NEUROENDOCRINE INTEGRATION OF STRESS AND SIGNIFICANCE OF STRESS FOR THE PERFORMANCE OF FARM-ANIMALS

Recent studies have indicated complex relationships between the neuroendocrine system, immune system, and behaviour. These systems are functionally linked in order to restore homeostasis during stress. There is now evidence for a relationship between stress and disease susceptibility. Stressors containing both physical and psychological components have successfully been used to investigate the link between stress, fear/anxiety and immune modulation. Reproduction performance depends on the production of sexual hormones and may therefore be suppressed when stressors interfere with sexual hormones. Glucocorticosteroids and opioid peptides are known to interfere with reproductive function. There is some evidence that acute stressors impair reproductive performance during critical periods of the reproductive cycle, early pregnancy and lactation. The impact of social stress on production performance is significant. Stressors such as mixing unfamiliar animals and crowding may cause substantial growth depression. Stress does not always influence the performance and health negatively. For example, there are circumstances where stress seems to increase resistance to specific diseases. It is therefore questionable to evaluate and explain stress by observing single behavioural phenomena or physiological alterations. As a consequence, multiple criteria, such as ethological, physiological, health, production, and reproduction criteria should be used to evaluate possible stress situations under various production and management systems.