The poultry industry's 'secret weapon': What exactly is sexing chicks?

© Hendrix Genetics Laying Hens

Leviathan Press:

When I was a kid, I always had a question: since there are so many chicken farms, what should we do with the roosters that hatch there, except for a small number that are used for mating? More importantly, it is difficult to distinguish between male and female chicks when they are just born. After raising them for several weeks, I realized that I had raised a lot of roosters...

What's the weirdest job you've ever had? Snake venom squeezer? Professional cuddler? Dog food taster? Professional line man (yes, these are real)? Well, if you're interested in something a little offbeat, why not consider a career in chick sexing? Oh no, not the wonderful time spent with our delicious chicken legs, but the exquisite craft of determining the sex of a chick shortly after it hatches.

The profession is the poultry industry’s “secret weapon,” saving factory farms millions of dollars each year and key to keeping our grocery store shelves stocked with chickens and eggs . It’s also a highly specialized and surprisingly difficult skill to learn, with experienced practitioners developing an almost supernatural ability to spot the nearly imperceptible differences between male and female chicks. As a result, the profession of chick sexer has historically been highly sought-after and lucrative, even helping an entire generation of immigrants survive and thrive during some of the most dire times in the United States.

© Tenor

For most of human history, poultry farming was a fairly simple process. After a hen laid eggs, some were collected and eaten, while the rest were used for incubation. On average, there was a 50/50 chance that these eggs would hatch into either a rooster or a hen. Both would grow and mature naturally, and the mature hens would either be slaughtered for food or kept to lay eggs. Meanwhile, some of the mature roosters would be kept to mate with the hens, while the rest would also be slaughtered for food. Once a hen's egg production began to decline, she would also be served on the table.

But all that began to change in the early 20th century, as agriculture became increasingly industrialized and certain hens (known as broilers) were selectively bred to produce more meat. Suddenly, roosters became a liability . Not only did they not produce enough meat to be economically viable, but they also had bad tempers and were prone to fighting, injuring or even killing other roosters and hens.

But eliminating these unwanted roosters is a thorny problem. Chickens don’t have penises, which means it’s nearly impossible to tell the difference between hens and roosters until the roosters start to develop secondary sexual characteristics, such as their distinctive combs and wattles. Those characteristics don’t appear until five to six weeks after hatching; in the meantime, the worthless roosters continue to take up space and consume feed, costing the poultry industry millions of dollars each year.

Due to human ignorance, chicken farmers have traditionally used a variety of folk methods to predict whether an egg will hatch into a hen or a rooster. For example, a ring suspended by a string is said to swing one way above the egg for a rooster and the other way for a hen, while the shape of the egg is also said to indicate the sex of the chick inside. In reality, the shape of the egg is related to the breed and even the individual hen, and these methods are not much more accurate than random guessing. If the industry wants to further develop and become more efficient, a better method is needed.

© Commoncog

The first attempt at a solution was made by Cambridge University geneticist Reginald Punnett in the early 1920s. Punnett developed the world's first auto-sexing chicken breed, the Cambar, which had different color patterns for males and females, making them easy to tell apart immediately after hatching. While a significant advance, unfortunately, the Cambar and subsequent auto-sexing breeds such as the golden, silver, and cream Legbar did not produce particularly good meat or eggs compared to conventional chicken breeds. It was thought that these traits would eventually be bred into these lines, but the research was interrupted by the development of more effective sexing methods on the other side of the world.

In 1925, Dr. Kiyoshi Masui of Tokyo Imperial University discovered a reliable method to determine the sex of common chicken breeds within 24 hours of hatching. This method requires opening and observing the chick's cloaca - the cloaca of a rooster usually has a small papule-like protrusion at the lower edge, which is the rudiments of its sexual organs, while the cloaca of a rooster does not. However, things are not that simple, as the word "usually" mentioned earlier implies. In fact, about 20% of roosters have no obvious sexual organs, while 40% of hens have a protrusion structure very similar to that of roosters.

But Dr. Masui managed to catalogue dozens of subtle differences and clues. For example, the female protuberances tend to have a concave surface or a brighter pearly sheen that temporarily disappears when rubbed with a finger. In 1933, Masui and his colleague Juro Hashimoto published their findings in a landmark paper titled "The Rudimentary Copulatory Organs of the Male Domestic Fowl and the Difference of the Sexes of Chickens."

Initially, the differences described in Masui and Hashimoto's paper were considered too subtle for practical use in the poultry industry; it would take too much time to examine each chick and accurately distinguish their sex . However, Japanese poultry workers soon succeeded in developing a practical and rapid cloaca identification method and established the All Japan Chick Sexing School to teach the method.

The method, which takes two years or more of intensive study to master, requires an almost Zen-like focus and the manual dexterity of a surgeon . A trained sextologist grabs a chick, turns it over, and gently presses on the abdomen to dislodge feces from the rectum. The pressure applied must be precisely controlled, as excessive force can injure or even kill the chick. Once the digestive tract is empty, the sextologist opens the cloaca with his thumb and carefully examines the internal structures to determine the chick's sex.

© Daily Mail

Initially, trainees can sex chicks with just over 50% accuracy, but as experienced mentors continue to guide them, their speed and accuracy steadily improve until they can sex 800 to 1,400 chicks per hour with 98% accuracy. Many graduates achieve even more impressive results, with the fastest sexters sexing 10,000 chicks in an eight-hour shift. In a typical 100-day hatching season, a sexter can sex at least 300,000 chicks.

Chick sexer Shigeyuku Suzuki, after four years of learning his craft, became the world champion in chick sexing in 1956. He was able to sex 12,000 chicks in a single working day, sorting the roosters and hens into two separate boxes.

This accuracy is all the more impressive given the short time the sexers spend observing each chick —less than three seconds on average—during that short time, the sexers must consider dozens of extremely subtle clues to pick out edge cases that don’t fit the protrusion rules. It’s a skill that takes years of hard practice to master and, oddly enough, seems to transcend conscious analysis.

© Imgur

In fact, when asked how they make their choices, many sexters can’t explain it—they just know instantly whether a chicken is male or female . Cognitive scientist Richard Horsey writes in The Art of Chicken Sexing:

“To process 800 to 1,200 chicks per hour over long periods of time with close to 100% accuracy, intuition plays a role in many of your decisions, even if you’re not aware of it. As a former colleague of mine put it to me… ‘there’s nothing there, but I know it’s a rooster’. That’s intuition at work.”

The work is so intense and engrossing that, as RD Martin, author of Specialist Chick Sexer, writes:

"If I go more than four days without sexing a chick, I start to experience 'withdrawal symptoms.' Several of my students have also said they feel similarly if they haven't sexed a chick for a week or so."

But, I mean, who hasn’t been there…

The intuitive and unconscious nature of chick sexing has attracted the attention of many psychologists, who have tried to figure out how chicken sexers' brains process the subtle clues they perceive so quickly.

© Campbell River Museum

In his article, Richard Hawes compares chicken sexers to World War II pilots, aerial gunners, and ground observers who were trained to quickly identify aircraft and distinguish friend from foe at a distance. These observers were trained to systematically analyze aircraft based on the shape of the wings, engines, fuselage, and tail (the so-called WEFT system), but with enough practice, these observers were able to instantly identify an aircraft based on its overall "feel." A similar concept exists among bird watchers, Hawes explains:

"Experienced birders develop similar skills. With a lot of practice, many birders can identify birds by their 'looks', even when they are too far away to identify individual features. They even have a name for this trait, calling it the 'jizz' of a bird. This skill takes some time and effort to develop, and is similar to sexing a chicken, where birders see the jizz as a whole but cannot tell what features make up the whole."

© Arran Birding

Some psychologists believe that airplane spotters, bird watchers, and chick sexers perceive their targets as a unified whole, or gestalt, and do not engage in conscious sequence processing. In fact, this has been suggested as a possible model for how we learn to read written language. As Hawes explains:

“For skilled readers, the reading process is fast, accurate, and unconscious – that is, we are not aware of the actual process of converting visual stimuli into meaning as we read. In fact, most people have the impression that they can recognize entire words at a glance, without having to pronounce them aloud.

It is this impression that forms the basis of the “whole-word” approach to teaching reading. In this approach, children learn how to recognize a basic vocabulary word at a glance through rote memorization. They then gradually master new words by seeing those words used in stories. This contrasts with the other main approach to teaching reading, phonics, which explicitly teaches the connection between letters and phonemes.

However, experimental studies have shown[1] that this premise is actually wrong:

"In a series of experiments, Van Orden (1987) and colleagues began by asking subjects questions such as 'Is it a flower?' Subjects were then presented with a word (e.g., rose) and asked to decide whether the word fit into the category. Sometimes subjects were given a homophone (which could be a word or a nonword), such as 'rows.' Subjects often incorrectly judged these words to fit into the category, suggesting that readers typically convert letter strings into phonological representations and then use these representations to access semantic information about the words."

Studies have shown that when bird watchers, airplane spotters, or chick sexers are given a new piece of information to distinguish between different targets (e.g., two very similar birds can be distinguished by the stripes on their wings), this will improve their so-called automatic intuitive abilities over the long term, despite their conscious awareness of the information. However, Hawes argues that this “intuitive” classifier does in fact engage in sequence processing, with its extremely fast analysis resulting from a specific order and method of processing perceptual cues:

"I would like to focus on a rather novel explanation of object categorization, proposed by Berretty et al. in 1999 in the framework of Gerd Gigerenzer's ' fast and frugal heuristic '. This framework proposes a few simple rules that allow us to make accurate decisions under time pressure. For example, imagine a mountaineer hiking in the Alps who stumbles upon a bird. To identify the bird, the mountaineer pulls out his bird book and uses multiple features (cues) of the bird to correctly identify it. Second, we are asked to consider the case of a rabbit. The rabbit has a much more limited purpose than the mountaineer, and when it sees a bird, it needs to quickly identify whether the bird is a predator or a non-predator.

The key is that, with survival at stake, the rabbit does not have time to adopt a strategy like the climber—considering a relatively large number of cues, some of which may be redundant, to arrive at an accurate identification. In particular, the rabbit needs to decide as quickly as possible whether the bird is a predator or not, so it will use the fewest number of cues. At the same time, it will also want to stop the identification process as soon as it can make a decision, rather than using all available cues.

Beretti et al. proposed a classification procedure called 'classification by elimination'. The clues are visited in a predetermined order, and each clue eliminates some candidates from the set of all possible categories of an object. When only one category remains, the procedure stops and the object is classified into that category. If all clues are exhausted and multiple possible categories remain, a random assignment is made.

The psychology of this high-speed mental analysis is being closely watched because it could have practical applications in interpreting complex data such as seismograms, mammograms and other medical imaging, or even wine tastings.

Whatever the psychological nature of these extraordinary abilities, graduates of the All Japan Chick Sexing School soon revolutionized Japan's poultry industry, making hatcheries and farms more efficient and productive by eliminating the need to stock useless roosters.

In fact, official records indicate that by 1932, Japan’s poultry production had increased by 12 million birds, while the average egg production per hen increased from 107.2 to 122.8 eggs. Globally, it is estimated that cloacal sexing could reduce the cost of raising chickens by 50%.

© Nikkei Chicago

As expected, the Japanese cloaca identification technique spread quickly, and soon the All Japan School of Chick Sexing was sending consultants around the world to teach the technique. For example, in 1933, Hikosaburo Yogi demonstrated the technique during a visit to the United States with nearly 100% accuracy. The following year, Dr. Kiyoshi Oxawa introduced the technique to Australia, and the year after that, Kiochi Andoh introduced it to the United Kingdom. In 1937, Shigeru Nitta founded the American Chick Sexing Association (Amchick), with branches in Lansdale, Pennsylvania, and Nokomis, Illinois.

However, few foreign sexers could reach the extremely high level of proficiency of graduates from all-Japanese schools, which meant that chicken sexers in Japan remained in high demand. This high level of specialization and demand was particularly beneficial to first-, second-, and third-generation Japanese immigrants, who at the time faced widespread prejudice and discriminatory laws in the United States, such as the Alien Land Laws, which prohibited foreigners without citizenship from owning or leasing land in Arizona, Arkansas, California, Florida, Idaho, Louisiana, Minnesota, Montana, Nebraska, New Mexico, Oregon, Texas, Utah, Washington, and Wyoming.

An advertisement for a chick sexing school in Japan. © Nikkei Chicago

The Japanese Chick Sexing Association has successfully cornered the American poultry market by leveraging cultural ties to Japan and recruiting from within the community, allowing its members to obtain stable, well-paying jobs despite continued social prejudice. In fact, even beginners can earn $6 to $7 per hour, while skilled sexers can make nearly $3,000 in a 100-day incubation season—a huge income in the mid-20th century. Even today, starting salaries for chick sexers can reach $60,000 per year, double what most hatchery workers make. Roy Akune, who began sexing in the early 1950s, recalls:

“That was one of the highest wages back then. Even carpenters made about $2.50 an hour. If you were good, you had to get it at least 98 percent accurate. Usually you had to get it at least 97 percent, but if you got it less than that, you had to pay a penalty. If you made too many mistakes, you had to pay the hatchery.”

But this handsome reward did not come easily. As Akune recalled, sexing chicks was hard, tedious work:

“Maybe the Japanese are more patient than the whites. Sometimes you have 10,000 chicks behind you and you have to process 1,100 to 1,200 per hour, very quickly, and you work long hours, sometimes 24 hours straight without sleep, because you have a contract with the chicken hatcheries, so you have to go all over the place, and when you finish one, you stop to rest, order a sandwich, and eat it while driving to the next destination.”

These tight deadlines are an integral part of the job, because the older the chicks get, the harder it is to tell the sexes apart. Ideally, sexing should be done within 12 hours of hatching, but with hundreds of hatcheries across the Midwest, a sexer’s life is a matter of driving long distances to sex as many chicks as possible before the short hatching season ends.

Japanese Americans suffered a great deal of discrimination in the 1920s and 1930s, and the situation became worse with the attack on Pearl Harbor on December 7, 1941, and the United States' declaration of war on Japan. Fearing that Japanese Americans might be disloyal and help their compatriots by engaging in espionage or sabotage, on February 19, 1942, President Franklin Roosevelt signed Executive Order 9066, ordering the forced deportation and incarceration of all Japanese Americans on the West Coast. Hundreds of thousands of Japanese Americans lost their homes and businesses, and about 120,000 were rounded up in specially built internment camps, with many more fleeing to the Midwest, East, and Southern states.

Yet Japanese chick sexers were so important to American agriculture that on the same day Executive Order 9066 was signed, a California official warned the USDA that their removal would severely disrupt the poultry industry. So he asked that the sexers be allowed to stay until the end of the spring hatching season and that the federal government begin training white trainees. The USDA agreed, and immediately set up chick sexing schools at several institutions, including the University of California, but they worried that the trainees wouldn’t be ready in time for the next hatching season.

In 1943, the War Resettlement Administration began distributing loyalty questionnaires, allowing Japanese internees who were deemed loyal enough to the United States to be given the opportunity to leave the internment camps and work in other areas. Most of the chick sexers who escaped to the East were able to find stable work due to the highly specialized nature of their work and the labor shortage caused by the war. At the same time, the FBI closely monitored the chick sexers' every move. Regardless, this amazing skill of chick sexing helped thousands of Japanese Americans survive one of the darkest periods in American history.

After World War II, with the abolition of forced resettlement, Japan’s chick sexing industry flourished again. In 1947, West Coast refugees George and Ann Sugano founded the National Chick Sexing Association and School at 821 LaSalle Street in Chicago, with tuition of $300 per year, plus the cost of chicks used in students’ final exams.

Japanese Americans who had served in the military flocked to the school because their tuition could be paid through the Servicemen's Readjustment Act, passed in 1944. At the same time, another school and professional association was established in Atlanta, Georgia, with the curious name "Speed-o-Sex," but unfortunately, this school only lasted a year. Second- and third-generation Japanese Americans continued to dominate the U.S. poultry industry, providing much-needed income and pride to this suffering ethnic group.

But by the 1970s, as more efficient sexing methods emerged and the poultry industry consolidated into large factory farms, the thriving profession waned: Where once there were thousands of chick sexers, today there are only a few hundred in Japan, the UK and the US.

A Rockchick with white spots on its head. The female has narrower spots. © Jacquie Jacob

Today, several alternative methods of sexing chicks are available on an industrial scale. For example, starting in the 1950s, Ginard Puneet’s automated sexing system was eventually optimized to improve efficiency in meat and egg production, resulting in breeds such as the California Gray, Rhode Island Red, New Hampshire Red, and Rock, where hens and roosters can be easily sexed after hatching.

For example, male Rock chickens have a large, distinct spot on their heads, while Rhode Island Red and New Hampshire Red chicks with chipmunk-like stripes are almost always hens. Other breeds of chicks can also be distinguished by the silver/gold or Ss gene, which is linked to sex, with female chicks having a darker, brown down and males having a lighter, yellowish down.

© The Chick Hatchery

Another common chick identification method is feather identification, developed by Tegel Poultry Breeding in New Zealand in 1969. This method uses selective breeding to make the primary wing feathers of female chicks grow faster than those of male chicks, so the two can be easily distinguished shortly after hatching.

Another method that is now largely obsolete is instrumental sexing. This involves using a special sexing instrument, similar to the otoscope that family doctors use to examine the inside of the ear. As with cloacal sexing, the instrument sexer gently squeezes each chick to force feces out of the anus, then inserts the sexing device into the cloaca and large intestine. A bright light in the instrument illuminates the chick's body, allowing the sexer to see the distinctively shaped testicles or ovaries on either side of the spine.

Seeing this, you may be wondering: What will happen to the male chicks that have been identified?

If you are timid or have a soft heart towards cute animals, it is recommended that you don't read this, because what we are going to talk about next is a bit cruel.

The answer to that question is simple: They get destroyed—and quickly. The exact methods of disposal vary over time. At the National Chick Sexing Society and School in Chicago, male chicks are thrown directly into the incinerator. As Patti Sugano, whose mother was a chick sexer in the 1960s, recalls:

"I remember my mother telling me that someone called the police because they thought someone was burning bodies in the building, because the way to identify the sex of chickens is that female chickens lay eggs and have more economic value, so the male chickens had to be sent to the furnace."

According to Sugano, other treatments have also been used:

"Roosters would sometimes be thrown into a big steel drum and suffocate to death. I remember my mother bringing home the chicks and driving them to Lester Fisher (Lincoln Park Zoo veterinarian) because the snakes would eat live chicks. That was it."

Today, at factories like the Hy-Line International hatchery in Spencer, Iowa, the world’s largest , newly sexed male chicks are immediately dumped down a chute and ground alive in a high-speed grinder. More than 30 million male chicks face this fate each year at Hy-Line and similar facilities, drawing angry protests from animal rights groups like PETA.

© Reddit

Fortunately, recently developed technology has the potential to put an end to this horrific treatment. In 2016, German scientist Roberta Galli published a paper titled “In ovo sexing of poultry eggs by Raman spectroscopy” [2]. Galli’s method, developed as part of the SELEGGT project – a joint venture between the University of Leipzig, agricultural company HatchTech and German supermarket chain REWE – is able to sex fertilized eggs after just 3.5 days of incubation. The method uses a laser to burn a 0.3 mm hole in the eggshell, through which a small amount of allantoic fluid is extracted. The sample is then processed with a special chemical marker and exposed to ultraviolet light of a specific wavelength. A specific color change indicates the presence of the sex-specific hormone estrone sulfate, which indicates that the chicken is a female. Eggs without estrone sulfate are then destroyed or turned into animal feed without causing any pain to the male embryos in the eggs, as they have not yet developed a nervous system.

The SELEGGT method has been measured to be 90% accurate, and although no hatcheries have adopted the system as of this writing, it holds the promise of making the poultry industry, which produces more than 100 billion eggs per year in the United States alone, a more humane and ethical industry.

References:

[1]pubmed.ncbi.nlm.nih.gov/2969938/

[2]pubs.acs.org/doi/10.1021/acs.analchem.6b01868

By Gilles Messier

Translated by tim

Proofreading/Rabbit's Light Footsteps

Original article/www.todayifoundout.com/index.php/2024/09/the-insanely-lucrative-and-psychological-job-of-chick-sexing/

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