Hen vs. Rooster - The Art, History, and Science of Sexing Chickens
A farmer wanted to be able to tell which of his baby chicks were boys and which were girls so he enlisted the aid of a scientist. “Well!” said the scientist, “It’s really quite easy! You simply scatter some crickets in the coop. The boy chicks will only eat boy crickets and the girl chicks will only eat girl crickets.”
“That’s great!” said the farmer. “But how do you tell the boy crickets from the girl crickets?”
“Why are you asking me about crickets?” the scientist retorted. “I’m a chicken expert!”
And for the bulk of history after the domestication of chickens, sexing baby chicks wasn’t too far from that mark. The bad news is that baby chicks are pretty much small, cute, fluffy, and indistinguishable, with their boy and girl parts mostly inside their bodies and out of sight. The good news is that for a long time, it really didn’t matter a whole lot.
Hen or Rooster? Historically, Nobody Cared
Chicken husbandry back in the day went something like this: In the spring, hens would make a nest, lay eggs, and brood them. The farm wife (and it was almost always women taking care of the chickens) would risk the ire of the broody hen to collect some of the eggs and then everybody got fried eggs. Other hens either got left alone, or hid their nests in places where nobody could find them. After about three weeks they would show up with a string of peeping baby chicks behind them. These babies – maybe a couple dozen of them on the typical farmstead—would follow their mom around, eat bugs and spilled grain, and grow. By late summer the pullets would look like pullets and would be laying their first little eggs while the cockerels would look like cockerels and would be making some practice runs at crowing. Then the cockerels would start showing up on the dinner table. The pullets would be kept over the winter and would become the broody hens the next spring. Most likely before their second winter, they would wind up in the stew pot since their egg production would tail off the second year.
It was a pretty good system and there wasn’t a lot of need to differentiate the baby hens from the baby roosters. Things began to change in the early part of the 20th century with the advent of chicken breeds that were specifically designed as meat birds. Suddenly, the roosters of the egg-laying breeds had no purpose and keeping them around until they started to crow was a waste of feed and resources. Somebody needed to develop a way to tell baby roosters from baby hens.
Autosexing Chickens
That somebody was Professor Reginald Punnett a geneticist at the University of Cambridge. Punnett developed the first of a series of “autosexing” chicken breeds in the 1920’s. Autosexing baby roosters have different color patterns from baby hens when they hatch. Dr. Punnett exhibited the Cambar at the World Poultry Congress in 1930—the world’s first autosexing chicken. While the Cambar and subsequent autosexing breeds, the Gold, Silver, and Cream Legbars were not particularly good egg or meat producers, everyone was sure that autosexing breeds would ultimately revolutionize the poultry industry once better egg and meat production was bred into their lines. As it turned out, everyone was wrong. Cambars and Legbars turned out to be a mere sidebar in the history of the poultry industry due to a development that occurred around the same time on the other side of the world.
Vent Sexing
In 1925, Dr. Kiyoshi Masui at Tokyo Imperial University reported on certain anatomical differences he found between male and female chicks. This work eventually resulted in the scientific paper “The Rudimentary Copulatory Organs of the Male Domestic Fowl and the Difference of the Sexes of Chickens”. The gist of the report, in laymen’s terms, was that to tell the difference between little boy and little girl chicks, you just had to do what you did with every other baby animal—pick them up, turn them upside down, and look at their private parts. It was just that the differences between boy and girl chicks were reeeaaallly subtle. While the report generated interest around the world, the general consensus was that sexing baby chicks by this method would never be commercially viable because the difference was so very subtle that it would take too long to examine each chick.
It was two Japanese poultrymen, Kojima and Sakajiyama, who turned Dr. Masui’s discoveries into a practical application that soon became widespread on the farms and in the hatcheries of Japan. A skilled chicken sexer could sex baby chicks in rapid fashion with an accuracy of 95% or greater.
What do chicken sexers look for? Most baby roosters will have an “eminence” that looks like a small pimple in the middle of the lower rim of their vent. Most baby hens will not. Please note that I used the word “most” in both of the previous sentences. That’s because a certain percentage of both hens and roosters will have confusing bits in their vents—not pimples but sort of tiny pimple-like things. Being able to sex these chickens is very, very difficult, and both teaching and learning how to discern all the subtleties is almost impossible. This knowledge can’t be transmitted through a book, requires in-person tutoring, lots of practice, and is as much art as science. Consequently, chicken sexers are in high demand, and are paid well. Interestingly enough, a large number of chicken sexers today, worldwide, are Japanese.
Feather Sexing
Because vent sexing is so difficult, the poultry industry has incorporated a sex-linked gene that affects feather growth into many modern commercial chicken breeds and hybrids. Chicks with this genetic component can be sexed by comparing the length one set of wing feathers, the primaries, with the length of another set, the coverts. Baby girls’ primaries will be longer than their coverts, while baby boys’ primaries will be shorter or the same length as their coverts. Got that? It sounds a little complicated when the whole process is reduced to one sentence, but is actually so easy that it allows hatcheries to get rid of all those wonky, high-buck vent sexers and instead rely on practically anybody who can tell the difference between the length of feathers. The only caveat is that it only works with breeds who have that sex-linked gene.
Gear Up - Gruesome News Ahead
While vent and feather sexing have revolutionized the poultry industry, it has not been good news for roosters. Baby chicks are sexed shortly after hatching, in a production line sort of setting and immediately after being sexed the baby roosters are euthanized, usually by being tossed into a grinder.
Hence, we catch sight of the dark underbelly of modern poultry in all of its forms. Regardless, of whether we enjoy chickens through cracking open a dozen fresh pasture raised eggs, by digging into a box of fast-food fried chicken, or by tending our backyard pet chickens, we are in collusion with an industry that kills half of the baby chicks as soon as they hatch because they’re roosters.
Science Is Developing a Solution
Scientists are working on a way out of this inhumane dilemma. In 2016, a German scientist named Roberta Galli and her colleagues published a paper entitled “In Ovo Sexing of Domestic Chicken Eggs by Raman Spectroscopy”, which describes a technique for determining the sex of a chick while it is still in the egg and after a mere 3.5 days of incubation. The procedure doesn’t contact the chick embryo at all beyond the creation of a small hole in the egg. A special light is beamed into the hole and is then analyzed. A sexing accuracy of 90% was obtained using this method. If this technique becomes commercially viable, hatcheries could remove eggs containing male embryos four days into incubation for use as egg products (it is generally accepted that chicks gain sensitivity around day 7) and the need for killing male baby chicks would be eliminated.
This promising technique has garnered attention from around the world. PETA announced "Reports that countless male chicks could potentially be spared the horrors of being thrown into high-speed grinders…would be celebrated by animal campaigners…” The United Egg Producers, the egg industry trade group in the US has pledged to eliminate the culling of day-old male chicks by 2020 “or as soon as economically feasible alternatives are available.” Shortly after the scientific report was published in 2016, Germany's food and agricultural minister, Christian Schmidt, promoted having the new method operating nationwide by 2017 so Germany could be a "pioneer for better animal welfare in egg production in Europe."
Progress
Nearly three years have passed since Dr. Galli published her original paper. 2020 is almost upon us—the year the UEP pledged to eliminate baby rooster culling. Sadly, it seems pretty obvious that we won’t make that deadline. But good progress has been made. Dr. Galli has quietly continued her research. In a paper published in February, 2017, she reported on replacing pricey Raman analysis used in her original report with cheaper fluorescence and suggests that this cheaper methodology may make the technique more appealing.
And while Germany didn’t meet it’s 2017 deadline, it continues to be on the forefront of developing real, practical solutions to this problem. The German supermarket group, Rewe, has partnered with a Dutch company called HatchTech, which has developed a market-ready process for sexing chick embryos. The process uses a laser to burn a small hole in the eggshell. Then a tiny amount of fluid is extracted and analyzed for a sex-specific hormone called estrone sulfate. This process doesn’t harm the developing chick and has been scaled up to process 3000 eggs per hour. Rewe has named this process “Seleggt”, and next year their Penny supermarket chain in Germany will begin offering Seleggt eggs. Seleggt eggs will cost a few more pennies per dozen than regular eggs, which will still be available, but the supermarket will be clearly informing its customers that they, with their shopping behavior, can put an end to the practice of culling baby roosters.
Other start-up biotech companies in the US, Turkey, Israel, Australia, and around the world are examining other methods including laser spectroscopy, MRI scans, genetic engineering, and even precise measurement of egg shapes
It is obvious that a lot of effort is being expended and a lot of research money is being spent around the world to develop a method to sex chick embryos still in the shell. What, exactly, is at stake? Dr. Galli summed it up very well in her 2017 paper: “On an international scale, development of a practicable technique for in ovo sex determination has the potential to contribute to the prevention of annual culling of 7 billion male layer hybrids, whose female siblings produce the current global demand of about 68.3 million tons of eggs per year.”
For chickens everywhere, and for the humanity of chicken keeping, I hope that these new methods will be in place in the near future.
(This post is an updated and edited version of my October 17, 2017 post entitled “Sexing Chickens: The Art, Science, and History of Hen vs. Rooster.”)
