Document type: Scientific article published in Frontiers in Animal Science
Authors: C, Alonso WJ, Hartcher K, Chiang C, Pereira PA, Veit W, Mendl M, Nicol CJ, and Lecorps B
Abstract in French (translation): The “pain echo chamber”: how poor environments amplify pain in captive animals
Pain does not result solely from tissue damage, but can be strongly influenced by the environmental context. Its perceived intensity, duration, and likelihood—the fundamental characteristics of the affective experience—are modulated by various factors, including opportunities for behavioral activity, control over environmental conditions, the social environment, physical activity, sleep quality, maternal stress, and pain experienced early in life. All these factors influence pain responses in captive animals, yet most welfare assessments and mitigation protocols treat pain as if it were context-independent. Here, we review extensive evidence indicating that environmental and husbandry conditions modulate pain processing and healing in captive animals. We demonstrate that poor and confined environments disable several endogenous analgesic mechanisms, while simultaneously activating multiple neurobiological pathways that intensify nociceptive signaling and delay healing. Heightened pain perception and impaired healing are particularly likely when captivity is combined with intensive and poor environments. The implications of these findings are significant. First, they highlight the need for animal welfare assessment models—and animal welfare research animal welfare general—to explicitly account for environmental modulation of pain. Similarly, certification and regulatory frameworks must recognize that seemingly identical conditions or procedures can produce fundamentally different welfare experiences depending on the environment in which they occur. Furthermore, analgesic dosing protocols and laboratory pain models must be reevaluated for their translational validity. More broadly, these findings call into question the acceptability of the austere housing systems prevalent on farms, in laboratories, and in other settings. Given the substantial evidence indicating that poor environments amplify and prolong pain resulting from common routine procedures and medical conditions, the transition to housing systems that promote greater well-being becomes an ethical and scientific imperative.
Preview: Pain is not solely a function of tissue damage but can be strongly shaped by environmental context. Its perceived intensity, duration, and likelihood—the core features of affective experience—are modulated by factors including opportunities for behavioral engagement, control over environmental conditions, social environment, physical activity, sleep quality, maternal stress and pain early in life. All of these factors affect pain responses of captive animals, yet most welfare assessments and mitigation protocols treat pain as if it were context-invariant. Here, we review multiple lines of evidence indicating that environmental and rearing conditions modulate pain processing and healing in captive animals. We show that barren, confined environments disable multiple endogenous analgesic mechanisms, while simultaneously activating several neurobiological pathways that intensify nociceptive signaling and delay healing. Pain perception amplification and impaired healing are particularly likely when captivity is associated with intensive and barren environments. The implications of these findings are substantial. First, they highlight the need for animal welfare assessment models, and animal welfare research in general, to take environmental modulation of pain explicitly into account. Likewise, certification and regulatory frameworks must acknowledge that seemingly identical ailments or procedures can produce fundamentally different welfare experiences depending on the environment where they take place. Additionally, analgesic dosing protocols and laboratory-based pain models must be reevaluated for translational validity. More broadly, these findings challenge the acceptability of barren housing systems ubiquitous in farms, laboratories, and other settings. Given the substantial evidence that barren environments amplify and prolong painful states from common routine procedures and ailments, the transition to higher welfare housing systems becomes an ethical and scientific imperative.
