[Health and fertility in relation to production. Stress and its interaction with resistance]

Stressors, environmental factors which stress animals, can influence the resistance capability of the animals. Adrenal hormones play a significant role, through the modulating of many functions of leucocytes and immune competent cells by glucocorticosteroids. There are indications that immune competent cells can produce a number of hormone-like substances. It is suggested that there is a complex relationship between the immune and endocrine systems. It may later appear that both of these must be considered as parts of an integrated system.