Research authors: Cynthia Schuck-Paim, Wladimir J. Alonso, Kate Hartcher, Chiawen Chiang, Patricia Alves Pereira, Walter Veit, Michael Mendi, Christine Nicol, Benjamin Lecorps
Summary: Elisa Autric
In November 2025, Rethink Priorities hosted “Errors in estimating pain in factory-farmed animals,” a webinar that examined how environmental factors significantly influence pain perception in captive animals. The session featured Dr. Cynthia Schuck-Paim, Scientific Director and co-founder of Welfare Footprint Institute (WFI). Dr. Schuck’s presentation was based on the upcoming paper “The Pain Echo Chamber: How Barren Environments and Intensive Rearing Amplify Pain in Captive Animals,” which she is publishing with her co-authors.
This post summarizes the presentation. It shows how barren, intensive rearing environments systematically amplify pain in farmed animals, and what this means for advocates, researchers, and policymakers working to improve animal welfare.
The pain paradox
Picture a laying hen with a keel bone fracture. Now imagine two scenarios: one hen in a battery cage, another in an enriched aviary system with opportunities for perching, dust bathing, and foraging. Both have identical injuries of the same size and severity. Should you expect them to experience the same level of pain?
The answer is almost certainly no. The conventional approach in animal welfare science treats injuries and diseases as having fixed pain responses: a fracture is a fracture, a lesion is a lesion, regardless of where they occur. But this assumption is challenged by empirical findings.
Pain is also a product of place. This observation has profound implications for how we assess and address farmed animal welfare.
How external factors shape subjective pain experience
To understand why the environment matters so much in the subjective experience of pain, we need to examine the neurobiological mechanisms that either suppress or amplify pain.
Natural pain suppression mechanisms
Animals, including humans, possess several built-in systems that reduce pain perception:
Behavioral engagement: When animals move, explore, or forage, they activate large nerve fibers that detect touch and vibration. According to gate control theory, these signals literally “close the gate” to incoming pain signals, preventing them from reaching the brain. This creates an immediate analgesic effect during active movement.
Rewarding experiences: Highly motivated behaviors such as social play, nesting, and environmental exploration stimulate the brain’s descending pain-control circuits. These activities trigger the release of natural opioids like endorphins, which block pain-promoting neurotransmitters. This constitutes a form of endogenous analgesia.
Positive social contact: The presence of familiar individuals and affiliative behaviors triggers oxytocin release. Oxytocin has both analgesic and anxiety-reducing properties, dampening both the sensory and emotional qualities of pain. In essence, positive social bonds buffer animals from pain.
Cognitive distraction: The brain has limited attention capacity. When an animal engages in complex tasks (e.g., navigating terrain, solving problems, searching for food), the brain has less capacity to process pain signals. This principle is well-established, for example, in human pain management, where distraction techniques are routinely used, particularly in resource-limited settings.
Pain amplification mechanisms
Just as certain conditions can partly suppress pain, others can intensify it:
Chronic stress: Long-term inescapable stress floods the brain with corticosteroids like cortisol, leading to a pro-inflammatory state and central sensitization. This means stimuli are perceived as more painful than they would otherwise be, a phenomenon called hyperalgesia. Additionally, chronic stress suppresses immune function (increasing infection likelihood), dysregulates inflammatory responses, and delays healing. Wounds, injuries, and fractures take significantly longer to heal under chronic stress.
Pain itself: Continuous, unrelieved pain can amplify future pain perception. Due to a phenomenon called temporal summation, each successive pain signal is perceived as increasingly intense. In addition, prolonged pain can physically rewire pain circuits. This is a process in which touch-sensing nerve fibers sprout connections to pain pathways. These processes lead to allodynia, where normally non-painful stimuli, like gentle touch, are perceived as painful due to the animal’s pain history.
Early-life adversity: Painful procedures or maternal stress during gestation can permanently rewire an animal’s nervous system for heightened pain sensitivity. Through epigenetic changes, pain receptor genes may be upregulated while natural opioid receptor genes are downregulated. The offspring are essentially programmed for greater pain sensitivity throughout their lives. This means that pain amplification in breeding animals, through the previously mentioned mechanisms, has cascading effects on their offspring. Importantly, this relationship is not straightforward: while severe or chronic early-life adversity tends to increase pain sensitivity, moderate and controllable challenges can build resilience. It is the extreme conditions typical of intensive farming (chronic maternal stress, painful procedures without pain relief, and premature separation) that are most likely to push offspring toward lasting hypersensitivity.
Where do these conditions occur?
The pain-amplifying conditions cluster densely in factory farm environments:
High stocking density (overcrowding stress)
Unstable social environments (isolation or excessive crowding)
Chronic deprivation of highly motivated behaviors
Lack of movement and extreme confinement
No agency or perceived control over the environment
Poor air quality
Disrupted rest and sleep
Constant noise from ventilation, equipment, and handling
Improper lighting (no natural light cycles)
Chronic feed deprivation (especially in breeding females like broiler breeders and sows)
Painful procedures in early life
Maternal stress during gestation
The pain echo chamber in factory farms
When you combine the absence of pain-suppressing opportunities with the concentration of pain-amplifying factors, you create what Dr. Schuck and co-authors coined the “pain echo chamber.”
In this environment, a standard pain signal is amplified through multiple mechanisms simultaneously. The natural pain-suppressing mechanisms that would normally be available (i.e., movement, behavioral engagement, positive social contact, cognitive distraction) are absent. Meanwhile, chronic stress, social instability, confinement, and deprivation all work together to heighten pain perception and extend pain duration.
Consider these examples:
Pigs in gestation crates experience extreme confinement, inability to turn around, chronic behavioral deprivation, and social isolation, all while potentially suffering from lameness or pressure sores.
Chickens in battery cages with keel bone fractures have no opportunity for the distraction of foraging, dust bathing, or perching—behaviors that could activate natural analgesic pathways.
Fish in intensive aquaculture face overcrowding, poor water quality, chronic stress, and extended healing times for wounds or sea lice infestations.
Additionally, while the presentation focused on physical pain, it’s important to note that barren captive environments also induce psychological suffering. Research has documented how captivity can induce depressive-like states in animals, adding another dimension to the welfare impacts of intensive rearing.
Implications for farmed animal welfare advocacy and policy
These findings suggest that welfare advocates and scientists may have underestimated pain in factory-farmed animals kept under intense conditions. They also call for a rethinking of welfare research agendas and of advocacy strategies.
Research priorities
Quantify environmental pain modulation: We need studies measuring how pain intensity, duration, and prevalence differ across housing systems. What are the correction factors we should apply when comparing welfare across environments?
Score pain differently by environment: Certification schemes and welfare assessment frameworks may need to assign different pain severity scores to identical injuries depending on whether they occur in barren or enriched environments. WFI is considering incorporating this into its Welfare Footprint Framework.
Evaluate healing environments: When assessing painful procedures, we must consider the recovery environment. Does it offer opportunities for pain suppression, or does it compound suffering?
Validate analgesia in real-world conditions: If pain research is conducted in enriched laboratory environments but medications are used on factory farms, the tested doses may be insufficient. Analgesia protocols require validation in the actual conditions in which they’ll be applied.
Possible advocacy strategies
Prioritize removing pain amplifiers: Cages, crates, barren tanks, high densities, and feed restriction don’t just constrain animals: they magnify the pain of every injury and illness they experience. Eliminating these systems can yield major welfare gains.
Reframe enrichment: Space, movement, and meaningful behavioral opportunities are not luxuries. They activate analgesic pathways and reduce pain perception, likelihood, intensity, and duration.
Focus on breeders and early life: Given the cascading effects of maternal stress and early-life pain, improving conditions for breeding animals and young animals should be a strategic priority.
Include rest and agency in welfare asks: They directly affect animals’ capacity to cope with pain and stress.
Update advocacy narratives: Factory farms don’t just cause injury, disease, and deprivation but also amplify these conditions until pain may dominate the conscious experience of animals.
Learn more
Dr. Schuck and colleagues are preparing the paper titled “The Pain Echo Chamber: How Barren Environments Amplify Pain in Captive Animals“ for publication in 2026. The paper will provide detailed mechanisms and comprehensive evidence for the findings described in this post. Sign up here to get notified when the paper is published.
For a more technical presentation covering the neurological mechanisms in greater depth, Dr. Schuck delivered a talk to the Universities Federation for Animal Welfare (UFAW), which is available to watch here.
Stay tuned to Welfare Footprint Institute’s communications for updates on their work!
If you have questions about this research, you can contact Dr. Schuck through the Welfare Footprint Institute.
Acknowledgments
Many thanks to Dr. Cynthia Schuck-Paim for sharing her expertise in the webinar and for her feedback on this post. The research findings are indebted to Cynthia Schuck-Paim, Wladimir J. Alonso, Kate Hartcher, Chiawen Chiang, Patricia Alves Pereira, Walter Veit, Michael Mendi, Christine Nicol, and Benjamin Lecorps. Elisa Autric and Urszula Zarosa organized the webinar and summarized its contents.
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Thank you for this article. I am literally writing a chapter touching on this right now. So this will be very useful for me
If animals were able to formulate a religion, it would depict the Devil in human form — William Ralph Inge