Evidence-Based Methods and Tools for Recognizing and Measuring Pain in Farm Animals
Pain is one of the most significant welfare problems in livestock farming. Routine husbandry procedures (castration, dehorning, tail docking, beak trimming), disease, injury, and parturition complications all cause pain that often goes unrecognized and untreated. Unlike companion animals, where pain recognition and management have advanced significantly, farm animal pain management has historically been minimal due to cost concerns, time pressures, and inadequate pain assessment tools.
This has changed dramatically in the past decade. Validated pain scales now exist for cattle, pigs, sheep, horses, and some poultry species. Facial Action Units (FAUs) — anatomically based systems for scoring pain from facial expressions — have been developed for multiple species. These tools are transforming how veterinarians, farmers, and researchers detect and manage farm animal pain.
Developed by Gleerup et al. (2015). Scores 5 facial action units: orbital tightening, tension above eye, ear position, facial tension, nose/cheek flatness. Validated against known painful conditions. Can be scored from photographs. Widely adopted in research and increasingly in clinical practice.
Developed by McLennan et al. (2016). Scores orbital tightening, cheek tightening, ear position, lip shape, and nostril shape. Validated for acute and chronic pain. Used in assessment of foot rot, post-surgical pain, and routine procedure pain.
Developed by Di Giminiani et al. (2016). Scores orbital tightening, nose bulge, cheek bulge, ear position change, and tail posture. Validated against castration and other painful procedures. Particularly useful for post-procedural pain monitoring.
Developed by Dalla Costa et al. (2014). Most widely adopted equine pain scale. Scores orbital tightening, ear position, tension above eye orbit, facial muscle tension, and nose/lip position. Now used globally in equine clinical practice.
Assesses lameness/pain through locomotion scoring on a 0–5 scale. Scores 3+ indicate significant welfare concern. Used as a routine welfare outcome measure at processing and in welfare audits. Cannot detect pain in non-ambulatory contexts.
Multidimensional scales combining physiological (cortisol, heart rate variability) and behavioral indicators. Used in research contexts where precision is required. The Composite Measures of Pain (CMP) scale integrates multiple domains for comprehensive pain characterization.
| Category | Low/Moderate Pain | Severe/Chronic Pain |
|---|---|---|
| Posture | Altered weight-bearing, reluctance to move, kyphosis | Recumbency, inability to rise, abnormal stance |
| Activity | Reduced movement, reluctance to approach, slower gait | Immobility, isolation, complete behavioral cessation |
| Feeding | Reduced feed intake, slower eating, selective feeding | Complete feed refusal, significant weight loss |
| Social | Reduced social engagement, avoiding conspecifics | Complete social withdrawal, aggression if disturbed |
| Grooming | Reduced self-grooming, attention to painful site | Complete grooming cessation, self-mutilation at painful site |
| Vocalization | Increased vocalizations during handling, guard behavior | Spontaneous vocalizations, distress calls |
| Facial | Mild orbital tightening, ear position changes | Severe facial tension, eyes partially closed, flattened ears |
Non-steroidal anti-inflammatory drugs (meloxicam, flunixin, ketoprofen) have become increasingly affordable and available for farm animal use. Research consistently shows that meloxicam administration before and after painful procedures significantly reduces pain scores, improves feed intake, and improves production outcomes. The economic case for analgesia is increasingly clear: pain reduces growth, milk production, and reproductive efficiency — making analgesia cost-neutral or positive in many contexts.