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What is Animal Slaughter and How Are Animals Slaughtered?

December 21, 2021

While many people don’t like to think about the everyday realities of slaughter, farmed animals have no choice but to endure them. Fish suffocate, pigs scream, and chickens drown in scalding tanks. When you see packets of meat on a supermarket shelf, it’s easy to forget that what you are looking at was once part of a living, breathing animal. 

The distance of the public from how meat is made helps the slaughterhouse industry to thrive. Yet for the sake of the one million chickens, 14,000 pigs, and 4,000 cows killed per hour in the United States, we should open our eyes to what goes on inside the four walls of a slaughterhouse. 

What Is Animal Slaughter?

Slaughter is the act of killing animals for human purposes and happens primarily so that the animals’ flesh can be sold as meat. Around 10 billion land animals and 47 billion aquatic animals are slaughtered in the U.S. each year.  

How Are Animals Slaughtered? 

Slaughterhouse workers are employed to kill and cut up hundreds, or even thousands, of animals per hour on high-speed disassembly lines. Broiler chickens, for example, can be processed at a rate of 2.33 birds per second

One common method of slaughter is bleeding. This involves major blood vessels in an animal’s neck being sliced with a knife or automatic blade (a process known as sticking). In a best-case scenario, animals are stunned prior to sticking and remain unconscious until they lose enough blood to die from a lack of oxygen supply to their brain. There is, however, a risk that animals will not be effectively stunned and will still be awake when their throats are slit, as was vividly described to The Washington Post by a slaughterhouse worker in 2001. 

Pre-Slaughter Handling 

The overwhelming majority of farmed animals in the U.S. spend most of their lives tightly packed inside massive, windowless sheds, yet the process of slaughter means that the final hours of these animals’ lives are often marked by even more inhumane practices. When animals reach a profitable weight, they are either grabbed by the legs and stuffed into crates (in the case of birds), or prodded with electric goads and forced into overcrowded trucks. From there, some will be taken straight to the slaughterhouse, and others may first be sold at an auction


Water is typically taken away from animals soon before workers begin collecting them for transport. Due to the sheer number of individuals being loaded onto trucks, this process often takes a long time, leaving the animals without anything to drink for several hours. If that wasn’t enough to make them dehydrated, they might then spend up to 28 hours on the road without water.

Cruel Transportation

The journey from the farms where the animals are raised to the slaughterhouses where they are killed is long, often crossing state lines or even international borders. Throughout this, animals are trapped inside metal shipping containers that offer little to no protection from hazardous weather conditions. In one tragic incident in 2018, 34,000 chickens who were left on a truck overnight froze to death.

Torn Skin, Bruising and Injury

The lack of space during transport can cause animals to fight or step on one another. Rough handling while being moved on and off of trucks further adds to the risk of animals getting hurt. 

Sickness and Disease

Transporting stressed animals in a tightly packed space with little ventilation creates the perfect environment for sickness and disease to spread. Many animals die during transport as a result.

Fecal Soiling  

While being transported,t farmed animals often have no choice but to sit or stand in their own feces. Not only is this unpleasant for the animals, but it also poses a hygiene risk since their bodies are soon to enter the human food chain. 

Slaughter of Large Animals

By the time they reach the slaughterhouse, animals are scared, hungry, and exhausted. Cows, pigs, and sheep are unloaded from the transport container and taken to the lairage where they wait until the time comes for them to be killed. 


Firearms such as shotguns, handguns, and rifles are used for the on-farm killing of large sick and injured animals or for pre-slaughter stunning. A free bullet is shot into the animal’s head. For worker safety, however, penetrating captive bolt guns are usually preferred. 

Penetrating Captive Bolt

A penetrative captive bolt gun, a tool commonly used to stun cows, fires a metal rod into the animal’s brain and then retracts it. When used correctly, this should instantly knock the animal out. 


For pigs and sheep, electrical stunning or electronarcosis involves a pair of tongs that send a current through the brain. The effects of this, a loss of consciousness and violent muscle contractions, closely resemble an epileptic seizure. If there are any delays between this and sticking, animals can start to recover before they die.

Alternatively, electrodes can be applied to the animal’s head and back to cause cardiac arrest and kill them. This painful process, known as electrocution, is not necessarily a reliable method of slaughter, and the animal may need to have their throat slit to stop them from regaining consciousness. 

Gas Stunning/Killing 

Pigs are commonly stunned or killed with high concentrations of carbon dioxide. This involves them being lowered into a gas chamber where some try forcefully to escape before writhing in pain as they slowly suffocate

Chicken Slaughter 

Chickens who manage to live through their harrowing journey to reach the slaughterhouse are then removed from their crates and put on a conveyor belt that takes them to the automated kill line. 


Exsanguination is when the major blood vessels in an animal’s neck are cut to cause a rapid loss of blood. In poultry slaughterhouses, chickens hang upside down, unable to move and typically (but not always) unconscious as they have their necks sliced with an automatic blade. The high speed of chicken processing means that some birds miss the blade and are still alive and awake when they are plunged into scalding water to loosen their feathers. 


Manual cervical dislocation, the breaking of a bird’s neck by hand, is a common way for chickens to be killed on factory farms. Workers wade through a sea of birds, picking out dead ones and breaking the necks of any who are lame. 

Gas Killing

In slaughterhouses that use Controlled Atmosphere Systems (CAS), birds are stunned or killed with noxious gases, such as carbon dioxide and argon, that deplete the air of oxygen and therefore cause the birds to suffocate. While gas killing is considered to be more humane than other methods since animals don’t need to be handled or restrained, it still does not cause instant death. 

Electrical Stunning

For electrical stunning, the most common system used in poultry slaughterhouses, chickens’ legs are first forced into shackles. Hanging upside down from a metal conveyor, they are dragged along so that their heads pass through a bath of electrically charged water. While this can reduce the suffering of some birds during slaughter by making them unable to feel pain, this form of stunning comes with its own set of problems. Shackling causes pain and fear, birds can suffer shocks and seizures, and the electric charge is not always effective at rendering them unconscious. 

Do Animals Feel Pain When Slaughtered? 

Although animals are typically stunned so that they cannot feel pain when slaughtered, stunning does not always work. Its effectiveness varies depending on the worker doing the stunning, the animal, and the method. Moreover, due to the massive scale on which animals are slaughtered, even a tiny percentage of fails means that millions of individual animals suffer terrifying and painful deaths. 

Slaughterhouses claim to prioritize the welfare of the animals they kill, but thanks to the work of undercover investigators, we know that they frequently do not. Numerous secretly captured videos reveal animals being dragged, punched, thrown, and tormented in their final moments. 

Is There Such a Thing as Humane Slaughter? 

While more could be done to reduce the suffering of animals at the time of slaughter, animal rights advocates argue that slaughter will never be humane. The view of animals as primarily commodities and the search for efficiency that drive industrial animal agriculture work againstefforts to create tangible welfare improvements. Moreover, regardless of how it is carried out, slaughter involves taking the life of an animal who does not want to die. Unlike euthanasia, which is carried out by veterinarians to save an animal from future suffering, slaughter is always harmful to an animal’s welfare because it denies them their healthy, future lives. 

National Laws on Humane Slaughter

The Humane Methods of Slaughter Act, the federal law that is meant to protect animals at the time of slaughter, has a major flaw: it excludes chickens and fish, who make up the vast majority of individual animals killed for food. The act dictates that all cows, pigs, sheep, and goats in USDA-inspected slaughterhouses should be handled in a way that minimizes pain and distress and should be stunned on the first attempt. This law, however, is  often not enforced

Religious Guidance on Animal Slaughter

People of some faiths practice the ritual slaughter of animals according to the rules of their religion. Under Islamic law, Halal slaughter requires an animal who has either not been stunned, or is stunned but still has a beating heart, to have their throat slit and die from a loss of blood. Under Jewish law, Shechita, or kosher, slaughter also requires an animal who has not been stunned to bleed to death from a cut to the throat. 


In light of the pain and suffering caused by slaughter, it is worth questioning the ethics of eating animals. If you would find it hard to take a knife to a cow, pig, or chicken’s throat, why pay for this to happen on an industrial scale? Not everyone is ready or willing to go vegan, but by swapping at least some meat products for plant-based alternatives, you can help create a food system that does not rely on the violent deaths of billions of sentient individuals, and that offers a more sustainable future for people, animals, and the environment.