Stress-induced changes in immune response of dairy ewes

Abstract

Two groups of 16 Comisana ewes were selected from a group of 30, and divided, according to their cortisol secretion after isolation in a novel environment, into HC ewes, having a cortisol secretion >90 ng/mL, and LC ewes having a cortisol secretion <80 ng/mL. Blood samples were collected immediately before and immediately after isolation, and 60, 120, 300min and then 24h and 48h after isolation, to evaluate the percentage of lymphocyte T-helper (CD4+) and lymphocyte T-cytotoxic (CD8+) by flow cytometry analysis, and IL-1β and IL-6 concentrations by ELISA. The day before the isolation test, the ewes were milked in the afternoon at 1500h (-19h from isolation), and then milked for the three days starting from the day of the isolation test (at 0, 5, 24, 29, 48 and 53h from isolation) to evaluate milk cortisol secretion, and IL-1β and IL-6 concentrations. Results suggest that the levels of cortisol secretions can influence the immune competence of dairy ewes and cytokines concentrations. Milk cytokine concentrations, and not milk cortisol concentrations, can be considered indicators of the magnitude of the hypothalamic-pituitary-adrenal axis activation.