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GMO chicken: What is it and are all chickens genetically modified?

Photo: Andrew Skowron / We Animals Media

An observant consumer might have noticed that over the last several decades chicken breasts on supermarket shelves have grown larger and appear more marbled. These changes are the result of genetic modification, a method through which generations of birds are bred to maximize the profit of the animal agriculture industry, with scant regard given to their welfare. This process is distinct from genetic engineering, which is the use of modern technology to edit a genetic structure.

Are chickens GMO?

Chickens, like almost every other animal raised for food  around the world, are the result of intense breeding  aimed at emphasizing certain characteristics that increase their profitability. In other words, and by the USDA’s definition of “genetically modified,” yes—chickens are genetically modified organisms (GMOs).

What is GMO meat?

Any meat that is the result of genetic modification is considered GMO. This genetic modification can take place in a variety of ways. One of the most common is selective breeding. Virtually all species of animals raised for their meat have been genetically modified through selective breeding practices. According to a Pew Research Center report, in the last 100 years, the growth rate of chickens has skyrocketed while their intake of feed has gone down. In 1925, it took 112 days for a chicken to reach 2.5 pounds, the size at which she would be sent to slaughter. For each pound gained, she would consume about 4.7 pounds of feed. In 2010, a chicken was sent to slaughter at 5.7 pounds after only 47 days. To pack on so much weight so quickly, she ate only 1.9 pounds of feed to produce each pound of growth.

Another, far less common way animals raised for food can be genetically modified is through gene splicing. This type of modification is rare in commercial animal farming and consists of changing an organism’s genetic makeup by introducing, eliminating, or rearranging specific genes using modern scientific techniques. Very few breeds of animal that have been gene spliced can be raised for the purpose of producing food in the United States. One is farmed Atlantic salmon, who have been modified to grow to market size in half the time that they would normally. The most recent case is Angus cattle who have a lighter coat so that they can be raised in warmer climates and experience a lower rate of heat stress. While the former went through a lengthy approval process before first being sold in 2021, the cattle were determined to be “low-risk” by the Food and Drug Administration less than two years after the initial proposal, meaning that no additional regulatory approval is required before the cattle are used to create products for the market, including meat.

What is a GMO egg?

A genetically modified egg is one which has been laid by a genetically modified chicken. In 2021, the average chicken in the United States laid 285 eggs. This is almost double the 150 eggs a year that the average backyard hen laid in the 1930s. This increase in productivity comes with serious welfare concerns for the mother hens, including bone fractures due to the laying that starts before the hens are fully grown, and fractures that occur because the increased egg production robs much of the calcium that the hens would otherwise use to maintain their bones.1 Such fractures have markedly increased over time thanks to the genetic modification of the chickens.

What is genetically engineered chicken?

The USDA defines genetic engineering as “Manipulation of an organism’s genes by introducing, eliminating or rearranging specific genes using the methods of modern molecular biology, particularly those techniques referred to as recombinant DNA techniques.” While the production of modern broilers does not rely on recombinant DNA techniques (“gene splicing”), it is indeed genetic engineering by the USDA’s definition, as it depends on manipulating specific genes using the methods of modern molecular biology. The genetic engineering that industrial chickens have undergone has occurred through inserting genetic sequences via intensive breeding that relies more on modern molecular biology techniques than on the traditional breeding of animal husbandry. To produce a single “hybrid” bird, producers cross 15-20 lines of sometimes freakish birds who never go to market, but exist solely to pass on specific genetic sequences. These efforts have resulted in two distinct types of hybrid chickens: those modified to produce a large number of eggs, and those modified to grow very large very quickly.

Both types of chickens suffer from their genetic modifications. Laying hens often experience painful fractures of their keel bones, which run along the underside of the birds’ bodies. The fractures are likely caused by a number of factors, including the young age at which hens now begin laying eggs, the sheer size of the eggs, and weakened bones because egg production requires much of the calcium in the hens’ diet.2 Chickens raised for meat, or broiler chickens, experience a variety of health issues resulting from intense breeding. These issues include leg disorders, cardiovascular disease, and high mortality rates.3

Are all chickens GMO?

In 2021, 9.13 billion broiler chickens were raised for meat and 111 billion eggs were laid by hens in just the United States. The vast majority of these chickens are GMOs, as they have been bred purposefully to select for certain traits that stand to increase profit margins. There are, however, a few small farms raising heritage chickens—which belong to breeds recognized by the American Poultry Association prior to the mid-20th century—who are able to naturally breed, can live long lives outdoors, and have a slow growth rate. However, extinction threatens many heritage breeds because they are not as economically advantageous as more popular broiler breeds. Heritage chickens represent the closest thing to a GMO-free chickens in the United States today.

What is non-GMO chicken feed?

What is sometimes referred to as non-GMO chicken feed is feed that has not been genetically engineered through recombinant DNA techniques, though it will likely have been modified in other ways. These foods may also fall under the category of organic because organic certification in the U.S. prohibits gene splicing. While this means that the ingredients in the feed have not had their genes edited to better tolerate herbicides or withstand certain insects considered pests, it is important to realize that virtually all crops grown on a large scale, including the corn and grains that make up a lot of chicken feed, have been bred over decades so that they bear more fruit.  There is no evidence to suggest that using chicken feed that includes genetically modified ingredients of any type is less safe or healthy for birds than using one that is labeled GMO-free.4 However, some feed producers are creating formulas using crops that are grown in a system of regenerative agriculture. Regenerative methods of growing feed crops have better outcomes for the soil than industrial methods of growing feed crops.

Which ingredients in chicken feed are typically genetically modified?

The crops that are most frequently genetically engineered are maize, soybeans, cotton, and rapeseed, all of which can be found in chicken feeds. Even the ingredients of organic and so-called “non-GMO” feeds have ingredients that are modified, in that they have been bred over generations, but these ingredients should not have been altered through gene splicing.

What is the difference between GMO-free and non-GMO?

The terms “GMO-free” and “non-GMO” are both used to describe foods that are free of genetically engineered ingredients. The primary difference is where they are used, as different countries tend to favor one term or the other.


The term “GMO-free,” and variations such as “Ohne Gentechnik” in Germany, can be found gracing many products in Europe.


In the United States, the term “non-GMO” tends to be favored more.

Who benefits from GMOs?

When it comes to genetically modified chickens, those that stand to benefit the most are the two companies that control the genetics of chickens, Cobb-Vantress and Aviagen. In 2016 Cobb-Vantress alone controlled almost half of the global market for breeder chickens who hatched the broilers raised for meat. In addition to these two companies, the integrators that contract with the farms that raise the chickens also stand to benefit from the genetically modified birds, since they can save money on the resources used to raise the birds and to ensure that competitors who raise other breeds are not able to make the same profit margins.

Which countries use the most GMOs?

The global market for chickens raised for meat consists almost entirely of chickens from only two breeds that have been genetically engineered through intensive breeding, Ross and Cobb. These birds can be found on farms in the United States, the European Union, China, the Philippines, and virtually every other country in the world.

Which countries have banned GMOs?

Several countries around the world have opted not to grow crops engineered using recombinant DNA techniques. There are, however, no restrictions on genetically modified chickens despite the impacts that genetic modification has on the well-being of the birds and the quality of the resulting meat.5

Countries that have banned the growth of gene-spliced crops include:

  • Turkey
  • Belize
  • Ecuador
  • Bolivia
  • Algeria
  • Greece
  • Hungary

Should GMO food be labeled as such?

In the United States all foods that contain ingredients that have been genetically engineered through recombinant DNA techniques must be labeled, a requirement that began in January 2022. The labels can take the form of a symbol, text, or a direction toward an online resource showing that the food has been genetically engineered. The labeling requirements are specific to foods that have ingredients that were “modified through certain laboratory techniques and for which the modification could not be obtained through conventional breeding and could not be found in nature.”

What are the disadvantages of GMOs?

Genetically modified chickens suffer tremendously due to selective breeding, which has been carried out on lines of chickens with little to no regard for their welfare and health. Instead, the focus is almost entirely on maintaining or increasing those traits that are most profitable.

The chickens are not the only beings that suffer due to GMOs. Farmers are forced to return to the massive, corporate chicken breeders due to the birds’ inability to breed themselves. This means that the farmers lack agency over their own decisions when it comes to the types of birds they want to raise.


Genetic modification through breeding of certain crops has allowed us to feed more people with increased efficiency, but when it comes to chickens we have taken efficiency beyond ethical limits and allowed it to harm not only the birds themselves but also farmers and consumers. Chickens deserve better than the lives filled with suffering that have resulted from intensive breeding. There has never been a better time switch to higher welfare chickens, or to cut back on, or eliminate, chicken products from our diets.



Anja B. Riber, Teresa M. Casey-Trott, and Mette S. Herskin, “The Influence of Keel Bone Damage on the Welfare of Laying Hens,” Frontiers in Veterinary Science (February, 2018),


Riber, Casey-Trott, and Herskin, “The Influence of Keel Bone Damage on the Welfare of Laying Hens.”


K. M. Hartcher and H. K. Lum, “Genetic Selection of Broilers and Welfare Consequences: A Review,” World’s Poultry Science Journal 76, no. 1 (2020),


V. Tufarelli et al., “Genetically Modified Feeds in Poultry Diet: Safety, Performance, and Product Quality,” Critical Reviews in Food Science and Nutrition 55, no. 4 (2015): 562–9,


Shahram Golzar Adabi and Eda Demirok Soncu, “White Striping Prevalence and Its Effect on Meat Quality of Broiler Breast Fillets under Commercial Conditions,” Journal of Animal Physiology and Animal Nutrition 103, no. 4 (July, 2019): 1060–1069,