Stress is a broad term which implies a threat to which the body needs to adjust. Stress may originate from physical, psychological, or internally triggered stimuli (stressors), but usually contains components of all three classifications. The adjustment to stress induces a broad range of neuroendocrine, physiological and behavioral changes to allow for a rapid recovery or adaptation to the change.
In the past, housing systems and handling procedures for farm animals were mainly assessed by descriptive behavioral studies using indicators presumed to be related to stress (i.e., so called abnormal or disturbed behaviors deviating in frequency, intensity and in the context of occurrence from the normal range such as stereotypic, destructive or apathetic behaviors). Physiological indicators included endocrine changes on the pituitary-adrenal-axis by measuring adrenocorticotropin (ACTH), corticosteroids and catecholamines. The neuroendocrine and immune system has been studied in relation to stress effects at a cellular or neural level during the last decade. All these studies were often conducted in an isolated manner without considering that the neuroendocrine and immune system are communicating with each other via neuro- and immunotransmitters and are ultimately influenced by the animals individual perception of a stressor.
Transportation and associated handling procedures are considered as major stressors for farm animals and might have deleterious effects on the health, well-being, performance and ultimately on product quality. Studies on the assessment of stress during animal transportation require non-invasive methods as classical approaches of collection with direct human interference (i.e., for blood collection and heart rate measurement) might directly alter the stress response. Telemetric devices for measuring heart and respiration rate, body temperature and blood pressure are useful tools to obtain undisturbed responses. Also, non-invasive measurements of stress indicating metabolites in saliva, feces or urine has been recently developed and validated. Parallel to behavioral observations (via video recordings), these physiological measurements provide valuable information on how livestock handling and transportation can be improved in the near future.