Plasma ß-endorphin and cortisol in sheep during isolation stress

Abstract

Many stressful procedures have been shown to cause elevation of plasma ß-endorphin (ß-EP) and Cortisol in sheep. These include shearing and electroimmobilization (Jephcot, McMillen, Rushen, Hargreaves and Thorburn, 1986), routine surgical procedures (Shut, Fell, Connell, Bell, Wallace and Smith, 1987), hypoglycaemic stress (Owen, Smith, Green and Falconer, 1984) and procedures such as handling, transport and slaughter (Fordham, Lincoln, Ssewannyana and Rodway, 1989) as well as change of environment (Fordham, Al-Gahtani, Durotoye and Rodway, 1991). The aim of the present study was to examine the effect of a very reproducible and easily applied stress, namely Isolation from other animals, on plasma ß-EP and Cortisol and also to study the effect of suppression of hypothalamo-pitultary axis with dexaniethazone during isolation. Six ovarlectomlzed ewes (48±3kg) were housed in groups of two in separate pens without visual contact between pens. In each experiment one ewe of each pair was removed from the pen. The remaining ewe was therefore isolated both physically and visually from its partner and was blood sampled every 10 min via a jugular catheter.