The influence of stress on the secretion of various hormones, on the metabolism of vitamins and on the immune system of sheep

Stress reactions in sheep are induced notably by infections, parasites and poor nutrition. Short-term stress influences are high temperature, isolatio n, transport, surgery and shearing. Following stress, the concentration of beta -endorphin, beta -lipotropin, ACTH and cortisol in blood plasma increa ses. The more protracted increase in the concentration of cortisol reduces the activity of the immune system and the consumption of ascorbic acid and vitamin E increases. In chronic stress, the immune system is activated by i ntra-muscular injection of a cocktail of vitamins A, DJ and E and ascorbic acid. Protected periods of stress inhibit growth and reproduction. During t he winter feeding period a supplement of 70-100 mg vitamin E per sheep and day is recommended.