Physiological consequences of the induction of auto-immunity to adrenocorticotropin (ACTH)

• Published in: Livestock production science Vol. 42; no. 2; pp. 247 - 254
• Main Authors: Wynn, P.C., Shahneh, A.Z., Rigby, R.D.G., Behrendt, R., Giles, L.R., Gooden, J.M., Jones, M.R.
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 01.06.1995
• Subjects: ACTH; AGNEAU; CORDERO; CORTICOTROPHIN; CORTICOTROPHINE; CORTICOTROPINA; Energy; ENERGY METABOLISM; ESTRES; Exercise; IMMUNISATION; IMMUNIZATION; INMUNIZACION; LAMBS; METABOLISME ENERGETIQUE; METABOLISMO ENERGETICO; RUMIANTE; RUMINANT; RUMINANTS; STRESS; ACTH; Immunization; Exercise; Energy
• ISSN: 0301-6226; 1872-6070
• DOI: 10.1016/0301-6226(95)00027-I

Stress is a component of the productive life of grazing ruminants that results in the modification of metabolic efficiency due to the preferential re-direction of nutrients to essential tissues in order for them to maintain their physiological integrity. This process is co-ordinated by hormones of the hypothalamic-pituitary-adrenal (HPA) axis that regulate the secretion of the glucocorticoids that are responsible for chronic adaptation of the animals metabolism. This report summarizes the results of studies investigating the influence of the active immunization of animals against the adrenal stimulatory hormone ACTH on carcass composition, endocrine function and energy metabolism in growing lambs. Decreases in carcass fatness in ACTH immune animals were associated with greater sensitivity in growth hormone (GH) and insulin secretion to stress, however, no differences in feed conversion efficiency or nitrogen balance were found. ACTH immunization did increase energetic efficiency by up to 20% during exercise as assessed by the consumption of oxygen, particularly when the exercise was intensive which suggests that the animal resorted to anaerobic processes to generate sufficient energy. This difference in oxygen consumption was partly attributable to changes in both cortisol and endorphin status, since the replacement of cortisol in immune animals and the blockade of μ and Σ opioid receptors with naloxone decreased the difference in oxygen consumption between the treatment groups. It would appear that immunologically induced changes in the stress hormone status of ruminants has a marked influence on metabolic efficiency and therefore productivity of sheep.