really... It's an ethical 'Man shalt not do that,' kind of statement.

But she acknowledges that there is significant public concern about genetic modifications.

If people's worries have to do with transgenesis or, you know, 'Frankenfish' or whatever, it's really a different technique to that.

But I -- I guess I would -- would step back and ask, 'What is it that concerns you?'

Um, and -- and to -- to understand where that -- that discomfort is coming from.

I mean, I don't think people would argue that it's better to burn off a horn than to genetically dehorn an animal.

And so I'd like to have a discussion not only about risks which is what the GMO discussion is only ever focused on, and discuss both benefits and risks.