Adrenocortical Stress Hormones and the Development of Adipose and Lean Tissue

Abstract

This thesis describes the role of the Hypothalamo-Pituitary-Adrenal Axis in the role of controlling fat deposition and partitioning and muscle degradation in the mammal. The adrenal stress hormones (glucocorticoids) are also implicated in the function of the immune system and could be considered to be limiting animal production when they are significantly elevated. A review of past and present techniques for the measurement of body and carcase composition is included in order to justify the use of techniques in the experiments carried out in this study. An attempt to validate long standing techniques carried out on the carcase at slaughter and measurements on the live animal using image analysis derived from CAT scans is made with strong correlations. The series of experiments in this study attempt to improve the growth of lambs, reduce fat deposition per se, increase skeletal muscle mass and to improve the components of immune function by reducing stress induced elevated plasma glucocorticoid levels.