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).
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.
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.
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.
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.
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.
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!