Project: bioengineering an all-female breed of chicken to end chick culling
In this post, “I” refers to Cienna’s point of view, with Q&A answers and accuracy checking by Zane.
I’m backing the research crowdfunding campaign Can bioengineering be used to create an all-female breed of chickens? which asks, what does it take to get male chickens to lay eggs so the egg industry won’t cull them? This experiment is a step toward a possible solution to ending the cruel and wasteful practice of male chick culling in the commercial egg industry. Mr. Zane Oberholzer, PhD candidate at the University of the Witwatersrand in South Africa, will be testing regulator sequences for their ability to selectively suppress the expression of the gene DMRT1 in gonadal tissue, resulting in the development of ovaries instead of testes. We’re posting here about this project and our conversation in case others are interested in funding this research experiment too.
This all-or-nothing raise is open until EOD Pacific Time on May 4th, 2022 (unless it gets extended, which sometimes happens).
The problem
Commercial chicken meat and chicken eggs come from different specialized breeds. For the egg industry, laying hens are needed, but only enough males to maintain the breeding population. Chickens have a sex ratio of roughly 50⁄50, so the male chicks are regarded as a wasted investment and culled.
One attempted partial solution to this problem is egg-sorting machines, which separate the eggs by sex before hatching. This saves part of the time investment, but despite having been around for a while, this tech is still disappointingly cumbersome.
An on-paper partial solution would be to transfer the unwanted male chicks to the meat industry, where they would live several weeks longer and maybe die a less painful death. But in practicality the laying breeds are physiologically very different from the “broiler” meat chickens and would not be wanted. Broilers have been selected for rapid growth and efficient conversion of high-protein feed into muscle mass. Layer breeds take longer to mature and have different physical proportions. A marketing premium would be needed to compensate for the higher cost of raising smaller, slower-growing birds.
The project
Well, what if the male chicks could grow up to lay eggs too? Then all the chicks would be wanted. No sex sorting would be needed. The same size breeding flock with the same resource inputs could produce twice as many egg layers.
Here’s a background bit of clarification: hens lay eggs regardless of whether those eggs are fertilized. Ovulation results in egg laying. No roosters are needed for hens to lay eggs, only for those eggs to have the potential to develop into chicks. So a chicken doesn’t have to be genetically fertile in order to lay eggs. The question is, does a chicken have to have the female combination of sex chromosomes in order to ovulate?
Creating a breed of chickens where all the adults lay eggs is beyond the scope of this small experiment; luckily, other researchers in the same lab are working on synergistic projects toward the shared goal of engineering such chickens. I’ll let you read about this experiment’s scope, details, methods, budget, timeline, ethics documents, et cetera on the project page, since Zane has already covered those.
Our conversation
At first the idea of an all-female breed of chickens sounded pretty “out there” to me. I took a coffee walk to sort my thoughts, and found I could imagine that it was doable, just not how it could be done. I returned with a bunch of poorly formed questions about sex determination in birds, and a curiosity to learn what I didn’t know that made this seem doable to someone else. I reached out to Zane, who agreed to a video call.
I really enjoyed our conversation! Zane is competent, bright, and curious, with an admirable combination of sweet openness and fortitude. He smoothly chose the right level of difficulty for his explanations so he could teach me a lot without losing me in the technical details. I learned a lot of background that didn’t make it onto the project page, and got to ask my questions that were beyond the scope of the project.
Here’s a loose reconstruction of the conversation from memory and my sparse notes. I’m not a biologist or anything, so any inaccuracies or bad explanations reflect my ignorance. If something I wrote here is wrong or nonsensical, please feel free to correct me or ask Zane to clarify.
Q: From what I remember about mammalian sex chromosomes, this shouldn’t be possible. What makes it possible in chickens?
A: In chickens, those with both a W and a Z chromosome are female and those with two copies of the Z chromosome are male. We don’t know whether it’s the double dose of Z that makes a male, or the presence of the W that makes a female, or some of both, but it currently looks like the answer will turn out to be some of both.
Sex determination in chickens is more robust than in humans for at least two reasons: 1) hormones have less influence because each cell has it own autonomous sex identity according to its chromosomes, and 2) chickens don’t have a centralized “master switch” comparable to the human SRY gene. The closest thing we’ve found is the DMRT1 gene which is located on the Z chromosome. In males, there are two copies of DMRT1 whereas in females there is only one copy of DMRT1. It has been shown that the higher levels of DMRT1 expression in males promotes testes development. In prior work, other researchers showed that knocking out DMRT1 on one allele (so, half as much expression of DMRT1) resulted in ZZ adults with ovaries and egg-laying organs, but male-typical coloration and no eggs. This shows that DMRT1 is important for healthy development in other ways, so this project will build on previous work by searching for enhancer sequences which only affect DMRT1 expression in gonadal tissue, which will hopefully enable the reproductive system to develop as a female without interfering with normal development elsewhere in the bird’s body.
Q: But no eggs. What if the W chromosome has something essential for egg-laying?
A: That’s very possible! My Master’s project investigated the possible role of a W-linked gene in female gonad development. The W chromosome is short and messy (like the human Y chromosome) which makes it difficult to sequence. There are presently 28 known genes on the W chromosome, of which our lab has investigated two so far. It still remains unclear, however, whether any W-linked genes play an instructive role in female gonad development.
Q: Let’s say this works and you succeed in creating a heritable genetic construct which results in ZZ individuals growing up to lay eggs instead of becoming roosters. Doesn’t that mean the end of the genetic lineage? How can this be a breed?
A: It’s very speculative to try to describe today how a self-sustaining breed might work because there is so much we don’t know yet about what it will take to get ZZ individuals to ovulate. But laying hens today are usually hybrids between two breeds: every generation has a parent from each, in order to maintain the sex-linked plumage coloring that results in pale yellow male chicks and reddish female chicks to enable easy sorting by sex. Crossing two breeding populations instead of having one self-perpetuating flock may continue to be the solution for getting consistent expression of the desired trait. We’re currently looking at altering individual roosters for breeding purposes by ablating and repopulating their germline tissues with a modified genetic profile—similar to bone marrow self-transplants for cancer patients. That would circumvent the problem of how to get healthy fertile roosters to develop despite carrying an allele that thwarts testicular development. Those (very expensive) roosters could be bred with normal laying hens.
Q: And what about genetic escape: if some of these got out and interbred with other chickens, could this accidentally end other chicken lineages?
A: Genetic escape is a concern, of course. We do, however, take it into consideration as we plan our experiments.
Q: How did you decide to work on this project?
A: Honestly, it was my supervisor’s idea. It was one of those essay prompt-type questions that makes you think critically; she walked in and told us, ‘The commercial egg industry is killing billions of male chicks annually. What will you do about it?’ I hadn’t heard about that before she told us. I had to really think about it. It’s one of those grim realities that go under the radar… I like that this research will visibly result in the world being different.
Q: Are you familiar with the Effective Altruism community? As research into how to improve farmed animal welfare, this project totally sounds to me like something that could have grown out of that community.
A: No, I haven’t. What’s that? Please send me a link!
Q: Cool, will do! Um, they have a Forum where people from around the world coordinate and talk about how to help the most with what they have, and create a good future. May I write about this project and conversation there?
A: Yes please, that sounds great!
Things I like about this project
The leverage point: this project aims to preempt a recurring problem instead of mitigating its costs.
The different, synergistic angle of approach to improving farmed chicken welfare: there are projects to lessen the demand for chicken products, regulatory change projects to provide chickens with better conditions, and now here’s a bioengineering project to halve the number of lives created for the purpose of egg production. Even if/when egg-laying hens and their parent breeding flocks get to live a life of luxury, this work won’t be moot.
The champion: this campaign is raising funding for a project by an early-career researcher with an unusual specialty, who might choose to continue doing high-leverage, practical work. …And I think Zane has what it takes to go the distance. Often, when someone encounters a truth painful to contemplate, they will choose to forget and continue on with their lives as if they’d never heard of it. But when he learned about chick culling, Zane chose to face the present grim reality—and work to end it. After doing his Master’s on a W-linked female sex determination factor, he chose to work against chick culling a second time with his PhD project. And he’s not alone: if this idea can be realized with current technology, this lab sounds from afar like they might be the team to achieve it.
Ways this project could fail
The research could fail to be completed as planned.
any of the usual drama that can sink a research lab: interpersonal dynamics, university policies, budget constraints, etc.
supply chain problems with specialty supplies
changes to ethics board standards
maybe more expensive tooling is needed than the budget can accommodate
maybe the regulators and promoters are too multifactorial to tease apart in the time it takes to do a PhD, and Zane will have to focus on something else to finish in a timely manner.
maybe the data won’t meet some standard for publication
The idea could turn out to not be viable.
maybe the current configuration of genes is too intertwined to change anything without creating health problems
maybe the W chromosome carries an cluster of genes which are essential for ovulation and can’t be moved elsewhere
The idea works, but it’s not adopted.
maybe the ZZ egg layers lay undesirable eggs.
maybe the approach with the individually altered roosters remains too expensive to become commercially competitive.
maybe the egg sorting machines will improve enough that it wouldn’t make a big enough difference to the egg industry to bother trying this alternative.
maybe the egg sorting machines are so expensive and work just well enough that the purchasers are bought in and won’t consider switching.
The platform
Experiment.com is a crowdfunding site for scientific research projects, ranging from high school competition projects to work published in big journals. I quite like it; I’ve been active as a backer for several years. What I dislike about Experiment.com is the 0.89 multiplier: 2.9% +$0.30 credit card fees + 8% platform fees. Though maybe 8% is a good value for providing a crowdfunding platform and the support of the project review process: each proposed project get reviewed by platform staff and by a scientist to ensure the idea is well-founded, the experimental design is sound, the researchers are committed, and the project page is well-written for accessibility by interested laypeople. Or that’s the idea anyway, I don’t know how good that process is behind the scenes.
Conclusion
I hope that by supporting this experiment, beyond its direct goals, we can in a small way contribute to a general feeling among bright young researchers that there are people out there who care and will support them in tackling problems that are hard to face.
I’m very curious to see what happens with this line of inquiry.
Zane:
As the experiment progresses, I plan to share lab note updates, and the link to the final publication on Experiment so backers can follow along and hear how it went. If you have questions, you can ask me either below in the comments, or in the discussion section on the Experiment.com page—I’m happy to talk about my work!
How do you think this approach (make male chickens lay eggs if I understand correctly) compares to other solutions being proposed/rolled out:
the various in-ovo sexing technologies to find the male eggs and destroy them/or process them into commerical eggs before they hatch- Respeggt eggs are already available for sale in Germany, France, and The Netherlands and Open Phil has funded the Egg-Tech prize
change the sex of the embryo in the egg https://www.theguardian.com/food/2021/jan/31/good-vibrations-sound-waves-eggs-ethical-slaughter-male-chicks
creating hens which only lay female eggs/the male embryo never develops https://www.i24news.tv/en/news/israel/technology-science/1643625207-israeli-firm-develops-hens-which-only-lay-female-eggs
raise the male chicks as meat chickens
develop plant-based/Cultured/fermented eggs
1. The various in-ovo sexing technologies to find the male eggs and destroy them before they hatch- Respeggt eggs are already available for sale in Germany, France, and The Netherlands and Open Phil has funded the Egg-Tech prize
The company respeggt GmbH has two projects:
Seleggt’s in-ovo sexing technology is similar to a gender test. Allantoic fluid from eggs is extracted and the hormone content is analysed for sex-specific differences. The drawback is that the technology requires expensive machinery and currently the technology cannot meet industrial demands. This technology is also not very suitable for small scale hatcheries. Another consideration is that males can only be sexed after 9 days of incubation. Indeed, this is an improvement over culling day-old male chicks but male chicks are still being produced so it only saves part of the time investment and there will still be costs involved in disposing of the males.
Respeggt GmbH’s second project pledges to hatch the male chicks that are part of the Seleggt project. These chicks are reared alongside the female chicks. This “dual-purpose” approach is unfortunately not financially viable for every hatchery to adopt.
2. Change the sex of the embryo in the egg https://www.google.com/amp/s/amp.theguardian.com/food/2021/jan/31/good-vibrations-sound-waves-eggs-ethical-slaughter-male-chicks
This looks like a very interesting technology! I wish there was more information available on how it works. Their technology (SOOS) uses a combination of environmental factors including sound waves to induce male-to-female sex reversal in the egg. A couple of questions I have about their technology though is whether the sex reversal persists into adulthood and whether the male chickens need to remain in the same environment to keep their “femaleness”. The principle of their technology, however, is the same as the approach I’m proposing: by selectively suppressing the expression of the gene DMRT1 in gonadal tissue, it will result in male-to-female sex reversal and ovary formation. I, however, want to target the regulatory sequence(s) that controls DMRT1 expression in gonadal tissue.
It should be noted though that this technology (SOOS) only has a 60% success rate. In other words, 60% of the batches they test are female but this includes ZW females as well. So they don’t have a very good success rate at the moment.
3. Creating hens which only lay female eggs/the male embryo never develops https://www.i24news.tv/en/news/israel/technology-science/1643625207-israeli-firm-develops-hens-which-only-lay-female-eggs
The technology is trying to create a genetic trait that is passed down only to males. This mysterious trait is sensitive to blue light, such that when embryos with this trait are exposed to blue light, it causes development to stop. I couldn’t find much more information on the trait or how early development stops.
This technology is trying to prevent male chicks from developing as early as possible whereas the approach I am proposing will allow those males to be hatched and used for egg-laying.
4. Raise the male chicks as meat chickens
There are some countries in Europe that are proposing to do this. Known as “dual purpose” chickens, the male chickens (of egg-laying breeds) are reared to be used for meat consumption. For many hatcheries, this isn’t a financially viable option though.
5. Develop plant-based/Cultured/fermented eggs
Plant-based eggs are another alternative. Currently though, production costs are still very expensive (plant based eggs are more expensive than free-range, organic eggs). Additionally, they’re not as nutritious as chicken eggs and on average contain less protein than chicken eggs. Plant-based eggs also contain lots of preservatives and additives. Therefore, I think plant-based eggs have potential, however, they’re not a sustainable alternative to chicken eggs.
In summary, the approach I’m proposing will enable the male chicks to be hatched and used as egg-layers. No culling, no expensive sorting machinery but twice as many eggs may be produced with the same resource input.
FYI in-ovo sexing is currently done on country scale in both Germany and France, both have completely banned chick culling since the start of this year. Germany is also set to ban discarding eggs after 6 days of incubation by 2024.
Thanks for your thoughts on the different approaches Zane, do you have an estimate of when your proposed approach would bear fruit in terms of a scalable intervention?
As Sebastian noted, in-ovo is already being done in two countries with chick culling prohibition legislation, and the Metaculus forecasting community median estimates most eggs produced in the EU will be sexed before hatching by October 2025, and most eggs produced in the USA will be sexed before hatching by 2033 (but a major U.S. supermarket chain will sell “no-kill eggs” in at least 25 states by 2031 ).
RE #3, the company’s website includes a helpful infographic. It sounds like they added an optogenetic control on the Z chromosome (I couldn’t find anything more specific than that). The breeding hens contain one altered and one normal Z chromosome, and the breeding roosters are normal. Female chicks receive a normal W from their mother and a normal Z from their father and are “wild-type”, but male chicks receive an edited Z chromosome from their mother and a normal Z chromosome from their father. Shining blue light on all the eggs “deactivates” the edited Z chromosome in male eggs, disrupting development when the embryo is “only two layers of cells.” Maybe we can find out more about how the optogenetic control works if someone with paid Academia.edu access searches for Dr. Yuval Cinnamon’s papers? I tried a title search and didn’t find anything.
Maybe I missed it in the article, but I think a project like this could be a little premature. The chicks are culled, true, but if they were engineered so that they were saved instead, then they’d be condemned to a horrible life of pain in cages (laying hens have it the worst, I think). Of course, it is perfectly plausible that a project like this might somehow instigate change in the way laying hens are treated and thus kill two… birds (darnnit) with one stone, but I don’t see how.
The benefit is that half as many birds will be killed if some version of this technology is widely implemented because half as many will be born in the first place. Rather than the male chicks being born female, they just won’t be born at all.
Well these are two different problems: 1). The practice of male chick culling and 2). The treatment of laying hens.
Although these two problems are linked, I don’t think it’s fair to say “it’s better to kill day-old male chicks than allowing them to live horrible lives in cages”. Both problems are equally grotesque and require intervention.
I think that both problems have “gone under the radar” so if they were discussed more and given more public attention, it will prompt other researchers to look into alternatives and solutions.
Dear Effective Altruism community,
It is my great pleasure to announce that this project has been fully funded.
A huge thank you to everybody who backed, shared, and showed interest!
If you are interested in following the developments/findings of the project, I will be posting lab notes on Experiment’s platform (link: here).
Congratulations!
Thank you for highlighting this opportunity, which seems like the sort of cool research that this community is into funding (including me, I chipped in a little bit), as well as for doing so much investigation of the project in order to write up this report.
Thank you Tessa for your support!
My worry is that you’re probably trying to identify then add/turn-on too much (i.e. all of the genes that code for egg laying).
I’m sure its probably not straightforward to change shell colour, which would be the best method of identification of chick sex (maybe shell development is determined by the hen rather than the embryo?), but there’s probably still a couple of additions you could make to the Z and W chromosomes to ultimately achieve the same outcome. And a couple of additions would likely be at least an order of magnitude easier than identifying then adding/turning-on a bunch of genes.
At least one idea that comes to mind is using insights from gene drive theory to disrupt male embryo development enough to be identifiable using a light shined through an egg. For instance, you could insert a gene into both Z chromosomes coding for a CRISPR complex that disrupts some key embryo development process. Additionally, you insert a gene into the W chromosome that codes for a CRISPR complex that modifies/disrupts the CRISPR complex on the Z chromosomes.
Maybe there’s a really obvious reason why that wouldn’t work or wouldn’t be that simple, but I suppose my point is that maybe you should aim to find and pursue a more simple solution unless you’re sure that no obvious and simple strategies would work.
Either way, I really hope you and your efforts succeed.
So the project is not looking to target the genes that code for egg-laying. We are testing regulatory sequences for their ability to selectively suppress the expression of the gene DMRT1 in gonadal tissue, resulting in the development of ovaries instead of testes. In other words, we are causing male-to-female sex reversal by targeting a single gene: DMRT1. There is the possibility, however, that a gene on the W chromosome either promotes ovary development or ovulation. We do not know this for certain.
The genetics of eggshell colour hasn’t fully been elucidated. It involves several pigments and enzymes but the genes encoding them haven’t been functionally tested and it’s still uncertain how the pigments are synthesized, transported etc. So I think this approach would be very cumbersome and challenging.
But I do agree, pursing a more straightforward solution will have the greatest chances of success.
I appreciated the… ruthlessness.