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Chickens

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This article provides information about chickens that should prove useful to those advocating for animal rights, as well as to those exploring the rationale for veganism.

It covers various aspects of farmed chickens in the context of animal rights, including injustices and suffering, humane labels and certifications, chicken sentience and cognition, the environmental consequences of farming chickens, the health risks of chicken meat and eggs, and impacts to workers.

Read it through or use the table of contents to go directly to your section of interest.

General Information

Lineage

It's commonly thought that the domesticated chickens used for meat and eggs are primarily descended from the red jungle fowl of Southeast Asia. More recent research paints a more complex picture—birds from India, Cambodia, Ceylon, and other areas may also be involved in the lineage.[1]

Chickens were used widely in Southeast Asia, India, and Tibet and were a common fixture in ancient Greece. Their exploitation in the West spread from Greece to Rome and then on to Europe and the Americas.[2]

Numbers

Globally, over 76 billion chickens are slaughtered annually for meat, and another 11 billion laying hens are slaughtered when their female reproductive systems are used up and they are no longer profitable.[3] In the United States alone, the figures are 9 billion and 375 million.[3] Far more chickens are slaughtered than any other farmed animal.[3]

A PEW report points out that "in just over 50 years, the number of chickens produced annually in the United States has increased by more than 1,400% while the number of farms producing those birds has dropped by 98%."[4]

The Sentience Institute used USDA and FDA data to estimate that 98 percent of chickens in the United States are raised in factory farming conditions.[5] It seems tenable that the percentage is similar in other industrialized nations.

Injustices and Suffering

The injustices inherent in exploiting chickens and other non-human animals stem from seeing them as commodities having only instrumental value, lacking any inherent worth apart from their usefulness to humans.

As Tom Regan put it, the animals we use "have a life of their own that is of importance to them, apart from their utility to us. They are not only in the world, they are aware of it and also of what happens to them. And what happens to them matters to them. Each has a life that fares experientially better or worse for the one whose life it is."[6]

As shown in the section on sentience and cognition, chickens not only have a will to live and value their lives, just as humans do, but also have desires, preferences, emotions, families, social communities, natural behaviors, a sense of themselves, and a sense of the future.

The injustices discussed below—all arising from a failure to recognize the inherent worth of other sentient beings—are either standard practice or not unusual. And, as shown in the section below on humane labels and certifications, this is true even for those chicken products with a humane label or certification. To omit a significant number of these injustices would likely increase costs to the point of rendering chicken meat and eggs unaffordable by all but the most affluent.

Loss of Life

We have no nutritional need for chicken meat or eggs, so denying chickens their lives is unnecessary, as are the other forms of suffering enumerated here.[7]

Not only are we taking their lives—we are doing so after allowing them to live only a small fraction of their natural eight-year life span. Chickens used for meat are slaughtered at six weeks, which is about one percent of their life span. Chickens used for eggs are slaughtered when their female reproductive systems are used up and they are no longer profitable—at 18 months, which is 20 percent of their natural life span.[8]

To take the life of any sentient being is to harm that being by depriving them of opportunities for fulfillment, even if it is done suddenly and painlessly (which it is not, as explained below).

Slaughter

Several methods of killing chickens are used, including manual throat slitting, neck breaking, decapitation, and gassing, all of which are painful.

In the United States, where there are no federal regulations for chicken welfare, the industry claims that 99 percent of the birds are "totally unconscious" after an electrical stun, which is administered in some facilities just prior to slaughter.[9] However, research shows that the industry uses low-voltage stuns in order to avoid damage that might render the carcass unsellable. The low voltage stuns are not effective, which results in many (if not most) chickens being alive and fully conscious when their throat is slit, and many remain alive as they enter the scalding tank.[10][11][12]

Mass Extermination of Male Hatchlings (Culling)

Because laying hens are bred specifically to lay eggs, males hatched from laying hens are not profitable—they don't yield sufficient meat, and they can't lay eggs. And because they are not profitable, the males are ground alive in a macerator, gassed, or suffocated—all shortly after they hatch.[13] This industry refers to this practice as chick culling. (Weak and struggling females are also discarded in this manner.)[14]

Hatchlings are about 50 percent male and 50 percent female. So statistically speaking, every laying hen has a brother who has been violently slaughtered. This is true even for backyard chickens, as the female hatchlings are sold not only to commercial producers but also to individuals keeping backyard chickens.

In the United States, over 375 million male chicks are slaughtered annually via culling. Worldwide, it's in the billions.[15]

Overcrowding and Confinement

Extreme crowding is the reality for the 98 percent of chickens living in factory farming conditions, regardless of whether they are in battery cages.[5]

While hens in battery cages spend their lives confined to a space smaller than the size of a standard sheet of paper,[19] chickens in commercial chicken houses don't fare much better. While they may not be confined to a cage, they are still entrapped by the mass of other chickens surrounding them.

The egregious ramifications of this crowding are discussed below.

Denial of Natural Behaviors

Crowding prevents or hinders chickens' ability to engage in their natural behaviors of preening, roosting, perching, spreading their wings, establishing a social order, pecking and scratching for food, and teaching their young to peck and scratch for food.[23] The denial of these behaviors due to living in such close quarters results not only in discomfort but also the constant psychological stress of fear and anxiety.[24][25][26]

Filth and Stench

The ammonia-laden air in the chicken houses is so noxious that the birds commonly suffer respiratory disorders, severe flesh and eye burns, and even blindness.[27]

Numerous videos and investigations document the filth and stench of urine, feces, feathers, and dander in chicken facilities. They show birds covered in feces and so weak that they cannot clean themselves. Some are stuck in manure so deep it could be described as a manure pit.[28][29]

Sickness and Disease

Numerous undercover videos show that sickness and disease are common. Some chickens are so sick you can hear them struggling to breathe. Some hens don't have the strength to stand on their own two legs. Some are barely able to move or respond to anything around them. Birds are found dead, dying, and emaciated.[28][29] Research and reports bear this out.[30][31][32]

Debilitating Selective Breeding

A laying hen produces more than 300 eggs a year, but the jungle fowl from which they are bred lay fewer than 10 eggs in a year. This causes both physical and physiological stress.[33] The large increase in the number of eggs laid is from a combination of selective breeding and hens' tendency to lay more eggs when eggs are removed so they can follow their instinct to form a proper brood.[34]

Laying hens are also bred to lay large eggs for which they have not evolved, which stresses their reproductive system and causes such problems as osteoporosis, bone breakage, and uterus prolapse.[35]

The modern broiler chicken is unnaturally large and has been bred to grow at an unnaturally fast rate and have large breasts. This selective breeding comes with serious welfare consequences, including leg disorders, skeletal, developmental and degenerative diseases, heart and lung problems, breathing difficulty, and premature death.[36]

Debeaking

Debeaking is painful, causes lasting suffering, impairs feeding, eliminates exploratory pecking, and contributes to lice from impaired preening.[37]

Rough Handling and Transport

When chickens raised for meat reach their desired slaughter weight, they are caught, crated, transported, unloaded, and placed in holding pens until slaughter.

A review of videos of these activities shows squawking birds being grabbed four at a time by their feet and roughly thrown or shoved into crowded crates, birds suffering dislocations and broken bones, wings and heads crushed in crates, birds dying from suffocation, hot and cold conditions, and birds unable to stand from exhaustion.[38][39]

Research bears this out—a 2016 study in Poultry Science reveals that in addition to the physiological stress these procedures inflict, it is not unusual for a bird to experience dehydration, disease, injury, pain, and even death. The injuries include wing and leg fractures, lesions, bleeding, bruising.[40]

Humane Labels and Certifications

Investigations by Consumer Reports and the Open Philanthropy Project reveal that these certifications and labels are largely meaningless, as shown below. These investigations show that the standards are weak and unenforced, audits and inspections are rarely done, and if they are done and violations are found, which is infrequent, no one gets fined.[41][42]

Cage-Free

Consumer Reports advises you to “ignore cage-free claims” for chickens.[43] Cage-free does not mean the chickens had access to the outdoors. It only means the chickens were not confined to a cage.[44]

Cage-free chickens, like free-range chickens, may be confined not by a cage but by crowding so extreme that turning around and engaging in the natural behaviors of preening, nesting, foraging, dust bathing, and perching is difficult or impossible. Such extreme crowding in large metal warehouses is the norm.[45][46]

Free Range

The USDA standard for free-range requires only that chickens are given some access to the outdoors. There are no stipulations for the size or quality of the outdoor space, and there is no requirement that the chickens actually spend time outdoors.[47] Also, the claim does not have to be verified through inspections.[48]

So it's not surprising that investigations by Consumer Reports (and others) reveal that most chickens labeled free-range spend their lives confined inside a crowded chicken house. The free-range space itself may be nothing more than an enclosed concrete slab that the chickens never use. These individuals lack the room even to turn around, much less engage in their natural behaviors of preening, nesting, foraging, dust bathing, and perching.[48] This has led Consumer Reports to say that free-range is one of the most potentially misleading labels because of the discrepancy between what it implies and what is required to make the claim."[48]

Only one percent of eggs are from free-range hens that have the option to go outdoors, but like the other 99 percent, even those hens have likely never actually been outdoors.[49]

Jonathan Foer, in his well-researched and fact-checked book[50] Eating Animals, sums it up well in saying that "the free-range label is bullshit" and "should provide no more peace of mind than 'all-natural,' 'fresh,' or 'magical.'"[51]

Whole Foods Market (GAP)

Whole Foods Market spearheaded the development of the Global Animal Partnership (GAP) certification program and sells various products, including eggs and chicken meat, with GAP labels.

The Open Philanthropy Project criticized GAP for having weak enforcement and for providing only slight improvements over standard factory farming conditions.[52] For example, according to Consumer Reports, "standards for slaughter do not exist at any level for chickens and there is no limit on their rate of growth."[53]

Organic

Some have the perception that chickens with the organic label mean they are humanely raised, but that is not the case. Organic farmers are free to treat their animals no better than non-organic farmers. This is because the USDA, which controls the organic label in the United States, ruled that the label does not allow "broadly prescriptive, stand-alone animal welfare regulations."[54]

Consumer Reports informs us that while there are organic standards relating to animals, they lack clarity and precision, letting producers with poor standards sell poultry and eggs.[55]

United Egg Producers Certified

Consumer Reports says that while the label is verified, "it is not meaningful as an animal welfare label because certain basic conditions, such as the freedom to move, are not required."[56]

American Humane Certified

According to Consumer Reports, "the requirements fall short in meeting consumer expectations for a 'humane' label in many ways."[58]

Animal Welfare Approved

This is the only certification that Consumer Reports says has strong standards, yet the standards still allow for mutilations[59] and other injustices. Also, products with this label are challenging to find. A search using their own product finder reveals that it's unlikely you will find any products with this label at a grocery store near you.[60]

Certified Humane Raised and Handled

Consumer Reports says that "we do not rate Certified Humane as a highly meaningful label for animal welfare, because the standards do not have certain requirements that a majority of consumers expect from a 'humanely raised' label, such as access to the outdoors."[61]

Backyard Chickens

Although backyard chickens are not associated with a certification or label like the others that we are covering here, they deserve a closer look. A considerable number of people regard the practice of keeping chickens in the backyard for food as innocuous.

Baby chicks often die in transport. A quick search will find numerous reports of chicks being shipped alive to backyard hobbyists and dying in transport—and reports of those that make it being greatly stressed.

Backyard chickens are the same or similar varieties as commercial chickens and are subject to all of the abuses that result from culling and selective breeding, as discussed above.

Backyard hens are likely to be slaughtered when egg production wanes, preventing them from living out their natural lives. As one hobbyist euphemistically put it, "when the expenses outweigh the value, then changes have to be made."[62]

The slaughter of backyard chickens, whether laying hens or broiler chickens, is usually done by slitting the throat and waiting for the convulsing chicken to die its slow death. The slaughter is violent, cruel, and painful, just as with commercial operations.

Sentience and Cognition

While we are not suggesting that the degree of moral consideration given to an animal be based on their cognitive capacity, it seems that most people are unaware of the rich cognitive, emotional, and psychological lives that chickens experience, including their ability to experience happiness, boredom, and frustration.[63]

In her book on chicken behavior and intelligence, prominent animal neurobiologist Leslie J. Rogers says that "the cognitive abilities of some avian species may actually rival those of primates," and that "recent findings challenge assumptions that have been made about brain size and the superiority of the mammalian line of evolution."[64] This is not as far-fetched as it might seem—the chicken's forebrain is similar to the forebrain of mammals.[65]

Experiments show that chickens have a sense of the future and thus have an interest in continuing to live.[66][67] It is clear they can anticipate future events, exhibit self-control, and delay gratification.[68]

In the paper "Thinking chickens: a review of cognition, emotion, and behavior in the domestic chicken," Lori Marino examined 266 research articles in 16 peer-reviewed journals and found that chickens, among other capabilities…[69]

  • possess the capacity for episodic memory, which provides "evidence for an autobiographical sense of self in the past, present, and future"
  • exhibit self-control, a capacity not found in humans until age four and is associated with self-awareness and autonomy—the ability to think about and choose future outcomes
  • are capable of reasoning and logical inference
  • are as "emotionally and socially complex as most other birds and mammals in many areas"
  • can perform simple math and understand the ordinality of numbers
  • have self-awareness—"a subjective awareness of one’s identity, one’s body, and one’s thoughts through time, distinguished from others"
  • are capable of a wide range of emotions, including happiness, fear, anxiety, boredom, and frustration
  • "are behaviorally sophisticated, discriminating among individuals, exhibiting Machiavellian-like social interactions, and learning socially in complex ways that are similar to humans."
  • "have distinct personalities, just like all animals who are cognitively, emotionally, and behaviorally complex individuals"

Environmental Consequences

Chicken production, like other areas of animal agriculture, has a profoundly negative impact on the environment.

A 2008 report from the United Nations concludes that "the environmental impacts of the [poultry production] sector are substantial. Poultry production is associated with a variety of pollutants, including oxygen-demanding substances, ammonia, solids, nutrients (specifically nitrogen and phosphorus), pathogens, trace elements, antibiotics, pesticides, hormones, and odor and other airborne emissions." This substantial impact is on surface water, groundwater, air, and soil.[70]

The impact of chicken production on global greenhouse gas emissions is not as great as for cows, but at eight percent of the total for animal agriculture, it is still substantial.[71]

The poultry industry points to chicken production being less environmentally damaging than other species of farmed animal production because "chickens are the most efficient converters of feed into meat of all land-based livestock species."[72] But their calculations ignore the total impact on the environment that accrues because far more chickens are produced than any other animal.[3]

It's ironic that chickens that actually are free-range to some extent (which are a small minority of the birds labeled free-range, as discussed above) place a greater environmental burden in the areas of energy use, land use, and the potential for global warming, eutrophication, and acidification.[73]

Human Health, Nutrition

Eggs

Eggs contain no nutrients that cannot be easily obtained from plant-based sources. About 70 percent of egg calories are from fat (much of which is saturated), and eggs are loaded with cholesterol.[74] Also, eggs have zero fiber. So it would be disingenuous to say that eggs are healthy because they contain other nutrients when these other nutrients can easily be found in other foods.

It's telling that even the USDA, arguably the best friend animal agriculture could ask for, has told the egg industry that it is not allowed to say eggs are healthy or nutritious.[75]

The links between eggs and heart disease, cancer, and diabetes have been known for years.[76] But this has become controversial because most of the more recent egg studies have been funded by the egg industry,[77] resulting in misleading conclusions and sowing confusion about the topic.[78][79] If you are interested in exactly how the egg industry has rigged the results, see this explanation.[80]

Hopefully, a 2019 study that was published in the Journal of the American Medical Association will correct the public's perception of the issue. It finds that eating even small amounts of eggs daily significantly raises the risk for both cardiovascular disease and premature death. And the more eggs consumed, the higher the risk for stroke, coronary heart disease, and heart failure.[81]

Chicken Meat

It is commonly believed that white meat is healthier than red meat, and this belief is at least partially responsible for the 1,400 percent increase in the number of chickens bred and slaughtered for meat over the last 50 years.[82]

But a 2019 study published in the American Journal of Clinical Nutrition says that there is no reason to choose white meat over red meat for the reduction of cardiovascular disease, and it recommends plant-based food for lowering the risk of cardiovascular disease.[83]

All animal protein, chicken or otherwise, carries risks that are not associated with plant protein. A review by Dr. Sofia Ochoa cites 42 studies showing that animal protein…

  • elevates hormone insulin-like growth factor-1 (IGF-1), which stimulates cell division and growth in both healthy and cancer cells and "has been consistently associated with increased cancer risk, proliferation, and malignancy"
  • "results in us having higher circulating levels of trimethylamine N-oxide (TMAO)," which "injures the lining of our vessels, creates inflammation, and facilitates the formation of cholesterol plaques in our blood vessels"
  • causes the overproduction of the hormone fibroblast growth factor 23 (FGF23), which damages our blood vessels, can "lead to enlargement of the cardiac ventricle, and is associated with heart attacks, sudden death, and heart failure"
  • can result in the overabsorption of heme iron, causing the conversion of other oxidants into highly reactive free radicals that "can damage different cell structures like proteins, membranes, and DNA" (heme iron "has also been associated with many kinds of gastrointestinal cancers")
  • can result in a higher incidence of bone fractures because of animal protein's high concentrations of sulfur
  • contributes to atherosclerosis—plaques of cholesterol that accumulate in the lining of our vessels; this condition is far less common on a vegan diet because absorbable cholesterol is not found in plants

Social Consequences of Chicken Production

Poultry workers suffer serious injuries at twice the rate of other industries and are more than six times as likely to have sickness related to work, according to the Occupational Safety and Health Administration (OSHA).[84]

OSHA data from 2013 reveals poultry workers suffer carpal tunnel syndrome seven times more than the average worker and that they are 4.5 times more likely to identify repetitive motion for serious injury.[85][86][87]

The GAO also finds that workers are hesitant to speak up about the injuries for fear of retaliation, which suggests the problems may be underreported.[88]

The Union of Concerned Scientists concludes that with the increase in chicken-processing line speeds allowed by the USDA in late 2018, the situation will only get worse.[89]

Footnotes

  1. Smith, Page, and Charles Daniel. The Chicken Book. Athens: University of Georgia Press, 2000, 11-13.
  2. ibid.,16-30.
  3. 3.0 3.1 3.2 3.3 Derived from United Nations FAO statistics for 2017: “FAOSTAT.” Accessed June 10, 2019. http://www.fao.org/faostat/en/#data/QL
  4. “Big Chicken: Pollution and Industrial Poultry Production in America.” Accessed July 6, 2019. http://pew.org/2yIxE4p.
  5. 5.0 5.1 Institute, Sentience. “US Factory Farming Estimates.” Sentience Institute, April 11, 2019. http://www.sentienceinstitute.org/us-factory-farming-estimates.
  6. Archive:Tom Regan Speech at the Royal Institute of Great Britain in 1989
  7. In reply to: We need animal products to be healthy
  8. “Overview - Facts - Aussie Abattoirs | Slaughterhouses, Killing Animals for Human Consumption.” Accessed June 12, 2019. https://www.aussieabattoirs.com/facts.
  9. “National Chicken Council Brief on Stunning of Chickens.” The National Chicken Council (blog), February 8, 2013. https://www.nationalchickencouncil.org/national-chicken-council-brief-on-stunning-of-chickens/.
  10. Shields, Sara J., and A. B. M. Raj. “A Critical Review of Electrical Water-Bath Stun Systems for Poultry Slaughter and Recent Developments in Alternative Technologies.” Journal of Applied Animal Welfare Science13, no. 4 (September 17, 2010): 281–99. https://doi.org/10.1080/10888705.2010.507119.
  11. Pitney, Nico. “Scientists Believe The Chickens We Eat Are Being Slaughtered While Conscious.” HuffPost, 24:58 400AD. https://www.huffpost.com/entry/chickens-slaughtered-conscious_n_580e3d35e4b000d0b157bf98.
  12. “Welfare at Slaughter of Broiler Chickens: A Review.” Accessed June 12, 2019. https://doi.org/10.3923/ijps.2008.1.5.
  13. Aerts, S., and J. De Tavernier. “11. Killing Animals as a Matter of Collateral Damage.” In The End of Animal Life: A Start for Ethical Debate, 167–86. Wageningen Academic Publishers, 2015. https://doi.org/10.3920/978-90-8686-808-7_11.
  14. “What Happens with Male Chicks in the Egg Industry? – RSPCA Knowledgebase.” Accessed June 10, 2019. https://kb.rspca.org.au/knowledge-base/what-happens-with-male-chicks-in-the-egg-industry/
  15. Estimated from 2017 data: “FAOSTAT.” Accessed June 10, 2019. http://www.fao.org/faostat/en/#data/QL.
  16. “United Egg Producers Statement on Eliminating Male Chick Culling.” UEP Certified (blog), June 10, 2016. https://uepcertified.com/united-egg-producers-statement-eliminating-male-chick-culling/.
  17. https://www.huffpost.com/entry/egg-producers-killing-male-chicks-stop_n_575b0adde4b00f97fba8406f
  18. Daley, Jason. “A German Grocery Chain Is Selling First-Of-Its-Kind ‘No-Kill’ Eggs.” Smithsonian. Accessed June 10, 2019. https://www.smithsonianmag.com/smart-news/what-no-kill-eggs-are-now-available-berlin-supermarkets-180971117/
  19. Friedrich, Bruce, ContributorExecutive Director, and The Good Food Institute. “The Cruelest of All Factory Farm Products: Eggs From Caged Hens.” HuffPost, 13:29 500. https://www.huffpost.com/entry/eggs-from-caged-hens_b_2458525.
  20. “A Decade Later, Another ‘Cage-Free’ Measure Is on the California Ballot.” Civil Eats, October 25, 2018. https://civileats.com/2018/10/25/a-decade-later-another-cage-free-measure-is-on-the-california-ballot/.
  21. “Cage-Free Commitments.” Accessed June 10, 2019. https://welfarecommitments.com/cage-free/.
  22. “United Egg Producers Statement on Eliminating Male Chick Culling.” UEP Certified (blog), June 10, 2016. https://uepcertified.com/united-egg-producers-statement-eliminating-male-chick-culling/.
  23. Prescott, N.B. and Wathes, C.M., (2002). Preference and motivation of laying hens to eat under different illuminances and the effect of illuminance on eating behavior.  British Poultry Science, 43: 190-195
  24. Eugen, Kaya von, Rebecca E. Nordquist, Elly Zeinstra, and Franz Josef van der Staay. “Stocking Density Affects Stress and Anxious Behavior in the Laying Hen Chick During Rearing.” Animals : An Open Access Journal from MDPI9, no. 2 (February 10, 2019). https://doi.org/10.3390/ani9020053.
  25. Appleby, M.C. “What Causes Crowding? Effects of Space, Facilities and Group Size on Behavior, with Particular Reference to Furnished Cages for Hens.” Animal Welfare13 (August 1, 2004): 313–20.
  26. Marino, Lori. “Thinking Chickens: A Review of Cognition, Emotion, and Behavior in the Domestic Chicken.” Animal Cognition20, no. 2 (2017): 127–47. https://doi.org/10.1007/s10071-016-1064-4.
  27. “Ammonia Toxicity in Chickens.” PoultryDVM. Accessed October 25, 2018. http://www.poultrydvm.com/condition/ammonia-burn
  28. 28.0 28.1 Direct Action Everywhere. Truth Matters: DxE Investigators Expose “Humane” Fraud at Whole Foods. Accessed April 2, 2018. https://www.youtube.com/watch?v=yU4PJCuslD0
  29. 29.0 29.1 “Chicken Videos Living Condiitons - Google Search. https://www.google.com/search?q=chicken+videos+living+condiitons
  30. Adams, A. W., and J. V. Craig. “Effect of Crowding and Cage Shape on Productivity and Profitability of Caged Layers: A Survey.” Poultry Science 64, no. 2 (February 1, 1985): 238–42. https://doi.org/10.3382/ps.0640238.
  31. Lawrence, Felicity. “If Consumers Knew How Farmed Chickens Were Raised, They Might Never Eat Their Meat Again.” The Observer, April 24, 2016, sec. Environment. https://www.theguardian.com/environment/2016/apr/24/real-cost-of-roast-chicken-animal-welfare-farms.
  32. “Diseases of Poultry | Mississippi State University Extension Service.” Accessed June 18, 2019. http://extension.msstate.edu/agriculture/livestock/poultry/diseases-poultry.
  33. Cheng, H.-W. “Breeding of Tomorrow’s Chickens to Improve Well-Being.” Poultry Science 89, no. 4 (April 1, 2010): 805–13. https://doi.org/10.3382/ps.2009-00361
  34. Rutherford-Fortunati, Rutherford-Fortunati on. “Do Chickens Mourn the Loss of Their Eggs?,” June 29, 2012. http://gentleworld.org/a-chickens-relationship-with-her-eggs/
  35. Jamieson, Alastair. “Large Eggs Cause Pain and Stress to Hens, Shoppers Are Told,” March 11, 2009, sec. Finance. https://www.telegraph.co.uk/finance/newsbysector/retailandconsumer/4971966/Large-eggs-cause-pain-and-stress-to-hens-shoppers-are-told.html
  36. Stevenson, Peter. “Leg and Heart Problems in Broiler Chickens.” Compassion in World Farming, January 2003. https://www.ciwf.org.uk/media/3818898/leg-and-heart-problems-in-broilers-for-judicial-review.pdf
  37. “Welfare Implications of Beak Trimming.” American Veterinary Medical Association, February 7, 2010. https://www.avma.org/KB/Resources/LiteratureReviews/Pages/beak-trimming-bgnd.aspx
  38. “Chicken Loading and Transportation - Google Search.” Accessed June 12, 2019. https://www.google.com/search?q=chicken+loading+and+transportation
  39. “Chickens Suffer during Catching, Loading, and Transport.” Accessed June 12, 2019. https://www.helpthechickens.ca/transport.php.
  40. Jacobs, Leonie, Evelyne Delezie, Luc Duchateau, Klara Goethals, and Frank A. M. Tuyttens. “Impact of the Separate Pre-Slaughter Stages on Broiler Chicken Welfare.” Poultry Science96, no. 2 (February 1, 2017): 266–73. https://doi.org/10.3382/ps/pew361.
  41. Consumer Reports “Labels.” Greener Choices (blog). Accessed July 6, 2019. http://greenerchoices.org/labels/
  42. Global Animal Partnership.” Open Philanthropy Project, March 26, 2016. https://www.openphilanthropy.org/focus/us-policy/farm-animal-welfare/global-animal-partnership-general-support
  43. “A ‘Cage-Free’ Claim: Does It Add Value?” Greener Choices |Consumer Reports, March 5, 2018 http://greenerchoices.org/2018/03/05/cage-free-add-value/
  44. What Does ‘Cage Free’ Mean?” Greener Choices | Consumer Reports, February 6, 2017. http://greenerchoices.org/2017/02/06/cage-free-mean/
  45. Ibid.
  46. Dan Flynn, “Cage-Free Hens Don’t Improve Egg Food Safety, Nutrition Levels,” Food Safety News, March 1, 2017, http://www.foodsafetynews.com/2017/03/cage-free-hens-dont-improve-egg-food-safety-nutrition-levels/
  47. “FSIS.” Food Safety Inspection Service, USDA, http://www.fsis.usda.gov/wps/portal/fsis/topics/food-safety-education/get-answers/food-safety-fact-sheets/food-labeling/meat-and-poultry-labeling-terms
  48. 48.0 48.1 48.2 “What Does ‘Free Range’ Mean?” Greener Choices | Consumer Reports, April 25, 2017. http://greenerchoices.org/2017/04/25/free-range/
  49. “A Hen’s Space to Roost.” New York Times, August 15, 2010. http://graphics8.nytimes.com/packages/pdf/weekinreview/20100815-chicken-cages.pdf
  50. Yonan, Joe. “Book Review: Eating Animals by Jonathan Safran Foer,” November 22, 2009. http://www.washingtonpost.com/wp-dyn/content/article/2009/11/20/AR2009112001684.html
  51. Foer, Jonathan Safran. Eating Animals. Little, Brown, 2009, 102 “A ‘Cage-Free’ Claim: Does It Add Value?” Greener Choices |Consumer Reports, March 5, 2018
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This article was originally authored by Greg Fuller and copy-edited by Isaac Nickerson. The contents may have been edited since that time by others.