Could Gene-Edited Hens Stop the Great Chicken Massacre?
Researchers have designed a light-activated genetic kill switch to prevent male chicks from hatching, since they have no economic value.
Every year, billions of male chicks are killed in hatcheries worldwide when they are just a few hours old.
The reason for this constant extermination is that they are considered an unwanted agricultural byproduct of breeding egg-laying hens. They can’t be raised for meat because they grow too slowly. And obviously they can’t produce eggs. So as soon as their sex is determined and they’re deemed not economically viable, they are simply destroyed—usually by gassing them to death or grinding them up in a process known as maceration.
Some consider this one of the most objectionable of the many controversial so-called horrors of the poultry industry, which include inhumane overcrowding as well as mental and physical suffering. Now, it’s finally getting the attention of regulators. In Europe, several countries are now attempting to ban the practice, which in the European Union alone accounts for the culling of 330 million male chicks a year. In the United States, where maceration is the predominant method, the figure stands at 300 million. Some global estimates go as high as seven billion chicks culled a year.
When bans take effect, hatcheries are forced to move to “in-ovo” sexing, which happens around halfway through the egg’s 21-day incubation period. It can be done by either extracting a liquid sample from the eggs and genetically testing it, or using a light beam to check for differences in the color of feathers that are linked to gender. However, these methods come with caveats such as added cost, imperfect accuracy levels or failure to work on specific breeds, meaning that some male chicks will continue to hatch and be culled under the new rules until a flawless solution emerges in the industry.
Researchers at the Volcani Center, an Israeli state-owned agricultural innovation lab near Tel Aviv, now believe they have such a solution, based on gene-edited hens that lay eggs from which only females hatch. Sex chromosomes in chickens are called Z and W, and it’s the mother hen that determines the sex of the embryo. Volcani’s hens carry a modified Z chromosome, similar to the human X chromosome, which is passed onto male embryos only. It contains a genetic kill switch that is inactive until the egg is exposed to blue light, which interrupts development so that the egg doesn’t hatch.
“This solution was designed from the very beginning to meet the industry’s needs,” says Yuval Cinnamon, the principal investigator of the Volcani Center. “Being in a hatchery, you realize there’s no place for any kind of sophisticated technology nor a high cost to identify the sex of the embryo, because that would not be viable,” he adds.
A gender reveal that sways the sex
The effect occurs within minutes of flashing the eggs with the blue light, but to guarantee complete accuracy the current exposure time is set to six hours. For hatcheries, it’s a relatively straightforward extra step that comes with operational benefits, Cinnamon says.
“The eggs can be sorted as early as 48–72 hours from incubation, which is really fast,” he says. “This will allow the hatcheries to either save half of the energy needed to operate or double their capacity, because the male eggs will be eliminated from the incubators.”
It’s still unclear what would happen to the unhatched eggs. Cinnamon says they are “as good as table eggs” in terms of protein quality and content, but they do contain genetically modified material, which means their use will be regulated by local laws: “They could be used as a liquid egg material in some countries, or as a source for protein in animal feed in others,” he suggests.
The genetically modified breeders will require growing under certain conditions and regulations that do not yet exist, and Cinnamon sees this as the biggest legal hurdle. However, he says that the female embryos they produce, as well as their eggs, do not carry any genetically modified trait, which means they can be marketed without any regulation. (Hens pass their Z chromosomes onto their male offspring only and female chicks inherit their Z chromosomes only from their fathers.)
“Only when the male embryo within the egg is exposed to blue light, this molecular switch turns on and stops its development. All the generations above it are healthy and normal,” he says.
To address welfare concerns, Cinnamon and his team have for years invited representatives from Compassion in World Farming, a U.K.-based animal welfare group, to check on the project in Tel Aviv. Among them was Chief Policy Advisor Peter Stevenson. “This is an important development, but our support for it is in principle,” he says. “With selective breeding, genetic engineering, cloning, and now gene editing there are many examples of serious health and welfare problems which were not anticipated. We need to see that these female chicks can go through their lifespan with no unexpected problems.”
“They’re killed without any purpose—but they’re not waste, they’re living animals. And this is what makes this problem so devastating.”
Whether or not consumers are going to buy the unhatched eggs is another problem, Stevenson says: “There’s a long history in Europe and the U.K. of opposition to cloning and then genetic engineering, and I think we will see the same consumer concerns about gene editing.”
Both Stevenson and Cinnamon agree that two more years of work are required before the eggs can hit store shelves, but the Volcani team is already working to license the technology through a spin-out company, Huminn Poultry.
For the poultry industry, ending the culling could save between $500 million and $2.5 billion a year, depending on estimates, by avoiding the extra cost of incubating the eggs that would hatch the male chicks. The cost savings could be even greater if the unhatched eggs had some commercial value as well. Sparing the animals from brutal slaughter would be priceless. “The issue with culling these male chicks is that they’re killed without any purpose—but they’re not waste, they’re living animals. And this is what makes this problem so devastating,” Cinnamon says.
“In terms of animal welfare, this is a game changer.”