1. How Much Heavier Were Modern Chickens Than 1957 Chickens When Raised on the Same Feed?
The most interesting part of this comparison is that the researchers controlled the environment. They used lines from 1957 and 1978 that had been preserved without further selection, and compared them with a 2005 commercial line (Ross 308). All groups were given the same commercial feed to eat freely [1].
At 42 days old, the 1957 line weighed 586g, and the 1978 line weighed 1205g. The amount of feed needed to gain 1kg of body weight, known as the feed conversion ratio, was 2.88 for the 1957 line, 1.90 for the 1978 line, and 1.67 for the 2005 line. This means the 2005 line could gain the same 1kg using only 1.67kg of feed, compared to 2.88kg for the 1957 line [1].
The paper reports that growth increased by more than 400% and the feed conversion ratio dropped by 50% between 1957 and 2005. Note that this is a comparison of 1957 and 2005, which is separate from the 586g and 1205g figures mentioned earlier [1]. Because the feed and days were the same, the difference in weight is thought to be related to the genetic line itself. So, where did this change begin?
2. The Legend of Cecil Steele's 500 Chicks from a 50-Chick Order in 1923
In 1923, a woman named Cecil Steele in Delaware, USA, is said to have ordered 50 chicks but received 500. This story is told on state tourism and industry websites, but it has not been verified with primary sources [2].
According to the story, Steele raised the chicks that arrived for meat. After 18 weeks, 387 birds remained, weighing about 2.25 to 2.5 pounds (roughly 1kg or slightly more). She sold them for 62 cents per pound. The following year, in 1924, she ordered 1,000 chicks, and by 1928, she was selling 26,000 birds a year [2].
Whether the order mistake actually happened is less important than the numbers. The business of raising and selling chickens for meat expanded many times over in just a few years. Once that happened, the next step was for someone to decide what kind of chicken was best for meat.
3. What Kind of Chicken Did the 1948 "Chicken of Tomorrow" Contest Look For?
In 1948, a contest called "Chicken of Tomorrow" was held, sponsored by the major US supermarket A&P. The role of the US Department of Agriculture varies in different accounts [3]. The goal was to find a chicken with a wide breast, large thighs, and plenty of white meat [3].
Finalists sent 720 eggs each to a central facility. There, the chicks were raised for 12 weeks and evaluated together [3]. This method of comparing birds under the same conditions is very similar to the research mentioned earlier.
A strong performance was achieved by a cross between New Hampshire and Cornish breeds from the Van Tres hatchery in California. The prize was $5,000 [3]. This suggests that chickens suited for meat were created through efforts to compare, select, and cross-breed them.
4. How Did Chicken Bodies Change After Years of Selective Breeding?
The results of selection showed up in the body structure. The same paper reports that the yield of the large breast muscle (pectoralis major) increased by 79% in males and 85% in females between 1957 and 2005, while abdominal fat decreased [1]. This aligns with the direction the contest sought: a chicken with a wide breast.
The time needed to grow also shortened. News articles state that the raising period was about 16 weeks in the 1950s, but is now about 4 to 7 weeks [3]. However, these are figures from news reports and are separate from the values in the research paper.
On the other hand, the authors state that challenges remain regarding muscles, skeleton, immunity, and the management of parent birds [1]. Balancing fast, large growth with physical robustness is still a theme that breeding programs face.
5. When Did Broiler Chicken Farming Begin in Japan?
The first broiler farming in Japan is said to have started in 1957, when the poultry wholesaler Torichi Shoten in Senju, Tokyo, partnered with the Gunma Prefectural Economic Federation to try raising broilers imported from the US. This is described in the company's history [4]. Interestingly, 1957 is also the baseline year used for the "non-selected line" in the research mentioned earlier.
The Ministry of Agriculture, Forestry and Fisheries explains that, until the period before the war, chicken meat was a luxury item, more expensive than beef. It became affordable after the war, when the introduction of broilers, a breed dedicated to meat, began. Broilers are usually shipped for sale after about 50 days [5].
Records from a hatchery in Kagawa Prefecture show that during the 1950s and 1960s, the method shifted from raising male hybrids of mixed breeds for eggs to crossbred broilers. In 1963, dedicated breeds like White Plymouth Rock from US breeding companies were introduced. At that hatchery, the era of dedicated breeds began in the 1960s. Demand for broiler chicks increased, and hatching, which had only been done in spring and autumn, became a year-round activity [6]. Since this is a record from one hatchery, it cannot be said to represent the exact timeline for all of Japan.
6. How Can You Visualize the Difference in Feed Amount at Home?
You can try this in your kitchen. Use a kitchen scale and water in 500ml PET bottles to visualize the numbers. The feed needed to gain 1kg of body weight was 2.88kg for the 1957 line and 1.67kg for the 2005 line. The difference is 2.88 minus 1.67, which equals 1.21kg. This is roughly the weight of two 500ml PET bottles of water and a little more. In a poultry farm that raises tens of birds every day, this difference accumulates, giving an idea of the scale.
If you want to read more, the Ministry of Agriculture, Forestry and Fisheries' public relations magazine "aff" (December 2016 issue) and the "Livestock Information" report from the Agriculture & Livestock Industries Corporation are available in Japanese [5][6].