The slaughtering process evokes many questions around animal welfare, especially for intelligent animals like pigs that show signs of distress. Read on as we dive into the science and research behind pig slaughter to find out if and why pigs cry.
If you’re short on time, here’s the quick answer: Research shows that pigs do not technically ‘cry’ when slaughtered as crying involves tear production. However, pigs do vocalize loudly at slaughter in what appears to be a stress response.
The Slaughtering Process for Pigs
Stunning Methods Used
There are several stunning methods commonly used in pig slaughterhouses to render the animals unconscious before slaughter. This is considered more humane as it reduces the animal’s pain and distress.
- Electrical stunning – An electric current is passed through the brain via electrodes to induce unconsciousness. This is the most common method used.
- Carbon dioxide stunning – The pig is lowered into a chamber filled with CO2 which leads to unconsciousness. However, this method has faced criticism for being inhumane if not done properly.
- Captive bolt stunning – A captive bolt pistol is used to strike the forehead of the pig to damage the brain and cause immediate unconsciousness.
In all stunning methods, it is crucial to ensure proper application so the pig is fully unconscious before being shackled, hoisted, and bled out. Stunning methods that are botched can cause immense suffering to the animal.
Cutting the Throat and Bleeding Out
Once the pig has been rendered unconscious, it is shackled by its hind leg and hoisted upside down on the bleed rail. A worker then uses a sharp knife to make an incision across the pig’s throat to sever the carotid arteries and jugular veins. This causes rapid blood loss, leading to death.
On average, it takes 90 seconds for a pig to bleed out after the arteries have been cut. The blood is collected during the bleeding process.
Proper bleeding out is vital to ensure the pig dies quickly and does not regain consciousness. According to slaughter guidelines, pigs should not show signs of sensibility or revival after they have been bled out.
While this throat-cutting process may seem inhumane to some, it is standard practice in slaughterhouses. When done correctly following proper stunning, it leads to a swift death for the pig.
Do Pigs Have Tear Ducts and Physically Cry?
Anatomical Analysis of Pig Tear Ducts
Pigs do have tear ducts and the anatomical structures necessary for tear production, however there are some key differences from human eyes. Pigs have a nictitating membrane, which is a third eyelid that sweeps horizontally across the eye to protect it and spread tears.
The lacrimal glands in pigs are positioned differently than in humans, located underneath the nictitating membrane rather than above the eye.
Research analyzing pig eye anatomy and tear composition found that pigs produce tears in response to irritants or emotions similarly to humans. Tears contain water, mucin, lipids, glucose, urea, sodium, and potassium.
This indicates pigs likely experience reflexive, basal, and psychogenic tearing like humans do.
Lack of Tears at Slaughter
Despite having anatomical tear structures, pigs are rarely observed crying with tears falling down their faces, even in distressing situations like at slaughterhouses. There are a few potential explanations:
- The nictitating membrane may absorb tears before they overflow.
- Fast heart rates from stress may reduce tear production.
- They produce fewer emotional tears or tears may not visibly overflow.
So while pigs likely feel emotions like fear, stress, or sadness, external tears are anatomically less likely to form and overflow. However, just because tears are not visible does not mean pigs do not cry on the inside when facing traumatic events like slaughter.
The Sounds Pigs Make and Why
Screams and Squeals as Signs of Distress
Pigs are highly vocal animals that use various sounds to communicate. Unfortunately, the screams and squeals pigs make during slaughter are signs of extreme distress, anxiety, and suffering.
According to animal behavior research, pigs have an extensive vocal repertoire. Their screams and squeals communicate different emotional states ranging from pleasure to anger and distress. High-pitched screams are associated with negative situations that cause pain, fear, or frustration.
During slaughter, pigs are subjected to several stressful procedures – handling, restraint, stunning, and slitting of the throat – which provoke desperate screams of panic. Studies analyzing pig calls during these procedures confirm they result from negative emotional states. The calls are so loud and disturbing some slaughterhouse workers suffer from PTSD.
Possible Explanations for Pig Vocalizations
There are several hypotheses for why slaughtered pigs scream and squeal:
While the exact emotional states of pigs during slaughter are still debated, the evidence overwhelmingly indicates they suffer tremendously and their screams are desperate cries of fear and agony. More humane alternatives would avoid this immense animal suffering.
Assessing Pig Stress and Welfare at Slaughter
Behavioral Signs of Stress in Pigs
Pigs show several behavioral signs when they become stressed, anxious or fearful during handling and slaughter. These include vocalizations like squealing, grunting or screaming, escape attempts like running away or jumping fences, freezing in place, and defecating or urinating more frequently.
Pigs may also show aggressive behaviors like biting when feeling threatened. Careful observation of these stress behaviors allows slaughterhouse staff to identify problems and improve handling methods.
Measuring Stress Hormones
In addition to visible behaviors, scientists can measure biological signs of stress in pigs by analyzing stress hormone levels. When pigs become stressed, their bodies produce more cortisol, adrenaline, noradrenaline and other hormones.
By collecting blood samples at different stages of handling and slaughter, researchers can pinpoint which practices are most stressful for pigs. Some key findings show that electric prodding and unfamiliar handling greatly increase stress hormones compared to moving pigs calmly in groups.
Measuring stress hormones provides objective data to improve welfare.
Impact of Handling and Environment
Studies consistently show that the way pigs are handled and the slaughterhouse environment greatly impact their stress and welfare. Some best practices include:
- Using food rewards and familiar handlers instead of electric prods.
- Providing non-slip flooring and lighting that does not startle pigs.
- Avoiding mixing unrelated pigs together in holding pens.
- Minimizing waiting time before stunning.
- Using well-maintained equipment to ensure quick loss of consciousness.
Following these guidelines will result in less stressed pigs during slaughter, which is better for both animal welfare and meat quality. More work is still needed to continuously improve slaughter practices.
For more information, check out these research articles on pig stress and welfare at slaughter:
- https://www.sciencedirect.com/science/article/pii/S1751731116302186
- https://www.mdpi.com/2076-2615/6/9/57
Conclusion
While pigs do not technically ‘cry’ tears when slaughtered, research shows they vocalize loudly in what appears to be a stress response. More humane handling methods and proper stunning technique can help improve pig welfare at slaughter.