How CRISPR could save 6 billion chickens from the meat grinder

Each year billions of day-old male chicks are killed in industrial grinders. CRISPR could change that.

Jackson Ryan Former Science Editor
Jackson Ryan was CNET's science editor, and a multiple award-winning one at that. Earlier, he'd been a scientist, but he realized he wasn't very happy sitting at a lab bench all day. Science writing, he realized, was the best job in the world -- it let him tell stories about space, the planet, climate change and the people working at the frontiers of human knowledge. He also owns a lot of ugly Christmas sweaters.
Jackson Ryan
10 min read

We need to talk about chickens.

Wherever human beings exist on the planet, they are almost certainly eating chickens -- or chicken eggs. From Delhi to Beijing, Moscow to Oona-Woop-Woop, the humble fowl completes our roasts, soups and breakfast plates.

Fifty billion chickens are reared every year, but more than 6 billion male chicks never make it past a day old. Hatcheries across the world wait for the boys to poke out of an egg, only to send them to their assured deaths: a high-speed, industrial grinder that instantly macerates them.

It's a gruesome fate, but it's currently the most economic and -- remarkably, some would say -- the most humane way to deal with these "useless" birds. An unfortunate truth of chicken biology: Males do not produce eggs. Any male hatched to be an egg-laying chicken is worthless, destined to die.

But if there was a way to determine the sex of the chick before it hatches, the culling of day-old males could cease for good. That might be seen as a win for animal advocate groups, which view the slaughter as unethical and barbaric, but it would also count as a win for the egg-laying industry, which has searched for an alternative method to the killing that makes economic sense for decades.

The past 10 years have seen biotech startups catch on and begin searching for the industry's golden egg: a breakthrough that would enable in-egg (in ovo) sex determination and change the fate of billions of chickens every year.

Some pioneering researchers at Australia's Commonwealth Scientific and Industrial Research Organisation ( CSIRO ) think they've found an answer -- and it involves lasers. Using the revolutionary genetic engineering tool known as CRISPR, the team can splice the genes of a sea anemone into the chicken genome and create a special, glowing egg. By shining laser light on the shell, they can detect the sex of a chicken on the day it's laid.

Though the idea is simple, it has the power to fundamentally change the chicken forever, placing a genetically modified organism in the food chain. That means that soon, we may be faced with a decision: Do we want to stop the killing of day-old chicks? Or do we want to use biotechnology to bend nature to our will?

Kriengkrai Kontasorn/EyeEm/Getty

What came first?

Genetics is the laying industry's biggest problem -- and its potential solution.

The chicken on your plate is not the same chicken that laid the eggs in your omelette. Chickens are specifically bred for either purpose. Those used for meat production are known as broilers, while those used for egg production are known as layers. At a genetic level, these two types of chicken are slightly different animals.

Broiler chickens are genetically programmed to turn their feed into muscle, getting as big as possible, as quickly as possible. Laying chickens, on the other hand, are predisposed to laying eggs instead of plumping up their muscles. While male and female chickens can both be used as broilers, layers are a different story. The females grow up to be egg factories, but the males are basically an unused byproduct. They can't produce eggs, and due to their genetics, they're not all that great at building muscle either.

"Their genetics is such that they are elite at whatever they do. They are either elite at making meat or elite at making eggs," says Mark Tizard, a geneticist at the CSIRO.

"The outcome of that is it takes three times as long, on average, and much, much more feed to grow a male laying chicken up to a sensible size that can be turned into a meat product."

China, the world's biggest producer of eggs, needs about 1.2 billion layer hens to produce over 1 billion eggs every day. The US has around 325 million layers, which pump out around 75 billion eggs a year. In the act of breeding layer hens, half of the mother hen's offspring will be male.

Little chicks at farm feeding

Male laying chicks are deemed "useless" because they cannot lay eggs or put on the bulk required to be sold for meat.

Dancu Aleksandar/Getty Images

As it now stands, all the eggs a mother hen lays go through the same 22-day incubation cycle, which at the end produces a chick. Then, a specialized "chicken sexer" inspects the newborn chicks, either by looking "between their legs" or by examining their wing feathers, which vary slightly between males and females. Sexers make their decision -- rapidly -- based on a small bump visible in the bird's anal vent.

"The girls go off to a lovely farm where they are looked after and fed and housed," explains Tizard. "The boys go down a conveyor belt and then straight down into a high-speed spinning blade."

The result is more than 6 billion male chicks destroyed every year.

This may appear merciless and cold, but international animal welfare organizations like the World Organisation for Animal Health, don't condemn such clinical killings. The American Veterinary Medical Association's guidelines for chick euthanasia state that one of the chief advantages of the method is "death is almost instantaneous," but that argument does little to convince welfare organizations the practice is ethical.

"As an organization, we believe that animals have every right to life that we enjoy," says Alex Vince, farmed-animal campaign coordinator at Animal Liberation Australia. "We do not believe there is an ethical way to use another animal for any purpose when we have a myriad of alternatives available."

Short of shutting down every chicken farm across the world, male chickens will continue to be fed to the grinder. Solving the problem while the chicken is still in the egg is less gruesome than the alternative -- and many companies around the world are trying to do just that.

Moskow/Getty Images

Count your chickens

Determining a chicken's sex in ovo is not a new idea.

One German biotech firm, Seleggt, brought its world-first "no-kill" product to a Berlin supermarket chain in November 2018. Seleggt's technology punches tiny holes into the egg shell on day nine of incubation, sucking out some fluid. The fluid is used to determine the chick's sex by testing for a female biomarker.

Using a similar method, Dutch startup In Ovo has been working toward its own solution. The company recently received millions in euros to continue developing its method which, as in the case of Seleggt's eggs, takes a sample of the fluid inside the egg on day nine of incubation and looks for a different biomarker.

"The problem with that is, those kind of procedures are slow and expensive," says Tizard. "They're too slow and too expensive to be economic to replace the process of just removing the males once they've hatched."

Tizard and his colleagues at Australia's CSIRO are using a different approach that they hope will be much faster: genetically engineering the chicken to produce a special type of egg. One that emits a bright, red light. This simple gene edit would be akin to a third eye -- it would allow us to see inside the egg. Notably, it could be used on day one, right after the egg is laid.

"We've got a simple interrogation which doesn't involve drilling any holes or taking any samples and processing those samples and waiting for the response," says Tizard.

All you need is a laser and a handful of geneticists.

Red light, green light

When a fertilized egg is laid, the chick inside is nothing more than a bundle of 60,000 cells.


Early experiments by the CSIRO used a green protein to determine the sex of a chick. Here, a 2.5-day old chicken embryo glows green under a fluorescent lamp.


Those cells already contain genetic material, chromosomes full of genes, genes full of DNA. As with humans, chicken chromosomes determine sex. If a chicken receives two Z chromosomes, it will be male. If it receives a Z and a W chromosome, it will be female. That gives CSIRO's genetic engineers a target: the female Z chromosome that's passed down to male chicks.

The technology at the center of the breakthrough is CRISPR, a powerful tool discovered in 2012 that is so versatile it can edit almost any gene in almost any species. Often called a "pair of molecular scissors," CRISPR can make a cut in the DNA sequence of a gene and "paste" a new gene in the gap.

In the case of CSIRO's genetically engineered chickens, CRISPR would paste a gene derived from a sea anemone into the male-only chromosome. That gene produces "red fluorescent protein" (RFP), which glows under laser light, causing the cells to give off a red-orange fluorescence. Just like a red traffic light tells you to stop, seeing the red light reflecting from within the egg tells a handler (or machine) there's a male chick inside, and the incubation process is terminated.

"It's a straightforward test for the presence of the chromosome by light in that egg ... before you even put it into the incubator," says Tizard.

What happens if the egg doesn't glow red? Then the chicken is female, the egg is placed in an incubator and 21 days later a hen is born. She is then sold to a farm and throughout her life she will pump out the eggs that fill cartons on supermarket shelves.

The benefits of removing the egg from the production line shortly after laying are twofold: the incubator would have double the free space, so you can fit in double the eggs, and the male eggs may also be repurposed, say for vaccines or feed production.

Carton copies

One of the most crucial elements of creating a genetically modified chicken for this purpose is to educate a public still concerned about the risks of eating genetically modified foods. While scientists generally agree that GM foods are safe to consume, many people still oppose their use.

"The choice is: Do you want to continue to cull male chicks?" asks Tizard. "Or do you want to have a process in which biotechnology is put in and taken out, with nothing changed in the food product that you go and collect at the supermarket?"

The eggs that CSIRO is developing are essentially carbon copies of the eggs you're already buying from the supermarket. That's because the females -- the chickens that lay our edible eggs -- never receive the genetic modification. It can't end up in our cakes or omelettes because it's tied to the male chromosome.

This solution elegantly sidesteps the issue of regulation surrounding genetically modified organisms for human consumption. And regulation has been notoriously tricky in this space. The first GM animal to be approved for consumption, the AquAdvantage salmon, spent 25 years struggling to gain approval from the US Food and Drug Administration and from Health Canada. The FDA finally approved sale of the GM salmon in 2015, but complications regarding how products are labeled still prevent it from coming to market in the US.

Tizard suggests that regulatory bodies will see their GM chicken differently and is confident they wouldn't label the eggs at market "GM." Even so, he realizes the need for their eggs to undergo the same regulatory processes other genetically modified organisms go through. "I would like to see all the boxes are ticked before we get to a stage where the public are faced with this," he says.

Cavan Images/Getty Images

For the consumer, there's also the issue of price. In Germany, where "no-kill" eggs went on sale for the first time in December 2018, prices of a carton have risen by 2 to 3 cents. Not enough to be readily noticeable, perhaps, but a difference nonetheless. Factoring in the need to fit out hatcheries with new equipment, there's a potential those increases would be seen with CSIRO's chickens, too.

Chris Delforce, executive director at environmental advocacy group Aussie Farms, suggests the economics don't add up.

"Switching all of these facilities to use pre-hatch sexing would represent a substantial cost with no clear economic return, particularly when the practice of macerating day-old chicks is still largely unknown to the egg-consuming public."

Some of the costs may be partially offset for egg producers as new revenue streams are created with the excess male chicken eggs. Eggs are an important part of vaccine production, with up to half a billion eggs per year used to produce around 90 percent of the world's flu vaccines. Egg whites are also prominent in the cosmetic industry due to their high protein content, where they can be used in shampoos and hair treatments.

Tizard believes his chickens could fit seamlessly into the production line, albeit with slight adjustments to current practices. "It would need some small tweaks to how things are done at the moment but we're confident that it could be done," he says.

Hatching a plan

Through selective breeding, we inadvertently designed male chicks to be completely useless to the laying industry. That's created an ethical nightmare: They're born only to die. Now we have to design our way out of it.

Inspecting chicks at hatchery, Salisbury, Maryland

Chick inspection at a hatchery in Salisbury, Maryland.


Unilever, one of the world's foremost food manufacturers, announced a drive to stop chick culling in 2014. That seemed to kick-start the research and development progress and even saw United Egg Producers, which represents 95 percent of the egg producers in the US, commit to ending the practice by 2020, three years ago.

But bringing a product to market has been difficult. Besides the German "no-kill" eggs, there are few success stories. As the 2020 deadline approaches, it's unlikely the target will be met, but new initiatives are underway to spur new development.

The latest comes via the Foundation for Food and Agriculture Research. The US government-backed organization announced a $6 million "Egg-Tech Prize" in October 2018 to "stimulate development of new technologies" that provide high-speed, early sex determination in ovo. Applications for seed funding are expected in early 2019.

Timothy Kurt, scientific program director at FFAR, explains that current sexing solutions still suffer from a number of pitfalls: They're too slow, function too late during incubation and have low sensitivity.

For animal welfare groups, none of this matters. Despite the scientific advances, chickens will continue to be killed and put on our plates, fried in our fast food and roasted in our ovens . And groups such as Animal Liberation and Aussie Farms will continue to oppose the inhumane treatment of the world's most populous bird.

"Our position is that there is nothing ethical about breeding, exploiting and killing sentient beings for profit," says Delforce. "It will always remain an inherently and unjustifiably unethical industry."

In the end, neither the chicken nor the egg ends up coming first. That spot is reserved for us, our breakfast spreads and our stomachs. But diverting 7 billion eggs a year from assured destruction by high-speed grinder has to count for something, right?