Physiopathology and pain recognition in horses

Pain is considered the fifth vital sign. Defined as an unpleasant sensitive and emotional experience associated with a real or potential tissue injury, or described in terms of that injury. It is a mechanism responsible for changing the physiological, behavioral and emotional mechanisms of the animal, being extremely harmful to physical and mental well-being. Pain is classified by temporal (acute or chronic), pathological (nociceptive or neuropathic) and local (somatic or visceral) charcateristics. Acute pain acts as a form of protection for the organism to prevent or minimize tissue damage, contributing to the animal's survival. Chronic pain is related to animal suffering, perpetuating for long periods. Nociceptive pain is part of the routine during consultations and is due to trauma and inflammatory processes. Neuropathic pain leads to sensory deficit. Nociceptors are responsible for nociception, and this is the physiological component of pain that includes the processes of transduction, transmission, modulation and perception by a nociceptive stimulus. Pain scales are useful tools for identifying pain in horses, and the assessment is made based on behavior and facial expressions. This review was prepared with the aim of presenting the physiopathogeny and recognition of pain in the acute abdomen and in the post-operative period of castration in horses through pain scales.