Differential stressor effects on the concentrations of cortisol, prolactin and catecholamines in the blood of sheep.

Adult wether sheep (n = 8) were subjected to 60 minutes of psychological (isolation) or physical (transport simulation/standing in water) stress, or a control handling procedure in the home pen. Blood samples were taken before and during these treatments and the plasma concentrations of cortisol, prolactin, noradrenaline and adrenaline determined. All the stressors significantly increased plasma cortisol concentrations (P < 0.001) whereas only transport simulation increased prolactin secretion (P < 0.005). Noradrenaline concentrations showed little change in response to the various treatments, with the exception of isolation which produced a small non-significant increase (P < 0.08). All the stress procedures stimulated adrenaline release within the first 10 minutes but the most marked effects were seen after transport simulation and isolation, both of which induced a significant increase throughout the treatment period (P < 0.01).