Satisfaction of farm animal behavioral needs in behaviorally restricted systems: reducing stressors and environmental enrichment.

In modern intensive husbandry, systems often restrict farm animal behavior. Behavioral needs will be generated by external stimuli such as stressors deriving from environmental factors or the method of animal care, or some internal factor in farm animals. This means that behavioral restriction would induce maladaptation to stressors or chronic stress. Such a risk of behavioral restriction degrades an animal's physical and mental health and leads to economic loss at a farm. Methods to reduce the risk of behavioral restrictions are to ameliorate the source of a stressor through adequate animal management or to carry out environmental enrichment. This review is intended to describe the relation between animal management and behavioral needs from the perspective of animal motivation.